Friday, 1 May 2015

T-72

URAL





The T-72 is either the most famous or the most infamous main battle tank in modern history, depending on your nationality. What isn't subjective, though, is that the T-72 is one of the most prolific tanks in modern history, and for very good reason.


According to Steven Zaloga, a single T-72M cost $1,200,000 in 1992, or $1,800,000 with spare parts and ammunition (but he does not specify how long these spare parts and ammunition are supposed to last). The T-72B3 modernization costs $800,000 per overhaul in 2014, hiking up to $1,000,000 in late 2015.




But before we take a look at the T-72 in earnest, we must first remember that the original Ural variant has undergone several major upgrades throughout its lifetime, creating significant discrepancies between each successive model, and to complicate matters, each model in itself may have subtle improvements implemented during overhauls, identifiable only by batch year.




COMMANDER'S STATION


From Stefan Kotsch's fantastic website

The commander's station is rather cramped, which is exacerbated by bulky winter clothing, but still noticeably less cramped than the gunner's station, which is suitable since his duties involve more movement. If we refer to this diagram from "Human Factors and Scientific Progress in Tank Building" by M.N. Tikhonov and I.D. Kudrin as provided by Peter Samsonov, we can see that the commander of a T-72 has much less space (0.615 cubic meters) compared to a T-55 commander (0.828 cubic meters), but this is obviously not possible. For one, the commander in a T-55 has to wrap his legs around the gunner, because there is simply not enough legroom. The commander's station in the T-72 is completely separated from the gunner's station, and there is enough legroom for him because there is nothing in front of him.

His main means of battlefield surveillance is a forward-facing TKN-3 pseudo-binocular periscope, augmented by two rectangular TNP-165 periscopes on either side of it and two narrow TNPA-65A viewing prisms aimed to his rear quarters. There is no periscope that allows the commander to see directly behind the turret. For that, he must spin the cupola just a little to one side, and look out of either one of his TNPA-65A viewing prisms. All viewing devices are electrically heated to prevent fogging in cold weather.




A snug fit ensures that the commander will not be rocked around too violently while traversing difficult terrain, but that's supposed to be the job of the suspension, and it can get uncomfortable in hot weather. Like with the gunner's station, the commander's ventilation is provided by a single adjustable plastic fan, which is about as powerful as your typical USB-powered desk fan. However, because the commander has his own hatch, he may opt to simply stick himself out of the hatch and ride on the turret. Still, the negatives of the crampedness of the station outweigh the benefits.




As for equipment, the commander's station is packed chock full of various knick-knacks essential for commanding the tank. There is also an assortment of accessories that are not directly related to his job, but are placed near him because it was the only available space in the squeezed turret.





In the photo above, we can see the R-123 radio transceiver (BLUE) at the very bottom. The silver-gray box above it is a switch box (RED) for the communications system to switch between radio and intercom communitcation, and the white box beside it is a master control panel (GREEN) for most of the functions in the tank. This control panel (pictured below) gives the commander dominion over things like the lights and the ventilator, and behind the silver and milk-white metal flaps at the corners of the panel are the emergency engine stop button and the emergency fire extinguishing system engagement (activates all the fire extinguishers connected to the automatic firefighting system in the fighting compartment) button, respectively. This control panel also enables the commander to initiate the autoloader.




The commander is responsible for setting the fuse on HE-Frag shells, and this control panel enables him to do so. Pressing one button partially activates the autoloader so that it stops before the ramming cycle commences. The commander will then use his special fuse setting tool to set the fuse to either High Explosive (HE) or Frag (F) mode. Then, another press of a button finishes the loading procedure.


The silver box (YELLOW) to the right of the intercom switch enables the commander to control the autoloader for the purpose of unloading it. The box flips open to reveal control toggles for operating the individual elements of the autoloader system, like raising and lowering the casing catcher, opening and closing the ejection port, activating the rammer, etc. If the autoloader is only partially malfunctioning, the commander can operate some parts of the loading procedure manually, and operate other parts automatically.


Above that is a dome light and the already-mentioned plastic fan. At the upper left corner is a wooden dowel with a rubber head. This is a ramming stick for the commander to use when manually loading the cannon. It may also be used as a baton to knock enemies on the head. Beside the dome light is the gyroscopic tachometer for the stabilizer system.


Underneath and just slightly forward of the commander's seat is a pair of levers. You can just barely see them in this photo (they're black):





The commander uses these to cycle the autoloader carousel manually. This is done by stamping down on the levers repeatedly.


Toggle switches for turning on the external and internal lights and the periscope heating system are located around the cupola ring.


The commander's station is quite well lit. There is one domelight directly above the gun breech, and another one in front of him, behind his TKN-3M periscope and above the co-axial machine gun. This makes it quite easy to operate the autoloader manually or load and unload the autoloader at night, and also quite easy to use all of the controls he is furnished with. It also helps when the co-axial machine gun needs reloading at night.



TKN-3M/ TKN-3MK



The TKN-3M is an pseudo-binocular periscope with night vision capability in two modes; passive and active. In the passive mode of operation, the TKN-3M employs light intensification, which is usable in lighting conditions as dark as a typical moonless, starlit night (0.005 lux). As the amount of light increases, the effective viewing distance increases. A tank-sized target is discernible at up to 400m with 0.005 lux ambient light, but identifying the same tank is entirely possible at distances of up to 600m in moonlit nights or even up to 800m during the brighter part of twilight hours. Any brighter and the image would be overexposed. Overall, the TKN-3M offers very poor night viewing capabilities compared to modern thermal imaging sights, but it was equally advanced as other IR sighting systems built in the 60's (the TKN-3 first appeared in the early 60's), and the use of light intensification technology was completely novel feature, up until the late 70's.

The TKN-3 itself has a fairly average angular FOV of 10 degrees in the day channel, or 8 degrees in the night channel. It has a fixed 5x magnification in the day channel and 3x magnification in the night channel. This is quite limited, making long-distance observation problematic, especially if the weather is unfavourable. It can be manipulated to elevate and depress to a reasonable degree, offering some limited aerial view for the commander. Overall, it is not a great system, but it is still a much better one than the x3 sight for the CWS (Commander's Weapon Station - that's the remote controlled M2HB machine gun on the commander's cupola) that the commander of an Abrams would have to rely upon. This did not change until the M1A2 was introduced in the early 90's. A T-72 commander would also get a much better downwards view. The CWS sight has very little downwards visibility, because it is blocked by the "doghouse" - the gunner's sight. See the photo below, kindly supplied by Chris Connors from the afvdb.50megs website.





The TKN-3MK is a slightly updated variant with a 2nd Generation light intensifier, giving it better image quality and a slightly greater identification range of 500m under the same lighting conditions stated before (moonless, starlit nights with ambient light levels of 0.005 lux). All T-72Bs are equipped with it.

Due to the fact that the periscope is unstabilized, identifying another tank at a distance is very difficult while on the move over very rough terrain. However, the commander is meant to bear down and brace against the handles of the periscope for some improvised stabilization, which is adequate for keeping the target within view for average off-road conditions, but not good enough for range finding or precise target designation, but the latter does depend on the skill of the commander somewhat.

The active mode requires the use of the OU-3GA IR spotlight which is mounted on the rotating cupola. The distance at which a tank-sized target can be identified in this mode is apparently around 400m, although the spotlight can in fact illuminate objects much further away than that. The main issue is the low magnification, which is simply not enough for spotting camouflaged tanks. Surplus OU-3GA spotlights have become rather popular on the civilian market in recent times as floodlights for off-roading 4x4s, or just for recreation. In this site here, you can see the spotlight in action. The photo below perfectly illustrates the power of the spotlight.




The spotlight clearly illuminates an apartment building 700 m away, though the effect is not as pronounced because of the nearby streetlamps increasing the amount of ambient light. Also, the OU-3GA that they used was battery powered and ran on only 55W. The spotlight is designed to run on 110W when connected to the tank's electrical system.


The TKN-3's aperture has a small wiper



Rotation of the cupola can be done by either using the TKN-3's set of grips to slide the cupola around the race ring, or the cupola-mounted anti-aircraft machine gun cradle's handles, if the commander is outside the hatch. By rotating the cupola, the commander can attain a full 360 degrees of vision.

Contrary to popular belief, a hunter-killer regime is not at all exclusive to modern Western tanks. Rudimentary hunter-killer cooperation dates back to WW2, where commanders would have to yell out the direction of the target by referring to the angle indicated on his cupola's race ring. The gunner can slew the turret towards the target by referring to an azimuth indicator corresponding to the commander's, usually marked out on the turret ring. In 1951, the T-54 obr. 1951 pioneered a semi-automatic system where the commander only has to press a button to activate the electrical powered traverse drive and slew the turret towards whatever target he is viewing through his optic. The T-72, like the T-64 and T-62 before it, has this feature as well. As you would expect, the commander performs as the hunter in the hunter-killer system. On the end of the TKN-3MK's left hand grip is a button to initiate turret slewing to aim at whatever the commander has his crosshairs on. But even that isn't new. The T-62 tank, which began production in 1963, already featured the TKN-3 binocular sight and the same automatic target designation capability, but the T-72 features an additional electric motor that automatically counter-rotates his cupola so that his original orientation is preserved. Most Western tanks of the 50's and 60's already had the same hunter-killer feature, with some notable exceptions like the M1 and M1A1 Abrams, which did not have a similar feature until the M1A2 variant came about.


Notice the toothed external ring on the cupola. Also notice the red electric motor in the upper right corner of the photo

Once the turret is slewed towards the target, the gunner will see the target, lay the gun more precisely, and then engage. The commander has duplicated controls for ammunition selection, so can select the most appropriate shell type for the type of target he has spotted in advance for the convenience of the gunner, allowing him to fire as soon as he has aimed. This sort of cooperation between the gunner and commander allows the T-72 to potentially attain its maximum rate of fire of 7 to 8 rounds per minute (with a round already in the chamber), if there are enough things to shoot at, of course.


The TKN-3M sight has a stadia reticle intended for approximate manual range estimation of tank-sized targets 2.7m tall from a distance of 800m to 3 to 3.2km, although this might be slightly optimistic for most situations. However, it is entirely possible for the crew to see and engage targets at such distances if weather conditions and the geography of the battlefield allows for it. Example of such geography should include plenty of high ground. Stadiametric ranging is not an accurate way to determine target distance. At long distances, distance errors may be up to hundreds of meters,

 
Diagram of the view through the TKN-3M


View through the TKN-3MK. Notice the cross reticle, distinguishing the sight from previous versions. The stadia-reticle rangefinder remains the same.



A horizontal stadia rangefinder is objectively superior to a "choke" type stadia rangefinder, like the type found on M551 Sheridan light tanks. Whereas a "choke" rangefinder indicates target distance based on width, a horizontal rangefinder depends on height instead. A "choke" rangefinder would not be able to accurately determine distance if the target tank was not oriented directly towards the observer, which meant that against both stationary and mobile targets, and especially targets moving side-to-side, it would be mostly useless for actually finding range. Keep in mind that depending on the direction which a tank could be travelling, the observer could be seeing the tank lengthwise and not its actual design width. It would also be impossible to accurately guess a target's real width given a silhouette of an unknown size. A horizontal-type rangefinder, on the other hand, can measure distance no matter which direction the target is travelling in, and if a tank was in a hull-down position, the height of a tank would generally be halved, given that only the turret is exposed, giving the observer a fighting chance to approximate target distance.


As mentioned before, the TKN-3 sight depends on an OU-3GA xenon arc IR spotlight for illumination when operating in the 'active' mode. An inherent shortcoming to the usage of IR spotlights is that enemy tanks using a sight operating on the same type of system can see the light as well, along with its source. The SVD sniper rifle, for example, was fitted with the PSO-1 scope with an IR filter that let the sniper exploit this trait and allowed him to see enemy tanks at night. This makes it easy for the T-72 to be caught in an ambush at night by other tanks of the era like M48s, M60s, Leopard 1s, Chieftains, etc, although it must be said that the inverse also applies. The T-72 can easily see and engage enemy tanks maneuvering in the dark without switching on its own spotlight. Like turning on a flashlight in the dark, you may not be able to see very far, but anyone can spot your torch from miles away. 




COMMANDER'S FIRE CONTROLS



None of the Soviet era T-72 models featured a set of firing controls for the commander. This feature only came on the recent T-72B3 modernization. Before, the commander only had access to the autoloader controls, but in the T-72B3, the commander is now equipped to override the gunner entirely. He has a flatscreen display linked to the Sosna-U sight, and the necessary controls for firing the main gun and the co-axial machine gun at his disposal in the form of a set of handgrips similar to the gunner's. This arrangement is no different from what most Western tanks already had for decades.




The control unit is almost exactly the same as the type installed in the T-80 tank as part of the PNK-4 fire control system. Control of turret traverse and gun elevation is accomplished using the thumbstick. The decision to use a thumbstick was because a full joystick could not be easily manipulated with precision if the operator's body and arm was rocking around if the tank were going over rough terrain. However, the thumb would be completely stationary if the hand was securely gripping a handle. The index finger rests on the trigger.






COMMUNICATION





The T-72 was originally supplied with an R-123 radio. The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could instantly switch between four preset frequencies for communications within a platoon. It had a range of between 16km to 50km. The R-123 had a novel glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had an advanced modular design that enabled it to be repaired quickly by simply swapping out individual modules.

Beginning in 1984, the R-123 was replaced by the R-173 radio in the new T-72B. The R-173 had a frequency range of between 30 MHZ to 75.999MHZ and 10 preset frequencies. It had an electronic keypad for entering the desired frequency, and a digital display. Both the radio and intercom system are directly routed to the throat mike and headset, which are integral parts of the iconic Russian tanker's helmet.


The throat mike gives very good voice clarity and doesn't pick up any ambient noise, which makes the throat mike system inherently superior to open mikes.


Communications through the R-173 are rather easy to intercept and jam or listen in to. For instance, Chechen fighters during the Chechnya campaign were able to listen in to radio chatter and even interject bogus commands over Russian airwaves. For this very reason, the new, frequency-hopping R-168-25UE-2 was rapidly launched into service in the 2000's to replace it.

R-173

The R-168-25UE-2 frequency-hopping encrypted radio set is used for communications on all levels. It replaced both the R-173M and R-123 radio stations in the T-72B3 modernization.

R168-25UE-2

The R-168 family of radios is now the standard throughout the Russian ground forces, from infantry platoons to tank companies. It can produce frequency hops 100 times a second, and the data is encrypted as well.

Command variants of the T-72 were equipped with an additional R-123 radio. As of today, the R-123 radio is completely antiquated. It is an analogue design first used in the T-62 back in the early 60's to replace the R-113. Command variants were identifiable via their distinctively elongated second antenna.

The modern day Russian army no longer fields command variants of the T-72 due to a drastic shift in combat doctrine. Instead, all modern T-72B3 tanks have only a single R-168-25UE-2 radio. Command variants of Soviet era T-72s have been reverted to their base variants.

Besides the updated communications hardware, the tank's intercom and radio control panel was also replaced with an all-new digital one shown below:





It's worth noting that the ventilation system for the T-72 draws air from the same port as the engine air intake, at the engine deck directly behind the right quadrant of the turret. The ventilation system has filters that ensures a supply of clean air. The same filters are responsible for filtering out radioactive particles or biochemical agents in NBC-contaminated areas. The ventilator housing and the white pipe leading to the air intake can be seen tucked away in the rear corner of the fighting compartment:




Unlike some NATO tanks like the M60A1, the commander's means of surveying the battlefield is conducted with periscopes and not with vision blocks. The commander's head is located below the cupola ring, too. The implications of this design decision is that the commander has rather unremarkable - substandard, actually - all-round visibility. But like all design decisions, this one does have its advantages. The commander is completely withdrawn from large-caliber sniper fire (12.7mm-type) and deliberately concentrated machine gun fire. There is absolutely zero chance that his eyes may be injured by broken glass, since the internal periscope aperture is protected by ballistic glass.



For forward observation, two TNPO-160 periscopes are provided. Each has a total horizontal range of vision of 78 degrees, and a vertical field of view of 28 degrees: 12 degrees above the horizontal axis and 16 degrees below

Two TNPA-65A periscopes bring up the 4 o'clock and 8 o'clock positions. They are mounted directly in the hatch, and thus view the rear two quadrants of the turret. Unfortunately, there is a glaringly obvious blind spot directly behind, since this is where the hatch's locking latch handle is located.




TNPA-65A provides only 14 degrees of binocular vision horizontally and 6 degrees of vertical vision, meaning that its width is within the normal and acceptable range, but it is very narrow.


The TNPO-160 periscopes with the TKN-3 binocular periscope comprise the forward vision assembly of the commander. Despite the limited all-round visibility (compared to NATO tanks) offered by the commander's five periscopes, he can still compensate by simply rotating his cupola. This essentially negates the smaller number of observation devices, but it does not compensate for the periscopes being more constricted than the type found in typical NATO tanks. Nevertheless, while the commander may not have perfect immediate all-round awareness, he has a very reasonable degree of coverage.





The commander's hatch is of a forward-opening, 500mm-diameter half-moon type, mounted on the rotating cupola. The hatch is fully airtight and watertight up to a depth of around 3 meters. The hatch is quite small, and exiting through it in a hurry may be problematic if the commander is wearing winter clothing.

It is spring-loaded, so that it can stay open when the commander wishes to view the battlefield with binoculars, or when he needs to use the complementary AAMG. A simple rotating handle locks the hatch when closed, preventing it from bouncing up and down when the tank is in motion.



Because it opens forward, the thick hatch gives the commander full-body protection from machine gun fire whenever he wants to pop out for tactical assessment with binoculars. To look over the hatch, all he needs to do is to stand on his seat.

The commander is shielded from machine gun and sniper fire by his hatch

In some modifications beginning in the mid-70's, the commander's cupola may also feature a rather peculiar shield, mounted forward of the hatch. All T-72s operated by the Russian ground forces today feature this shield.




The lower part is a simple hanging canvas sheet, which isn't intended to be part of the protection scheme per se. The upper part is just a face shield for the commander for if he were to sit outside on the turret while on road marches, to shelter him from the dust cloud kicked up by the lead tank in front.




The shield made of very thin sheet steel with an equally thin polycarbonate or perspex window and is thus not bulletproof, splinter-proof or fragmentation-proof (though the commander's hatch is). Therefore, the protection afforded to the commander does not change. The only ballistic protection the commander gets still comes from his hatch, only now he has dust and bug protection. See the photos above and below.






GUNNER'S STATION


The gunner's station is dominated by the massive GPS (Gunner's Primary Sight), which tips the scales at 80kg. He is responsible for all of the weapons-related equipment, including the autoloader, stabilizer, cannon, co-axial machine gun, the sighting devices and their associated instruments.


The gunner's station is the most cramped position in the T-72, and even more so if he is wearing winter clothing. However, it would be a mistake to consider the cramped nature of the gunner's station as a unique and defining feature of the T-72. As a whole, the T-72's turret does indeed have a much smaller volume than most tanks, but the space delegated to the gunner is very much on par with its contemporaries. Though few would think it, the gunner's station here is no smaller than that of the vast majority of NATO tanks, where the gunner is wedged between his sight and the commander's knees, with the gun breech to his left and the turret wall to his right and barely any shoulder room. Case in point:




Chieftain:

Mr. Cutland in this picture can lean back only because the commander's seat behind him is not occupied


Abrams:

The gunner of an Abrams is crammed into a small corner, with the gun breech inches from his head (The gunner does not have a shoulder guard) Photo credit: Chris Conners from afvdb.50megs




The commanders, loaders and drivers in most NATO tanks are living in luxury, of course, but this is usually not the case for the gunner. The gunner's station in the T-72 is also not inferior to its predecessors, the T-62 and T-55. In fact, now that the gunner no longer has the commander's legs interfacing with his torso, it is slightly better deal to be in the T-72, cramped though it is.

Looking again at this diagram from "Human Factors and Scientific Progress in Tank Building" by M.N. Tikhonov and I.D. Kudrin as provided by Peter Samsonov, we can see that the space afforded to the gunner is seriously tight, only 0.495 cubic meters. However, this is a big improvement over the T-55, which gave its gunner only 0.395 cubic meters of space.

In any case, internal space in this tank seems to be more psychological than physical. Volume and comfort-wise, the gunner's station in a T-72 is quite adequate for a legacy tank, though still undoubtedly cramped. However, that is not to say that crampedness of the gunner's station is entirely negative. A snug fit ensures that the gunner will not be knocked around too much while the tank is in motion, which is undoubtedly a small benefit to targeting precision while driving on uneven ground. It isn't so much an issue while on long marches, because both turret occupants may simply sit on the turret roof instead. In this respect, the T-72 has a slight ergonomic advantage over many tanks in that the gunner has his own hatch and he can exit whenever he likes to sit on the roof, or to stand upright. In the event of an internal fire, the entire crew can bail out with no fuss. This is quite unlike tanks like the T-55, Leopard 1, Abrams, or indeed, any other manually-loaded tank except for a few oddball designs like the M60A2. Usually, the gunner is not provided with his own hatch. On long marches, he might be forced to stay put in his decidedly cramped station for hours at a time.


Case in point; in Part 2 of his "Inside The Chieftain's Hatch" video review of the Centurion tank, Mr. Nicholas Moran from Wargaming noted that after just 20 minutes, it was beginning to get uncomfortable in the gunner's seat. If it began to get uncomfortable in his seat, the gunner of a T-72 can open his hatch and sit on the roof, or just stand on his seat and stretch. Additionally, in a typical manually loaded tank, if the commander were incapacitated or killed, the gunner would have to squeeze through the commander's body or shift it aside in order to bail out. This is not a problem for the T-72.





Ventilation is provided by a single adjustable hard rubber fan mounted on a ball joint. It is more than enough in European climates where temperatures are usually around 20° C (68° F) or less, but in hot, desert regions averaging 30° C to 40° C is only useful for increasing air circulation to stave off stuffiness, and little else. Still, it's better than some tanks that do not provide any personal ventilation.


For general visibility, the gunner is provided with a single forward-facing TNPO-165 periscope and another TNPA-65A periscope on his hatch, pointing to the left. The TNPO-165 periscope has a large field of view. It is placed there for the gunner to check the orientation of the gun barrel, and to make sure that if the tank is entering a ditch or a trench, the gun barrel is elevated safely. In daytime, the periscopes are also sources of light.


1A40-1 sighting complex and 1K13-49 night vision/auxiliary sight


As you can see in the photo above, the gunner is supplied with a duplicate of the commander's master control panel. Besides being able to initiate the fire control system, control the ventilation, turn on the lighting system, and much more, having the master control panel enables the gunner to set the fuse on a HE-Frag shell in lieu of the commander if necessary. This means that technically, the T-72 can fully operate on a 2-man crew: One gunner, and one driver.

The box farthest to the left is the autoloader control box. With it, the gunner can select the ammunition type, and initiate the loading procedure. In a high tension tank duel, a good gunner will have his right hand on the handgrips to pull the trigger, and his left hand on the loading switch, so that at the moment immediately after firing, the autoloader will kick into action. Below the master control panel is the turret azimuth indicator.




The indicator is akin to a clock, with a minute arm and a second arm. The larger arm roughly shows the direction the turret is pointing to, being a tool of convenience, but also points out the turret's traverse in degrees. The smaller arm (which rotates very rapidly if the turret is turning) is the arc minute arm. It points out the orientation of the turret in increments of 1/60ths of a degree. It is only of any real use when the tank is called upon for indirect fire.



The gunner is provided with a single half-moon hatch. Its most distinctive feature is the smaller circular port hole at its center, intended for snorkel installation. The hatch is spring loaded to hold it in place when open, and to give a little leeway for the gunner when opening it. It is locked with a simple rotating latch. There is a single TNPA-65 periscope embedded in it, pointing to the left (mentioned above). It is rather small and slit-like, but it provides the gunner with some precious limited sideways visibility. It provides only 14 degrees of binocular vision horizontally and 6 degrees of vertical vision.



In the gunner's case, periscopes are not very useful on a day-to-day basis. For one, the gunner must concentrate on his job of gunning the gun, and he will not be able to see much from out of the few vision devices that he has. Still, the periscopes are useful for letting outside light in, and they give him a decent sense of his surroundings, all the better for the gunner when buttoned up.



SIGHTING COMPLEXES


Because of the T-72's status as a "mobilization model", the more expensive parts were usually kept as affordable as possible. It was to be manned by conscripts with minimal training (though I emphasize that it was still much better and more thorough training than what many 3rd world country tank crews received), and T-72 crews received fewer opportunities to conduct firing exercises during peacetime than T-64 and T-80 crews. The sighting systems suffered the most from this practice. The T-72 never had a true ballistic computer and the fire control system required far more manual input than the best analogues of the time. Nevertheless, it must be noted that T-72s still had very comparable protection to its domestic contemporaries (in the case of ammunition placement, it was undoubtedly superior) and comparable firepower, although T-72 units usually received the latest ammunition later than T-64s and T-80s. This fact considerably helped offset the lack of sophisticated sighting devices, but the shortage of technology (but not the lack thereof) in an increasingly technological stage of the Cold War was not comforting.




TPD-2-49


  The T-72 first entered service in 1973 sporting the TPD-2-49 optical coincidence rangefinder. It can be used to identify and engage tank-type targets and bunkers at up to 4000m in the direct fire mode.

  The optic aperture is split into two halves, top and bottom. The two input lenses see different parts of the same target, and the gunner must use the adjustment dial near his hand grips to line up both halves and obtain a seamless picture. This process was cumbersome and somewhat inaccurate - the error margin was 3 to 5%, which meant that the range could be off by up to a shocking ±200m at 4000m, or a much less serious ±30m at 1000m range. However, it's worth considering that the average tank engagement distance expected in Europe was estimated to be 1500m, relieving the TPD-2-49 somewhat. Plus, the use of hypersonic APFSDS ammunition meant that the error margin could usually be ignored since the ballistic trajectory was so flat that amount of drop was completely negligible at out to 1500m or more. The problem was much more pronounced with HEAT and HE-Frag ammunition, which were heavier, had worse ballistic coefficients and traveled at much lower velocities. With the advent of long range ATGM systems mounted on jeeps, scout cars, IFVs and even light tanks, accurate long-distance fire with HEAT and HE-Frag shells was imperative.





The gunner turns a wheel located just above his hand grips to line up the two halves:



A major flaw with optical coincidence rangefinders in general is that they don't work very well on camouflaged targets. Even tanks simply painted the same shade as the environment can be difficult to accurately range because the outlines of the tank may not be very clear to the gunner. Ranging errors were more or less irrelevant to the T-72 because it fired very-high-velocity APFSDS ammunition, but firing HEAT on targets would be very difficult at longer ranges, not to mention moving ones.

All in all, optical coincidence sights were generally considered wholly unsatisfactory due to their cost and complexity of operation, which the TPD-2-49 was no exception to. They were also fragile, despite extensive shockproofing and anti-vibration bushings. Any misalignment as a result of shocks from tank shell impacts could cause the sight to be misaligned so that it becomes useless, and this was a big problem with the T-72 (and indeed, every other tank with such a rangefinder) because an optical tube connecting the first aperture to the main sighting unit ran across the turret roof above the gun. Hitting anywhere in that vicinity could put the sight out of commission. This, in addition to the issues mentioned above, meant that production was summarily discontinued just two years later in 1975 and all T-72 Urals were refitted with TPD-K1 laser rangefinding sights in the T-72 Ural-1 modernization later in that same year (The Ural-1 modernization retained the turret of the Ural, but swapped out the sight). Since it was of no use anymore, the TPD-2-49's second optic port was blocked off and permanently welded shut.

Still, the fact of the matter is that the TPD-2-49 placed the T-72 Ural on at least equal footing with the best NATO tanks at the time, including the Leopard 1. As the optical coincidence rangefinder was integrated into the sight, the TPD-2-49 can be considered an advanced sighting complex, on par with the fire control system of the Leopard 1 and superior to the setup on the M60A1, which had a separate primary sight and M17 rangefinder unit. While the gunner of an M60A1 would have to conduct ranging and then switch over to apply the range data into his sight, the TPD-2-49 sight was adjusted concurrently with the rangefinder, and target acquisition time was slashed accordingly.



T-72 Ural-1 & T-72A


1A40 Sighting Complex, TPD-K1




The TPD-K1 is part of the 1A40 sighting complex, which included the TPD-K1 itself, plus the internal ballistic calculator and the sight-stabilizer interface. It was first installed on the 1975-76 upgrade of the T-72 Ural, which became the 'Ural-1', later carrying over to the T-72A in 1979 and to the T-72B in 1983. It is the gunner's primary sight, mounted directly in front of him. It has a fixed 8x magnification and a 9° field of view. Though it might not be anything special today, it was a huge leap in optronic gunnery technology in 1975. In fact, the TPD-K1 gave the T-72 a 3-year head start over its Western nemesis the M60, which received its own AN/VVG-2 laser rangefinder unit in 1978 as part of the M60A3 upgrade. Leopard 1s did not receive their own laser rangefinders until the 80s rolled around, and Chieftains had to wait til 1988 to get theirs.

The sight aperture housing on the turret roof is armoured to withstand small arms fire, and a thin steel shroud extension shelters the aperture from thrown mud, rain, sand and snow. The extended side walls are of a much thicker steel meant to protect from bullets and fragmentation. The aperture itself has a layer of bolt-on SET-5L ballistic glass (19mm thick) to protect it from bullets and shell splinters. It is provided with a small wiper to remove any debris or mud that might obstruct the gunner's vision.

The sight aperture itself is just a periscope. There are no integral components in it, just a high-quality mirror with linkages to the internal stabilizer, so the financial loss from a destroyed sight aperture is totally negligible. Tank crews carry an extra sight aperture in internal stowage for quick field replacement.
  

Armoured sight housing and shroud



The TPD-K1 incorporates a removable solid-state IR laser rangefinder (pictured below). It has a maximum error of 10m at distances of 500m to 3000m. From 3000m to 4000m, the maximum error threshold increases to 15m. The rangefinder becomes somewhat unresponsive and inaccurate past 3000m.


Detached rangefinder processing and readout unit


Attached to the right side of the TPD-K1 sight module



It has a digital display for precise readouts, and range information is ported through to the range indicator dial on the top of the gunner's viewfinder, which the gunner can read for manual input if necessary. To lase a target, the gunner must place the illuminated red circle over it and fire off the laser for 1 to 3 seconds, less at closer ranges, adding about 1 second per every 1350 m. If the target is mobile, it must be tracked within the boundaries of the red circle until the range is obtained. The rangefinder unit must take 6 seconds to cool down between uses.

Range input unit

Range information is automatically routed to the sighting unit, and the sight makes the necessary corrections and adjusts the reticle accordingly. The illustrations below shows what happens duing the ranging process.




Firstly, note the circle at or near the center of the viewfinder. That is where the target must go in order to initiate the rangefinding process. Once that is done, the reticle instantly lowers appropriately, and the range indicator dial at the top spins to show the distance with an accuracy of within 10 m (for future reference). The lasing circle stays where it is for lasing the next victim.

This procedure is completely normal in the realm of tank fire control systems, but one oversight is that the path for the laser beam is not merged into the same lenses for the main optic. Rather, the laser rangefinder has its own optical path parallel to the lens tube which the gunner uses. This is evident when you closely inspect the sight aperture:





As you can see, the mirror is divided into two halves by an opaque block in the middle. Underneath the mirror, you can see two apertures. One for the laser rangefinder, and one which the gunner sees out of. This means that the rangefinder circle is always located slightly to the right of the reticle, and not on the reticle. The gunner must lay the rangefinder circle over the target, lase it, and then finish by laying the reticle on the target. There are a multitude of disadvantages to this. Instead of laying a reticle on the target once and letting the fire control system handle it, the gunner do so twice. This creates room for operator error and consumes precious seconds of time.


The TPD-K1 features a stadia-reticle rangefinder with distance indicators for ranges of 500m to 4000m that can be used to gauge target distance if the laser rangefinder is malfunctioning. This and the manual gun laying drives allow the gunner to continue engaging targets even if all aiming systems have completely lost power. The sight's vertical stabilization system is linked to the vertical manual drive for cannon elevation.





All reticle lines can be illuminated (red colour) by an internal light bulb for better discernability in cloudy weather or at night.

The TPD-K1 is independently stabilized in the vertical plane. Thus, the gunner's view is not affected by any deficiencies in the gun's stabilization drives. However, the sight is not stabilized in the horizontal plane. This has implications that we will explore later.


1 - Ranging scales for co-axial machine gun (ПУЛ stands for Pulemyot, or machine gun), 2 - Ranging scales for HE-Frag shells (ОФ stands for High Explosive), 3 - Laser range finder distance indicator dial, 4 - Stadia-reticle range finder

The sight includes graduations for firing the PKT machine gun to a maximum range of 1800m, for firing HE-Frag shells to a maximum range of 5000m, for manually applying lead on moving targets, and an auxiliary stadia rangefinder for manually determining the distance to a tank-type target or a bunker 2.7m in height at distances from a minimum of 500m up to 4000m (there is no need for a ballistic solution for targets closer than 500m). The stadia rangefinder is for emergency use only. On the top of the sight picture is the range indicator dial for the laser range finder, which is also capped at 4000m. Once the gunner has lased the target, the range will be displayed here for reference is necessary. The range data is automatically inputted into the ballistic calculator.

To operate the sight, the gunner must first toggle the type of shell into the sight beforehand. This is done with a dial on the sight itself. Once this is done, the sight will automatically adjust itself for appropriate elevation, assuming that the target has been lased. All the gunner must do now is to place the center chevron onto the target and fire. Subsequent shots do not require the process to be repeated, even if the gunner changes shell types or uses the co-axial machine gun. All he must do is select a new ammunition type.



1A40-1 Sighting Complex, TPD-K1M





The 1A40-1 sighting unit is a slightly improved TPD-K1M primary sight modified to include an additional eyepiece for the gunner's left eye, which is a part of the UVBU system. The new UVBU unit calculates the necessary amount of lead for a moving target and displays it in figures which can be manually applied by the gunner on the lateral scale in the TPD-K1M. It works by determining the rate of rotation of the turret as the gunner is lasing the target and then translating that information into mils, which is displayed in the eyepiece for the gunner to read. The gunner will then know which secondary chevron on the lateral mil scale on the reticle he should adopt as the new aiming point. The use of an eyepiece rather than a separate digital display is so that the gunner does not need to break visual contact with the target. As the UVBU eyepiece displays a virtual number on a black background, the gunner can keep both eyes open (and see the number floating in his vision), see the mil figure, and then apply it, all done without tearing his eyes away from the TPD-K1M eyepiece.




Technically speaking, the precision of the UVBU unit should not differ much from that of the systems employed in more advanced fire control systems, as it can calculate down to ± 0.5 mils. This is more than enough even for very long range shooting as the tank travelling sideways would be presenting its side profile, which is very large anyway. Its most serious drawback is the lack of automation. In the fire control system for, say, an M60A3, lead for the target is calculated and automatically applied to the reticle by the ballistic computer after the target is lased, meaning that the sight automatically adjusts horizontally (via horizontal stabilization) so that the reticle has already compensated for lead. This allows the gunner of an M60A3 to press the trigger immediately after lasing - no need to use secondary markings to engage. This is much faster than the system employed on the T-72B, but in all honesty, the ability of the T-72B to engage moving targets should still be decent, only that it takes a few seconds longer and requires a calm professional in the gunner's seat. Overall, the system is somewhat crude, and was technologically obsolete the moment it was introduced. By 1983, the entire 1A40-1 sighting complex could be considered outdated, especially considering the fact that the T-72B did not have a ballistic calculator like the T-64B with its 1A33 fire control system.


The TPD-K1M sight itself differs from the TPD-K1 by the presence of mil values printed on the secondary chevrons.





With both the 1A40 and 1A40-1 complexes, the gunner must first input the shell type in order for the sight to obtain a firing solution. Once set, the sight automatically accounts for different ballistic characteristics of different projectiles, and adjusts the elevation of the cannon accordingly. Shell type selection is done with the rotary dial above the left handgrip, or directly underneath the UVBU eyepiece in the 1A40-1 complex. It can set the sight for all ammunition types, including the co-axial machine gun.






It is possible to use different shell models by simply twisting a dial on the UVP control unit, pictured below.


Notice the blank spaces on the indicator card; these are left in anticipation of new ammunition. The introduction and use of 3BK-29, for example, would necessitate reprogramming the UVP unit at a depot. The card would then be filled in. Each ammunition type (APFSDS, HEAT, HE-Frag) has 4 slots for different ammunition.

The UVP unit allows the gunner to instantly reset the sights for different types of each category of ammunition. For instance, T-72s could go into battle loaded with Chinese or Indian 125mm ammunition, and cycle between completely different rounds with completely different ballistics made by completely different manufacturers from different nations while in combat by simply setting one of the dials, assuming that the UVP had been reprogrammed, of course. It is also possible for the T-72 to use "exotic" ammunition this way. For example, one of the blank spaces on the indicator card for HE-Frag (labelled OF in the photo above) can be filled for flechette rounds. The gunner can then toggle the sight for the HE-Frag ammunition type, and then cycle the HE-Frag dial on the UVP panel to the flechette slot. This means that the T-72 can fire up to 12 different types of ammunition with different ballistics, and switch between them at the flick of two switches.


Unlike the handgrips for the gun laying systems of previous Soviet tanks, the handgrips are permanently attached to the TPD-K1 sight. The handgrips have a protruding ledge at the base for the gunner's hands to rest on. The handgrips have two buttons each. The left trigger button is for firing the co-axial machine gun and the left thumb button is resetting the laser rangefinder. The right trigger button is for firing the main cannon, and the right thumb button is for firing off the laser rangefinder. An ex tanker has remarked to the author that he found it difficult to operate the handgrips sometimes as it was rather confusing for him. He had previously operated a T-55 tank, and the thumb buttons were for firing the cannon and co-ax. With the T-72, the trigger buttons had not only moved, two more buttons were added! The price of progress is high indeed.




AUXILIARY SIGHTS


The gunner has access to a secondary gun sight primarily intended for night operations, although this may also be used as a backup in case the main sight is damaged. The auxiliary sight of the T-72B had the dual purpose of guiding the gun-launched anti-tank missiles.


TPN-1-49-23





The TPN-1-49-23 is the gunner's auxiliary sight for the T-72 Ural and T-72A variants. It can either use ambient light intensification or use infrared light conversion and intensification by relying on the L-2AG "Luna" IR spotlight for illumination. The Luna spotlight is mounted co-axially to the main gun, and swivels along with it. Like the commander's OU-3GA spotlight, the L-2AG Luna spotlight is a xenon arc lamp with a simple IR filter slide. Removing the filter transforms the IR spotlight into a regular white light spotlight. The level of ambient infrared light and therefore visual clarity can be cumulatively improved if multiple vehicles sporting IR spotlights, like BTRs, BRDMs, BMPs and other T-series tanks are illuminating the battlefield.

Like the main sight, the TPN-1-49-23 is protected by a squarish, squat armoured housing, with a bolt-on steel cover for the aperture.

As you can see, there is also small IR light (the filter is removed here) mounted outside of his hatch, to the left of the sight housings. Its purpose remains unclear.


The sight can be relied upon to identify tank-type targets at around 800 m in the active mode with the IR spotlight, but the distance at which the gunner can see a vehicle - but not distinguish it - is a few hundred meters farther. The passive setting allows the same target to be spotted at ranges of up to 800m if the ambient light is no less than 0.005 lux, which is the typical brightness of a moonless, starlit night with clear skies. Clarity and spotting distance improves with increasing brightness. The identification distance is expanded to around 1000m on moonlit nights, and it is possible to spot tanks at distances of more than 1300m during dark twilight hours, although low magnification and mediocre resolution complicates viewing beyond that range. Soviet enthusiasm for light intensification technology gave the T-64 and T-72 a significant night fighting advantage over their Western counterparts, whom relied solely on IR imaging technology for decades. Case in point: The M60 received a light intensifier sight only in 1977 with the M60A1 Passive modernization, and the original 1978 production M60A3 had the passive nightsighg before receiving the AN/VSG-2 thermal imaging sight in 1989. As for IR imaging itself, the TPN-1-49-23 was on par with the M60, but narrowly loses out to the Chieftain, which benefits from a massive 2 kW 570mm spotlight while the L-2AG ran on just 600 W.

If used as a backup sight, it can be used to identify tank-type targets at up to 3000m in daylight or more, if the geography and weather permits it. It has a field of view of 6 degrees at maximum magnification. Variable zoom allows reduction of magnification to 1x to give the gunner much better general visibility for spotting targets. The sight is independently stabilized in the vertical plane with 20 degrees of elevation and 5 degrees of depression. This sight does not have the ability to guide gun-launched ATGMs like the Svir.

Though the cover can be removed and the sight used during daytime, light intensification must never be activated, because excessive light input will overload the sight unit and possibly damage it. In accordance with this, the aperture has shutters linked to the trigger unit. Upon firing, the shutters automatically close to shield the unit from the intense flash of cannon fire at night. The shutter may also be manually opened and closed via a handle, if the situation calls for it.

This sight first appeared with the T-72 Ural in 1972.



1K13-49





The 1K13-49 sight was implemented in part due to the introduction of GLATGMs (Gun-Launched Anti-Tank Missiles) for the T-72. The maximum range of guidance is 4000m. Aside from this feature, 1K13-49 also represents a significant improvement over the TPN-1-49-23 in target engagement capabilities; With a fixed 8x magnification in the daytime channel and 5.5x magnification in the nighttime channel, its useful range for tank-type targets is expanded in daylight mode. Its active infrared optoelectronic imaging system is also improved over the TPN-1-49-23. Now, the viewing range in the active mode is increased to 1200 m, though the light intensification unit has not been improved, meaning that the 1K13-49 sight still only has an 800 m viewing distance (under ambient lighting conditions of no less than 0.005 lux). As with the TPN-1-49-23, the identification distance and image clarity improves with increasingly brighter lighting conditions, but excessive brightness can oversaturate the image, and overwhelming brightness can overload and possibly damage the sight.


Daytime mode
1K13-49 image in the passive light amplification mode, aimed at nothing in particular (Photo credit: Stefan Kotsch)

The sight has a field of view of 5 degrees in the daylight setting or 6°4' in the nighttime setting. It is independently stabilized in the vertical plane, with +20° elevation -7° depression.




The sight aperture has two protective housings; one enclosing the sensitive optical workings of the aperture itself with a tempered glass window and a shock-proof shell, and another very heavy duty steel carapace covering that, along with a thick steel window shield.




Like the TPN-1-49-23, it too has automatic shutters. Key exterior differences lie in its distinctly larger armoured housing, and the aperture window cover is now openable from inside the tank via a pull lever.



1A40-4 Sighting Complex, SOSNA-U






SOSNA-U is a multi-channel thermal imaging sighting complex with capabilities matching those of its contemporaries, giving the T-72 a much needed boost in target acquisition and engagement capabilities. SOSNA-U uses the French-designed 2nd generation Catherine-FC thermal imager. The SOSNA-U sighting complex features an internal ballistic computer that enables it to automatically detect targets, track them, and calculate a ballistic solution including lead using the data from its internal rangefinder, its image processing software and its internal gyroscope (to calculate cant). As you would expect, the sight is stabilized in two planes. The sight has a very limited 3x optical magnification with an equally disappointing 6x maximum digital magnification. Contemporary thermal imaging sights are typically capable of very high digital zoom with double digit magnification factors.


The sighting unit can be seen in the photo below.





The view through the eyepiece in the optical day channel can be seen below.





Apparently, SOSNA-U can be used to identify and engage tank-type targets at a nominal distance of 5000 m in daytime in the normal optical channel, and up to 3500 m in either day or night through the thermal imaging channel, but this is not very realistic for two reasons: Firstly, there is hardly any place in Central and Western Europe that is flat and featureless enough that tanks can be spotted at such a distance, and secondly, the limited 6x digital zoom of SOSNA-U makes it very difficult to tell apart one tank from another at long distances. At the quoted distance of 3500 meters, a tank will appear as a white blob on the screen. Like the 1K13-49 sight it replaces, SOSNA-U has a missile guidance unit that allows it to be used to guide existing gun-launched missiles as well as newly developed missiles.


The gunner has two means of looking through SOSNA-U - the eyepiece, which is for the right eye and comes with a very comfortable forehead pad, and the 640x480px (5.7 inch) flatscreen display.




In addition to the sight itself, the T-72B3 upgrade also came with a new digital ballistic computer of unknown make, as seen below. SOSNA-U cannot accept data from peripherals such as wind sensors, thermal sensors, an MRS (Muzzle Reference Sensor), and so on, so in order to make use of such data, a ballistic computer is necessary. The addition of a digital ballistic computer elevates the fire control system of the T-72B3 up to a level on par with, and quite possibly exceeding the T-90A.




The addition of the flatscreen display and the digital ballistic computer eliminates the possibility of stowing ammunition in the turret on the wall behind the gunner, as the gunner's master control panel is now moved to a spot behind his left shoulder, and the ballistic computer housing occupies quite a lot of space behind his seat.


The SOSNA-U is considered the de facto main sight for a T-72B3 gunners, relegating the TPD-K1 to the back-up role instead. The UVBU lead calculator device installed parallel to the TPD-K1M sight has been removed as it is now totally obsolete, thus retrograding the 1A40-1 sighting complex into the 1A40. Unfortunately, the designers apparently didn't see it fit to swap the placement of these two sighting units, resulting in less than optimal placement of the SOSNA-U, which is only somewhat negated by the use of a separate flatscreen display. Another rather strange quirk is that the sight aperture window cover has to be manually opened by unbolting it, which seems to be a step backwards from the 1K13-49's safer and more convenient recourse.




Also note the IR lamp mounted next to the sight. As SOSNA-U is a thermal imaging sight, this lamp is not necessary for its operation. This lamp has been present on T-72 tanks since the Ural. The retention of the IR lamp even when the tank has transitioned over to a thermal imaging sight is evidence that the IR lamp is intended for illumination for the driver at night. This lamp is turned on and off by the commander.




STABILIZERS



Stabilizer precision and sensitivity is a crucial factor in overall engagement capabilities, especially when on the move. In a continuation of the endearing Russian tradition of naming military hardware after innocent, peaceful things, the stabilizers are named after flowers. The hydraulic pump and power supply system are located in the hull, while the electric motor for turret traversal is at the turret ring in front of the gunner, behind the sights.


Turning on the stabilizer is done with the toggle switch located just above the handgrips on the TPD-K1/M sight. It is also possible to put the stabilizer in standby mode, so that the manual flywheels can be used can be used without turning off the stabilizer, which remains idle and ready to power up fully when needed. A well trained gunner would know not to keep the stabilizers on for too long, as it will overheat if left in the ready mode for more than a few hours. This is a bigger problem in hot climates.




2E28M "Sireneviy" (Lilac) Electric/Hydroelectric Stabilizer



The 2E28M 2-axis stabilizer is the first stabilizer ever to be used in the T-72. It is too imprecise to guarantee hits on the move at very long ranges, but it is extremely valuable for its ability to automatically lay the gun on any given target quickly and precisely on short stops. It can provide very workable accuracy against tank-type targets at average European combat distances, which is 1.5km. The precision of the stabilization devices cannot be less than the 2E15 "Meteor" stabilizer used in the T-62 tank since 1961. As such, although the author was not able to find any data on the 2E28M itself, it is inferred that the accuracy of stabilization is improved by at least a little bit.

Using this stabilizer, the turret is very slow to turn at only 18° per second. It would take it a minimum of 20 seconds to do a complete 360° revolution. This has the effect of inhibiting the T-72's ability to react to the unexpected emergence of a dangerous target from different directions. At least it's not worse than the T-62.

As usual, the stabilizer system revolves around the use of a pair of gyrostabilizers to measuring angular velocities in order to enforce corrections. Turret traverse is done electrically while gun elevation is accomplished using a hydraulic actuator.

An inherent shortcoming of hydraulic components is the heightened risk of an internal fire in the event of a full turret perforation. Hydraulic fluid is highly flammable, and it would most likely cause and spread an internal fire very quickly. This is an especially serious concern to the T-72, since it has numerous shells in loose storage which can accidentally detonate from uncontrolled fires.

The hydraulic fluid used is MGE-10A, a type of mineral hydraulic oil with very low temperature sensitivity, having an operating range of between -65°C to 75°C. The entire system operates at 7.25 psi. This is quite dangerous, as with all hydraulic systems, because hydraulic oil may spurt out from burst tubes at high speeds, spraying large portions of the interior with the flammable liquid.



Vertical Stabilizer

Maximum Cannon Elevating Speed: 3.5° per second
Minimum Cannon Elevating Speed: Estimated 0.06° per second (?)


Horizontal Stabilizer

Maximum Turret Traverse Speed: 18° per second
Minimum Turret Traverse Speed: Estimated 0.06° per second (?)

Average time taken for complete rotation: 20 to 22 seconds


For a minimum traverse and elevation speed of 0.06° per second, the stabilizer should have an accuracy of 1 mil, equivalent to a stabilization accuracy (not mean deviation) of 1 meter at 1000 m. The speed of turret rotation is reasonable enough, considering that earlier Soviet tanks like the T-55 were not very good. The turret of a T-55 with a Tsyklon stabilizer could spin around at 15 degrees per second, and the turret of a T-62 could do 16 degrees per second. Sirenevny is an improvement over earlier stabilizers in every possible way.

The sum total of the components belonging to the stabilization system (dry) weighs 320 kg.



2E42-2 "Zhasmin" (Jasmine) Hybrid Electro-Hydromechanical Stabilizer


Hydraulic pump, relay box and high-precision electric motor, from left to right.

The 2E42-2 is still very conventional as it combines an electric turret rotation and stabilization drive with a hydraulic cannon elevation and stabilization drive. It was first used on the T-72B. The hydraulic pump for powering the cannon elevation system is located under the cannon's breechblock, and the electric motor for turret traverse is installed in front of the gunner, behind his TPD-K1 sight unit.

This stabilizer is much more precise than the "Sireneviy". "Zhasmin" is precise enough to lay the gun to within 0.5 mil on the vertical axis and 0.9 mild on the horizontal axis of the target, meaning that the gun can be lain with an accuracy of at least 0.5 m on the vertical plane and 0.9 m on the horizontal one at 1000 m.


Vertical Stabilizer

Maximum elevating speed: 3.5° per second
Minimum elevating speed: 0.05° per second


Horizontal Stabilizer

Maximum turret slew speed: 24° per second
Minimum turret slew speed: 0.054° per second


The turret traverse speed is even further improved to 24 degrees per second.



2E42-4 Electric/Hydroelectric Stabilizer


The 2E42-4 two-axis stabilizer is an improved modification of the 2E42-2, now including a much more powerful horizontal drive for much faster turret rotation. The T-72B3 is equipped with this stabilizer.



Vertical Stabilizer

Maximum elevating speed: 3.5° per second
Minimum elevating speed: 0.05° per second


Horizontal Stabilizer


Maximum turret slew speed: 40° per second
Minimum turret slew speed: 0.054° per second


The 2E42-4 stabilizer offers a significant weight reduction of 120 kg over the 2E42-2 stabilizer, for a total weight of 200 kg. This is mainly because of the design simplification of the electro-hydraulic gun elevation drive, the improved turret traverse motor, and the usage of solid state electronics in the digitized control systems.


MANUAL


  Manual traverse and elevation is possible with all T-72 turrets through the use of two flywheels located behind the hand grips. There are two gear settings; coarse and precise. The former allows the turret to turn as fast as the gunner can work the flywheel, while the latter produces minute changes to the turret and gun's positioning. Gun laying with the manual traverse can be just as accurate as with stabilizers, if not more so given that extreme care is taken, though obviously much, much slower and nearly impossible to achieve on the move. The gun elevation flywheel has a solenoid button for firing the main gun.




METEOROLOGICAL MAST


  The T-72 first received a meteorological sensor unit with the T-72BA sub-variant. This manifested in the form of the DVE-BS unit, which can detect changes in wind speed and automatically register it in the ballistic computer. The maximum calculable winds speed is 25m/s. The information gathered is synchronized with the automatic lead calculation unit found in the 1A40-1 sighting complex. The T-72B2 and T-72B3 are also equipped with a DVE-BS unit.





D-81 CANNON




The T-72 is equipped with the ubiquitous 125mm smoothbore D-81 cannon - otherwise known as the 2A46 - and its variants. It can fire a wide range of shells including; APFSDS, HEAT, HE-Frag - and from 1981 onwards - ATGMs.


The original T-72 Ural, however, sported the 2A26M2 gun (D-81T), a derivative of the 2A26 gun first mounted on the T-64. It had a barrel length of 6350mm, or 50.8 calibers. All variants of the 2A46 series had a barrel length of 6000mm, or 48 calibers. This is shorter than the 55-caliber 120mm British rifled L11 and L30 canons (6600mm) and shorter than the smoothbore Rheinmetall L/55 cannon (6600mm), but longer than the Rheinmetall L/44 (5280mm) cannon. One of the main problems encountered with the original 2A26M2 gun was related to its excessive length. The barrel was so long that after a period of sustained firing, it could warp heavily enough to effectively un-zero the sights, and the insufficient stiffness meant that as the tank traveled across rough terrain, the vibrations and rocking motions caused the barrel to oscillate, and continue to oscillate even when the tank has stopped.


2A46M
The 2A26M2 cannon had an electroplated chrome lining but lacked a thermal sleeve and had generally poor longevity. The barrel had a life of a measly 600 EFC (Effective Full Charge). Replacing it was no easy task, either. The turret had to be lifted by a crane and positioned so that the gun assembly could be removed through the rear. This was a highly time-consuming process that required specialized equipment. In this regard, the Soviet tank industry was very much behind their Western counterparts. The 90mm gun on the M48 Patton, a 50's tank, already featured a quick change barrel. The 2A26M2 cannon had a rated maximum chamber pressure of 450 MPa.


In 1974, NII Stali mastered and implemented several advanced material processing technologies, which were subsequently transferred to the production of new 2A46 guns (D-81TM). These new technologies included electroslag remelting, differential isothermal quenching and thermomechanical processing. This enabled the 2A46 to become much more durable than the 2A26, and much more accurate to boot. The barrel life for this model is around 900 EFC. The T-72A mounts this gun. Interestingly, it appears that exported T-72M1s never received this new gun. It would seem that Warsaw pact states that also produced the T-72 never did acquire these technologies either. The maximum rated chamber pressure was not increased and remained at 450 MPa.
  In 1983, the T-72B was introduced and with it, the 2A46M. The chief modification was the improvement of barrel life by the usage of a new, more durable chrome lining to reduce wear from new high-energy APFSDS shells. Accuracy when firing on the move was improved by a very substantial 50% due to improvements to barrel stiffness. Overall, the barrel life was increased to 1200 EFC. The 2A46M was also a milestone product in another way - its mounting enabled quick replacement in the field through the front, without removing the turret. The procedure took about 2 hours. The maximum rated chamber pressure was increased to 500 MPa in accordance with the appearance of said high-energy APFSDS shells.


The introduction of the 2A46M can also be seen as a good example of the T-72's status within the Soviet tank fleets. Whereas the T-72 had to wait until 1983 to receive it, the T-64B and T-80B were already ahead by three years with their own 2A46M-1.


The T-72B3 build upon the T-72B with the inclusion of the 2A46M-5 gun (D-81TM-5), which was first introduced in 2005 and can be considered the most perfect of the entire series. The barrel's seating has been improved such that it is optimized in tune with barrel oscillation, and the trunnions that secure the gun itself to the turret have been improved. Plus, the dynamic balancing of the barrel during the firing procedure (while the shell is still in the barrel and after it has left) have been better tuned, thus minimizing detrimental oscillations at the muzzle. All this helps produce superior shot groupings. The design of the gun itself decreases the dispersion of all shell types by an average of 15% to 20%, and the accuracy when firing on the move has been increased 1.7 times, thanks to a decreased inclination to vibrate when the tank is in motion over rough ground. There is a distinct probability that the fortification of the barrel has led to an increased barrel life. If so, the barrel life rating should be around 1500 EFC. The maximum rated chamber pressure was further increased to 600 MPa. This is slightly lower than for cannons like the 120mm Rh L/44 or the M256, but be reminded that the 2A46 series of guns has a 8.5% larger bore area, and that area is a factor in pressure, and that the barrel of the 2A46M-5 is longer than the 120mm Rh L/44.


Here are three super large GIFs of the 2A46M-5 hitting long distance targets using HE-Frag shells. These GIFs are taken from the RT Documentary series "Tanks Born In Russia". The target is a T-54 or a T-62 tank husk. One shot struck the engine compartment, and the other two hit the center of the hull, directly underneath the turret. It is recommended that you open these GIFs in a new tab.






Here is a video of the 2A46M-5 in production:





Worn out barrels also tend to exhibit worse accuracy. This was especially noticeable during the war in Iraq, where Iraqi T-72s often urgently needed barrel replacements, because they had been used since the Iran-Iraq war. Because of the embargo on military equipment, they had no access to fresh barrels and they lacked the technology to produce their own. Firing APFSDS shells, especially the first generation ones that Iraq was supplied with (steel sabot with copper driving bands, and bore-riding projectile fins), was especially harsh on the barrel. The 2A28M2 cannons that Iraqi T-72Ms (analogues of T-72 Ural and Ural-1) and T-72M1s could only tolerate 160 to 170 of such APFSDS shells before becoming unsafe to fire. The 2A46M-2 on the T-72B could fire 220 contemporary APFSDS shells (high energy APFSDS), but the latest 2A46M-5 can let off at least 500 of the currently most common shells (3BM-44).





Needless to say, firing from a worn-out gun barrel is highly dangerous. Critical fracturing is possible, but thankfully, the fuses of explosive ammunition like HE-Frag and HEAT shells exclude the possibility of premature detonation. Still, disintegrated fragments may potentially harm people and equipment in the vicinity.


The gun can elevate +14 degrees and depress -6 degrees when facing the front, but elevate +17 degrees and depress only -3 degrees when facing the rear, with the engine compartment in the way. This is generally sufficient for cross-country driving with lots of minor dips, dives and bumps, but the T-72 is unable to fully take advantage of certain hills for hull-down shooting, but it is free to take cover behind mounds, rocky outcrops, or maybe in a self-made tank hole dug into the ground. The lackluster gun depression as compared to NATO tanks tends to become an issue in highly irregular terrain. 

All of the D-81 cannons have a normal recoil stroke of between 300 to 340mm, more for the high-pressure APFSDS rounds and less for HEAT and HE-Frag rounds.


The commander has the ability to fire the cannon from his station, but only manually unless the tank is the T-72B3 model. Located on the side of the cannon breech is a manual hammer and trigger. The commander can pull the hammer to cock the cannon, and press the trigger to fire it.


AMMUNITION STOWAGE




 AUTOLOADER



The circular notch on the electric motor top disk (center) marks where the tray lines up flush with the trap door on the carousel cover. The notch allows projectiles 720mm long to pass through even though the tray itself is only 680mm in length.

The T-72 uses an AZ electromechanical carousel-type autoloader with a 22-round capacity. Each shell and propellant charge stored within the carousel is housed within a 680mm-long two-tiered steel tray, which has extended bills to properly line up the shell or propellant charge with the gun chamber. The carousel is approximately 1880mm in diameter.





Below, you can see the ammunition trays being dropped in place. You can also see the tank's escape hatch to the left of the photo. The carousel's memory drives and electric motor are in the center, and the protruding leg is the means by which the carousel is manually rotated




Carousel rotation motor (Left), Carousel memory unit (Right)





To load ammunition into the autoloader, the commander must use his control box to cycle between trays. After stocking up the tray, he must input the ammunition type into the memory unit by either turning a dial or pushing one of three optional buttons, depending on the model of memory unit. T-72 Ural and T-72A both use a dial type memory unit. A T-72B uses a button type memory unit (pictured above). He can then complete the loading procedure and cycle to the next tray. With a dial type memory unit, he must press the dial to cycle to the next tray. With a button type memory unit, pressing one of the ammunition type input buttons will simultaneously input the ammunition type and cycle.


The time needed for a shell to load is 6.5 seconds, but in reality, the carousel must rotate to present fresh ammunition, so the actual total cycle time can be between 7 to 8 seconds, if switching ammunition types. This ensures a maximum rate of fire of 7 to 8 rounds per minute. Because the gunner's primary sight is independently stabilized, he can conduct ranging and aim at the target before the loading procedure is finished, whereby the cannon, which is slaved to the sight, will elevate to the proper superelevation automatically, thereby allowing the T-72 to achieve this maximum rate of fire in practical terms. This is no different from all tanks with independently stabilized gunsights. Here is a video of the T-90 firing (link). If a T-90 can fire 2 shots in 13 seconds, then rest assured that a T-72 can too. As far as I know, there is no difference between them save for certain unrelated modifications which we will discuss later.






The T-72 does not have a significant disadvantage when compared to human loaded counterparts, which include the majority of NATO tanks. Most examples can achieve a 4 to 5 second loading time - when their tank is immobile. However, it's a whole different story on rough terrain.  An advantage to the autoloader is that a bumpy ride, change of direction or slope traversal will never affect the autoloader's operation in any way. It can maintain its normal cyclic loading rate in whatever condition or orientation the tank is in. In manually-loaded tanks, the whole vehicle will pitch and dive as it drives over ruts and mounds while the gun, which would be disconnected from the stabilization system in certain tanks like the Abrams, will jump around on its own volition (called "drifting" by tankers). If the gunner is engaging another target after firing his shot, the turret might be rotating as well, which might throw off the loader's delicate balance. It's not very easy to load a 20kg+ unitary cartridge, and this could mean that the average loading time for each shell might be anywhere from 4 seconds to 8 seconds, in addition to fatiguing the loader. This problem is an alien concept for the T-72, since all loading processes are automated.

Besides, the autoloader can maintain its cyclic loading speed throughout an extended engagement until the carousel is exhausted. A human loader, on the other hand, will be exhausted from his duties long before the ammunition is exhausted, whether it be from excessive heat, excessive cold, shortage of food, shortage of water, anything you can imagine.

All in all, the T-72's autoloader is entirely satisfactory for generating a sustainable rate of fire for realistic encounters. While NATO tanks with human loaders were intended to put out as many shots as possible on huge formations of approaching Soviet tanks while staying stationary behind cover, the T-72 never had such a requirement. In modern shoot-and-scoot combat where tanks rarely stop moving or risk getting hit themselves, the advantage of human loaders become much less apparent. In this sense, the T-72's autoloader is not a hindrance at all, but an advantage, if the system is not at least on par with its Western counterparts.

With that in mind, having compared firing rate, it would be illogical to not also compare ammunition capacity, especially against the T-72's most famous rival - the Abrams. Surprising as it may be, the T-72 carries more ready ammunition; 22 in the carousel compared to 18 in the Abrams' bustle ready racks. Neither carousel nor bustle are easy to replenish once emptied.



First, the cannon's stub catcher needs to pivot up and clear the way. Then, each tray is lifted up by the electrically-powered "bicycle chain" elevator through a trapdoor to breech-level, whereby the rigid chain rammer rams the projectile into the gun chamber first, followed by its propellant charge.


Autoloader elevator behind the stub catcher, lowered

Trapdoors located just underneath the gun breech

Shell casing stubs are automatically ejected by a stub catcher and ejector through a small port at the rear of the turret, visible below:




The autoloading/ejection cycle requires the gun to be locked at a pre-programmed elevation of +3 degrees, which is done so automatically as the cycle begins. Originally, there were some problems with sight-and-cannon zeroing because the sight was independently stabilized, and the cannon's vertical stabilizer would sometimes fail to synchronize with the sight's stabilizer as it finished its loading cycle. That small misalignment might cause slower shells like HEAT and HE-Frag to miss pinpoint targets, though it really wasn't a problem for APFSDS shells. However, this issue was only ever mentioned by second hand testers of captured T-72s, specifically Iraqi T-72s, so the issue might stem from either great age, battle wear, lack of maintenance during service and during storage afterwards, or all of the above. The later 2E42-2 stabilizer likely removed the issue completely.


The carousel's overhead bulkhead acts as a false floor for the turrets' occupants. Although the bulkhead rotates in line with the turret, both the turret's occupants are still provided with foot rests.




Here is the armoured autoloader cover.




The bulkhead provides protection for the shells within by preventing residual high-energy fragments from shattered projectiles and cumulative jets from reaching the ammunition below. This, of course, applies only when turret penetrations occur. The carousel has no side protection.


The carousel underneath the bulkhead operates independently. It can rotate to line up new shells at a speed of 72 degrees per second, which is basically instantaneous if the same type of ammunition is used. The updated T-90 autoloader carousel can spin in both directions, but the original Ural autoloader could only rotate counterclockwise. This needlessly prolonged the loading cycle when switching ammo types, but this may not be a problem if that is not required. This would not have any effect in a fight against armoured vehicles as long as APFSDS ammunition is stowed to the right of HEAT ammunition, and HEAT ammunition is stowed to the right of HE-Frag ammunition. That way, the gunner can start with APFSDS, and then switch to HEAT without delay with APFSDS is exhausted. Switching to HE-Frag from APFSDS takes longer, but if the target is supposed to be engaged with HE-Frag, then it can be assumed that it is less pressing than an armoured target like, say, a tank. The T-72B3 uses the updated T-90 autoloader, so that problem is solved there.

Here is a video of the autoloader spinning:




Unfortunately, the autoloader can only accommodate projectiles 720mm or less in length due to the size constraints of the carousel and the size of the gap available between the autoloader elevator and the gun breech. The updated T-90-type carousel fitted in the T-72B3 can hold shells up to 740mm in length, and the old ones can hold shells only 680mm in length. Apparently, this was to allow them to accommodate the lengthier Svinets-2 (?) APFSDS shell.


Video evidence has shown that new autoloaders are programmed to initiate an additional step immediately after firing, and that is to momentarily open and close the shell casing stub ejection port without actually ejecting a case stub, most likely to evacuate any fumes present.

The autoloader has an average malfunction rate of 1 per 3000 cycles, if it is properly lubricated throughout its use. Malfunctions typically stem from worn-out parts. Customers of exported second-hand T-72s usually encounter autoloader issues far more often than with newly manufactured units mainly because of this. Repairing the autoloader itself is quite simple thanks to its simplicity.



LOOSE STOWAGE





Aside from the carousel itself, ammunition is stored in racks located throughout the interior of the tank in various nooks and crannies of varying accessibility. There are twelve propellant charge spaces in a vertical conformal fuel tank/rack hugging the carousel, easily accessed by either the gunner or commander. There are another six shell spaces on the engine-fighting compartment bulkhead above and behind the vertical conformal rack. More shells and propellant charges are stowed on top of the carousel cover itself.






There are another three shell spaces on the port side hull, in the form of tension latched clip holders. These are visible on the right side of the photo above.


Here are the shells stowed behind the carousel, in front of the engine compartment bulkhead.


Rear shell racks, coloured green

Shell racks coloured green, propellant charge containers below


Then, there are three more shell spaces along with an adjoining three propellant charge spaces in a conformal fuel tank/rack located on the starboard side (pictured), and three more shell spaces in a similar conformal fuel tank on the hull's port side.




It is possible to fill the three hull fuel tank-cum-ammo racks with water instead of diesel, thus transforming them into wet storage bins. (Read the "Road Endurance" section of this article under "Mobility" for a full explanation)


In the T-72 Ural and T-72A, two shells and a propellant charge are stowed behind the commander's seat, and two more shells are stowed on the turret wall behind the gunner. These represent all of the ammunition stowed above the turret ring for the T-72, but they are usually removed as they intrude into the crews' personal space. The racks behind the gunner's seat can be seen in The Challenger's video review of a Czechoslovakian T-72M1 tank.




In later T-72 models like the T-72B3, the turret wall behind the gunner is occupied by control panels, as mentioned in the Gunner's Station segment of this article.




All in all, there can be up to 22 additional cartridges stowed outside the carousel for a total of 44 rounds of ammunition. However, in practice, crews tend to ignore certain spaces such as the shell stowage rack on top of the carousel cover (as seen above), or the spots behind the commander's seat (in exchange for personal effects), and some crews may decide not to have any ammunition in loose stowage at all, so the actual sum total of loosely stowed ammunition can be anywhere from 22 to none. Nevertheless, from adesign standpoint, the fact that the T-72 has a total ammunition capacity of 44 rounds when the T-54/55 had only 43 and the T-62 had just 40 - while having smaller cannons and slightly larger silhouettes - is a highly noteworthy achievement and a grand step forward in design efficiency.

The gunner has a full set of autoloader controls for selecting ammunition to fire, or to replenish the autoloader. In order to fill up the autoloader - which is not by any means quick or convenient - the loading process has to be reversed. The type of shell entered must be inputed into the autoloader control boards for it to "memorize" for future use. The total time needed to refill the autoloader is between 15 minutes to 20 minutes.

The commander also has a full set of autoloader controls at his disposal. He can either aid the gunner in selecting the appropriate shells for the target type (which he identified), or load shells for his own use as with in the T-72B2 and B3 variants.


If the autoloader elevator malfunctions, it is still possible to operate the elevator mechanism manually using a crank wheel (pictured). The commander will be responsible for loading while the gunner engages targets. The benchmark time needed for a complete manual loading cycle is 26 to 30 seconds.




It is also possible to load the gun with ammunition from the stowage racks located all around the interior, but as they are not very accessible (to put it mildly), the benchmark loading time would still be in the 20 to 30-second region. As such, manual loading is something to be done in emergencies only, not only because it is much slower than normal automated loading, but because it also forces one of the two crew members to abandon his usual duties. However, the propensity for autoloaders to malfunction either from wear and tear to a knock on the turret is greatly exaggerated by a few vocal anti-autoloader persons on the internet.


Loose ammunition stowage is the leading cause of catastrophic destructions involving ammunition detonation. While the carousel is decently protected from overhead fragments, the shells and propellant charges located behind it and behind the commander's seat are not. The easiest course of action is, of course, to simply remove these loose shells before entering battle, and apparently, this was what Russian crews did during the Chechen campaign.






AMMUNITION





There are 4 main types of ammunition for the 125mm gun. There is no predetermined mix of ammunition. A typical loadout for a breakthrough assault or troop support mission would see that HE-Frag shells are loaded in large quantities, for example, while more HEAT and APFSDS shells would be loaded for ambushes where light vehicles and other MBTs are expected.


PROPELLANT CHARGES

 


125mm ammunition for the D-81 gun series is two-piece - propellant and projectile. Each propellant charge is contained within a thin TNT-impregnated pyroxylin-cellulose outer shell that is consumed upon firing, and the entire assembly is embedded into a steel cup, much like a shotgun shell.

The GUV-7 electric/percussion primer is used, giving the option to either fire the shell normally using the fire controls on the gunner's hand grips or the button on the manual traverse flywheel, or to use the manual lever-operated striker pin incorporated into the gun's breechblock.




Zh 40




Original propellant charge designed for the 2A46 used in the first T-64. It uses 15/1TR VA propellant compound. It's most distinctive quality is the ghastly amount of fumes it produces upon firing.

Charge mass: 5.66 kg
Length: 408mm



Zh 52





Newer propellant charge modified to produce minimal smoke upon firing without changing its ballistic potential to maintain compatibility with all shell types excluding high-energy APFSDS ones. It uses 12/7 VA propellant compound. This model has completely replaced the Zh40 in frontline use. Here is a video of the Zh52 propellant charge being opened up: click. Nowadays, HE-Frag and HEAT rounds are fired exclusively with Zh 52.


Charge mass: 5.786kg
Length: 408mm

Zh 63


High-energy propellant to launch APFSDS shells at even higher velocities. It uses 16/1TR VA propellant compound. It is used with newer APFSDS shells, but it seems that there is nothing to stop it from being used with older models.


Charge mass: 5.8kg (?)
Length: 408mm

Fuses



V-15

Two part superquick, distance armed piezoelectric fuse. Point-detonating design that has provisions for graze initiation to allow detonation despite steep angles of incidence. It is distance-armed by inertia at a distance of 2.5 meters from the muzzle.



V-429E


The V-429E fuze is point-detonating, distance armed and with variable sensitivity settings. It has two settings - superquick and delayed. The superquick setting detonates the shell with a 0.027 second delay and the delayed setting detonates the shell at 0.063 seconds. Superquick action guarantees reliable detonation in snowy or swampy ground, and delayed action gives a small time allowance for the shell to penetrate its target before detonating. The shell is set to the Fragmentation mode when the fuze is set to the "O" position. HE mode is set when the fuze is set to the "O" position but the safety cap is left on. Delayed HE or "bunker busting" mode is set when the fuze is set to the  "З" (a Cyrillic "Z") position, and the safety cap is left on. The additional delay enables the shell to penetrate more deeply into hardened targets.

The fuze is armed by inertia; the shell experiences a momentary braking effect from the unfolding of the stabilizer fins 5 to 20 meters from the muzzle, and this is used to arm the fuze.


V-429V


The V-429V fuze is an updated version of the V-429E fuze. The safety cap has been replaced with a safety pin with a protruding ribbon. To deactivate the safety "cap", the ribbon is pulled to tug the pin out. This is much faster than unscrewing the old safety cap.




HE-Frag


The T-72 normally carries 12 HE-Frag shells in the autoloader, although this will almost certainly vary by situation. These shells have traditionally been predominant in Soviet armoured tactics, where tanks were regarded as the tip of the spear during breakthroughs. Bunkers, ATGM teams and troop concentrations - not tanks - were the bane of any and all armoured targets, and thus became high priority targets. Heavy breakthrough tanks with thick armour for charging down anti-tank guns to clear the way for calvary tanks were once the main counterforce, but with the advent of the Main Battle Tank and the phasing out of heavy tanks, the T-72 takes over this role in full, fulfilling both the role of a breakthrough heavy tank and calvary tank. HE-Frag shells therefore comprise the most important part of the T-72's loadout.





The V-429E fuse gives 125mm HE-Frag shells a great deal of flexibility. When attacking infantry in the open, such as anti-tank teams, advancing troops, or machine gun nests, the fuze should be set in the "superquick" mode, giving it a delay of 0.027 seconds to ensure that the shell will detonate instantly upon meeting soft ground like mud and snow, allowing it to exploit its thick steel shell to its fullest as shrapnel.

When attacking reinforced concrete targets like bunkers and pill boxes, the shell could be set in the "penetrating" mode, giving it a delay of 0.063 seconds (as mentioned above), allowing the shell with its thick steel casing to travel a fair distance into target material before detonating. This is great for bunker busting because the impact of the big, heavy shell creates fractures, cracks and fault lines in concrete, making it a lot easier for the explosives to blow apart the entire structure. If targeting non-hardened buildings like houses, the shell would have no problem at all passing through cinder block or brick walls, allowing it to explode inside a building for maximum effect.

With that in mind, HE-Frag may even be used as a substitute to more specialized anti-armour shells like APFSDS and HEAT against heavy armour under certain circumstances, like when all other ammunition has run out, or if effective destruction cannot be achieved. A direct hit will likely result in the debilitating disability of the cannon, destruction of aiming devices and the destruction of the driver's vision blocks, producing a firepower and mobility kill. In many cases, the driver of a modern tank has an unsettlingly high probability of being killed or at least severely injured by a hit to the turret or glacis due to insufficient blast attenuation. The explosion of a large caliber HE round on the turret ring will most certainly send spall and fragments shooting down into the driver's neck through the thin hull roof. The T-72 is vulnerable to this, as the roof over the driver's head is a mere 20 millimeters of steel, but conversely, the T-72 is very capable of inflicting the same damage on most legacy NATO tanks, which often do not have spall liners. This makes it exceptionally easy for a 125mm HE-Frag shell to kill, maim, and injure the crew behind the armour of all-steel tanks like the M60, Chieftain, Leopard 1, AMX 30, and so on. However, modern tanks sporting composite armour arrays and spall liners are somewhat alien to this problem.


When set in the HE mode, 125mm shells are extremely deadly to lightly armoured vehicles. There are a few good reads available on the internet on this topic, but Peter Samsonov's translation of a report on the effects of 76mm HE-Frag shells at tanks with a variable fuse is especially enlightening. Here is a fascinating paragraph from that report:

"When firing 85 mm HE shells from mod. 1931 guns consider that they can penetrate 45 mm of armour at 30 degrees from 500 meters, and 50 mm of armour under the same conditions can be penetrated from 300 meters or closer."


If 85mm HE shells are capable of defeating 45mm of armour plate angled at 30 degrees at 500 meters, imagine what a 125mm HE shell could do?


When adjusted to the HE setting, the shell is able to punch huge holes in relatively thick armour and explode inside. The 38mm layer of steel applique armour on an M2A2/A3 Bradley will be entirely insufficient to stop such a shell even at long distances, and many legacy NATO tanks may be threatened across the flanks as well. The Chieftain's thin side skirts may offer too little resistance to set off the V-429E fuse, with the result being total destruction as the tank's thin (1.5-inch) side hull armour is easily perforated. The Leopard 1's thin side armour is extremely vulnerable to this shell as well. With hull side armour measuring only 30mm thick and turret sides measuring 40mm (angled at 30 degrees), even the aforementioned 85mm HE shell may potentially defeat the Leopard 1 from 500 meters! The addition of a 30mm spaced applique plate on the turret in later Leopard 1 variants might still not be enough to defend it from a 125mm HE shell, and even if the shell was successfully stopped, the explosion might produce enough spall to eliminate internal components anyway.


Even though the T-72 carries more HE-Frag shells than anti-armour shells, you can see that this is not always a problem as HE-Frag shells have a very substantial multi-role capability. The use of 3V-21 fuses introduces a new field of possibilities for 125mm HE-Frag.


HE-Frag shells are quite barrel-friendly. They have an EFC rating of 1, meaning that if a barrel was rated for 1000 EFC, it would be able to fire 1000 HE-Frag shells before needing replacement.




3OF19


Regular shell with copper driving bands. The shell has the shape of an ogive. There is little else to talk about.


Total Shell Mass: 23 kg
Muzzle velocity: 850 m/s

Explosive mass: 3.148 kg
Explosive composition: TNT


It's worth noting that TNT is a relatively sensitive explosive compound. The risk of an ammo detonation is significantly higher if these shells are present.


3OF26



Improved HE-Frag shell with compressed explosive charge of a different composition designed to provide added incendiary effect. Explosive compression means that the explosive charge has increased in density - that is, it has a greater mass for the same volume.

This shell uses plastic driving bands instead of copper ones, in an effort to reduce barrel wear.



Maximum Chamber Pressure: 3432 bar

Total Length: 676mm
Total Shell Mass: 23.3 kg
Muzzle velocity: 850 m/s

Explosive mass: 3.4kg
Explosive composition: A-IX-2 (Phlegmatized RDX + Aluminium filings) (Aluminium is pyrophoric. Detonation produces incendiary effects, increasing the chance of igniting or burning objects in its proximity)

A-IX-2 is much less sensitive than TNT. The risk of ammo detonation is much lower if these shells are stowed.




Practice HE-Frag



Practice HE-Frag shell that emulates the ballistic characteristics of live HE-Frag shells. Contains a 200-gram TNT charge to produce a bright flash that acts as a visual hit marker for the trainee gunner.


Maximum Chamber Pressure: 3432 bar

Total Length: 676mm
Total Shell Mass: 23.3 kg
Muzzle velocity: 850 m/s



HEAT-MP



The T-72 carries a substantial number of HEAT shells in stowage for its proven flexibility, high performance and economy. They are powerful enough to pierce contemporary armour in most cases and their explosive factor allows them to be used against light or unarmoured vehicles with a much better result than with APFSDS shells. HEAT shells may also be used against hardened concrete bunkers or simple earthen fortifications with good results, and it is entirely feasible to engage personnel owing to the very thick steel case containing the charge which is able to produce high-velocity splinters magnificently.


When engaging armour that is too heavy to defeat, HEAT shells are still able to damage optics and weapons thanks to their explosive effect. One might even call it insurance. Like HE-Frag shells, each one is almost guaranteed to put a tank out of action or at least cripple it with varying degrees of success.

Against thickly armoured targets, HEAT shells produce deep but small holes. The secondary methods of destruction aside from the cumulative jet itself (which is the primary one) is the blast of the explosion of expanding gasses rushing through the hole in the armour, the flash of heat (capable of causing flash burns) and the spray of high velocity fragments of armour and shaped charge material following perforation, which can set internal equipment alight and injure the crew. It is difficult killing crew members without a direct hit by the cumulative jet unless there is a very significant armour overmatch, forcing HEAT shells to rely mostly on causing internal fires. But still, due to the enclosed nature of tanks, there is a high likelihood of striking at least one crew member if one could score a hit on the occupied sections of the tank.


HEAT shells also retain a characteristic advantage over APFSDS shells in that they wear down the barrel at a greatly reduced rate. Whereas firing one HEAT shell is equivalent to one EFC, an APFSDS shell can be equivalent to 3, 5 or even 7 EFC. This makes them the preferred choice of training ammunition during live fire exercises, besides HE-Frag shells. Training with APFSDS is not held quite as often, as scoring a hit with hypervelocity shells is obviously not quite as challenging as doing the same with shells that are travelling at almost half the speed. HEAT ammunition is also more expendable than APFSDS ammunition, as it is now almost entirely useless against modern tank armour.



Glossary:

Wave Shaper: Object or device that infleunces the propagation of blast waves in a way that is beneficial to jet formation. Typically composed of an inert material with low sound speed.

A-1X-1: Phlegmatized RDX, consisting of 96% RDX and 4% wax.

OKFOL: Explosive compound composed of 75% HMX and 25% RDX.

Standoff Probe: Extended structure to increase the distance between the shaped charge cone and the target material, i.e, standoff.

Explosive Pressing: The process of increasing the density of explosive compounds by high-pressure mould pressing. The result is more explosive mass per volume, translating to more energy.


All of the information presented below are backed by either photographic or videographic evidence, or official documentation.


3VBK-7

BK-12


First 125mm HEAT shell, originally for complementing the T-64. By the time the T-72 emerged, it had been long replaced by the 3BK-14.

Projectile weight: 19kg
Muzzle velocity: 905 m/s

Explosive Charge: A-1X-1
Explosive Charge Weight: 1760g

Shaped Charge Cone material: Steel
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)


Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration: 420mm RHA

This shell is still effective against semi-modern tanks such as the M1 Abrams, Challenger 2 and Leopard 2 and most of their updated variants, but only on side engagements. Both the hull side and turret side of the above tanks are vulnerable.


3VBK-10

BK-14


Updated HEAT shell with similar dimensions as the 3BK-12, but with minor internal differences. It is characterized by distinct knurls around the top edge of the main body surrounding the standoff post, probably to enable the shell to fuse even on extremely high obliquity impacts by tilting the tip towards the armour plate on a glancing blow. This shell uses a cylindrical wave shaper with a slight taper.

Maximum Chamber Pressure: 2900 bar

Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: 1760g

Shaped Charge Cone material: Steel
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)


Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration: 450mm RHA   



BK-14M




The BK-14M warhead uses a copper liner ("M" stands for "med", which means "copper" in Russian). This results in improved penetration performance, but at slightly higher cost. The wave shaper is different.


Maximum Chamber Pressure: 2900 bar

Total Length: 678mm
Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: 1760 g

Shaped Charge Cone material: Copper
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)


Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration: 480mm RHA


3VBK-16

BK-18





Improved version of the 3BK-14. Visually identical to the 3BK-14, but differs in that it features an aluminium shaped charge cone. Aluminium is pyrophoric, meaning that it burns when finely pulverized and when under extreme stress. Under those conditions, it can produce a very fierce incendiary effect, increasing its killing power in the event of a perforating hit. The noxious fumes produced by burning aluminium may also force the crew to leave their vehicle.

Unlike the lightly tapered wave shaper of the 3BK-14, it has a cylindrical one, which coincides with the usage of a different cone material with different physical properties. Like its predecessors, it has distinct knurls around the top edge of the main body.

This model is very widespread in current Army stocks alongside the 3BK-18M.


Maximum Chamber Pressure: 2900 bar

Total Length: 678mm
Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: 1760 g

Shaped Charge Cone material: Aluminium
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration: 500mm RHA


This shell is still marginally effective in frontal engagements with semi-modern tanks like the M1A1 Abrams, Challenger 2 and Leopard 2, but only if the hull front is struck. And even then, there is very little overmatch and the beyond-armour effect is not very strong. There is no chance of this shell perforating the turret front of the above tanks.


BK-18M


Variant of the 3BK-18 using a copper cone.

This model is very widespread in current Army stocks alongside the 3BK-18.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: A-1X-1 or OKFOL (strangely, both have been encountered)
Explosive Charge Weight: 1760 g

Shaped Charge Cone material: Aluminium, >99.5% purity
Shaped Charge Cone diameter: 105mm
 Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: 550mm

This shell can better guarantee the penetration of the hull front of tanks like the M1 Abrams, Challenger 2 and the Leopard 2, and with much better beyond-armour effect. It is possible to defeat the turret of a Leopard 2A0-A3 with a hit on the side at an obliquity of 60 degrees or less. As the mantlet of the Leopard 2 and M1 Abrams were designed with 73mm PG-9V/15V (HEAT grenade for SPG-9 and BMP-1) in mind, protection was quite limited. It should be possible to defeat the mantlet armour of these modern tanks with this shell, even the more recent versions including the Leopard 2A5+ and the M1A2.



3VBK-17

BK-21



Improved shell featuring a dirty copper-coloured cone with extreme elongation. It uses a cylindrical wave shaper. It isn't seen very often.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: ~1400g (?)

Shaped Charge Cone material: Copper or Brass
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: ~650mm


BK-21B


Radically improved, using a DU-Ni alloy cone. DU-Ni cumulative jets exhibit superior jet consistency and will not break up in flight as quickly as other materials, offering very good overall performance. The new liner also seems to offer superior penetration against complex armour arrays. Unfortunately (or fortunately, depending on your perspective), production costs and the difficulty of controlling the variables associated with using it makes usage impractical. The shell uses an arrow-shaped wave shaper.

DU as a material for shaped charges is highly polluting. If perforation occurs, the interior of the tank will be filled with highly dangerous DU particles, which will be very difficult to remove. Whereupon the lack of perforation, the hole created in the armour array will still contain DU particles, posing a hazard for crew and technicians working in and out of the target object or vehicle.

DU is also pyrophoric, and like aluminium, will wreck havoc in the confined spaces of an armoured vehicle. 


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: DU-Ni
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle type: Medium, 60°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: >650mm


3VBK-21

BK-25



A HEAT shell that is very seldom seen. Cutaway photos show that it has a silvery-gray shaped charge cone, but its shape and dimensions betray that it is definitely not steel nor aluminium like the ones before it. It is very likely that it is tantalum, which is known to be a viable cone material. It uses a rather oddly rounded wave shaper. Very little is known about this shell other than these facts.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: Tantalum / Tantalum alloy
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle type: Medium, 60°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: ~600mm (?)


BK-25


Same interior configuration as its parent but with a bulkier bevel connecting the standoff post to the main body. Liner material is unknown, but all other components appear to be identical.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: (?)
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle:
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: ~600mm (?)


3VBK-25

BK-29



Relatively recent (late 80's) shell with tandem warhead configuration primarily to aid in penetration of complex armour arrays and to defeat ERA-equipped targets. Despite being heavier than its single-charge predecessors, it somehow travels slightly faster.

The precurser shaped charge is located halfway down the standoff probe and may be rightfully considered a fully-fledged warhead all on its own, having a considerable explosive charge and complete with its own standoff accounted for. The use of a precursor warhead makes it very effective against the special armour of NATO tanks from the early 80's, prior to the use of depleted uranium in the armour of the Abrams tank.

This shell is characterized by the lack of "teeth" on the front edges of the primary warhead case, and the new fuse, which is fully conical in shape. The shell uses a hemispherical wave shaper. Both charges have base fuzes.


Projectile Weight: >20 kg
Muzzle velocity: 915 m/s

Explosive Charge: A-1X-1
Explosive Charge Weight: ?

Shaped Charge Cone material: Brass / Steel / Aluminium (?)
Shaped Charge Cone diameter: 105mm
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Precurser Explosive Charge: A-1X-1
Precurser Charge Cone material: Steel / Aluminium / Tantalum (?)
Precurser Charge Cone diameter: 40mm

Precurser Charge penetration: >160m (?)

Standoff probe diameter: 67mm tapering to 45mm
Standoff probe wall thickness: 7.5mm


Primary charge penetration (without precurser/after reactive armour): ~620mm
Primary charge penetration (after precurser/without reactive armour): ~820mm



BK-29 should be considered the most important development in tank cannon-fired HEAT ammunition in recent history, as it is the only example of a tandem warhead HEAT tank shell. Now that we know of the armour composition of the M1 Abrams, we can easily deduce the armour composition of its upgraded variants; the M1A1 and M1A1HA. One of the things that we can be certain about with all of these variants is that there is a relatively thin steel plate in front of the NERA array, and that is all that protects it. The precursor charge of BK-29 could easily punch through this plate, enter and activate the NERA array until it is stopped by the steel main armour of the turret, leaving an open channel through which the main warhead can then pass through and defeat the main armour. Following this train of thought, it is apparent that BK-29 can defeat the front turret and front hull armour of an M1 Abrams, and perhaps even the M1A1 Abrams.

However, it will not be able to defeat the turret cheeks of a T-72B. The Kontakt-1 boxes that encapsulate the composite armour of the T-72B will reduce the effect of the precursor charge of BK-29 (and indeed, any tandem warhead projectile) so much that it will be easily stopped by the relatively thick front wall of the armour cavity in the turret, meaning that the primary warhead will still have to deal with the untouched NERA armour contained within, which we know now to be at least on par with the armour of the Abrams, if not superior.



BK-29M






The same shell as its parent, but with a copper liner. Whether both the precursor and the main charge use copper is unclear, but it is likely.


Explosive Charge: A-1X-1
Explosive Charge Weight: ?

Shaped Charge Cone material: Copper
Shaped Charge Cone diameter: 105mm
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Precurser Charge Cone material: Aluminium, Steel, Tantalum (?)
Precurser Charge Cone diameter: 40mm



3VBK-27

BK-31


Enigmatic and ingeniously designed triple-charge HEAT shell. It is probably not in service at present. It can penetrate 800mm of steel armour with a hardness of probably about 280 BHN, as demonstrated by a cutaway.


Total length: 665mm

Penetration: 800mm RHA (No reactive armour)


From Vasily Fofanov's website


Practice rounds


VP5



Single-charge inert HEAT warhead designed to exactly emulate the ballistic trajectories of the 3BK-14 and 3BK-18 shells. There is a 200-gram squib inside the warhead that acts as a visual hit marker for the trainee gunner.

Total Length: 678mm
Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s



BK-29I



Training round imitating the exact flight characteristics of the 3BK-29 shell.



APFSDS



Despite pioneering APFSDS shells with the introduction of the 2A20 115mm gun, the Soviets never had the technology to mass produce true long rod tungsten or depleted uranium projectiles until the mid-80's, whereas the Americans had already fielded the M774 DU APFSDS round since the mid-70s. So they were in a bit of a quandary. Their best APFSDS rounds were technologically crude sheathed core projectiles that were incredibly economical (very little tungsten is present in them), but limited in scope and growth potential.

The only way to improve their performance without any radical design changes was to increase mass and increase speed, but this could not be easily done with the 115mm gun. The HEAT rounds for the "Molot" were good, but undependable due to terrible accuracy, so they weren't of much use, even though they were more than capable of taking out any tank, bunker or anything in between. For the moment, the "Molot" was more than capable of killing any NATO tank at average combat distances, but it would not have been enough had there been even a modest uparmouring like the Stillbrew modification on the Chieftain. Of course, no one was smart enough to come up with something like Stillbrew until the mid-80's, but that's not the point. They never really got past this problem until the 80's when the Soviet ammunition industry finally matured enough to begin churning out sheathed long rod penetrators, but before that, in one form or another, all 125mm APFSDS rounds were made of steel, with an armour piercing cap, supplemented by a small tungsten slug - the same basic principle as the 3BM-3 introduced in 1961. Producing high-quality weapons-grade tungsten carbide and other tungsten alloys in slug form was difficult and expensive, and extruding tungsten alloy rods was no mean feat. The equipment simply didn't exist in the USSR.

The main defeat mechanism of APFSDS shells against armoured targets is by killing crew members with shards and fragmentation of the shell after armour perforation, but a secondary mechanism is setting internal equipment alight, just like HEAT shells. The huge kinetic energy and extreme forces imparted during armour defeat results in some of that kinetic energy being converted to heat energy, which results in a flash of heat and a shower of high velocity sparks from particles of both armour material as well as penetrator material. And of course, the flash and sparks work to set flammable items on fire.

The earlier Soviet APFSDS shells were made mostly out of steel, and had steel armour piercing caps at the tip to protect the rest of the penetrator from huge impulsive forces. The relative softness of steel meant that the performance of these early APFSDS shells was not at all comparable to modern APFSDS shells, which dispensed with armour piercing caps entirely. Whereas modern shells are generally completely unaffected by sloping of less than 70 degrees, early Soviet shells performed significantly worse on high incidence angles. Advances in materials' science alleviated this issue greatly in the early-80's, but only when fully-tungsten alloy or fully-depleted uranium shells were introduced in significant quantities in the mid-80's did the problem quite literally reverse itself. New APFSDS shells are able to penetrate more sloped armour than unsloped armour, thanks to the peculiar tendency of long rods to veer towards the perpendicular axis of the plate, which is rather inconvenient, since newly emerging NATO tanks like the Leopard 2, Challenger and the Abrams all had "blocky" composite armour that deprived the T-tanks the chance to flex their newfound muscles.


However, Soviet 125mm APFSDS ammunition never had any trouble killing NATO tanks of the same era. Indeed, during a Swedish test in the early 90's involving an Strv 103 and a T-72M1, a BM-22 shell was fired at the frontal armour of the S-tank, and it was so powerful that it went through the front and came out the back, at least according to this website here. It is not difficult to imagine that the BM-15 from which the BM-22 was derived would produce a similar result, and experience with the T-62 and its 115mm APFSDS ammunition had shown that it was more than enough against the Chieftain. While it may seem awfully imprudent to say so, it is all but impossible to argue that Soviet ammunition technology at the time was insufficient against the best that NATO could come up with. Until everyone's favourite tank the Leopard 2 came along. But new and advanced composite armour was not a panacea. The sides of the hull and turret were inconvenient places to armour up, but NATO found creative solutions to the Soviet 4.9-inch problem.


The Leopard 2 attempted to shield the crew compartment from the side with three heavy 100mm steel plate modules (consisting of two 50mm plates) bolted to the side of the hull just over the first two roadwheels (Source). From an incidence angle of 30 degrees, this arrangement yielded a 200mm thick sloped plate. Absolutely miserable protection against long rod penetrators and HEAT warheads, BUT, quite effective against the sheathed core APFSDS rounds common in the Red Army inventories. Refering to this report here (link), it's clear what they were going for. The 125mm APFSDS rounds that are so effective against individual homogeneous plates also shatter magnificently after passing through them. This would have been incredibly lethal to the older plain-steel legacy tanks like the M60 and Leopard 1, but these ballistic plates are capable of stripping the steel from the projectile, leaving only the small tungsten carbide core to travel on by itself. While lethal on its own right, its small size and limited fragmentation spread after passing through the 50mm base armour of the side hull makes it a dubious antagonist. The probability of achieving a first round kill was thus greatly reduced. The Abrams implemented a similar design with its 60mm composite sideskirts. These were thinner than the Leopard 2's 100mm plates, and the Abrams' base armour is much thinner at only 28.575mm (1 1/8 inches 420 BHN welded hard steel bilayer), but they covered the hull all the way down to the fifth roadwheel. Such a configuration should be sufficient against Soviet APFSDS rounds that had their tungsten carbide cores near the nose, and still somewhat effective against ones that had them near the tail, but much less so.


The Soviet standard for certifying armour piercing projectiles is V80, meaning that the expected consistency of achieving full armour perforation given a certain projectile velocity must be 80%. In formulas, V80 must replace V50 (50% chance of armour perforation). For example, if a certain projectile has to penetrate 500mm of steel, then at least 80% of all projectiles of that type must achieve that standard. This is very different from the NATO standard of only 50%. Soviet standards were not only stricter, but the steel they used for targets was of a greater hardness than NATO targets. In reality, the given penetration data does not correspond to the actual achievable penetration of these shells.





Format:

3BM-xx (Projectile assembly - projectile plus incremental charge)
3BM-xx (Projectile)


3BM-10

3BM9






An extremely rudimentary projectile with a maraging steel penetrator body. Maraging steel is preferred for its malleability, which prevents the high-velocity shell from shattering outright upon impact, but maraging steel is superior to normal steel in that it retains its strength with its malleability. However, the softness of the steel (about 300 BHN) hampers its ability to penetrate armour somewhat. The decision to use a pure maraging steel projectile without an armour piercing cap must have been a deliberate one, as tool steel with a hardness up to 600 BHN had been used as early as 1945 in the BR-412B 100mm APBC shell. 3BM-9 might be an attempt to conserve tungsten carbide, as it can penetrate the same armount of armour as 115mm 3BM-3 tungsten core rounds, but doesn't use any tungsten carbide itself. Add that to the fact that maraging steel is renowned for being very easy to work with and cheap, so the existence of 3BM-9 must be for economic reasons.

Overall, it had generally insufficient penetration capabilities, and it was somewhat prone to ricocheting on steep angles, resulting in spotty and unreliable performance on sloped armour. As all contemporary tanks at the time relied heavily on sloping - the Chieftain and the M60A1 come to mind - this made 3BM-9 rather unsuitable. Nevertheless, 3BM-9 is quite remarkable for being the first service munition that is fired at truly hypersonic speeds (Mach 5+). This shell used a steel "ring" type sabot with a copper driving band. Sabot construction is critical to shooting accuracy, and the steel "ring" type sabot was perfectly fine compared to any other APDS sabot at the time. Plus, any deficiencies in accuracy from the sabot would be unnoticeable given the gobsmacking speed of the projectile coming out of it.





This is all just speculation, but it is possible that 3BM-9 might have been what T-72 Urals were given for their first year of service as a sort of intermediary before the supply of 3BM-15 shells (introduced in the same year as the T-72 Ural) was assured. T-64s should be the first to transition to the newer ammunition, and the T-72 might have had to wait.



Muzzle velocity: 1800 m/s

Mass of Projectile: 3.6 kg
Mass of Sabot: 2.02 kg
Total Mass: 5.67 kg

Length of Projectile: 410mm
Minimum Diameter of Projectile: 36mm



Certified Penetration at 2000m:

245mm at 0°
95mm at 45°
70mm - 150mm at 60°


Certified Penetration at 1000m:

300mm at 0°
160mm at 60°



(According to Soviet GRAU documents)


Penetration at 2000m:


290mm RHA at 0° (Zaloga)


The achievable armour penetration of 3BM9 is quite a bit higher than its certified penetration capability. Post armour penetration effects are very powerful, due to the large hole created by the inefficient steel penetrator.




3BM-16

3BM-15

The 3BM15 is a steel-sheathed, tungsten-cored APFSDS shell with a tri-petal steel sabot, introduced in 1972. It is externally identical to the 3BM-9 projectile.

Although decently hefty and very speedy, the shell primarily relies on a small tungsten carbide subcaliber core to do the job. A ballistic windshield was crimped onto the maraging steel shock absorber cap, whose duty was to reduce the impact impulse to prevent ricochets and to reduce shock to the rest of the projectile body. The projectile body is maraging steel, which more or less peels away upon impact while the core continues onward - an extremely inefficient arrangement. The maraging steel body still creates a crater almost as large as the one created by the 3BM-9, but not quite so large.

All this doesn't mean that it cannot go through large amounts of steel, however. The 3BM-15 is certified to penetrate 150mm RHA at 60 degrees. The photo below shows the result of the shell penetrating a 200mm steel block (of unknown hardness) at 0 degrees, entering from the top and exiting from the bottom, leaving very large holes on either end. The 3BM-15 clearly outmatched all NATO armour at the time, which could not stand up to it even in the thickest places.

The steel body disintegrated inside the armour as it entered, but the tungsten slug passed onwards leaving a very clean tunnel (indicating that it still had plenty of momentum). It is unknown at what range this shot occured

 An extra tidbit lies in that in the event of a penetration whereby the steel body has not peeled off fully, it functions to blast the interior of the target tank with hundreds of large pieces of steel - absolutely devastating to interior equipment and crew members alike. Thus, while the 3BM-15 was lethal to all NATO tanks of the time, it was exceptionally lethal to tanks like the AMX-30 and Leopard 1, which had particularly thin armour. However, this shell became essentially useless against new NATO armour during the early 80's. These new tanks had thick steel sideskirts designed to expend the steel projectile. The tungsten carbide slug could not be stopped so easily, of course, but a small slug could do only a fraction of the damage that the full package would have done.

The tip of the penetrator is flat. This is to improve performance on sloped armour, but flat tipped penetrators tend to have worse penetration on unsloped or perpendicular armour.


3BM-15 uses the same steel "ring" type sabot as the 3BM-9. The photo below is from a Rheinmetall brochure on PELE ammunition, demonstrating a modified 3BM-15 PELE round in flight and the airflow around the components of the round. The sabot was unmodified.






Mass of Incremental Charge: 4.86kg
Maximum Chamber Pressure: 4440 bar

Muzzle velocity: 1785 m/s

Steel body maximum diameter: 44mm
Steel body minimum diameter: 30mm
Core diameter: 20mm

Length of Projectile only: 435mm

Length of Core: 71mm

Mass of Steel body: 3.63kg
Mass of Core: 0.270kg

Total Mass of Projectile: 3.83 kg


Certified penetration at 2000m:

310mm at 0°
200mm at 45°
120mm - 150mm at 60°


Average penetration at 2000m:
340mm at 0°


  


The steel "wedge" in front of the tungsten carbide slug is an armour piercing cap to protect it from shattering the instant it impacts the target. 


(Photos credit to PzGr40 from wk2ammo.com)


(Sourced from unisgroup.ba, wk2ammo.com, Vasily Fofanov)


3BM-17

3BM-18


This shell is essentially identical to the 3BM15 externally, but it lacked the tungsten carbide core of its parent and only had a modified AP cap, presumably to reduce ricochet probabilities. Thus, it was slightly superior to the 3BM9, but still far behind the 3BM15 in penetration performance.



Muzzle velocity: 1780 m/s


Total length: 548mm
Length of Projectile only: 435mm


Certified Penetration at 2000m:

310mm RHA at 0°


Average penetration at 2000m:

330mm RHA at 0° 


3BM-23

3BM-22

 


A derivative of the 3BM15. It began mass production in 1976, but only formally entered service in 1977. It features an enlarged and improved armour piercing cap in front of the tungsten carbide core, presumably to further improve performance on heavily sloped armour plate. The projectile is shorter than the 3BM15. It retains the steel ring-type sabot.

It is currently completely obsolete, though still usable in side engagements with modern tanks. Existing stocks are currently being expended in live-fire exercises, for which older projectiles are favoured since they are less harsh on the gun barrel.


Mass of Incremental Charge: 4.86kg
Maximum Chamber Pressure: 4440 bar

Muzzle velocity: 1785 m/s

Steel body maximum diameter: 44mm
Steel body minimum diameter: 30mm
Core diameter: 20mm

Length of projectile only: 400mm
Length of core: 71mm

Total projectile mass: 4. 485 kg
Mass of core: 0.270kg


Certified Penetration at 2000m:

380mm at 0°
170mm - 200mm at 60°


Average penetration at 2000m:
430mm at 0°













3BM-27 (Nadezhda)

3BM-26


The 3BM26 projectile is the most optimum APFSDS shell that is still based off the concept of a hard core wrapped in a steel body. Like the 3BM22, the 3BM26 projectile rides on a "bucket" type sabot made from a lightweight aluminium alloy. This shell was the first to use the high-energy Zh63 propellant charge, giving it an extra performance boost over previous models (the incremental charge has the same composition as 4Zh63).

Unlike the 3BM22 and 3BM15 that preceded it, the tungsten carbide core is located at the rear of the projectile body. This means that it will only begin to come in contact with the armour only when the steel body in front has been completely eroded from doing its share of the work. There is an air space forward of the core to allow it room for forward travel as the rest of the body decelerates within the target material. This is to allow the core to retain the same 1720 m/s velocity despite the rest of the steel body having decelerated to a complete stop.

At the very front is the ballistic windshield, crimped onto the armour piercing cap, now even larger than ever before. Not coincidentally, the enlargement of the armour piercing cap has further improved the penetrator's performance on sloped armour, perhaps even more so than the relocation of the subcaliber core to the rear of the projectile.

The new "bucket" type sabot greatly contributes to improved accuracy.


Mass of the sabot: 2.2 kg
Mass of the projectile only: 4.8kg
Mass of core: 0.270kg

Length of projectile only: 395mm
Length of core: 71mm

Maximum diameter of the projectile: 36mm

Muzzle Velocity: 1720 m/s

Certified penetration at 2000m:

410mm at 0°
200mm at 60°


Average penetration at 2000m:

450mm at 0°


Despite total obsolescence, this shell is still used in reserve units. Their fate is to be expended in live firing exercises. High readiness units in the Western military district have gotten rid of this shell long ago.






3BM-33 (Vant)

3BM-32


Having being informed of Western developments of advanced composite armour, GRAU set forth new requirements to defeat future dynamic armour in the mid-70's. In 1977, work began on new APFSDS projectiles to accomplish this. The new projectiles would be based on totally new design concepts in order to avoid the limitations of the previous cored design principle. The first result of the development process was Vant.

The 3BM-32 is a sheathed depleted uranium monobloc projectile introduced in 1984. It is quite short, but still longer than its predecessors. It has a tapered mild steel sheath over a depleted uranium-nickel-zinc alloy penetrator rod. The sheath was negligibly thin over the front and rear thirds of the projectile, but it was much more pronounced in the middle. The sole reason of its existence is to provide a suitable region for machining the sabot-projectile interface. It is likely to be medium hardness or mild steel, and it should peel off quite easily in order to not interfere with the physical interactions between the DU rod and the target armour material. By itself, the projectile is aesthetically similar to the 120mm DM13 APFSDS shell.

As you can see in the photos below, the type of damage inflicted by long-rod (left, 120mm APFSDS on T-72M turret) and cored shells (right, 3BM-15 APFSDS hit on T-72A turret marked "5") is drastically different. Whereas the long-rod shells enter cleanly and efficiently imparts its kinetic energy over as small an area as possible, cored shells tend to waste most of their energy blowing out a large crater. (Note the very deep impressions from the 3BM-15's steel fins in the photo on the right, as compared to the skin-deep cuts from the aluminium fins of the unknown 120mm APFSDS shell.)
 


The DU rod is made from an alloy based on Uranium-238. The reason why the depleted uranium penetrator was so short compared to the ones commonly used today is simple; they couldn't make them longer. It was very good by 1985 standards, though. The 120mm DM21A1 shell for the Leopard 2, introduced in 1983, had a penetrator that measured only about 350mm in length. Vant's stubbyness was somewhat compensated for by the benefits of the new Zh63 high-energy propellant charge, which was introduced alongside it. The "bucket" style sabot design from the 3BM-26 was carried over and slightly modified.



Mass of the projectile: 4.85kg

Muzzle velocity: 1700 m/s


Length of penetrator only: 480mm
Minimum diameter of the projectile: 34mm

Penetrator L/D ratio: 14.12:1



Penetration at 2000m:

430mm RHA at 0°
250mm RHA at 60°

(From plaque)


Certified penetration at 2000m: 

500mm RHA at 0°
250mm RHA at 60°


Average penetration at 2000m:

560mm RHA at 0°


The photo below shows a 120mm DM13 APFSDS shell made for the Leopard 2. It was introduced in the same year as its benefactor; 1979. The shell consists of five main parts. 1. Steel windshield and ballistic cap 2. Steel ballistic cap 3. Tungsten penetrator 4. Steel sheath 5. Tailfins and tracer assembly




As you can see, the resemblance is striking. The dimensions are also quite similar, and so is the mass - 4.85 kg for the Vant, and 4.6 kg for DM13. Form follows function, of course, and the Vant being a sheathed projectile meant that it didn't have many forms to choose from anyway. What is especially remarkable about the DM13 is that its tungsten penetrator is only about 240mm in length. What is even more remarkable is that apparently, it can penetrate 230mm RHA at 60 degrees at a distance of 2200m, despite the fact that most of the front section of the projectile is made of steel...

But given the performance of 3BM26, it is more than quite plausible, and giving credit where credit is due, the performance of the DM13 round is excellent by 1979 standards, though that might have more to do with the high power of the Rh 120 cannon. The 105mm DM23 was introduced years later in the early to mid-80's, and had a longer tungsten alloy core, with a better L/D ratio, and yet it offered much worse performance. As Vant can penetrate the same amount of armour regardless of whether it is flat or sloped at 60 degrees, it can be assumed that Vant penetrates up to 280mm RHA at 60 degrees. What is odd is that the Vant seems to come off better in comparison with the American M829, which began production in 1984 and entered service in the same year as the Vant (1985) to equip the freshly inducted M1A1 Abrams tank with their new 120mm cannons. The M829 had a 540mm long sheathless DU penetrator, capable of penetrating approximately 275mm RHA at 60 degrees at 2 km. M829 is only 30 m/s slower at 1670 m/s. However, this may be because that is the V50 value for M829, while the 280mm figure for Vant is the achievable penetration and not the certified penetration. In other words, it is a question of standards.




3BM-44 (Mango)

3BM-42



Developed in parallel with "Vant", "Mango" is a more advanced counterpart using tungsten instead of depleted uranium.

The 3BM-42 projectile has a two-part tungsten alloy penetrator, but technically it is a three-part penetrator, as the round is topped off by a short tungsten alloy armour piercing cap. It is possible that two-part penetrator was built this way simply because they were unable to produce a single full length rod, but then, why did they not do the same thing as the Germans with their DM13? Why did they not place the tungsten rod behind an elongated steel cap?

Nowadays, a two-part penetrator might be considered a "novel" penetrator, that is, it can defeat complex composite armour arrays or so called "special armour". The first rod (which is longer than the second rod) acts as a sacrificial spearhead, so to speak, and suffers the yawing and fracturing induced by the NERA armour array while isolating the rear rod from any damage. The role of the tungsten alloy armour piercing cap, the so-called "third segment", at the tip of the projectile is the same, except that it is likely to be intended to defeat reactive armour like Kontakt-5 in the same manner that the steel tip of M829A3 is intended for, except that instead of steel, tungsten alloy is used to preserve performance in case reactive armour is not present, which is the case with modern Western armour.




Whatever happens to the sacrificial secondary rod, the rod at the back continues forwards unhindered, and it only has to deal with the final backing plate, which it will do so at peak efficiency, having avoided any negative influences from the NERA armour array. It is known that the M829A3 was built around a very similar design concept, featuring a sacrificial front section just like the 3BM-42. In the M829A3, it is apparently referred to as a "spaced tip penetrator". This expendable tip of the M829A3 projectile was built to soften up Soviet-style bulging plate NERA array, and it could assist in bypassing heavy reactive armour like Kontakt-5 as well. Take a look at this cross-sectional drawing of the M829A3.



German tank expert, author and lecturer Rolf Hilmes has said that the German 120mm DM53 is specially constructed to deal with advanced composite armour and dynamic (reactive) armour. Its construction, he says, consists of a three-part tungsten alloy penetrator. The penetrator of 3BM42 is also three-part. Coincidence? I think not...

Perhaps the configuration of the 3BM42 projectile is not as efficient as the one on the M829A3 or the DM53. Perhaps the 3BM42 was uniquely tailored for what Soviet Intelligence thought Burlington-style was, whereas M829A3 was created with concrete knowledge of Soviet Kontakt-5 and bulging armour design, having several examples in their possession. If so, Soviet military Intelligence was extremely effective, as we now know every detail of the Burlington armour, and we know that it can be defeated by a multi-part penetrator design.

Truthfully, however, we only know all of these things with a 99% confidence, not 100%. However, it is impossible to dismiss the fact that the two-part penetrator of the 3BM42 projectile and its uniquely separate tungsten alloy tip segment exists, and that such designs were found to be used in Western APFSDS designs decades later.


The 3BM42 projectile is generally similar to the 3BM32 in external layout (midway taper) due to the use of a similar "bucket"-type sabot, but the projectile is significantly lengthier. This helps yield much better penetration performance. The sabot itself is made out of a lighter V-96Ts1 aluminium alloy, helping to decrease parasitic mass and thus increase firing efficiency. Like with the 3BM-32, the long-rod Tungsten alloy penetrator (or penetrators, in this case) are encased by a thin sheath. The sheath itself is composed of a EP-836 maraging steel.

Mango in the possession of a lucky individual

However, as you can see clearly in the photo above, "Mango" still has bore riding fins. The copper-coloured nubs on the apex of the fins you see above are copper ball bearings. Larger fins create more drag, leading to a lower velocity downrange.


Mass of sabot: 2.2 kg
Mass of projectile only: 4.85 kg

Length of projectile only: 574mm
Diameter of projectile: 31mm

Length of two-part core: 420mm
Diameter of core: 18mm

Penetrator L/D ratio: 20:1

Chamber pressure with Zh40/Zh52:  443.8 mPa
                               with Zh63: ?

EFC rating: 5

Muzzle velocity: 1715m/s

Certified penetration at 2000m:

450mm at 0°
230mm at 60°

(From Fofanov's website)



As 3BM42 was designed with composite armour in mind, it was subjected to special tests against projected NATO composite armour arrays. Among these attempts to replicate advanced and complex armour were two different types of 7 layer arrays and a 3 layer array. It is not known precisely what the layers of the array were made of, but it is assumed to be steel plates of different hardnesses, forming a type of advanced spaced armour.

7-layer array at an angled of 60 degrees (630mm LOS) could be defeated at 3300 m.

7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3800 m.

3-layer spaced array at an angle of 65 degrees (1830mm LOS) could be defeated at 2700 m.


Without knowing more specific details regarding these armour arrays, we cannot know how correctly they represent NATO armour at that time. It is quite possible that the armour of the M1 Abrams (1980) can be represented by the 7-layer arrays, excluding the NERA component of the armour. It is very possible that M1A1, which had a thicker but otherwise unmodified turret array compared to the M1, can be defeated by 3BM-42 at combat ranges. The use of DU plates in the M1A1HA in 1989 might increase its viability against 3BM-42, but without a total design overhaul (which is unlikely, with the information we have now), it would not affect the performance of 3BM-42 significantly. The Americans were probably unaware of the existence of such an advanced round in the Soviet arsenal, as they were very aware of the existence of Soviet special armour, but only came out with a segmented penetrator design in 2006 in the form of M829A3. Beware, this is only educated guesswork. There is a large body of solid evidence for these beliefs, but nothing truly and absolutely concrete, so please don't take it as established fact.


Introduced in 1986, this round became practically standard in high-readiness units in the decades thereafter.



ATGM


3UBK14 

9K119 "Svir"





The missile is soft-launched by a 9Kh949 reduced load piston-plugged ejection charge, giving the missile some momentum before the rocket motor kicks into action. The piston plug is designed to properly seat the missile in the chamber, but its primary purpose is to protect the laser beam receiver at the base of the missile from propellant gasses. Since the laser beam receiver is located at the rear of the missile, it is imperative to minimize the shock of firing the missile, which is why the piston has a buffer spring. The total weight of the 9Kh949 charge is 7.1 kg.




The missile itself has an efficient layout with the rocket motor placed in the middle, the warhead at the very rear, and the control surfaces and mechanism at the front along with the fuse at the tip. The missile uses a solid fuel motor, with four nozzles arranged radially. Flight stabilization is maintained via five pop-out tail fins with curved and angled surfaces to impart a slow spin onto the missile, while steering is accomplished by the two canard fins at the front. These are operated pneumatically, so the more corrections the gunner makes while the missile is mid flight, the less responsive the missile will be over time, though the gunner will have to be tracking a very difficult target like a moving helicopter for this to become noticeable.



Guidance is accomplished by the integrated 9S517 laser beam unit on the 1K13 sighting complex. The system is effective out to 4000 meters.


Missile Diameter: 125mm
Wingspan (Stabilizer Fins): 250mm

Shaped Charge Diameter: 105mm

Maximum Engaging Distance: 4000 m
Minimum Engaging Distance: 100 m


Hit Probability On Tank-Type Target Cruising Sideways At 30 km/h:
100 m to 4000 m =  >90%
4000 m to 5000 m =  >80%

Flight Distance Time:
5000 m - 17.6 s
4000 m - 11.7 s




3UBK20M "Invar"

9M119


Thermobaric missile.


3UBK20M-1 "Invar-M"



With nothing but a decade's worth of technological enhancement, the Invar-M boasts a more powerful tandem warhead, while maintaining the same flight distance and with no real changes to the dimensions of the missile body. Aesthetically, it is identical to the Refleks missiles. Invar-M was introduced in the latter half of the 90's, and is currently in service. It is unknown if T-72 tanks currently in active service have been equipped with Invar-M missiles.


Armour Penetration:

900 mm RHA (Without ERA)
850mm RHA (With ERA)


TRAINING ROUNDS


3P-35 Practice rounds were available. They emulated the ballistic trajectories of APFSDS shells, but were made of steel and were purposefully shaped so that the tip would begin to produce a vortex behind it to create huge amounts of drag to drastically slow down the projectile after it had traveled 3000m. To compensate for the inherently worse ballistic shaping, the shell's muzzle velocity is 1830 m/s.


SPECIAL



Blanks for replicating the recoil and flash of cannon fire. Mostly used during sales demonstrations.

The 4Kh33 blank charge consists of 12/1 TP smokelss powder housed in a simple cardboard cylinder.


SECONDARY



The PKTM is mounted as a co-axial machine gun, with 250 rounds readied per box and with 8 boxes carried in the stowage bins on the outside of the tank and inside as well. Ball and tracer ammunition are usually linked in a 2:1 ratio, though sometimes tracers are used exclusively. The theoretical maximum effective firing range is 650m against a running target, and up to 1500m against stationary targets. However, the actual practical ranges are much lower at around 600m for both running and stationary targets, depending on terrain and meteorological features. The gunner's ability to actually see and track personnel at extended ranges also plays a huge part in the co-axial's practical engagement envelope.


It is fired by the gunner using his "Cheburashka". The commander may also cut in on the action and use the 6P7.S6.12 electric solenoid switch attached to the machine gun, but he has no way of aiming except to walk the tracers onto the target via his TKN-3 periscope.

Notice the cable leading away from the PKT to the left



The machine gun is mounted to the right of the main gun, and protrudes from a pill-shaped port which provides vertical space for gun elevation. Since it is mounted alongside the main gun, it receives all the benefits of the stabilization system.


The co-axial machine gun is only a limited solution to the infantry problem, especially if hard cover is available. In practice, the co-axial is only useful in very specific situations, and desirable only when HE-Frag shells are not suitable due to concerns of collateral damage or (more brutally) when the concern is ammunition wastage. In essence, the PKTM is more of a weapon of opportunity than anything else.

 

TERTIARY






The T-72 has a pintle-mounted heavy machine gun for the commander, which is primarily intended for the anti-aircraft role, though it may be used to shoot at ground targets too. The mount can fit either the NSVT or the Kord machine gun, with a special buffered cradle. The NSVT is more commonly seen on T-72s, whereas the Kord is only sometimes seen on T-90s. However, there is no rule regarding which tank uses what machine gun; all are inter-compatible as long as the cradle is modified. All T-72B3s use the KORD machine gun.

The paddle-trigger is electric. Rotating the cradle and elevating the machine gun is done manually; the former by rotating the entire mount on the axis of the cupola, and the latter by turning a flywheel located to the right of the machine gun. The commander has to stand on his seat in order to reach the machine gun.


Pulling the trigger paddle
He releases it!

The AAMG has an inclusive supplementary K10-T collimator sight, which facilitates accurate aiming at both ground level and high altitude targets. It is tinted to reduce glare when aiming in the direction of the sun.






Using the collimator isn't compulsory. If it is damaged or unsuitable, the iron sights on the machine gun may still be readily relied upon.  

Hungarian Ron Swanson aiming through such a sight

View through the sight
The collimator projects a clear, crisp aiming reticle


The machine gun has a nominal effective range of approximately 800m against aerial targets, but this is variable. Obviously, the probability of hitting a hovering helicopter would be much higher than hitting a moving fixed-wing aircraft.

As a rule, anti-aircraft machine guns (AAMG) are more or less useless for shooting down aircraft. Although it isn't difficult penetrating some of the more obvious weak areas such as the plexiglass windscreen on a helicopter, the chances of actually hitting a fast, moving target is rather slim. On the contrary, the role of an AAMG is to be a deterrent; it's objective is to "shake up" the pilot(s) into pulling back from an attack, or perhaps even make him miss his shot. Serious anti-aircraft work is to be carried out only by the SHORADSs (Short Range Air Defence Sytems) accompanying the T-72.

The machine gun is fed from a 50-round box. Four additional boxes of ammunition are stored in metal bins in the turret and two more are strapped to the outside of the turret, which the commander can reach down and access. The commander has to pull a large charging lever to cycle the gun (pictured below).




PROTECTION


First and foremost - I did all of these estimates myself. Armour effectiveness is a hotly debated subject, and I have no intention of throwing unsubstantiated figures or confusing data around, so all of the information below (except the photos) is original. Prudence calls, and I must warn against directly estimating armour values if the armoured region is not visually identifiable, or if the armour employs a complex projectile-defeating mechanism. In case of uncertainty, a better way to determine armour effectiveness is by reading up tests and combat experience testimonies, and then determine effectiveness by noting which warhead or penetrator penetrated where.

A good indication of a tank's true survivability is its resistance to catastrophic destruction, which can refer to the tendency for a fire to start and the likelyhood of that fire spreading and consuming the entire vehicle or the possibility of the ammunition exploding. In this sense, the T-72 stands on equal footing with opponents of the era. But seeing as modern rivals now often include armoured or separated ammunition storage, the T-72 is clearly at a serious disadvantage. In spite of this, the T-72 maintains a very slight edge grounded in its use of diesel instead of extremely volatile jet fuel (as with the American Abrams tank). Although there really isn't much difference between the two if both are exposed to incendiary ammunition, the viscocity of diesel means that it won't spread quite as fast and the intensity of a diesel flame is much less aggressive as compared to petrol or jet fuel flames, so putting them out is much easier.

Protection qualities depend greatly on the variant being considered. As the years go on, the protection value markedly increases, reaching its zenith with the T-72B2 variant with the Relikt armour package. We shall examine the protection qualities of all the main variants in detail armour-wise.

The myth of the T-72's inferiority in terms of protection is just that - a myth. Various T-72s have proven their worth in various conflicts, but the lack of media coverage on the successes tend to skew views in favour of the image of burning wrecks. To list one incident in Grozny, in the year 2000, a T-72B tail number 611 took 3 hits from Fagot ATGMs and 6 hits from RPGs during 3 days of intense fighting and remained in battle with only minor damage. These are the same types of weapons that an Abrams or a Challenger 2 faced during campaigns in the Middle East. There are plenty of other cases. One only needs to be motivated to search.

The T-72 carries on the best traditions of top-notch metallurgy and steel processing, started since just before WW2. As a testament to its quality, an ex-GDR T-72M1 tested in Meppen (details here) withstood 24 hits from a mix of 105mm and 120mm APFSDS and HEAT shells on the turret front without a single fracture or crack. Of course, whether or not the shots defeated the armour is a different matter.


COMMON CHARACTERISTICS


The hull side, hull roof, hull bottom and rear armour of all T-72s are identical, regardless of the variant. The hull side and the turret side are both 80mm thick, but the hull thickness over the engine is slightly thinner at 70mm. The side armour is more than enough to withstand 20mm armour-piercing ammunition fired from various aircraft, such as the AH-1 Cobra firing the 20x102mm round, or A-1 Skyraider, firing the 20x110mm round. Ad hoc use of M61 Vulcan gattling guns on non-ground attack aircraft such as on the F-4 Phantom would not have yielded any better result.

Drive sprocket area. Note the thickness

This picture shows quite clearly how the upper hull side is thicker than the lower sloped side.

The side armour is thickest at the top half, visibly appearing bulkier (as shown in the picture above) both outside and inside, thinning down to 20mm with a modest slope at the roadwheel region. This seemingly illogical reduction is countered by the presence of the roadwheels themselves, which helps to (slightly) offset the vulnerability of this particular area. The interior of the hull side has a 20mm layer of anti-radiation lining, which can help absorb secondary penetrator fragments or even stop residual penetration from an autocannon shell. This is discussed later in the "Anti-radiation" section below.


The thickness of the side armour can be clearly seen here


  The hull roof is 20mm thick at its thinnest, the rear is around 40mm thick, and the hull bottom is 20mm thick. The hull bottom is only sufficient against explosive charges with a mass of less than 10kg detonated over the tracks and not directly under the hull. In general, up-armouring a tank to a level where it can resist even the simplest purely explosive anti-tank mine is unheard of with most Cold-war era tanks.

  A very relevant topic for discussion is geometry, which plays a huge role a tank's protection scheme. The T-72 has a traditionally sloped glacis and a rounded turret. Sloping is a relatively simple science. If expressed in graph form, a highly exploitable curve can be observed:

This graph uses sin instead of cosine, and measures angle from the vertical axis and not the horizontal axis. The theory is still the same.

   Calculating it requires only a very straightforward formula: 'y ÷ cos x degrees', where 'y' is the thickness of the plate, and 'x' is the amount of slope from the vertical axis. 'y ÷ sin x degrees' can be used as well, except 'x' is now the amount of slope from the horizontal axis. The T-72's glacis has a slope of 68 degrees from the horizontal, or 22 degrees from the vertical, which, as you can see in the graph, is right in the "sweet spot" for optimum angling.
  If placed on a reverse slope in near hull defilade, the angle of the glacis would be even steeper, which can compensate for the T-72's rather deficient gun depression, but only in certain cases.
  The heavy sloping of the glacis had an adverse effect on most types of APDS ammunition, which were naturally more vulnerable than long rod APFSDS shells.

Note that the hardness of "normal" steel for the T-72 is around 290-340 BHN, harder for the thinner, rolled plates and softer for the thicker cast turret, though the hardness of the turret varies greatly throughout. The HHS (High-Hardness Steel) employed in the tank has a hardness of  around 400 to 450 BHN. The applique armour plate used in the 1983 modification of the T-72A is probably medium hardness steel, as it is welded to the hull. This cannot be done with very high hardness steel.  


  Before we examine the protection value of the T-72's armour, we must first consider the presence of two drastically different types of kinetic energy penetrators and their significance, which are APDS and APFSDS. APDS projectiles are bullet-shaped, and are very badly affected by sloped armour because of their tendency to fracture and ricochet. This is, of course, correlated to the shaping of the projectile and its material, but generally speaking, all APDS projectiles shared this weakness. APFSDS projectiles are longer and thinner, and tend to be much more adamant to sloping than APDS because of this. It also helps that they do not rotate, which helps reduce strain on the penetrator body and thus minimize the chance of fracturing or outright disintegration upon impact. All armour value listings presented further down below revolve around protection from APFSDS projectiles, so the values against APDS projectiles are actually much, much higher in some cases (turret top edge, glacis, lower plate, etc).


SIDE, REAR TURRET


The entire turret is made of cast steel. The side has a considerable curve to it, exaggerated in the T-72B variant, while the rear of all variants have a distinct beak, which houses the autoloader rammer.

The stub ejector port is also visible here

As mentioned before, the side of the turret is 80mm thick, thinning to around 40mm at the rear. The vertical curvature of the turret provides a nominal increase in relative thickness to around 88mm even when viewed perpendicularly. The horizontal curvature of the turret gives much more significant gains. With a thick layer of anti-radiation lining backing it and with the storage bins - plus cargo - acting as rudimentary spaced armour, the sides are more than enough to withstand any 20mm and 23mm shell at point-blank and any 25mm autocannon shell at typical combat ranges (in the vicinity of 1500m). This is including the 25mm M919 APFSDS shell. However, the armour is not thick enough to reliably protect from the very latest 30mm and 40mm APFSDS shells. Still, with some extra angling, the side turret would have very good prospects. The rear, however, is completely hopeless.

The shape of the turret is such that the sides will be completely unreachable by enemy fire from within the frontal 70 degree arc. This means that if you shot at the turret at a relative angle of 35 degrees, you will only be able to hit the strong turret cheeks, never the sides. If the relative angle is increased to 45 degrees, the sides will be visible, but then the angle will be so steep (80 degrees) that shaped charge warheads will fail to fuse and all KE projectiles will ricochet, and given the 80mm thickness of the sides, the LOS thickness will be 460mm.


T-72 Ural


The T-72 Ural was the original T-72, and is the least technologically gifted among its "brothers". Although the hull glacis benefited from a rudimentary tri-layer composite armour array, the turret remained purely steel.


GLACIS



The original 1973-model upper glacis armour has a composite array consisting of a 105mm *STEF section sandwiched between an 80mm RHA front plate and a 20mm RHA backing plate. The total thickness is 205mm perpendicularly. The glacis is angled at 68 degrees, producing a total LOS thickness of 547mm. The heavily sloped steel-STEF-steel laminate is best at defeating contemporary APDS projectiles, because of the inherently poorer performance on APDS on heavily sloped armour and its tendency to create a larger penetration route when faced with heavily sloped armour. The thicker front steel facing first erodes the penetrator, breaking it up so that the kinetic energy is dissipated over a large area for the STEF layer to absorb (high flexural strength of fibers). Residual fragments are stopped by the 20mm RHA backing plate. The glacis armour defeats shaped charges by a combination of its composite nature and by being so heavily sloped that some warheads may not detonate properly. During the famous Yugo tests, the 90mm M431 HEAT shell with the M509A1 PIBD fuze was demonstrated to have a very high probability of failing to detonate against the 60-degree upper glacis of the target tank (a T-54) when the tank was angled 20 degrees sideways. 90mm guns were obsolete anyway, so what's the point? Well, the bad news is that the 105mm M456A2 HEAT shell also uses the M509A1 PIBD fuze, so the likelihood of having such a shell detonate on the 68-degree upper glacis of the T-72 is very slim indeed.


In 1976, a new glacis array was introduced. The new array retained the 105mm STEF section, but it now had a 60mm RHA front plate and a 50mm backing plate instead. The total thickness becomes 574mm when angled. The replacement of the 20mm backing plate in the 1973 variant might be for two possible reasons; a tendency to buckle or bulge excessively when struck, and/or the inability to reliably "catch" defeated penetrator elements of new APFSDS projectiles, which were much longer than bullet-shaped APDS projectiles. It is possible that the front steel plate was made slightly harder to compensate for the loss in thickness.


Blast attenuation is an aspect often overlooked when referring to tank armour. This is no different for the T-72 Ural, which has an advantage through its laminated hull armour. By placing two materials of drastically different properties in the path of the blast wave, the laminate array's effectiveness in attenuating the blast is significantly improved as compared to homogeneous materials of the same weight. This was quite important seeing as HESH (High-Explosive Squash Head) shells were and still are a British favourite.


In 1983, an additional 16mm of HHS (High Hardness Steel) applique armour was added on, which came about as a result of live fire testing of captured Israeli M111 tungsten-cored shells from Lebanon (in the 1982 war in Lebanon). Contrary to popular belief, the Israelis did NOT "discover" that their M111 Hetz could perforate the T-72 from the front "at about 650 meters". The Israelis never got their hands on an intact T-72, nor did they ever face them with 105mm guns. It has been conclusively proven on Tanknet that at best, the T-72s were destroyed in an ambush by ITOW shots to the side.




However, it is true that the M111 "Hetz" was acquired by the Soviet Union. A very popular theory is that these rounds came with the captured Israeli M48A3 that was until recently on display in Kubinka. The M48A3 doesn't have a 105mm gun, of course, but Israelis had a habit of upgrading their tanks. So knowing that the Soviets did capture M111 Hetz in some quantities, then evidently the hull upper glacis of the T-72 (as well as other autoloading T-tanks) was vulnerable to these new acquisitions, thus necessitating the installation of the applique plate. As the applique plate is only 16mm thick, the boost in armour protection is not that big. It is worth noting that M111 "Hetz" and the similar DM23 were the most advanced 105mm rounds of its time.

Therefore, we can assume that the hull glacis with the 16mm applique plate is proofed against the M111 Hetz (penetration of less than 320mm @ 1km) at short range (assumed to be 500 m), which gives us a figure of at least 400mm RHAe for the original hull for the T-72's type of armour. With the addition of the 16mm plate, the glacis should become totally immune even at short range, so its armour should be equivalent to just above 400mm RHAe.


The timeline of the evolution of the hull array is as follows (front to back):

1973: 80mm RHA + 105mm STEF + 20mm RHA

1976: 60mm RHA + 105mm STEF + 50mm RHA

1983: 16mm HHS + 60mm RHA + 105mm STEF + 50mm RHA


*STEF is a certain type and grade of glass-reinforced textolite, a material which consists of layered sheets of plain-woven glass textile suspended in an epoxy resin matrix. It is nearly identical to fiberglass.


Simple calculations indicate that the 16mm HHS applique armour plate weighs around 450kg, which fits in nicely with reports that some T-72 Urals and T-72As weighed 41.5 tons instead of their original 41 tons. The extra 0.5 tons can be attributed to the extra layer of armour.

HHS is best used as applique armour, as in the T-72's case. The hardness and thickness yields the best results for eroding high-velocity APFSDS shells, or any type of KE shell, actually. However, we must keep in mind that this was merely a temporary stopgap measure to keep the T-72 Ural (and the T-72A) viable for the next few years in light of the appearance of the radically better armoured T-72B succeeding them.

The lower front hull plate is around 85mm RHA plate angled at 62 degrees (determined through photo comparisons), resulting in a total thickness of 181mm. It should be noted that the first 200mm (starting from the glacis nose) of the lower front plate is backed by the glacis array, giving that area a far higher LOS thickness, almost equal to the thickness of the glacis plate itself plus 85mm. This area is something of a weak point, though a somewhat inaccessible one thanks to its very small size when viewing the tank from the front (less than a foot high at most).


TURRET




The turret is solid MBL-1 armour-grade cast steel, with the thickness being 350mm at the mantlet area, and the mantlet area only. The mantlet is the area immediately around the cannon. The machine gun port, barely a few centimeters away from the cannon, is already 475mm thick, and from there, the turret only gets thicker, so unless your shot goes right into the cannon, the weakest part of the turret can survive a hit from 105mm M392A2 APDS. Evidence of this comes from the CIA-produced diagram below.






We happen to be able to confirm this with the enormously important photo below. See how the turret armour is thinnest at the gun trunnion area (350mm), and how it jumps a much greater thickness (known to be 475mm) immediately beside the co-axial machine gun port and the gunsight interface port - the port that allows a mechanical connection between the gunsight and the gun.




As you may notice, the gun mantlet area is thickest near the bottom. This is the 350mm thick area. The area above it gets progressively thinner, until the thickness is practically halved, though with a much greater angle, but the thinnest part is a small triangle immediately above the ports. If you look closely, you will notice that area above the ports are not flat, but bumpy and irregular. This is what I meant: (see the areas above the triangles)




The area marked in the red tirangles are the weakest parts of the front of the turret. It may be pierced by all virtually all available HEAT and APDS ammunition of the era, but nothing less powerful than that will make it through, as it is still thicker than the thickest part of a T-54 turret. One consolation is that this part of the turret is so small that it is statistically insignificant compared to the rest of the turret armour.





The photo below was used to determine the thickness of the roof of the turret above the gun breech.





This area is especially thick at the bottom, but it thins down as it approaches the peak of the roof. The thickness along the entire area was obtained by scaling it with the front wall of the turret, which we know without a doubt to be 350mm thick, producing a variable value of 145mm to 115mm. Angled at 79 degrees, the armour there is 480mm to 415mm thick, but the peak of the turret presents less than 200mm. Adjusted for the lower effectiveness of cast steel, the true armour value is equivalent to at least 400mm RHA, without having accounted for the benefits of angling. With the advent of angle-insensitive monobloc and novel KE penetrators in the mid to late 80's, this area has become one of many weak points across the T-72's frontal profile, but faced with early APFSDS and late APDS ammunition, the roof of the T-72 was incredibly resilient. 79 degrees is no joke.


According to a CIA report, anti-tank guided missiles such as the M47 Dragon (450mm penetration) and TOW (450mm penetration) stood no chance of defeating the T-72 frontally in a realistic scenario. Another CIA estimate places the T-72's turret and hull glacis protection at 500mm to 550mm RHAe against HEAT warheads. Although the same report mistook the STEF layer for compressed polyurethane foam, it's a safe assumption that they weren't very far off.

The lack of a composite filling in the turret is disadvantageous when it has to deal with HEAT and HESH ammunition, but this is compensated by the extreme thickness of the steel. HESH works well on homogeneous plate, but there is a limit to how thick the plate can be. As far as the Ural is concerned, HESH is no more deadly than any other high explosive round. But what about shaped charges? M456A2 HEAT could only penetrate 425mm of steel armour. This is not enough to defeat 475mm of cast steel, and the fuze will not work on the roof of the turret due to the extreme slope. Unless the Ural was unfortunate enough to be hit in its small weak points, it could still boast of having truly world class armour protection.




In addition to solid armour protection elements, the T-72 Ural is also equipped with four flip-out panels, known as gill armour. Gill armour was notoriously fragile. These panels took the place of traditional side skirts and were originally found on the T-64 and were carried over. Why they did not combine both side skirts and gill armour is not known.




These panels acted as spaced armour; detonating HEAT warheads at a great distance from the tank's sides. However, the coverage offered by these "gills" was limited, as gaps will begin to appear past 35 degrees obliquity. Though they could still work at greater angles, the chance of intercepting an incoming warhead becomes slimmer and slimmer. From frontal angles, gill armour completed the T-72 Ural's invulnerability to even the most powerful ATGMs of the time.


Gill armour can provide much more standoff than traditional side skirts




The panels are made of hard rubber, mounted on sheet steel. They offer absolutely no noticeable protection whatsoever from KE projectiles.

The primary disadvantage to gill armour is that the gills are very easy to knock off when maneuvering in wooded areas. The gills are spring loaded, so they bend quite easily if they happen to cross paths with a tree, and the heavy duty hinges upon which the gills rotate are very robust, but for some inexplicable reason, the heavy duty hinges are secured onto the fragile miniskirt with only two small bolts, as you can see in the photo below:


Notice the thick L-shaped wire; it's the spring that flips these panels out.


Struck squarely in the center from a 30 degree angle, the panels provide a maximum of 2.2 meters of space from the hull side armour. Under such optimum conditions, a great deal of spaced protection can be achieved. This would have given the T-72 Ural a decent amount of protection from guided missiles and man-portable rockets of the era within a 70 degree frontal arc, but more modern missiles would have been minimally affected by this armour. Older missiles like the SS.11 (1956) using older shaped charge technology could not produce a sufficiently cohesive cumulative jet stream, so if there is enough spacing between the warhead and the target, the cumulative jet may dissipate sufficiently that the 160mm of effective side armour may be able to stop it. However, constantly improving shaped charge liner manufacturing technology made spaced armour obsolete in the 60's and 70's


Gill armour is useless from the side

These panels are no longer seen even on unmodernized T-72 Urals, having being rapidly replaced with conventional side skirts as seen on the T-72A. This could be due to two reasons already mentioned above; fragility and incomplete coverage. One concrete advantage of the conventional side skirts is that it keeps the amount of dust kicked up by the tracks under control.



T-72A



Protection-wise, the production model T-72A differs from the T-72 Ural mainly by the implementation of composite armour in the turret. The gill armour had also been replaced with conventional side skirts.


Glacis Array


The original hull glacis on the T-72A (1979) was identical to the one on the 1976 model of the T-72 Ural. In 1983, the T-72A received the same 16mm of applique armour as the T-72 Ural. The total thickness of the glacis with the applique armour plate now becomes 231mm, or 616mm when angled at 68 degrees, identical to its predecessor.

As you may have noticed, the newer glacis armour isn't much thicker than the older version, and the new version even employs the exact same primary components. The only notable difference is the thickening of the back plate and the thinning of the front plate. The reasoning behind this decision is probably related to the appearance of longer and faster APFSDS shells. One probable weakness of the previous array would probably be the tendency to deform owing to its disproportionately large surface area to thickness ratio.


On a side note: Determining the presence of applique armour is simple business. The tow hook area is a good indicator. If the overlay is present, then applique armour is present. This is a good way of distinguishing T-72 Urals and T-72As from T-72Bs, which do not have applique armour.




TURRET

  
Notice the characteristic ledge on the middle of the turret "cheek"

The T-72A has a composite turret featuring a filler known as "Kvartz", sometimes referred to as "sandbar armour" or "sand rods". "Kvartz" translates to "Quartz", so obviously quartz is the main ingredient, but the exact composition of this compound is unknown, though the name implies that it includes granules or powdered substances. The filler material is possibly refined sand, but compacted to a high density. However, there is solid evidence that contradicts this.





The tri-layer arrangement of the armour may help it attain greater standards of protection than homogeneous armour of the same volume. And again, as noted with the hull array, the composite nature of the T-72A's turret should give it an added damping effect against high explosives and high explosive squash heads.

All this does not yet factor in the sheer thickness of the turret, which is perfectly illustrated by the photos below:





If the turret cheeks of the T-72 Ural were 475mm thick near the mantlet, then it is quite clear that - based on the photo above - the cheeks of the T-72A turret exceeds that thickness handily. It is estimated to be 500mm thick at the minimum, going up to 600mm or more as we move away from the gun mantlet. From a 30 degree angle off axis, the turret cheeks should maintain a uniform thickness of 450mm to 500mm.

Based on these thickness values, it can be surmised that the cavity containing the "Kvartz" layer, whatever it is, is present in a 1:5 ratio to the steel aspect of the turret, as you can see in the photo below. If we take the total thickness to be approximately 500mm, then the cast steel portions of the cheeks should total up to 400mm or more. The outer wall of the cavity should be between 150mm to 200mm thick, and the inner wall should be thicker than that by a decent margin. The cavity containing the "Kvartz" filler should be 75mm to 100mm thick, assuming that it is about half the thickness of the outer wall.

Looking closely at the photo below, you will also notice that the filler material is clearly not sand. It has a metallic silver colour, and it appears to have some structural integrity, as it has not poured out.




Circular markings are visible in the photo below. These are filler plugs. Evidently, "Kvartz" is poured into the armour cavity. It is not sand, which would not need to be poured into the cavity, because sand is used in chill casting molds. To create that cavity, they definitely used sand, and that would mean that there would be no need to pour anything in! This is more evidence that "Kvartz" is not sand, but something else, possibly some plastic substance.  




Whatever it is, it is proven to be extremely effective. against 3BM-15 APFSDS. This was shown by the famous T-72A (or T-72M1?) turret in the Parola Tank Museum, Parola, Finland. Tag number 5 in the photo below marks the impact of a 3BM-15 shell into the left turret cheek.





According to the placard at the museum hosting the ventilated turret, the shell was stopped completely after digging only 170mm into the composite armour. This would mean that the shell passed through the cast steel wall of the cavity, but then apparently stopped dead in its tracks in the "Kvartz" layer. However, we do NOT know the range (simulated or otherwise) at which the shot occurred, and we have no idea how they determined the depth of penetration. The inner wall of the turret was obviously not cut up to examine the armour, so they must have poked a stick into the shell crater until they hit solid resistance. If the theory that the "Kvartz" filler is sand or some other easily powderized solid is correct, then it could be that the filler substance simply refilled the hole where the shell passed through and the measuring stick simply compacted the filler as it pushed in. It would not show how deeply the tungsten carbide slug of the 3BM-15 shell entered the inner wall of the armour array. Among other things, this proves that the outer wall of the cavity is around 170mm thick or less, which fits perfectly into our estimation.




Using the 3BM-15 as an example, it should be clear to the reader why the usage of "RHAE" is erroneous and misleading. 3BM-15 is known to be capable of penetrating 310mm of steel at 0 degrees at 2 kilometers. And yet, it could only penetrate 170mm into the composite armour of the T-72A turret. Composite armour simply cannot be expressed in terms of steel equivalency, because even if you separate the RHAE category in "KE" and "CE", you have to contend with the fact that there are are multitude of unique APDS and APFSDS penetrator designs. M735 APFSDS, for instance, has a tungsten alloy penetrator with a raindrop shape.



And the 3BM-15 along with all Soviet APFSDS designs pre-Vant comprise of a steel projectile encasing a small tungsten carbide slug. These penetrators will NOT behave in the same way as M735, or long rod penetrators when striking the same composite armour. As such, it would be rather foolish to assign a fixed armour value. That said, there is some justification to assign a fixed RHA equivalency value on the turret of the T-72A, because a majority of it is composed of cast steel, which would make the turret cheeks equivalent to about 375mm RHA when we don't factor in the "Kvartz" content. With "Kvartz", the value may be anywhere above that, but presumably more than 428mm RHA, which is what the armour on the T-72 Ural turret was worth. Some penetrator designs may be badly affected by "Kvartz", and some may be less so.

However, the point of the composite nature of the armour was to boost protection from shaped charge warheads, so we can say with great certainty that the armour equivalency of the turret cheeks will be much greater than 428mm. I would say that the cheeks are equal to 550mm RHA versus HEAT warheads, because it seems like a nice, reasonable number. The resilience of the cheeks against contemporary APDS against kinetic energy projectiles of all sorts should still be very high, definitely high enough to resist 105mm APFSDS from well into the 80's. It should not, however, be able to resist 120mm DM13 at combat distances of 1500 meters, unless the composite penetrator design of DM13 is badly affected by non monolithic armour. If we adopt a more optimistic perspective, then it is perfectly possible that DM13 cannot penetrate the cheeks at the upper boundaries of common combat ranges.

According to first hand accounts on the performance of ex-East German T-72M1s during Canadian testing, found here, new experimental 105mm shells, presumably designed in the late 80's, claimed to be "jazzed up" to match 120mm rounds in performance, failed to perforate the turret armour. Apparently, the impact only formed a "slight [dinner] plate sized bulge in the armour and cast some paint flakes around the turret wall". 

The hull armour fared slightly worse, but still quite respectably. These tanks were probably fitted with the 16mm applique armour plate. If true, these tests echo the initial relationship between M111 "Hetz" and the T-72A, as "Hetz" was able to defeat the glacis armour at close ranges, while the turret was evidently invulnerable (as shown by the lack of reinforcement, while the glacis received a 16mm applique plate). 





The T-72A introduced steel-reinforced plastic side skirts (interwoven textile skirt), which provided complete coverage for the sides, excluding the roadwheels. They were mounted 610mm away from the side of the hull, and could thus still drastically reduce a shaped charge warhead's effectiveness when fired at a steep angle, though certainly not to the degree that the gill armour configuration could achieve.




In general, "soft" side skirts like the type which the T-72A uses do not provide enough protection from serious shaped charge warheads at most angles of attack. At angles of 30 degrees or so, the amount of spacing provided (1220mm angled) would be enough to dissipate the cumulative jets from most tube-launched HEAT grenades and ATGMs of the 50's and 60's enough that the 80mm of side armour (160mm when angled) might be able to handle them, but the chances of even such modest hopes are slim.


T-72AV



Kontakt-1 is an ERA package first introduced in 1982. All T-72As promptly began an upgrading programme in 1983.

Mounting the blocks are easy. Each one is bolted onto a tinny spacer mounted all over the surface of the hull and turret. The ease of installing and replacing the blocks meant that the entire modification could be done as part of regular scheduled maintenance. However, simplicity comes at a price in this case. The ERA boxes are rather fragile, and can be quite easily knocked off when the tank is travelling through densely wooded areas, or perhaps traversing obstacles in urban sprawl. This is perfectly illustrated by the example below:






The operation of Kontakt-1 is quite simple, utilizing two angled explosive plates to disrupt cumulative jets through high-velocity shockwaves and the separation of the steel sheets which comprise the block itself .

Each Kontakt-1 block consists of two 4S20 explosive elements, which are plastic explosives packed into a flat steel plates. The mass of the explosive material in each element is 260 grams, equivalent to 280 grams of TNT. They have a low sensitivity to ensure that they can survive being hit by machine gun fire, autocannon fire, napalm or anything less powerful than a cumulative jet without detonating. Kontakt-1 is so safe from external damage that the one thing that you will always notice with destroyed Syrian T-72M1s is that even if they are completely burnt out from a cook-off of catastrophic detonation, all of the Kontakt-1 boxes will survive intact. Here are some examples:



Kontakt-1 on this T-72B:





And this Georgian T-72B:





And on this Georgian T-72AV:





The weight of each block is 5.3kg, and a full set covering the entire tank weighs approximately 1.2 tons.



Kontakt-1 is extremely easy and simple to install. All that are needed are some bolts and nuts.


METHOD OF OPERATION


When a cumulative jet passes through the explosive plates, the resulting explosions will tear apart the box and send the many steel sheets within flying in every which direction at breakneck speeds. These sheets will fly in the path of the cumulative jet and cut off most of its body (but not the tip, which travels at hypersonic speeds and is too fast to intercept). The steel sheets are the walls of the explosive cells themselves and the walls of the box containing them. Compared to the Israeli Blazer ERA (left photo), Kontakt-1 is much more powerful, has more flyer plates, is better angled, and more effective in general. 





The overall ERA coverage is uncompromising. The entire tank is covered in all areas save for the rear of the hull and turret. According to a fact sheet from NII Stali, each block can reportedly reduce the penetrating effects of cumulative jets by an average of 55% at 0 degrees obliquity, and up to 80% when angled at 60 degrees. Furthermore, NII Stali claims that it can retard the penetration power of a typical anti-tank missile like the Konkurs (130mm diameter) by up to 86%, or 58% for a 125mm HEAT shell, or up to a whopping 92% for low power warheads like the one on the 66mm LAW. Because Kontakt-1 is incapable of providing significant protective value against KE penetrators, only HEAT values will be listed.



The addition of Kontakt-1 blocks is also important for a different reason, which is that the crew now becomes much better protected (essentially invulnerable in covered areas) from air-delivered bomblets or submunitions as well as artillery shells with HEAT warheads, though the hatches are not covered.




T-72B



The T-72B and the series it spawned represented a very significant step in the evolution of the T-72, with the introduction of bulging armour in the hull and turret. Bulging armour is a type of non-explosive reactive armour (NERA), meaning that it has the effect of defeating the projectile rather than only passively resisting it. This will be explained in the Bulging Armour expository section below. The T-72B is also notable for being the first T-72 to incorporate an ERA package as part of its original factory configuration. That is, all T-72Bs were built with Kontakt-1 installed. But first, we'll talk about the "plain" T-72B.



Glacis

The glacis array of the T-72B represents the first major update since the original type found on the T-72 Ural. It is now thicker at 235mm, which when reclined is 627mm LOS. This is just as thick, if not in some ways thicker than the front hull plates of many of its competitors at the time which have now become famous through extensive media coverage. Among these are the Challenger 2, Leopard 2 and the M1 Abrams, all of which appear to have equal and perhaps sometimes even inferior hull protection on many counts sans the latest upgrades. However, thickness isn't the most important thing. What matters most is how effective the armour actually is.

Previous assertions made on this article on the T-72B having the same type of bulging armour as the turret as well as having that same armour throughout the T-72B's lifespan have been proven wrong by photographic evidence. Hence, it is assumed that the illustration below prepared by online user Wiedzmin is correct, as the descriptions correspond to all known evidences.






Arrays 4, 5, and 6 refer to the glacis configuration of the T-72B models obr. 1983, obr. 1985 and obr. 1989 respectively. 


  Configuration 4: 60mm RHA + 15mm Air Space + 15mm HHS + 15mm Air Space + 15mm HHS + 15mm Air Space + 15mm HHS + 15mm Air Space + 50mm RHA (215mm Total)

  
  Configuration 5: 60mm RHA + 10mm Air Space + 10mm HHS + 10mm Air Space + 10mm HHS + 10mm Air Space + 20mm RHA + 10mm Air Space + 20mm RHA + 10mm Air Space + 50mm RHA (220mm Total)
  
  Configuration 6: 60mm RHA + 35 Bulging Module (5mm Rubber + 3mm RHA + 19mm Air Space + 3mm RHA + 5mm Rubber) + 60mm RHA + 10mm Anti-Radiation Layer + 50mm RHA (215mm Total)


From 1983 to 1987, the T-72B incorporated simple spaced steel armour in different configurations, but progressed to bulging armour in 1989. Before we go into detail, be reminded that the T-72B is always outfitted with Kontakt-1, and the 1989 variant is always outfitted with Kontakt-5. Only a few T-72Bs went into service without Kontakt-1, and those were the ones that were used during Victory Day parades. Pausing to think, though, I can see no reason why those T-72Bs were not fitted for Kontakt-1 after the parade was over. Or perhaps they were special parade models that were never meant to be used in combat. But I digress: The armour estimations presented below will not be relevant for HEAT warheads where T-72B obr. 1983 and obr. 1985 are concerned, and not relevant for either HEAT or KE penetrators where T-72B obr. 1989 is concerned, due to the presence of Kontakt-5 reactive armour.



Obr. 1983




The photo above shows a destroyed T-72B from the first Chechen war. The glacis array of a different destroyed T-72B is visible down at the bottom half of the left side of the photo.

The glacis array of T-72B obr. 1983 is a textbook example of multi-layered spaced armour comprised of multiple thin steel plates. In this case, the armour works mainly by nothing more than chipping the tip a long rod penetrator multiple times. This is possible because the interaction between a long rod projectile travelling at near hypersonic velocity and a single monolithic armour plate is not the same as the interaction between it and multiple spaced armour plates. With a single plate, the rod tunnels its way through the metal via a process known as hydrodynamic interaction. The metal of both the rod and the armour plate flow almost like a liquid, as opposed to eroding away, as projectiles travelling slower than the critical velocity of 1.1 km/s do. However, this type of interaction only occurs in the center of the plate. At the face of the plate, the interaction between the rod and the plate is more conventional. The tip of the rod is fractured via interface defeat and a chunk falls off, thus forming the tip into a jagged, irregular shape.

Without an optimally shaped tip, a long rod projectile will not be able to properly overcome a steep slope, thus making it harder for the rod to defeat the next spaced plate, and the next, and so on. All this while, the chipping will remove increasingly larger portions of the rod as the tip becomes less optimum. The final steel plate will deal with the rest of the rod.

The most interesting thing is that the spaced plates are thinner than the diameter of the long rod projectiles attacking them. I have no idea what the implications are. One possible weakness in the design is that long rod APFSDS shells may normalize inwards due to the slope direction of the spaced plates, thus decreasing the effective thickness of the array. It is possible that the engineers realized this deficiency, but could not solve this problem without abandoning the glacis design entirely.


This array should be effective against early 120mm Western APFSDS munitions like the West German DM13, but that may or may not be due to the virtues of the array in itself so as much as it is thanks to the (presumably) sub par performance of DM13 on steeply sloped targets, given that it has a steel tip and no soft armour piercing cap, unlike 3BM-26. Pitted against 105mm APFSDS of the time, namely things like the DM23 and M833, the glacis should be immune at ranges of down to at least 1000 m. In all likelihood, the glacis will be no match for the M829A1 and DM23 at ranges in excess of 2000 m, but that might be a bit optimistic.  



Obr. 1985





The photo below shows the exposed glacis armour of a damaged T-72B3, taken during the 2015 Tank Biathlon. As you may recall, the T-72B3 program refurbishes and modernizes old T-72Bs.




The glacis array of T-72B obr. 1985 is similar to the obr. 1983 version, but slightly more effective due to a more rational design. The additional gains in performance against kinetic energy projectiles in this variation of the glacis array stems from its use of plates of different hardnesses, forming a spaced THS (Triple Hardness Steel) array. The 10mm steel plates at the very front are of a very high hardness of around 550 BHN, while the 25mm steel plates behind them are softer at around 450 BHN. The last and first and also the thickest plates are also the softest at 340 BHN. This, in combination with the spacing, is an effective regime, but it is not on the level of the NERA armour employed in the turret and in the latest NATO tanks when faced with shaped charge threats. However, it is more than likely that this array configuration (as well as the previous one) was chosen to focus more on kinetic energy threats rather than HEAT as shaped charges were thought to be nullified with the introduction of Kontakt-1.

This array design should be adequate for newer APFSDS shells such as the 120mm DM23, M827 and the M829. With Kontakt-1 installed as standard equipment, the glacis should also be invulnerable to the ITOW and the TOW-2.




Obr. 1989



The glacis array of T-72B obr. 1989 is more advanced, but it is not supposed to work on its own. It is designed to work in conjunction with Kontakt-5. The single bulging module immediately behind the front plate is comprised of two opposing bulging plates. These work based on the principle of penetrator yaw and deflection. As the long rod penetrator enters the array, it activates the first bulging plate, which bulges downward, enacting downwards force on the penetrator, and as the second bulging plate is activated, it bulges upward. This is practically the same as a single normal bulging plate sandwich. As far as I can tell, this configuration was made like this to complement and supplement Kontakt-5, serving to further destroy the long rod projectile after it has suffered the effects of the heavy reactive armour.

Stopping the rest of the rod would be the the job of the remainder of the array, 110mm thick in total. The 60mm steel plate, 10mm anti-radiation layer and 50mm steel plate combo could probably otherwise be described as a simple 60mm + 50mm spaced armour array.

This array, plus Kontakt-5, is proven to be resistant to the TOW-2 missile. This is shown later in the Kontakt-5 section of the article.



Turret






The new turret, dubbed "Super Dolly Parton" (quite a compliment), fully retains the usual T-72 layout, with the frontal projection up-armoured and the associated changes made to the armour profile. There are two aspects to the turret's frontal armour; the solid steel portions and the bulging armour. The steel armour has a hollow cavity for the insertion of bulging armour modules. The front wall of the cavity is approximately 130mm thick at its thickest at the front facing thinning to 90mm as it approaches the side of the turret. The rear facing is composed of a thickness of cast steel supplemented by a 45mm HHS rolled steel plate in front of it (pictured below).




We don't actually know how thick the cast steel is, but we know for a fact that the rolled plate is 45mm from the famous ARMOR magazine article. The thickness of the cast steel is estimated from the distance between the armour cavity and the gunner's primary sight aperture. Based on the photo below (one black/white segment = one inch) we can see that this thickness is greater than 3 inches, but less than 4 inches, but close to 4 inches. Therefore, we can assume that the thickness of the cast steel is around 90mm, and combined with the rolled steel plate, the total thickness of the plates behind the multi plate array is a healthy 135mm.






The bottom of the turret cavities is chamfered both inside and outside the turret ring. The interior chamfer links the turret array with the turret ring, since the armour is so thick that it actually extends a fair distance into the turret ring. The exterior chamfer, on the other hand, appears to be a design compromise to give the driver more passage space for egressing when the turret is aimed at the 10 o'clock to 2 o'clock positions, as the armour extends over the driver's hatch, possibly impeding a quick escape. The implication of this decision is simply that the turret ring area, which is a traditional weak point of all tanks, is now bigger. On the other hand, this also means that the driver can get out much more easily, unlike drivers of Western MBTs like the Abrams, Leopard 2 and Challenger 2. This could be considered one of the many mixed blessings of the T-72.

The multi-stack bulging plate array of the turret consists of 20 modules. This type of armour can be considered a form of integrated NERA (Non-Explosive Reactive Armour). 



Each bulging plate module may vary greatly in length, but all of them are uniform in their thickness, which each module being 30mm thick. The modules are composed of a 6mm-thick rubber flap sandwiched between a 21mm-thick HHS front plate and a 3mm-thick HHS bulging plate. The modules have 22mm of spacing between one another. The entire array is angled at 50 degrees relative to the barrel.

The placement of the plates places five or six plates into the direct line of fire of a projectile when the turret is being shot at head-on (further elaboration later), and two or three plates when fired on at an angle of 35 degrees. This is superior to the arrangement of the NERA plates in the front hull of the M1 Abrams, which places only four plates in the line of fire. Behind that is a spacer, which provides almost no armour value as it is only there to brace the NERA plates and provide proper spacing. Behind the spacer is the main armour, which is a rolled steel plate about 160mm thick




However, the slope of the plates set in the turret of the T-72B is less steep (50 deg vs 55 deg), thus making them slightly less effective per, without considering the merit of the design of the NERA plates themselves, which we shall do so now:



How Bulging Plate Armour Works:


The photos below illustrate the effect of a bulging plate module on the cumulative jet from a shaped charge.




As you may notice, the entire jet behind the tip itself is disturbed due to lateral forces imparted upon it from the movement of the bulging plates. The source of energy for this movement is the jet itself, which energizes and vaporizes the elastomer liner between the two bulging plates sandwiching it, thus causing both plates to be pushed away from each other with great force. But still, this type of armour is not particularly energetic or quick to react, as a large portion of the hypervelocity tip of the cumulative jet can still survive to travel forwards and penetrate a significant amount of armour.

According to the document MULTIPLE CROSS-WISE ORIENTED NERA-PANELS AGAINST SHAPED CHARGE WARHEADS penned by Ewa Lidén, Andreas Helte and Anders Tjernberg, (the same document contains the photos above) a single NERA panel can decrease the penetration of an 84mm shaped charge warhead from 410mm to just 70mm - a reduction of 83%! Very impressive, right? Well, NERA plates are great, but not that great. The witness block that actually records the penetration power of the cumulative jet is placed at a very significant distance away from the NERA plate. Spacing is not such a big deal for a well made shaped charge, but when the cumulative jet is disturbed by the NERA plate, space suddenly becomes very effective. The reason for that space is so that X-ray photographs of the behavior of the jets can be taken. Why did they not test NERA plates without that space? I have some vague ideas, but nothing concrete - but I digress.

Placing two NERA panels in parallel further reduces the penetration to 60mm, which is odd to the layman, but this is due to the natural "lag" of this type of armour. Remember that the tip of a cumulative jet travels at velocities of between 8 km/s and 10 km/s, or more. It is impossible to intercept and disrupt the tip simply for that fact, but it is possible to cut off the rest of the jet and prevent it from doing any harm. This fact is illustrated the photo below, taken from the aforementioned document




The very small reduction in performance offered by the second NERA panel is purely due to the erosion of the jet from impacting the two steel sheets of the panel.


Moreover, the efficacy of NERA panels will depend greatly on what the inert sandwich material is, and on how thick the bulging plates themselves are. The document COMBINATION OF INERT AND ENERGETIC MATERIALS IN REACTIVE ARMOR AGAINST SHAPED CHARGE JETS
by A. Holzwarth, K. Weimann, gives us perspective. A rubber-based NERA panel was also involved in their testing. However, their NERA panel could only effect a 22% reduction in penetration performance for a 64mm shaped charge warhead. Where did the 61 percentage point difference go? Well, here they used a sandwich of 8mm of rubber between two 2mm thick mild steel sheets. In the first document, they used a sandwich of 5mm of rubber between two 3mm thick sheets of Domex Protect 300, which is ballistic grade steel with a hardness of 300 BHN, much tougher and harder than mild steel, which has a hardness of only 145 BHN. Both examples were set at an obliquity of 60 degrees.

It is understood, then, that it is important to use strong and hard steel for your bulging plates. The potential reduction in penetration performance for a shaped charge warhead could be as high as 83% using 300 BHN steel sheets. Now, let's see what the T-72B uses.




How Soviet Bulging Armour Works:


The bulging plates in the T-72B work essentially as described above, except that the one plate is much thicker and therefore much more rigid than the other, forcing the thinner plate to bulge. It will also do it more violently, since all of the energy absorbed into the inert sandwich layer is used to propel only one plate. One bulging plate will be less effective than two, because there is one fewer plate to disrupt the cumulative jet but the directional bias can be highly beneficial, as shown below:




(a) "Backwards moving" means that the plate bulges against the direction of travel of the jet. This is known as an "in retreat" type NERA.
(b) "Forwards moving" means that the plate bulges in the same direction as the direction of travel of the jet. This is known as an "in pursuit" type NERA.


The pictures above are not of an actual simulation of cumulative jet hitting a NERA panel. The plates pictured were moved by explosives which were detonated before the jet reached the plate, but they achieve the same effect in its essence. The photos above shed light on an extremely important phenomenon, which is integral to the operation of the armour of the T-72B. In the turret, the NERA panels are all of the "in pursuit" type. This maximizes their performance, effectively reversing any penalties potentially incurred by the unidirectional design, or at least neutralizing the disadvantages.






The bulging armour design on the turret of the T-72B cannot be compared directly to its NATO counterparts like the Abrams. The Abrams uses conventional bidirectional bulging plates, which, as we have seen, cannot intercept the tip of the jet, but can be very effective at destroying the rest of it. Defeat of the tip of the cumulative jet is achieved by the minor erosion of the jet against the polycarbonate sandwich layer and by using a thick steel plate at the rear. This is not optimum against long rod projectiles, or any KE projectile, really, as polycarbonate plates will do very little against such threats and the bulging effects of the NERA armour will only do so much to the projectile before it impacts the main armour. Therefore, we can say that the NERA armour in the Abrams is capable of handling kinetic energy threats, but it is optimized for shaped charges. Given that all of the APFSDS rounds employed by Soviet tanks before the advent of Vant were of a composite design with a tungsten carbide slug, the NERA armour of the Abrams should be sufficient for its purpose.

The bulging plates in the T-72B are unique as they are geared specifically towards defeating KE threats. Unlike conventional NERA, the panels in the turret of the T-72B have thick, high hardness steel walls acting as spaced armour (in the same manner as the glacis array, which we have discussed) in tandem with bulging plates to defeat the projectile before it reaches the main armour, which is additionally reinforced. The substitution of bidirectional bulging plates for a unidirectional bulging plate with a thick armour plate could be a deliberate compromise to boost protection from KE threats, but the evidence shows that both KE and CE threats were taken into account. Therefore, the NERA armour in the T-72B can be said to be more than capable of handling shaped charges, it is optimized for kinetic energy threats. We can surmise that this was directly influenced by the appearance of M111 "Hetz", a long rod monobloc projectile the likes of which would become the spiritual prototype for all future APFSDS projectiles.

NERA armour can work with both KE and CE threats, but although bulging plates will not necessarily discriminate between either of these adversaries, the behaviour of these threats will differ when under the effects of NERA armour.

When faced with HEAT shells, the bulging armour array works mainly on the principle of jet disruption. As the first bulging plate bulges, the midsection of the jet (the tip is far too fast to be affected) are put under lateral stresses, thus interrupting its shape. Disruption of the rather delicate shape of the jet in addition to the velocity difference between the tip and the portions of the jet behind the tip cause the midsection to break up in-flight, leaving only the tip moving in the original velocity vector. The body of the jet, without the tip, cannot effectively penetrate armour while the tip, without a body to feed its mass, has too little mass to do much despite its great speed. The tip will be defeated by the multiple 21mm hard steel plates spaced in front of it, eroding against each one until it is gone; deposited as metal residue in the tunnels it created.

Bulging plates shot through with cumulative jets

Bulging armour works in a slightly different way against KE projectiles;

According to "The Relation between Initial Yaw and Long Rod Projectile Shape after Penetrating an Oblique Thin Plate" authored by M. Arad, D. Touati and I. Latovitz, even one degree of yaw before striking a thin angled plate would significantly reduce that projectile's penetration potential against any armour behind that plate as a result of the deformation of that projectile (read the paper to learn more).



The x-ray photos above show tungsten alloy rods interacting with a sloped armour steel plate with yaw, and no yaw. The rod with no yaw appears to be worse off, as it lost its tip, but that is simply the result of impacting a sloped armour plate (recall the glacis array of the T-72B). The rod with 1 degree of yaw, on the other hand, is seen visibly bent, although it retains its tip. Such a rod would fail to penetrate as much armour as the rod without yaw. However, the combination of both is the best, and the unique NERA design employed in the T-72B may work in that direction.


The greater the yaw, the greater the negative effect. The bulging armour on the T-72B may take advantage of this phenomenon. The hard steel strike plate behind the NERA array is angled in the opposite direction to the angle of the NERA panels, so that as the long rod penetrator passes through each panel is becomes increasingly deflecting away (both due to deflection from the bulging plates and due to the natural tendency of long rod penetrators to tunnel into the slope), the relative angle between the rod and the strike plate continually increases. Be reminded that there are at least five to six bulging modules in the projectile's flight path if the turret is shot head-on. Each individual bulging module in tandem with the next module directly behind it work together to put the penetrator under great stress, causing it to yaw, and inevitably to fracture as it passes through the multi-layer array.


According to German tank expert author and lecturer Rolf Hilmes, one method to augment the efficacy of NERA armour against kinetic threats is to incorporate a heavy armour plate in front of the NERA array, so that the penetrator is shattered or fractured before it enters the array. This is the function of the heavy cast steel front plate of the turret cheeks. Later on, this effect is augmented by Kontakt-5 heavy reactive armour.


If and when the projectile has gone through all of the NERA panels, it will meet the hardened rolled steel plate backing. Angled at the normal 50 degrees, the 45mm plate measures 70mm thick, equivalent to 84 to 90mm of RHA steel, but that is an oversimplistic approximation. The value of the great hardness of this plate cannot be accurately expressed as a simplistic armour thickness equivalence multiplier in calculations. The function of the plate is much more significant since the projectile that will be striking it will no longer have an optimal shaping, meaning that this plate could function to totally outright shatter the already fractured and damaged penetrator. The dissimilar hardnesses of the 45mm steel plate and the cast steel behind it turns it into a DHA (Dual Hardness Armour) pairing, making it inherently stronger and more resilient than a single monolithic steel plate of the same thickness. The softer cast steel behind the hard steel plate will also produce less spall. This, in addition to the anti-radiation lining acting as a spall liner, means that the after-armour effects in the event of full armour perforation would be greatly diminished.


Note that bulging armour shouldn't be specially affected by projectiles with impressive length/diameter ratios by any great amount. In fact, it's quite possible that greater length/dimater ratios will actually increase the effectiveness of the array if said projectile is longer but not wider, which would make bending and fracturing it easier, as the stiffness is decreased, while the material properties of the metal remain the same. Snapping of the rod is possible because of the forward momentum of the projectile, which naturally resists a change in the direction of motion. Pressure builds up in the rod due to the large forces opposing each other, and if there is a weakened point in the rod, the thing might fracture or snap. So why continue to increase the L/D ratio of modern tank ammunition? Because the benefit of increased penetration totally offset whatever drawbacks there are.

Also, a rather important point related to the effectiveness of the bulging armour array is their ability to perform when hit at abnormal angles, especially considering the regularity in which tanks are hit from the flank. The answer is that bulging armour would work even better at steeper angles, as it would be if the turret was struck from the side. But that is not to say that the tank is better protected from the side. Not at all; the array would still have more to lose than gain since fewer bulging modules would be there to intercept whatever is hitting the turret. It is in this situation that the HHS front plate of the bulging modules again become particularly useful as the already good thickness of the plate will further increase due to steeper angling. From an angle of 30 degrees relative to the cannon, the two 21mm front plates would measure a total 240mm in thickness, having a relative slope angle of 80 degrees. This angle is already so high that the behaviour of long rod projectiles will be unstable and self-destructive. See this simulation of a model of 3BM48 "Svinets" (whether it is accurate or not is irrelevant) interacting with a 50mm hard steel plate at an 81 degree slope, with catastrophic results.

Therefore, we can say that the T-72B is as strong, or at least nearly as strong when shot from a sideways angle as it is when shot directly to the front, making it essentially impenetrable from a frontal 70-degree arc by contemporary munitions unless the weak gun mantlet was hit. Needless to say, the T-72B was completely adamantine to any and all anti-armour weapons of its day.


The complex operation of the T-72B's armour does not allow an expression of its protection value in terms of "RHAE". However, we can give a good estimate of how it would perform against certain types of munitions on a case by case basis. With Kontakt-1, T-72B is immune to any and all single charge HEAT missiles, and still resistant against missiles with tandem warheads. The base armour in the turret cheeks is itself probably capable of taking on a shaped charge with at least 800mm of penetration. TOW-2 and MILAN-2 ATGMs will be ineffectual against T-72Bs, and it is very likely that the turret will be resistant to TOW-2A and MILAN-2T as well.

Contemporary APFSDS munitions like the M829, M829A1, DM23, DM33(A1), and so on and so forth will not be able to defeat the turret cheeks at any distance closer than 1 km. How do I know? Because the thickness of the steel in the turret itself already exceeds or meets the penetration capability of these APFSDS rounds.

One thing that must be noted is that penetration figures available on the internet can often be misleading. Obviously it is not possible to equate a monolithic steel block to an armour array designed to actively attack and defeat long rod projectiles, but the reader must also be wary of the fact that most of the penetration figures given are of penetration on a 60 degree obliquity target. On a 0 degree obliquity target (like the T-72B turret, whose cheeks have no slope at all), the difference in penetration can be between 17% and 20% higher in favour of the high obliquity target.


Of course, the steel alone is good and all, but spaced steel as present in the turret array will fare much better. That, plus NERA effects and we get a good foundation for our estimations.

Both the turret cheeks and the upper glacis armour would be able to handle M833 (1983) very well, as it is less impressive than the M829, but a little bit better than 120mm DM23. For reference, M833 has a 24mm diameter, 427mm long DU penetrator, travelling at 1495 m/s. Seeing as it would have been the most common ammunition available to M60A3 and M1 Abrams tanks prior to the introduction of the M1A1, this is rather important. Latecomers like the M900 (introduction in 1989 to 1990) would still be worse than its more powerful 120mm counterparts like the M829A1, as it travels as a lower velocity (1500 m/s) than the relatively slow M829A1, and it does not have a superior L/D ratio. For reference, the M900 has a 23mm diameter, 603mm long DU penetrator.


The T-72B's turret offers a great deal of modularity and repairability. The bulging armour is simply inserted into the turret cavity panel by panel - as simple as that. In the field, replacing the bulging armour is a simple matter of cutting off the top at the weld lines (very distinctly seen in the picture below), putting new panels in, and replacing the top. This makes battle damage very easy to repair, and it also eases the installation of upgraded panels.




Aside from that, it must be noted that despite the huge leap in protection relative to the previous T-72 models, the T-72B's turret remains just as inexpensive. The sheer commodity of steel and rubber makes the cost of producing bulging plates almost laughably cheap, while the workmanship required to process the cast turret does not demand any new skills or any retraining. This is undeniably an important asset during wartime, thus preserving the T-72's position as a "mobilization model" with excellent performance at minimal cost.

Some articles claim that the T-72B has 20mm or 30mm of applique armour on its glacis, but this is blatantly false. As you may notice in the photo below, the tow hooks are directly attached to the glacis, unlike the tow hooks on the T-72A. 

T-72A, notice the tow hook area
T-72B, notice the tow hooks

Although the glacis armour does indeed visibly protrude over the top of the hull roof, that is simply be due the increased thickness. Since the very definition of "applique armour" is armour that is applied as an add-on over the original base armour, one can hardly call that "applique".

Kontakt-1



All T-72Bs are outfitted with a set of 227 blocks of Kontakt-1 covering the most of the hull and the forward arc of the turret as well as the turret roof. As mentioned before with the T-72A, each block can reduce the penetrating effects of cumulative jets by an average of 55% at 0 degrees, and by up to 80% when angled at 60 degrees. NII Stali claims that it can retard the penetration power of a typical anti-tank missile like the Konkurs (130mm diameter) by up to 86%, or 58% for a 125mm HEAT shell, or up to a whopping 92% for low power warheads like the one on the 66mm LAW.  Kontakt-1 bears special meaning for the T-72B because of its bulging armour. Kontakt-1 is capable of reducing the penetration of a typical low yield rocket grenade to levels low enough that the front steel facings of both the turret and glacis arrays are able to absorb the residual penetration without even damaging the modules underneath, which is quite important given the single-use nature of bulging armour. Also, it wouldn't be wrong to consider the T-72B essentially impenetrable from the flanks with single-charge rocket grenades.



T-72B + Kontakt-5






Kontakt-5 is a form of integrated ERA, utilizing heavy, explosively-propelled flyer plates to disrupt cumulative jets or to damage KE projectiles. Being much heavier than the applique-mounted Kontakt-1, it was not possible to simply bolt the panels on, thus necessiting the incorporation of the modules into the armour array itself. The panels are non-replaceable, but are reusable if refilled and repaired.

The entire set weighs 1.5 tons. Most of it comes from the weight of the steel of the panels.

The exact value for KE penetrators is often quoted to be 250mm RHAe (as stated by NII Stali), but describing it as a solid figure is both illogical and misleading. Some describe the armour as being able to reduce the penetration of a generic long rod projectile by 20% to 35%, while official sources state that it is able to improve base armour by 1.2 times. Regardless, all given figures were clearly deliberately left vague.

According to a fact sheet from the manufacturer, Kontakt-5 can negatively affect KE pentrators by a listed minimum of 20%. This probably includes optimized penetrators designed to counter Kontakt-5. The penetrating capability of cumulative jets can be affected by a minimum of 50% to a maximum of 80%. The former value probably applies only to tiles struck at a shallow slope (30°), and the latter should apply to any and all shaped charge warheads regardless of their advancements - all shaped charges operate on the same principle. However, such claims have dubious bearing on real world performance, as Kontakt-5 will not be as effective against certain types of rounds as it will be against others.



How Kontakt-5 Works


Kontakt-5 works on the basis of explosively-propelled flyer plates. This type of defeat mechanism is similar, but different to that of bulging plates in that it is far more energetic, and the plate flies off and away from the module entirely. Against HEAT warheads, the general working principle of Kontakt-5 remains the same as that of bulging armour. The cumulative jet will be subjected to lateral forces which will break it up and disperse it, though the hypervelocity tip will invariably still continue forward; Kontakt-5 cannot destroy cumulative jets completely, but it can certainly render them harmless with an efficacy similar, but slightly lower than that of Konkakt-1. For kinetic energy projectiles, Kontakt-5 operates thusly: By utilizing explosively-propelled flyer plates, projectiles can experience catastrophic destruction from being subjected to intolerable lateral forces, thereby conditioning the projectile for defeat by the main armour. The defeat mechanism for KE projectiles is illustrated below:


Kontakt-5 uses a head-on flyer plate, meaning that the plate flies into the path of the penetrator. A forwards moving plate as shown in the illustration above is a plate that flies in the same direction as the penetrator, so the illustration is incorrect, but enlightening nonetheless
For present-day kinetic energy penetrators, bypassing the modules is impossible. The M829A3, for instance, was designed with a special spaced tip (see "Mango" APFSDS shell under the ammunition section) to "defeat" Kontakt-5 without exposing the actual penetrator to the flyer plate by sacrificing its dud tip. 

Kontakt-5 was originally designed to use 4S22 explosive elements. These are very potent plastic explosives sealed in a flat sheet steel box, pictured below.

The mass of each cell is 280 grams, equivalent to 330 grams of TNT. 




It is also possible for 4S23 explosive cells to be used instead of 4S22. 4S23 was developed for Relikt, but has broadly similar properties to 4S22. 4S23 has similar explosive power, weighs about as much, and has identical dimensions to 4S22. However, 4S23 is optimized to detonate practically instantaneously, yet remain insensitive enough that it will not detonate when struck by 30mm AP shells.


Kontakt-5 is composed of a welded steel body and explosive cells. The steel body acts to contain the immense pressure from the detonation of the explosive cells and to prevent premature damage from machine gun and autocannon fire, and the front facing of the steel body is the flyer plate. It is made of high hardness steel. The front plate measures approximately 15mm, or 40mm with the angling of the glacis accounted for. Each Kontakt-5 module contains 8 4S22 explosive cells, and so each module has the explosive power of about 2.64kg of TNT. Once the module is activated, the 8 cells detonate, producing so much pressure that the welded top is propelled (or rather, violently blown off) at tremendous speed away from the glacis. This means that the 15mm high hardness plate is attacking the penetrator at an angle of 68 degrees relative to its flight path. At such a sharp angle, the heavy high-hardness steel plate shall have no problem completely annihilating the front part of a long rod penetrator, leaving only the middle and rear parts to continue on. Kontakt-5 completely immunizes the T-72B from shells like the M829, M829A1 and DM43 at even short ranges, but the cost of this performance is the danger of sympathetic detonations of the neighboring modules. As you can see in the adjacent photo, the top of the welded body blew off. Since there is no hole under that module, it seems like the module beside it inadvertently set it off. Note that the partitions between the modules disintegrated under the pressure. This was long-known issue with ERA in general, and particularly with Kontakt-5 due to the sheer power of each module. Some ERA designs like the Ukrainian "Nozh" are practically guaranteed to wipe out neighboring modules from sheer explosive power.

Because of the thickness of the front plate, Kontakt-5 modules are protected from heavy machine gun fire from all distances. Their hardness, thickness and steep sloping also shield them from some forms of autocannon fire at extended ranges, and even if the front plate is perforated, the residual energy of the penetrator will probably not be enough to set off the explosive cells. The thick front plate may also help Kontakt-5 resist small secondary shaped charges from tandem HEAT warheads such as the 40mm warhead at the tip of a TOW-2A missile. This does not mean that the front plate is thick enough to resist the penetration of said 40mm shaped charge, just delay it enough by decreasing its velocity via erosion that the explosive cells will not detonate until the primary cumulative jet is more or less about to initiate, so that the Kontakt-5 flyer plate can have a chance at intercepting at least a part of the cumulative jet. By using 4S23 explosive cells instead of the older 4S22 cells, the reaction time of Kontakt-5 can be improved to the point where the flyer plate can intercept the cumulative jets of both the secondary warhead and the primary warhead of a tandem HEAT missile. The welded rear may also act as applique armour if the module is spent, thanks to its thickness, which is almost as much as the 16mm of applique armour on the T-72 Ural and T-72A.


The T-72B obr. 1989 configuration presents 9 modules on the hull. Three of the five modules on the bottom half are loaded with eight 4S22 explosive cells each, and the other two are loaded with six. The four larger modules on top are loaded with twelve each. There are 16 modules on the turret front, each loaded with six explosive cells. Some tanks have been seen with Kontakt-5 turret and hull modules, but with Kontakt-1 boxes on the roof. However, a dedicated hexagonal version is also available, which seems to be much more common. Presumably, Kontakt-1 was used before the proper Kontakt-5 version became widely available.

The middle of the glacis is protected by 8 Kontakt-5 modules, each with several sections which again contains even more tiles. Curiously, the designers made a conscious decision to leave the area on either side of the driver's periscope unprotected. Why they did this is a complete mystery.

Also note the visible vertical partitions between each module.

The photo above shows the applique HHS underlay for the Kontakt-5 hull modules. They are at least half an inch thick.



The photo above shows the thickness of the HHS box for the turret modules. The front plate is approximately 8mm thick and the backing plate is about the same. The turret modules are angled at 68 degrees, just like the hull modules, but due to the roundness of the turret, there is also some horizontal angling as well, which serves to further improve their effectiveness. The small amount of space behind the module enables the rear plate to fly backwards a short distance, augmenting the effectiveness of the front plate and counteracting the reduced thickness of the walls of the module.

The turret modules are so powerful that their detonation is often enough to crack the ballistic glass on the sight aperture of the TPD-K1, which is placed quite far forward. While that may seem like a negative, it really isn't. After all, anyone would agree that it is far preferable to the shell perforating the turret armour, smashing into the sight unit and killing the gunner. The sight aperture can be easily replaced, anyway. Besides, the explosion from a HEAT warhead would nullify the negative effects of an explosion from the Kontakt-5 module.

As noted above, a newer Kontakt-5 box for the roof is available. Closer inspection indicates that it is not simply a repackaged Kontakt-1 module, but a complete departure from it. Let us first take a look at the external differences:

Kontakt-1 on turret roof



Close inspection of these boxes when opened gives us an idea of the internal composition:


T-90A turret equipped with such boxes

It appears that the box itself only has space for one 4S22 explosive element, and the bolt-on top cover is quite thin, the box itself being only slightly flatter than a Kontakt-1 box. Thus, these boxes are definitely a form of explosive flyer plate. As the explosive cell within detonates, the bolt-on lid is blown off at lightning speed, just like the Kontakt-5 modules, and the lid acts as a flyer plate. This armour was probably meant to increase the ability of the heavily sloped turret top to deflect grazing hits from the front, rather than defeat shaped charge bomblets from above, though it should be able to do both.


The newer roof boxes are probably intended to help deflect APFSDS shells from the turret's peak, which is very steeply sloped but relatively thin (Photo credit: Vitaly Kuzmin)

There are three Kontakt-5 modules located on either side of the hull. Like the turret roof boxes, these are a type of explosive flyer plate. They use the same 4S22 explosive elements as the hull and turret modules in their construction. They provide coverage for the entire crew area in a 100-degree frontal arc, as illustrated in the photos below:

50 degree view


The side modules are a type of bidirectional flyer plate. The base is stamped out of sheet steel, with a bolt-on plate measuring approximately 10mm. Once the explosive cells inside are activated, the sheet steel flies off inward, and the bolt-on plate flies off outward. Their ability to confront incoming projectiles is augmented by the 1220 meters of air space behind it and the 160mm of steel armour which is the side armour of the tank (at 30 degrees obliquity). This isn't nearly enough to stop any modern APFSDS shells, but it would at least massively decrease their after-armour potency. Some older APFSDS shells like the L23, DM23 and M829 might be handily defeated by this arrangement given a high enough obliquity, but the side panels are totally inadequate for dealing with already obsolete shells like DM33, M829A1 and M829A2. They can, however, deal with shaped charges of all sorts, but these panels cover less area than Kontakt-1, and they do not offer better performance against HEAT.



Photo credit: Vitaly Kuzmin

As you can see in the photo above, the front plate is disproportionately thicker than the sheet steel compartment holding the explosive elements. As the obliquity decreases, the plates will begin to lose their effectiveness.  If struck perpendicularly, whatever effects that will be inflicted upon it will be very mild, which can be fully accredited to the explosive insert. There would be no useful effect on KE projectiles. Still, this application of reactive armour is far more weight efficient than bolting small 100mm steel plates to the sides of the hull, like the Leopard 2, and the Kontakt-5 side panels can stop shaped charge warheads too, unlike 100mm of steel.

It is worth noting how easily these modules may be installed. Although the standard configuration is three modules at the front, the entire flank may have them installed with no modification required. Knowing that tank crews often want to live, seeing the sides of T-72s brimming with this type of module salvaged from knocked out fellow tanks should be very likely during wartime.



Installing Kontakt-5



 

Inserting the explosive elements into the modules are quite easily done. Once filled, the modules are bolted shut.



The photo above shows the access panels opened. To fill up these, you'd need to insert the explosive elements one by one.

Each hull panel contains eight such explosive elements in a double stack of four. The turret panels house an unknown number of explosive elements, but probably six, in a double stack of three The side modules contain six individual ones.

Holding one of the explosive elements. The man is filling the side ERA sections

As mentioned before, more of these side panels can be installed if deemed necessary. All the preparation necessary is to drill some new holes in the steel spacer plate protecting the fuel tanks on the fender above the track. New side panels can be simply bolted on with no fuss. Repairing spent modules is as simple as welded a new steel body on and filling it with explosive cells.


Equipped with Kontakt-5, a late model T-72B, most likely the obr. 1989 model, has successfully resisted a TOW-2 missile hit to the upper glacis plate, as evidenced by the fact that the turret is still joined to the hull, and that despite two open hatches, there were no flames or smoke emanating from within. We can verify that the tank is a T-72B and not a T-90 as there is a cluster of smoke grenade launchers on the left side of the turret characteristic of the T-72B. The T-90 concentrates only four smoke grenade launchers on that side of the turret. Secondly, there are no IR dazzlers at the front of the turret, indicating that it is not a T-90.




It is possible to see what appears to be the flyer plate of Kontakt-5 shooting up into the air as the explosion occurs in the video. See this GIF here, stolen from Gur Khan's blog:







FUEL TANKS AS ARMOUR


Two fuel tanks are located on the two front corners of the hull (flanking the driver), which extend from the nose of the glacis to almost up to the turret ring. These fuel tanks provide a modicum of armour.





Diesel fuel is very capable as a form of liquid armour. Entering an enclosed liquid medium at high velocities creates shock waves, which reflect from the walls of the fuel tank and back into the penetrator entering it. This can collapse a cumulative jet. It wouldn't be wrong to consider the areas of the hull with fuel tanks underneath them to be essentially immune unless the warhead can overmatch the armour by a factor of more than 100 millimeters of RHA steel, though those same fuel tanks might also be a fire hazard if punctured or compromised. The fuel tanks do not have thick walls, and they are not foam-filled, and according to ex-tankers in Chechnya, they will visibly bulge and swell if penetrated by an RPG, though in those cases they were still strong enough to not burst or leak. In one incident during battles in Grozny, a T-72 was struck from the side by an RPG or SPG warhead in the driver's station. This T-72 did not have Kontakt-1 installed, but the combination of the spaced armour of the side skirt and the properties of the fuel tank managed to stop the cumulative jet from hitting the driver. Therefore, we can quite confidently say that the armour over the driver's station from the side aspect is equivalent to more than 400mm RHAe (with side hull armour and side skirt spacing factored in), which should account for its ability to resist a fairly typical PG-7VS rocket grenade. (Obviously, that is not a definitive value, considering the infinite variety of warheads available). The T-72 in that incident escaped with very minor damage.


In some other cases, like the T-72B obr. 1989 in the photos below, damage to the fuel tank may not produce any fire at all. Here, we see that the tank was pierced on the LFP by either a shaped charge warhead or an APFSDS shell from the front. The penetrator easily passed through the thin armour, passed through the starboard side fuel tank, and if the loosely hanging Kontakt-5 panel on the side of the hull means anything, the penetrator exited out the side. If the damaged Kontakt-5 panel was damaged in a separate incident, then the penetrator must have been stopped by the fuel tank. If it had continued, it would have hit the ammunition.








SMOKESCREEN






The T-72 can either lay its own smokescreen by injecting a fine mist of diesel fuel into the exhaust manifold, or make use of its smoke grenade mortars. The former option is an an ingenious, inexpensive, extremely useful and near-inexhaustible source of anti-IR smoke cover - A little-known fact is that the smoke generated from this method is the temperature as the exhaust, thereby completely masking the tank's thermal signature. The only shortcoming of this system is the time taken to envelop the tank. A large number of battlefield maneuvers revolve around the use of this method of smoke generation for concealment.

  
Low volume smokescreen while idling

High volume smokescreen while moving
  
But aside from this, the T-72 also features the Tucha smoke grenade system. It can launch two types of caseless grenades; the 3D6 and the 3D17. They take advantage of a high-low propulsion system much like 40mm VOG series of grenades to launch them out of their tubes at a relatively low velocity.


3D6


The 3D6 smoke grenade emits "normal" smoke that can only obscure the tank in the visual spectrum. This type of grenade has been rendered next to useless with the gaining popularity of thermal imaging sights in the mid-80's, now long supplanted by the 3D17 model. It is of the slow-burning type, emitting smoke from the ground-up. It travels anywhere from 200m to 350m after launch, and it takes between 7 to 12 seconds to produce a complete smokescreen 10m to 30m in width and 3m to 10m in height, depending on various environmental factors like wind speed, humidity, altitude, etc. This is not including the time taken from launch to the grenade actually hitting the ground. This is in accordance with frontal assault tactics where tanks advance and maneuver behind a continual wall of smoke generated every forward 300m until they literally overrun enemy positions. The smokescreen can last as long as 2 minutes, again depending on environmental factors.




3D17




The 3D17 is an advanced IR-blocking aerosol smoke grenade. It completely obturates the passage of IR signatures or IR-based light as well as light in the visible spectrum. It is effective at concealment from FLIR sights and cameras as well as at blocking and scattering laser beams for tank rangefinders and laser-homing missiles. Unlike the 3D6, the 3D17 grenade detonates just 1 seconds after launch, allowing it to produce a complete smoke barrier in 3 seconds flat. The drawback to this is that the lingering time of the smokescreen is only about 20 seconds, depending on environmental factors. This is enough for the tank to hastily shift its position, but not much more. This grenade detonates 50m away from the tank.
 


NAKIDKA


  Nakidka is a type of multi-wavelength infrared suppressant camouflage developed in 1971. Contrary to popular belief, the Soviet concept of warfare was centered around "deep battle" (rather than Zerg rushing), which greatly depended on "maskirovka" - the element of camouflage and deception. Implementation of "maskirovka" includes decoys, stealthy operations, concealment and surprise attacks. Nakidka plays an important role in this. It is a textile "dress" for the tank, which can neutralize the tank's IR signature (except at its exhaust outlet) and reduce its radar cross-section in addition to presenting a totally non-reflective camouflaged surface, thus drastically reducing the tank's likelihood of being detected in the visual and non-visual spectrums.

Nakidka is resistant to napalm and is unaffected by machine gun fire, though it is possible to destroy it with high-explosives. Still, the point of Nakidka is to prevent the tank from being spotted in the first place. It holds up fine against indiscriminate area weapons. A full suit of Nakidka only adds several dozens of kilograms to the tank's overall weight.


ESCAPE HATCH


An important survivability feature of the T-72 is the inclusion of a floor escape hatch. The (rather small) hatch is located directly behind the driver's seat, and therefore most easily accessible by him. The gunner and commander can get to the hatch as well, but they have to be very, very flexible in order to do so unless the turret is traversed to the rear. Nevertheless, it is indispensable in certain situations, allowing crew members to escape the tank if it is flipped over, or if the engine stalls and cannot be revived quickly enough underwater. The hatch is strong enough that it does not compromise the integrity of the hull against a 6kg to 10kg anti-tank blast mine detonated under the tracks.

Note how the hatch has additional armour




The hatch is far too small for anyone wearing winter clothes, and more rotund tankers will obviously find it impossible to exit through it. The hatch is fully air-tight, and drops out to open. The hatch is as thick as the rest of the hull floor, and is held in very, very firmly in place by four locks.



NBC PROTECTION SUITE


Soviet tank designers were very conscious of the dangers of nuclear warfare, especially artillery-fired tactical nukes. The T-72 perfectly reflected their seriousness, featuring a comprehensive air filtration system, overpressure generation system and radiation sensors paired with automatic tank sealing mechanisms. A radiation lining shielded the occupants from neutrons from gamma radiation.

The GO-27 sensor and automatic sealing system is responsible for detecting nuclear and chemical particles and for initiating the lock down protocol, which seals every gap and port exposing the interior of the tank to the outside environment and also activates the air filtration system.




Gaps and ports in the tank are sealed via pyrotechnic charges, which propel steel seals. Potential entryways for dangerous particles like the co-axial machine gun port are sealed.

Climate control is handled by the FVU filtration and ventilation system.


PKUZ-1A Digitized Protection Suite



The PKUZ-1A was introduced relatively recently as a way to improve the reaction time of the protection systems while simultaneously upgrading the quality of the interior ventilation and climate control systems for the comfort of the occupants.    


ANTI-RADIATION CLADDING AND LINER




Anti-radiation measures have been among the top priorities regarding crew protection, no less important than solid armour itself, given the nuclear environment that the T-72 was expected to thrive in. In accordance with this requirement, the T-72 has had an interior anti-radiation lining since the very beginning. All interior surfaces are furnished with this lining, which is 20mm thick.




The liner is composed of borated polyethylene - a type of high-density polyethylene infused with boron - woven into fibers and made into sheets, which are then laminated and molded to fit around the curves of the tank using a heat gun, and then topped off with some sort of resin for weather protection. According to Anderi Tarasenko, the name of the material is boron 2EP002. Boron is known to be extremely effective at capturing neutrons thanks to its large absorption cross section, making it suitable for use as radiation shielding. The fibrous construction of the sheets and the lamination process also makes it a suitable spall liner not dissimilar to early flak vests that used woven nylon plates. In the photo below, a T-64 sporting the same type of anti-radiation cladding displays the damage dealt by a 122mm HE-F artillery shell. Note the charred chunks of fabric.




It appears to be flammable, but not too flammable. A flame can be expected not to spread, and to die down within a few minutes on its own.


The 1983 model of the T-72A received anti-radiation cladding all around the occupied regions of the turret. It is 50mm thick in most places, including the turret cladding, most of the turret's interior, the side hull exterior, the hull's interior and most of the hatches. The lining for the driver's hatch is 20mm thick. T-72Bs received this cladding almost immediately after introduction, and are never seen without it.

20mm cladding on the turret exterior

The rear of the turret is almost completely covered with the anti-radiation cladding

The commander's hatch is liberally cladded with the cladding, and so is the gunner's hatch.



And the stub ejection port is obscenely covered both inside and outside with the anti-rad layer:

The stub ejection hatch is itself already around 20mm thick, or 28mm when inclined at 45 degrees

The lining and cladding not only function as neutron absorbers, but they perform admirably as a form of spall liner as well. According to Swedish trials of purchased ex-East German T-72M1s, it was concluded that the anti-radiation liner was perfectly capable of absorbing secondary fragments of penetrating cumulative jets, not only spall. Spall liners, depending on their efficacy, may reduce the spray cone angle of secondary fragments from a HEAT warhead by up to 50% or more if armour is greatly overmatched on the basis of their presence alone, and it is possible reduce secondary fragments by up to 80% or even to absorb all secondary fragments if the armour is not significantly overmatched. The T-72's lining and cladding should have good performance due to its substantial thickness both inside and outside. In fact, this feature has helped to saved lives in at least one incident:
 
In this instance, the T-72 was hit in the flank by an RPG attack which also blew off a part of the port side storage bins. The crew survived and the tank only suffered from a minor puncture wound thanks to the spaced armour effect provided by the bins in tandem with the extensive anti-radiation cladding and lining of the T-72
The presence of the lining is a huge factor in the preservation of the carousel ammunition in case of armour perforation, especially from the side. But that's not all, due to boron's large surface area-volume ratio, it does quite well at absorbing blast waves, thus mitigating some of the effects of blast damage.

Additionally, the lining helps to insulate the tank and prevent condensation. This helps preserve the myriad of electric and electronic components in the tank.



FIREFIGHTING


To prevent the spreading of internal fires in the engine and crew compartments, the 3ETs11-2 quick-acting firefighting system was installed. There are 12 TD-1 thermal sensors strategically placed in the engine compartment and crew compartment. The fire fighting system reacts regionally when a rise of temperature to 150°C is detected in the crew compartment or engine compartment. The reaction time for both the crew compartment and engine compartment is painfully slow at 10 seconds, meaning that it takes 10 seconds between detecting a rise in temperature to actually deploying the fire extinguishers. This is an anti-false alarm measure. Alternatively, the driver can manually activate the fire extinguishers wired to the automatic firefighting system from a red control panel to his right. There is also an additional manual fire extinguisher to the driver's left foot.





  Two handheld OU-2 carbon dioxide fire extinguishers are also provided to supplement the automatic fire extinguisher system. If the TD-1 fire detectors fail to respond (usually in the case of small flames), then these will be the only firefighting tools available to the crew, if the driver opts not to manually activate the extinguishers connected to the 3ETs11-2 system.




ENTRENCHMENT DOZER BLADE




  An a self-entrenchment blade is provided at the lower front hull of the tank. It is secured by two rotating latches, which need only to be turned with a wrench by a crew member for the dozer blade to be usable. Needless to say, it is an invaluable tool for self-fortification, allowing the tank to create a hull-defilade when natural cover is unavailable, or even augment existing cover with additional barriers.   

Bolted

Unbolted
With the dozer blade, the T-72 can create a soil barrier in front of itself from even ground in about 20 minutes or more, much less if on uneven ground, but depending on meteorological conditions. On snowed-over terrain, a snowbank may be created in as little as 5 minutes to help conceal the tank.





STORAGE


The T-72 is furnished with a plethora of stowage bins intended for the storage of various things. The most prominent ones are the two large bins located around the rear arc of the turret. These are used for storing the crews' personal effects as well and other accessories. The lids of the bins are sealed by tension latches. These latches are effective at keeping water from entering the compartments.


This is quite the improvement over the T-55 and T-62, as these tanks were not equipped with external stowage bins on the turret. As a result, places to stow day to day necessities was rather limited on these tanks. The Israelis gave their Tiran tanks with Centurian-esque external stowage bins on the turret for this very reason.

The photo below shows the stowage bin at the very rear of the turret. There are two isolated stowage compartments in the bin. One on the right hand side (the left side in the photo) for smaller things, and the central compartment, which is large enough to stow anything you want to. The bin is hinged to the turret, as you can see in the photo below.




The photo below shows the bin hinged open to allow easier access to the engine access panel. How it stays up isn't exactly clear.



Besides the rearmost bin, there is also the side bin. It also has two isolated compartments.





There is also bank of 4 storage bins on the port side of the hull, directly above the tracks.



The port side storage bins are usually used to store maintenance equipment and spare parts.






MOBILITY



The T-72 followed the T-64 in breaking the mold on the standards of mobility in the face of the need to compromise between the "Big Three": Firepower, Protection and Mobility. The T-72 had the world's most powerful gun, world's best armour, and was also among the world's fastest tanks at the time. Its on and off road performance almost reached the same level attained by the the speed-centric but paper-thin Leopard 1 and AMX-30, outmatched the heavily armoured tottering Chieftain and Challenger tanks and greatly outpaced the sluggish M60A1 and A3, all while weighing and costing less than any of them.
  
The superior engine power of the T-72 and its light weight meant that it could not only traverse difficult terrain, but that it could safely cross low-capacity bridges and make good use of the thousands of tactical bridge layers in Soviet army service, even including the ones derived from the then-already-antiquated T-54. Not only is it possible for the T-72 to exploit light load masonry bridges or pontoon bridges, it is possible for a convoy of T-72s to travel over such structures without needing take turns to drive at a snail's pace.
  
Swedish mobility trials of T-72M1s (and MTLBs) in Northern Norrland between 1992 and 1994 yielded very positive results. The T-72s in question displayed good performance over snow as deep as 0.8m, though it still failed at times to reliably traverse frozen ice banks, but it can be argued that that was because of the inexperience of the Swedish test drivers. The T-72 managed to pull off a few impressive feats such as leaping an 8m gap by slamming into a 1.5 meter-tall snow bank:




ENGINES



The T-72 has been host to several engines over the years, starting with the V-46, evolving into the V-84, and finally the V-92. All of the T-72 engines to date are V-12 4-stroke diesels, with some limited multifuel capability. They are able to consume gasoline (A-66 and A-72), diesel, and jet fuel (T-1, TS-1 and T-2). The driver can set the type of fuel by simply setting a dial located in his station. The engine does not need to be further modified beyond that.


The main method of starting the engine is via an electric starter. In cold weather, the engine can be started with the tank of compressed air located left of the driver's feet, or even perhaps by towing. In exceptionally cold weather conditions, the most dependable method of starting is a combination of compressed air and the electric starter. It takes around 20 minutes to start the engine in extremely cold weather, which is much longer than the 3 minutes needed by the GTD-1000T gas turbine engine used on the T-80, but diesel piston engines have their own advantages.




Air canister for compressed air starting system

The V-46 engine and its derivatives are exceptionally reliable, more so than some foreign rivals such as the modern day Perkins CV12 that powers the Challenger 2, or the infamous Leyland L60 that drives the Chieftain tank, widely considered the premier NATO tank of the 60's and 70's.


V-46-4 / V-46-6

The V-46 liquid-cooled engine is the baseline engine for the T-72 series, first appearing on the T-72 Ural and then the T-72A. It traces its roots to the V-2 which once powered the legendary T-34. True to its remarkable origin, it has a remarkable power density, far above its competitors such as the; MB 837, which powered the Leopard 1 series, AVDS-1790-2A, which powered the M60 tank series, and even the "lightweight" opposed-piston Leyland L60 series, which powered the Chieftain tank. When compared: AVDS-1790-2A - 0.324, MB 837 - 0.426, Leyland L60 - 0.535, V-46 - 0.795, the V-46 comes out on top. Overall, the V-46 and all its descendants are unquestionably robust, dependable engines in every way. A disadvantage of this engine is the amount of smoke it produces, which may expose its position to enemies equipped with thermal imagers.

Output: 780 hp
Rated speed: 2000 rpm
Idle speed: 800 rpm
Fuel Consumption: 1 g / 245 kWh or 1 g / 180hp.h
Torque back up: 9% ... 18%
Weight: 980 kg

T-72 Ural and T-72A power to weight ratio: 18.1 hp/ton

The exhaust port for this engine is characteristically long and narrow. It has very rudimentary sheet steel cooling vanes on top.





The V-46-4 is the variant which the T-72 Ural uses, while the V-46-6 is used in the T-72A. The only difference between the V-46-4 and the V-46-6 is a change in the placement of oil containersWith the V-46, both the T-72 Ural and T-72A can achive a top speed of 60km/h on asphalt, and set an average speed of 35 to 40km/h on dirt roads.


V-84-1 / V-84MS

 
The V-84 supercharged engine differs from its predecessor mainly by an increase in output, along with an insignificant weight gain. The additional power comes from the new centrifugal gear-driven supercharger, which provides better aspiration for combustion in the cylinders. The increased power offsets the added weight of the T-72B, allowing it to remain as nimble as its predecessors. This engine is much less smoky than the V-46 because the higher oxygen levels in the combustion chamber allowed a greater portion of the fuel particles to be consumed for more efficient consumption of energy, producing more output.




Output: 840 hp 
Rated speed: 2000 rpm
Idle speed: 800 rpm
Fuel Consumption: 247 g/kWh or 182 g/hph
Torque back up: 6% ... 18%
Weight: 1020 kg

T-72B, T-72B1, T-72BA power to weight ratio: 18.87 hp/ton 
T-72B3 power to weight ratio: 18.2 hp/ton 

The exhaust port for the V-84 is identical to the V-46. 
 

Like previous variants, the T-72B has a top speed of 60km/h on asphalt, and an average speed of 35 to 40km/h on dirt roads. This remains mostly unchanged even with the burdensome Kontakt-5 installed. Most T-72B3s are equipped with this engine.

V-92SF

 
The V-92SF turbocharged multifuel engine boasts an impressive power density of 1.02 hp/kg combined with high standards of reliability. The increased torque reserve greatly improves driving characteristics across rough terrain and the fuel efficiency has been substantially increased, boosting the T-72's already good fuel economy to a new high. The engine is virtually smokeless.








Output: 1130 hp 
Rated speed: 2000 rpm
Idle speed: 800 rpm
Fuel Consumption: 215 g/kWh or 158 g/hph
Torque back up: 25% ... 30%
Weight: 1100 kg


T-72B3M / T-72B4 power to weight ratio: 21.73 hp/ton

Variants outfitted with the V-92SF can be identified by the heavily modified exhaust unit, now much fatter and with much more extensive cooling vanes.




The cooling vanes comprise only half of the exhaust cooling system. The vanes help keep the exhaust outlet itself cool (or at least, as cool as you'd expect for the exhaust outlet of a 1130 hp engine), acting as radiators. The exhaust pipe is contained inside another pipe, which is perforated for air to enter. Cool air flows into the external pipe via the large empty space next to the exhaust outlet (as you can see in the photo above) and gets sucked through it via a pressure differential caused by the high velocity of the exhaust gasses - exactly the same in concept to a Bunsen burner - and the air cools the exhaust outlet by flowing through the vanes, thus lowering its temperature to a certain extent. Also, air flowing at high velocities is cooler than air flowing at low velocity, or not flowing at all. By constricting the size of the exhaust outlet, the hot air from the exhaust manifolds can be cooled.


The use of the V-92SF on the T-72B4 boosts its top speed to a blistering 75 km/h on paved roads and allows it to cruise cross-country at a speed of up to 60 km/h on dirt roads. This elevates the T-72B3's mobility to the level of the T-80U or the M1A2 Abrams speed-wise, and gives it parity when moving cross country despite the use of a gas turbine engine on the latter. This is thanks to the large torque back up of the engine, which gives the tank ample power to overcome obstacles and uneven ground without needing to slow down.



The MS-1 cyclone air filter used with all of the V-series engines is adequate for most environments. It requires a filter change once every 300km traveled under extremely dusty conditions. 




The T-72's engine deck is taken up by the engine access panel, the engine's air intake, radiator/air intake and the cooling system air outlet. All of them except the engine air intake have armoured covers to protect them from bullets and shrapnel coming from above. 





Left and right sides. Engine access panel up front, radiator/air intakes behind it (with armoured covers), and cooling system air outlet behind that (again with armoured covers)

The engine can be easily removed with the help of a 1-ton crane, which can be found at even the most modest depots. In the field, engine replacements are done with the help of engineering vehicles.


Engine access panel hinged open.
However, the T-72's engine is not integrated as part of a powerpack, like on the Leopard 2. Powerpacks are far more convenient to replace. It could take more than an hour to replace both the engine and transmission of a T-72, compared with only about 35 minutes or less for more modern vehicles, like the Leopard 2.


Air intake for V-46 engine, tucked away discreetly behind the turret


Modified air intake for V-84 engine


The engine deck is cool enough that people can ride on top of it.







COOLING SYSTEM



The liquid cooling system is of a convection type. It works with water and air, used to cool hot coolant oil that is pumped around the engine. The coolant oil first runs up to the radiator unit, where it is cooled by water flowing in a labyrinth of aluminium fins with turbulators, which is itself cooled by flowing air being sucked in by an engine-driven fan at the rear of the engine compartment. The unwanted hot air is pulled into the fan and ejected out of the rearmost outlet in an upwards direction. 





The biggest drawback of this system is that dust particles kicked up into the air from driving at high speed may be sucked up by the high velocity air stream from the cooling fan, thus creating a distinctive "rooster tail" dust cloud behind the tank. It is possible for an observant enemy to detect and distinguish a Nizhny Tagil tank from long distances through this method, as the basic operating principle behind the cooling system is derived directly from the system used in the T-54 and T-62, while the first widespread application of this cooling principle was the T-34.


All reports indicate that this system is slightly limited - sufficient for European climates at best. It was designed so that the engine will work with no loss in efficiency at an ambient temperature of up to 25° C, but the engine will begin to experience very marginal reductions in performance at temperatures exceeding that. Overheating becomes a major issue in ambient temperatures of up to 50° C, which is sometimes recorded at the Thar desert in India. At temperatures above 45° C, the engine will begin to suffer huge reductions in power (up to 33% loss). At such temperatures, the tank must be stopped every 25 kilometers to allow the engine to cool to prevent excessive wearing. The simplest solution, as practiced by most tank crews, is to remove the armoured covers, which helps to improve air intake volume to improve cooling capacity, but this is not sufficient on extremely hot days. At temperatures of 30° C or so, the cooling system is adequate.


Apparently, the V-92 engine series and its accompanying modifications have partially solved the overheating issue. Specific details are not known to the author, but it could only either be an increase in the centrifugal fan's power, or a simple modification of the water flow channels in the radiator, as Indian T-72s and T-90Ss apparently have.
  


Radiator cover removed, exposing the protective louvers within
Cooling system air outlet. Armoured covers for it are removed, but not for the radiator in front of it
  

The photo above shows the engine compartment with cooling pack and engine access panel removed. Note the crossbar to hinge both of the aforementioned accessories. Also note the centrifugal fan at the bottom left corner. It is directly powered by the engine, and thus increases or decreases its power in accordance with the engine's requirements. It is strong enough to throw water out of the engine compartment like a blowhole even while idling.

As you can see, the engine compartment is quite hollow. 40% of its volume is empty space for air flow, and the outer armoured plate of the cooling fan outlet plus the partition between it and the engine compartment can act as spaced armour to defend the engine from autocannon attacks coming frmo behind, particularly from aircraft.

Centrifugal fan

In the event of damage from air attack or whatever, maintaining or replacing the radiator is quite simple, since the entire unit can be hinged open.




The louvers that protect the radiator inlet, cooling fan outlet and engine air intake can all be shut or opened with the press of a button from the driver's station. Closing these louvers can help protect from attacks coming in various forms, from molotov cocktails to autocannon shells. With the louvers closed and the armoured cover on, the radiator and engine access panel - the largest and most obvious parts of engine deck - can in fact become immune to hits from various aircraft cannonfire from low angles of attack. Examples include 20x110mm AP-I rounds from A-1 Skyraiders, the USAF's main ground attack plane in the early-mid stages of the Cold War, or 20x102mm AP-I rounds fired from AH-1 Cobras and in many fixed wing aircraft such as the F-4 Phantom and F-16, which may be used ad hoc for the close air support role, or 30x113mm AP-I rounds fired from modern-day AH-64 Apaches, or even 30x173mm AP-I shells fired from the mythical GAU-8 on an A-10.





The photo above shows the engine access panel and armoured cover hinged open. Note the spaced armour arrangement. Note the thickness. Since ground attack aircraft and attack helicopters almost never fly at high altitudes to deliver cannon attacks due to the risk of being seen and shot down, the armour is more than enough to deflect hits from all manner of cannon fire. A-10 pilots are trained to approach targets at an angle of attack of around 3 degrees from treetop level. Reducing the obliquity by a few more degrees will not change the fact that the engine deck is too thickly armoured to be affected even by shelling from 30mm DU rounds.




TRANSMISSION



The T-72 uses a hydraulically assisted mechanical syncromesh transmission with dual planetary gearboxes and dual planetary final drives, a type of transmission that is known as a dual transmission system. This type of transmission is principally the same as one from the T-54, but better, of course. It is highly compact, rock solid, extremely reliable (practically unbreakable), and also quite precise, meaning that the driver can direct the tank between obstacles more easilyThere are seven forward gears and one reverse gear. The brakes are of a disk type, hydraulically operated. The T-72 is capable of neutral steering, but it can only turn on a false pivot, meaning that to turn the tank on the spot, one of the two tracks are locked in place while the other drives the tank around it. This system of neutral steering is mechanically simple, but inferior to a true pivot-type steering system where both of the tracks receive power, and one of the tracks is run at the desired speed while the other is run slightly slower in the opposite direction. Besides being slower, false pivot steering creates a huge amount of friction and places more strain on the inactive track, leading to a quicker gradual weakening of the track and a slightly shorter lifespan. As such, it is common practice to release the built-up tension in the track by letting the tank lurch forwards periodically during the turn.

The steering tillers (or levers) are hydraulically assisted, so that steering the T-72 is very light and easy even for an inexperienced driver. The synchromesh gearing system enables the driver to steer the tank smoother than on a  T-54 when he pulls on either one of the tillers, as the changing of gear ratios in the gearbox is smoother with a synchromesh system than with a typical constant mesh system. The synchromesh system is also less harsh on the gears, thus increasing the lifespan on the gearboxes. Driving the T-72 is a very pleasant experience, according to people with firsthand experience. One of the reasons besides the steering system is the low center of gravity of the tank itself. Being so low-slung, turning the tank simply feels better; after all, a double decker bus doesn't turn quite like a lowrider.

Nevertheless, the tiller system is inherently less ergonomic than a steering bar or wheel. The only advantage of the tiller system over the more complex steering bar system is that it is much easier and cheaper to manufacture, and also more durable - durability being a key factor in the decision to stick with tillers. It is no coincidence that the powertrain of the T-72 has a legendary reputation for reliability.


A little-known fact is that with the mud guards on, it is true that the T-72 can only climb vertical obstacles measuring around 0.85m in height. When they are removed, however, the T-72 can scale obstacles at least as tall as 1.2m (already taller than the tracks) or more. The GIF below shows the tank literally climbing straight up a concrete wall.  



(From 1992-1994 Swedish trials in Northern Norrland). Video credit goes to Ren Hanxue from the Swedish Tank Archives blog.



AUXILIARY POWER UNIT

  The T-72 can mount an APU, but only the command variants have one. The T-72AK and T-72BK were both equipped with an AB-1 petrol generator, producing 1kW.  


SUSPENSION


The T-72 uses full-length torsion bar suspension. Each wheel has its own torsion bar, which runs across the hull floor and to the other end of the hull. The front two torsion bar-wheel hub interfaces have reinforced bolts, since the T-72 is slightly front heavy and so they will bear the brunt of the tank's weight during forward movement, especially across pot-holed ground.


There are six 750mm roadwheels with three return rollers per each side. The roadwheels are die-cast aluminium alloy, with thick rubberized rims. The wheels weigh 180kg each. The T-72 Ural used an 8-spoked wheel design, but all subsequent models used a 6-spoked wheel.

The first, second and sixth roadwheel on both sides are augmented with hydraulic shock absorbers. The front two shock absorbers are highly beneficial as the tank crosses rough terrain, while the rearmost shock absorber is intended to assist recovery when driving through dips and bumps. This is necessitated by the tank's nose heaviness and forward momentum, which puts great strain on the front two roadwheels, particularly when driving cross-country.





 
The T-72 first came with single-pin RMSh tracks measuring 580mm in width. These tracks have rubber bushings that help reduce vibrations and thus, reduce wear and tear as well as noise levels (though still relatively high). A full set weighs just over 1700 kg.




Old drive sprocket

Newer UMSh dual-pin tracks are available, also measuring 580mm in width. Usage of the newer tracks requires modified drive sprockets to be installed. Thus, only the newer modifications of the T-72 have this installed, like the T-72B3, though many of the late production T-72B models have it as well. The main attraction of this track is the ability to install asphalt-friendly rubber pads, and the higher durability. These tracks are less noisy as well. This is a benefit to the stealthiness of the vehicle as well as to the comfort of the crew. An entire set weighs just a hair under 1800kg.




New tracks and new drive sprocket



Rubber pads installed (Photo credit: Vitaly Kuzmin)

There is a simple mud scraper bolted on to the side wall, just above the drive sprocket. It helps to prevent loss of traction from excess soil on the tracks, especially sticky mud.





Removing rubber pads on T-90
Throughout the T-72's evolution, it has "fattened up" somewhat, gaining the most weight in the T-72B upgrade. While the T-72 Ural and T-72A both weighed 41 and 41.5 tons respectively, the T-72B tipped the scales at 44.5 tons. The T-72BM weighs 46 tons thanks to its Kontakt-5 package, and Kontakt-1 adds around 1.2 tons.

The T-72 Ural and T-72A exerted 0.83kg/sq.cm of ground pressure, while the T-72B, being heavier for the thick bulging armour array inserts, put in 0.898kg/sq.cm of pressure. Compared to its immediate foreign counterparts, the T-72 had little to no advantage in soft terrain, despite being a great deal lighter than all of its adversaries. Against the Chieftain, Leopard 1 and M60A1 of its era, the T-72 Ural and T-72A fared slightly better in this respect, but the T-72B was neither better nor worse off than its more modern challengers like the Leopard 2, Challenger 1, M60A3 and the M1 Abrams. The weight discrepancy doesn't manifest in this regard, but it suddenly becomes apparent when we consider the infrastructure of Eastern Europe at the time, especially the bridges - both permanent and temporary ones - that a huge advantage lays in the fact that the T-72 remains light enough to cross many of the more modest bridges as well as light enough to be compatible with the weight limit of the old MTU-55 bridge layers and TMM truck-based bridge layers, both of which were and still are present in huge numbers in the Russian Army Engineers.  

If the T-72 were to be trapped in swamps, bogs or in extremely deep snow, it may escape with the help of the eponymous log.






By tying the log to track pins on both right and left tracks as illustrated below, the tracks will drag the log along and under them, thus forcing that section of the track to rise above the mud while simultaneously giving the track something more solid to drive over. This allows the tank to get out of the hairiest situations.
 
 



Here is a short video of a BMP demonstrating the use of a log during a show:







WATER OBSTACLES

The T-72 has exemplary water crossing capabilities. Safe fording depths are usually cited to be 1.2m, but water obstacles measuring up to 1.8m deep may be forded for short distances if necessary. Doing so will require the air intakes to be shut off, since the water level would be above the hull. With the installation of the proprietary OPVT snorkel, fording up to a depth of 5m is possible.  Pre-fording preparations are necessary in order to do so, requiring the edges of all hatches and the openings of various equipments and periscopes to be coated with a thick resinous waterproofing paste beforehand, as the water pressure at such depths is simply too much for rubber seals to handle. 


The driver must then reset the fuel pump which doubles as a bilge pump. It is located to his lower left side. 

The snorkel "breathes" for all three occupants. It is installed on the gunner's hatch, through a circular porthole, visible in this picture:



  Because the hatch can be simply swung open, installing the snorkel is not difficult. The snorkel comes with two floating markers to indicate the tank's position underwater to help rescue teams locate the tank if it has stopped underwater.


 
Preparing for underwater driving in an exercise


Also, the exhaust port must be replaced with a special valve bank to prevent water from entering into the exhaust manifolds.




T-72s equipped with the V-92S2 or V-92SF engines must use different valve units.


Crew members are each given a closed-circuit IP-5 rebreather for emergency use. It comprises a watertight, form fitting gas mask, a chemical respirator chamber containing potassium superoxide (KO2), and a flotation collar. The rebreather uses the chemical reaction between potassium superoxide and carbon dioxide, activated by water from the user's breath reduce the former two to oxygen and potassium carbonate. The freshly produced oxygen gas is mixed into the previously exhaled breath to replenish its oxygen concentration for rebreathing. The crew usually puts the IP-5 on before entering water as a precautionary measure.


IP-5


ROAD ENDURANCE


All T-72 variants have a total internal fuel capacity of 705 liters, spread across several fuel cells. Two tanks are located on the forward hull on either side of the driver. Another conformal fuel tank is located directly behind the right frontal fuel tank. It also doubles as ammunition racks, and so does the conformal fuel tank directly behind the autoloader, which holds 12 propellant charges. Another 495 liters of fuel is stored in conformal fuel cells located externally on the starboard side fender. The total fuel capacity is 1200 liters.





As you can see in the diagram above, the external and internal fuel systems are not interconnected. They each have their own separate fuel lines, but both connect to the same fuel pump.

Being entirely separated from each other, the driver-mechanic is able to shut off and isolate the internal and external fuel tanks from his station. Isolated fuel tanks will be disconnected from both the fuel pump and the fuel return lines, so the fuel within the tank will be left to sit. This can be beneficial in some circumstances, such as when there is an imminent threat of an internal fire spreading. By shutting off all of the internal fuel tanks, the fuel will not leak out as energetically as it is no longer being drawn by the fuel pump, or maybe even stop leaking entirely, depending on the specific location of the damage to the tanks. It is also possible for the driver to shut off all internal fuel tanks, and rely on external fuel only if the situation allows it. This creates the possibility of filling the internal fuel tanks with water, and since the majority of the volatile propellant charges are stowed in conformal fuel tanks, they can become ad hoc wet stowage racks for increased safety. 




The two externally mounted auxiliary fuel drums each have a 200-liter capacity. These connect directly to the fuel system, and both can be disconnected by the driver at the same time by the push of a button.


  The auxiliary fuel tank holders are hinged, and may be folded flush to the hull rear. 

The T-72 Ural can travel 480km on internal fuel alone, or 700km with external fuel tanks. Thanks to improvements in fuel efficiency on the T-72B3, it can travel 550km on internal fuel alone, or 800km with external fuel tanks despite having the same fuel capacity. As with all automobiles, fuel efficiency decreases while driving cross-country. The amount of engine power needed increases as the harshness of the terrain increases, and so does fuel consumption. 
  
Because of the T-72's relatively large fuel capacity and high fuel efficiency, refueling the T-72 isn't even necessary for short continuous operations (lasting no more than 3 days), and this greatly eases the logistical burden on the frontlines.


DRIVER MECHANIC'S STATION


According to user testimonies compiled by the author, the driver's station can be definitively said to be the most comfortable place to be in the T-72. The has approximately 80cm of shoulder space, which is plenty, and the length of the station is enough to let someone more than six feet tall to operate the pedals with a comfortable allotment of legroom. When driving, the driver must hunch slightly forward in order to operate the steering levers, step on the pedals and look through the periscope at the same time. Referring once again to this diagram from "Human Factors and Scientific Progress in Tank Building" by M.N. Tikhonov and I.D. Kudrin as provided by Peter Samsonov, we can see that the driver of a T-72 gets 0.864 cubic meters of space. That's more than the 0.621 cubic meters afforded to the driver of a T-55.

  
 


The driver is provided with a single forward-facing TNPO-168V periscope to facilitate driving. It is a very wide periscope (wider than the driver's head) with a binocular field of view of 38 degrees, and a total field of view of 138 degrees. The periscope provides 31 degrees of vision vertically - 15 below the horizontal axis and 16 above. The view from the TNPO-168V is superb (reportedly). Szabó István, a non-military person with extensive experience driving demilitarized Hungarian tanks, described the TNPO-168V periscope as "so wide that it looks like a small window from inside! Forward visibility is excellent for such a periscope! No complaints there.". Like all the other periscopes on the T-72, the TNPO-168V is heated through the RTC heater system.



View through the TNPO-168V

When not in use, the TNPO-168V periscope is stowed away in its aluminium tin.



 



For night time driving, the driver is provided with a TVNE-4B passive-active binocular periscope.  It is typically kept in its aluminium box and stowed away by the driver until necessary.





It can be directly inserted into the periscope slot without any modifications. Because of its binocular design, it has a horizontal field of view of 36 degrees and a vertical field of view of 33 degrees. It has a 60 meter view range in the active mode using the hull's single small IR headlight only (it may also pick up infrared light from the turret's three IR spotlights), or 120m in the passive mode under lighting conditions no darker than 0.005 lux (moonless, starlit night). It has 1x magnification.


This video shows how good the nightvision is:





Here is a screenshot from the video:





It seems to be more than adequate for nighttime driving. It appears that the quoted viewing distance of 60 meters is accurate.



There is also an accessory windshield that may be attached to the outside of the hatch. Its main purpose is to protect the driver from bugs and dust while driving in non combat conditions.





It is not unique to the T-72 in any way. Many other Soviet vehicles can mount these windshields.





The driver enters through a pill-shaped hatch. Two TNPA-65A viewing prisms are embedded in it, one looking in the 10 o'clock and the other in the 1 o'clock direction. Looking through them requires the driver to look upwards. This layout is generally far less convenient than the more commonly encountered bank of three viewing prisms found on the T-80 and Abrams as well as most others. The TNPA-65A periscopes are very narrow, almost slit-like. It is difficult to see very much other than the tracks and part of the road, but it would also be very hard to hit or damage them with machine gun fire. The TNPA-65A periscopes are meant to check the corners of the tank only. They are far too limited for driving during combat.






As mentioned before, the TNPA-65A periscope provides 14 degrees of binocular vision horizontally, and only 6 degrees of vertical vision.






The driver's hatch itself is 20mm thick. The rubber seals make them completely watertight down till a depth of around 1 or 2 (relative to the height of the hatch, not the turret roof). Unfortunately, the seals on the TNPO-168V periscope are not nearly as dependable. Being mostly watertight, the tank can ford streams as deep as 1.2m or deeper without the danger of excessive water ingress.

Steering the tank requires the use of two hydraulically assisted tillers, which are located on either side of the knees of the driver. Though the tiller steering system can be considered one of the more antiquated aspects of the T-72, it's worth noting that many of its rivals like the AMX-30, Chieftain and Challenger used the same system as well. However, most main battle tanks had already grown out of tillers and progressed into steering wheels even by the 1960s, like the M60 and Leopard 1 did. The Leclerc and Leopard 2 both use steering wheels and the Abrams tank uses motorcycle handlebars. The only exception is the Challenger 2, which (shockingly) still retains a tiller system as well.

The driver's throne is rather modest, but homely. It can be adjusted for height in order to accommodate persons of a wider range of height. When raised to its fullest, the driver is able to peek out of the hatch and drive with his full range of vision. It has been reported to the author that the driver of a T-72 gets quite a lot of legroom, and that it is quite comfortable, more so even than the commander's and gunner's stations.



Like the commander and gunner, the driver's "air conditioning" comes in the form of a small rubber fan.


All of the driving-related indicator gauges are placed on a board to the driver's left. The placement isn't exactly convenient, but looking at them while driving (in any tank) isn't really very necessary anyway.





Behind is the left front hull fuel tank. The fire extinguishers for the hull's automated firefighting system is located underneath it. 

Over at his left foot there is a rather rudimentary GPK-59 gyroscopic compass for directional navigation. It is particularly useful when driving underwater when nobody in the tank has any scenery to refer to for a sense of direction. The use of gyrocompasses can perhaps be labeled as a rudimentary form of an Inertial Navigation System (INS), advanced versions of which are often present in modern combat vehicles due to their independence from outside input contrary to a GPS-based navigation system. Sadly, the T-72 has not received either in any of its iterations.






REFERENCES

http://www.tank-net.com/forums/index.php?showtopic=14200&page=192

http://btvt.narod.ru/4/t-72.htm

http://topwar.ru/31292-sovetskie-bops-dlya-orudiy-semeystva-2a46.html

http://www.zavod9.com/?pid=10106 

http://www.kotsch88.de/l_t-72.htm

http://u-96.livejournal.com/1638297.html?thread=31413145

http://ofbindia.gov.in/products/data/ammunition/lc/25.htm

http://www.niistali.ru/security/2010-07-05-08-58-15?start=1

http://www.wk2ammo.com/showthread.php?7666-125mm-BK-14M-HEAT-for-2A46-125mm-smooth-bore-gun-Russia

http://btvt.narod.ru/raznoe/dz_2014/dz_2014.htm

http://chtz-uraltrac.com/articles/categories/37.php

http://www.optics-nj.cz/en/tanks.html

http://www.niistali.ru/en/about-nii-stali/major-milestones.php

http://www.yarz.ru/prod_r168-5un2ee.html

http://www.rbs.ru/vttv/99/firms/kotplast/e-index.htm

http://www.geo-army.ge/index.php?option=com_content&view=article&id=372%3A2012-04-26-09-32-02&catid=51%3A2012-03-25-05-57-06&lang=ka

http://www.photopribor.ck.ua/en/products/defense/equipment_for_armored_vehicles_control_systems/1k13_sighting_and_guidance_device/

https://www.youtube.com/watch?v=jU_-DntBBIQ

http://www.kotsch88.de/m_125_mm_d-81.htm

http://www.coeindia.com/products.php#head_lights

http://bulcomersks.com/index.php/ct-menu-item-4/ct-menu-item-12/50-ammunition-components/fuzes/514-fuze-v-429e

http://morozovkmdb.com/eng/body/t72msavan15.php

http://catalog.use.kiev.ua/index.php?page=catalog&view=category&cat_id=38

http://www.sklep.militariaanhol.pl/en/spare-parts/171-temperature-sensor-td-1.html

http://en.npoelm.ru/products-eng/specialproducts-eng/raduga-eng/td-1-eng/


http://www.excaliburarmy.com/en/t-72-parts?from=0#fotky

http://andrei-bt.livejournal.com/170864.html

http://www.russianarms.ru/forum/index.php/board,1064.25.html

http://forum.splav.ru/index.php?/topic/3141-%D1%80%D0%BE%D1%81%D1%81%D0%B8%D0%B9%D1%81%D0%BA%D0%B0%D1%8F-%D0%B0%D1%80%D0%BC%D0%B8%D1%8F-%D0%B2-%D1%84%D0%BE%D1%82%D0%BE%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%8F%D1%85/

http://ser-sarajkin.narod2.ru/ALL_OUT/TiVOut13/IT-1_New/IT-1_New002.htm

http://zhurnalko.net/=weapon/tankomaster/tankomaster-Special-T-80--num36

http://coollib.com/b/271581/read



Bibliography

T-72 Main Battle Tank 1974-93 by Steven Zaloga, Peter Sarson



24 comments:

  1. Excellent article. It makes me wonder what the Russians have in the T-14.

    ReplyDelete
    Replies
    1. Please notify me if there are any errors in the article. I've been very busy for the past few months, so I haven't really had the time to proofread the article before I posted it. I am constantly updating, but I don't think I've gotten rid of half of the mistakes in there.

      Delete
    2. I have checked everything so far but have not seen anything wrong yet.

      Delete
  2. I just did a brief writeup on the T-14 you may find of interest: http://www.battleswarmblog.com/?p=24451

    ReplyDelete
  3. Hello Tiles,

    I am asking something that has been on my mind for a while but constantly forget to ask. On the section regarding the T-72B's armor protection on the first image of the destroyed T-72 where do I exactly look to see the spaced armor array?

    Secondly on the section regarding how Soviet Bulging Armor on the two images comparing Forward and Backward moving plates seems mixed up. I think your description is good but it seems to conflict with the labeled images. Are the images wrong or are your descriptions wrong?

    BTW I hope your search for someone to take over the blog goes well. :)

    ReplyDelete
    Replies
    1. Hi!

      Well, let's just say that the "ramp" that the burned-out chassis is on isn't really a ramp. Notice the thing at the guy holding the RPG's feet - that's the front hull armour ripped right off from an ammo explosion. Notice the idler wheel socket.

      No, that's how the research papers I've read describe them. Backwards means moving in a direction opposing the cumulative jet, meaning accelerating towards it. Forwards means accelerating in the same direction as the cumulative jet. It is viewed from the cumulative jet's perspective.

      Thanks. But even that's not going that well. I've got one guy who seems willing, but I always forget to chat him up. I've got an even bigger workload now, and this blog project is very, very low on my priority list. However, having seen the overwhelmingly positive feedback from readers, I try to update my existing articles as often as I can, and maybe add a few paragraphs to the ones that are still on-the-way. I've got 18 article drafts, and most of them are half-finished. Maybe in September I'll binge upload 5 or 6 of them :)

      Delete
    2. Ah. It all makes sense now. My bad. :(

      Your work is excellent and I wish you well. We will be waiting patiently for more.

      Delete
  4. This comment has been removed by the author.

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  5. Did Algeria modernize its T-72s to the T-72M1M standard?

    ReplyDelete
    Replies
    1. As far as I know, they did not. Algeria did receive a number of Relikt kits (some 44 going off of memory), some of which have been fitted to in-service T-72M1's.

      Hope this answers your question.

      Delete
  6. This is a fantastic article. You should write a book!

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  7. This comment has been removed by a blog administrator.

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  8. Good article but I couldn't help feeling that there was some bias towards the t72 in this article. Where are the pictures of the burn out t72s, the section on the weaknesses versus the strengths of the vehicle etc.? I feel like the problematic nature of the ammunition placement deserves more coverage here

    ReplyDelete
    Replies
    1. I agree that there is bias, but maybe we should call it "positive bias"? Do the facts not corroborate the position which I have adopted in describing the tank? The ammunition placement, in my opinion, is no better and no worse than what many other tanks have, and I have been very consistent on this point for a long time. I hereby quote myself from one of the many, many debates I've had over this issue: "

      "If an M1 Abrams had its front turret armour penetrated with a significant overmatch, the penetrator would continue onwards and penetrate the bustle blast door and hit the ammunition. We get ammo deflagration, and a hole in the bustle to vent it all into the crew compartment. Let us also not forget the rather less well protected container in the hull, which lacks a blow-off feature, and is usually kept stocked full of ammo (according to the testimonies of tank veterans of ODS, OIF, etc). So we see, a frontal armour perforation with significant overmatch will result in catastrophic destruction. BUT... How likely is it that you could defeat the front turret armour so handily as so produce such a result? Nearly nil, unless we have 2016 technology to match up to the 1992 technology of the M1A2.
      Do you not agree that this is directly analogous to the situation for the T-72? As long as the frontal hull armour remains unpenetrated, the ammunition will never be at risk of detonation, and for a period of more than a decade, the T-64 and T-72 (they had identical hull armour for the better part of their existence) were as immune to 105mm APDS as the M1A2's turret is immune to all anti-tank weapons of the present. Very, very immune. I recall the case of the Greek Leopard 2A5 that sustained 30 hits to its front turret from DM53 APFSDS rounds fired from its own cannon, with only 27 armour perforations. As long as the frontal armour holds up, the issue of ammo detonation is irrelevant." -cont.

      Delete
    2. -cont. "'Ah,' you say, 'but the distance between the frontal turret armour and the blast doors at the bustle may well be considered an extra layer of defence as spaced armour!'. True enough. However, that's still a form of armour, and so the anti-spitting-flames-into the-crew-compartment mechanism remains solely reliant on the ability of the *armour protection* to prevent ammunition from reaching the ammunition.
      The validity of the protection offered by separated ammunition with blow off panels in the event of a side hit is indisputable. However, it is not as clear cut as that. A hit to the side of the turret that enters the crew compartment kills the crew. A hit to the bustle area of the side turret detonates the ammuition, but spares the crew. Knowing this, your average RPG-wielder would obviously aim for the center of the turret profile, which is invariably the natural point of aim for any assailant anyway, be they a tank, a plane or a helicopter - they'd aim for center mass, and a hit to the center of the turrets of both the T-72 and Abrams will result in the death of the denizens within. A hit to the hull produces the same effect for both tanks, which is catastrophic destruction. Neither have blow-off ammo compartmentalization in the hull. The point is that the T-72 doesn't have bustle ammunition, and only has hull ammunition, whereas the Abrams has both, so the chances of losing all of its ammunition in a single stroke is twice higher, while its survivability in the event of a hull penetration is not higher (if we assume that penetration begets ammo detonation with 100% consistency).
      As to the question of storing ammunition in recesses in the fuel tanks is not a straightforward one. Fuel burns, any idiot could tell you that. However, unless burnt in open air or in a closed container but in the presence of oxygen, fuel could actually extinguish fires. If an RPG round detonated against the sideskirt and had enough residual penetration to defeat the side armour, continued into the fuel cells, and hit the ammunition, the fuel would rush into the hole made in the propellant charge or warhead. The fuel that starts burning due to air rushing in from the hole in the side armour would also leak out from the side armour and burn outside the tank. In short, this is wet stowage. Of course, this only works if there wasn't much residual penetration to speak of, but then, if there was that much energy post penetration, ammo ignition via burning fuel would not happen, simply because the ammunition would detonate admirably without the help of flaming diesel anyway."

      Delete
    3. Richard Turner,
      I totally desagree. I am a military historian and former profesional soldier and I have served on the Leopard-2. This article about the T-72 is by far the most objective, solid and truth worthy I ever had the pleasure to read. In the military world we need much more propaganda-free and objective articles about military equipment. The T-72 for exmple has always been a big victim of western propaganda that on purpose lied about relevant facts about this tank. Here in the west we always tend to subestimate the russian equipment and in the wrong situation it can get you killed.

      By the way a Leopard-2 or a Abrams also stores ammunition in the chasis, if this ammunition gets hit it easily can kill the entire tripulation and even blow off the turret as well, but I agree that this is easier to happen in a T-72 compared to a tank that has stored the ammo in the same place instead of all over the compartment.

      Delete
    4. This article is not objective by far but thanks for your comment. Ill write a response to tiles later there are certain things he said that I both agree and disagree with

      Delete
  9. Check those photos you used on T-72A.....you have to have a clear idea about which is A and which is M/M1....

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    Replies
    1. Well, in the context in which those photos were used, it is irrelevant if they were M1s or As...

      Delete
  10. A fascinating account, thank you! A question though: the frontal fuel cells acting as side armor for the driver. I would have thought diesel fuel would be touched off by a penetrating HEAT jet?

    ReplyDelete
    Replies
    1. Thank you for reading!

      Yes, definitely. However, that hardly matters if the jet failed to penetrate all the way through, as the fire would be contained inside the fuel tank. Burning fuel shall leak out the outside of the hull instead. Alternatively, it is possible for there to be no fire at all, but this will only be possible if the fuel tank was near full capacity, so that there would be no air at all in the tank, and any little flame will be smothered by the fuel. It is also possible that the environment inside the fuel tank simply lacked the correct stoichiometric ratio of fuel and oxygen to ignite properly. Case 2 is what we are interested in, as fuel is only worth anything as armour if it contacts the penetrating elements. I hope that this adequately explains it.

      Delete
  11. All i can say is that thank you for this marvelous detailed article regarding T-72!

    ReplyDelete
  12. This comment has been removed by the author.

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  13. "Equipped with Kontakt-5, a late model T-72B, most likely the obr. 1989 model, has successfully resisted a TOW-2 missile hit to the upper glacis plate."

    Any idea if the contemporary 1985-1989 M1A1 and Leopard2A4 can withstand the tow 2?

    ReplyDelete