More often than not, the Soviet military industry had been plagued by lackluster technological capabilities in some fields. This was especially true immediately after the end of the war. Some factories were short of qualified personnel, worsening the quality of the tanks they built. Nizhny Tagil, for instance, was almost totally devoid of experienced and qualified staff after the war ended, as most of the Kharkov Design Bureau workers and engineers had decided to return to their headquarters in Kharkov in Soviet Ukraine once the war was over.
However, the poor quality of the products from some tank and tank component factories quickly became the exception, rather than the rule. The tenacious pursuit of mass production that practically halted the implementation of new and unproven technologies during the war fell away with the capture of Berlin, galvanizing the continuation of pre-war innovation that had led to the USSR having the best tank in the world at the start of Operation Barbarossa.
The T-54 is history's most enduring tank. Dozens of variants of the basic model have been produced, most of them used by the Red Army. As usual, we will only be covering the models used in the USSR but not abroad. We will be examining the most relevant variants of the T-54 except the models designed to fulfill supporting roles like firefighting and bridge laying.
There were a few prototype models, but the only one that made it to low rate production and small scale issuance was the T-54 obr. 1947, also known as the T-54-1. T-54-1 was first deployed to units in the Belorussian military district for crew familiarization and exercises, and it was there that a myriad of design flaws were discovered. As they were unfit for frontline use, most, if not all T-54-1s were relegated to reserves or storage soon after its more evolved brothers appeared. In the mid 60's, many T-54-1s and T-54-2s were taken apart and their turrets used as static pillboxes along the Chinese border and as coastal defence guns in the Far East.
Here are T-54-1 turrets installed on reinforced concrete pillboxes for coastal defence.
And here are T-54-2 turrets, one used for coastal defence as well and one used for land bound threats.
The T-54 is a descendant of the legendary but obsolescent T-34, but after revision after revision, the relationship had become largely historical by the 50's. On the technical side, there is very little in common between the T-34 and the T-54 save that they both share roadwheels of the same diameter and the same track pin retention system (T-34-85s held in reverse were later modernized with T-54 roadwheels in the 50's and 60's), and the same method of engine cooling.
Smaller, yet roomier. The T-54 is as good of an evidence of its ingenious design as it is of the inefficient one of the T-34. There is a plethora of good reading and viewing material available on paper and online, so if a historical breakdown is in order, I would recommend other sites. What this site does is take it all apart, so lets see what the T-54 is made of!
First thing to get out of the way - the T-54 has a turret ring diameter of 1.825 meters, and in all incarnations of the turret, the actual wall of the turret extends quite far away from the turret ring, so that there is actually a shallow shelf between the turret ring and the turret wall. The shelf space is taken up by the radio and control boxes, thus making up for the lack of a bustle. By right, the amount of room available in a T-54 turret should be at least comparable to a tank like, say, the Centurion MK. 2 and all subsequent models, which had a 1.88 m turret ring but no turret ring shelf and no bustle, but as we know from actual comparison, that is not the case, and this is at least partially due to the rather large D-10T gun.
The T-54 turret is significantly wider than the turret of an M46, which had a turret ring of only 1.75 m in diameter, and comparable with the M47, which had a turret ring that measures 1.85 m in diameter. A comparison between these tanks is fitting because they all have a similar needle-nose ballistic shaping with sloped turret sides, unlike the Centurion, which lacks slope on any facet of its turret. All of these tanks had rather narrow turret rings compared to the M48, as that had a 2.16-meter diameter turret ring. In a comparison between the T-54 and its closest counterpart, the M48, the T-54 definitely loses out in the amount of internal space available to the crew.
The low, sloping roof and the sloped front of the turret is excellent for armour protection, but it is not so conducive for the crew. With a maximum ceiling height of only 1.6 m, it was not possible for any of the crew members to stand upright in the turret unless they were especially short. For just sitting around, though, the turret is tall enough. From that perspective, the T-54 is directly comparable to the M26 Pershing and M46 Patton.
Although the tank is very cramped, the designers were not so sadistic as to purposely neglect the crew. The commander not only gets a perfectly decent padded seat with a padded backrest, but there is also a padded headrest. Unfortunately, the backrest is rather oddly curved, so that if the commander leaned into it, he would have to be slightly contorted sideways.
The shoulder guard isolates the commander from the big cannon right next to him, but the effect is that he has hardly any horizontal room at all. Thankfully, it is possible to remove the arm guard. This gives the commander some much needed breathing space, but this can only be done in non-combat situations, for obvious reasons. This is also done to enable the commander to move to the loader's station, or vice versa, but to do that, the deflector shield around the cannon must first be folded down as well, as seen in the photo below.
The commander and the loader can sidle over to each others' positions with relative ease once the deflector shield is folded down, although the keyword here is "relative". Furthermore, the commander's seat can be folded up for better access to equipment located below the turret ring and for maintenance and stowage purposes.
The commander gets a better deal than the gunner, who does not have a real backrest. The commander has a footrest but practically no legroom, so he must wrap his legs around the gunner. The advantage is that it is easy to nudge the gunner and give him quick orders. The disadvantage is that it quickly becomes very uncomfortable, especially in hot climates, but perhaps it would be the opposite in cold weather.
The commander has access to the turret traverse lock, which is located on the turret ring. Aside from that, he does not have any means of controlling the turret and weapons, as the T-54 does not have a commander's override system.
In 1955, all new production T-54s were equipped with the new R-113 radio transceiver set. A video of an R-113 radio in operation can be found here (link).
Inter-crew communication was done via their headsets and throat mikes, which were connected to the TPU-47 intercom system. The components of the intercom system can be seen on the wall of the turret at the left side of the photo below. The example below does not have a radio.
The commander's cupola is a ring of cast steel bolted onto the turret. The beveled external surface of the cupola provides excellent ballistic protection from machine gun fire, including heavy machine guns, but the main disadvantage of this style of cupola is that it limits the size of the commander's hatch. This cupola design stayed with the T-54 and all of its derivatives throughout its production lifetime.
The earliest production models of the T-54 obr. 1947 were very conspicuously descended from the WWII era-designed T-44 in many ways, including the sighting systems. Like in a T-44, the commander of a T-54 obr. 1947 was supplied with an MK. 4 periscope for general observation.
As MK. 4 is a direct vision periscope with no magnifying power whatsoever, the early T-54 obr. 1947 suffers from a bad case of short sightedness. Nevertheless, the independence of the periscope from the cupola gives the commander some extra breadth of view, and the little vertical freedom offered by the periscope is useful too, but the inadequacy of the MK. 4 meant that it was only ever a stopgap solution before the TPK-1 was ready for production.
TPK-1 came with the T-54 obr. 1949, and remained with the T-54 family for the next 9 years. It is an improvement over the old MK. 4 in long range viewing as it offers 2.5x magnification instead of nothing. A prismatic block above the binocular eyepieces duplicates the function of the MK. 4, giving the commander the luxury of both 1x and 2.5x magnification. For long distance viewing, TPK-1 is totally inadequate. Instead, the commander must rely on his personal 8x30 field binoculars, which are of superb quality, as most examples of this line of binoculars made in the USSR were built using tooling plundered from the German Zeiss-Jena factory at the climax of WWII.
What a pair of 8x30 field binoculars doesn't have, though, is a stadiametric rangefinder.
That, however, is not the biggest breakthrough from this new device. The special thing about the TPK-1 is that it could be used to designate targets for the gunner. This is done by simply aiming at the target and pressing the left thumb button. An electric signal is sent to the turret traverse motor, and by referring to a sensor attached to the cupola ring, the turret is automatically rotated to meet the target. Turret traverse will be conducted at maximum speed in order to open fire on the target as soon as possible. As the gun elevation mechanism lacked power controls, it was still up to the gunner to adjust in elevation. The commander does not need to hold the button to slew the turret all the way to the target. A single click will do. Holding the button will prompt the turret to slew to meet the target, and remain slaved to the periscope, thus allowing the commander to commandeer the turret, as its movement would then depend on the commander rotating his cupola. Small corrections made by rotating the cupola slightly will not cause the turret to jerk onto the new aiming point, even though turret traverse is done at maximum speed by default. This is because the traverse motor will need time to accelerate the turret to its maximum speed (due to inertia), so the turret will turn quite slowly if the arc of rotation is very small. The effect is that the commander can guide the gunner onto target quite gently if he turns the cupola slowly enough.
This arrangement can be described as a hunter-killer system, making the T-54 the first tank ever to implement such a system, followed by the Conqueror heavy tank in 1955. The commander of a T-54 is not provided with duplicated firing controls, so he cannot override the gunner completely, but this has little bearing on the definition of a hunter killer system.
The commander of an early issue T-54B was equipped with the TPKUB binocular periscope. The only difference between it and the much more common TPKU-2B was that it had only one handgrip as opposed to two. This new periscope is a step forward over the TPK-1 in many ways. Many older T-54 models were retrofitted with the TPKU-2B to bring it up to the same level of technology as the T-54B.
The sight has two modes of adjustable magnification of either 1x or 5x. Under 1x magnification, the field of view from the sight is 17.5 degrees. This is reduced to 7.5 degrees under 5x magnification. The general layout of the viewfinder and the reticle is the same as in previous periscopes. The viewing distance is improved by the higher magnification factor, but the rangefinding capabilities of the periscope are probably not improved at all. A report made available on tankandafvnews reveals some interesting information on the precision of rangefinding through the TPKU-2B; from the table in Page 64, the mean error in ranging tank-shaped screens, broadside tanks, oblique tanks (meaning: angled hull) and head-on tanks is 14.57%. The results of an analysis of the data were extremely counter-intuitive. Take a look:
Page 65 of the report mentions that the precision of rangefinding against hull-down tanks was surprisingly unaffected by the fact that half of the target was out of sight. The report does not say why, but we can conjecture that it is because stadia rangefinding is partly technique and partly guesswork. See for yourself:
I recommend reading the full report on tankandafvnews, as it is very enlightening. I will only give short comments, as the reports are self-explanatory and quite clearly framed.
The tests show that the commander is able to range the target in an average time of 3.3 seconds, and this section of the report concludes that the short time required to obtain a range estimate is unobtrusive to the loading and laying of the gun. This means that by the time the gunner has visually acquired the target, he will already know the range, and can open fire without delay.
Additionally, it must be noted the lack of stabilization in the rangefinders installed in the Patton series of tanks would have made it difficult to operate them while on the move, especially since they are fixed at a high magnification. The M17 rangefinder used in M60A1, for example, would have been next to useless if the tank was in motion over rough terrain since the rangefinder had a fixed 10x magnification, so the oscillations from the movement of the tank would cause too much jolting for the commander to keep the target focused. This means that the rangefinder is only useful when the tank is static, which is perfectly fine for the M60A1, as it was designed with NATO's defensive doctrine in mind. The T-54 lacks a dedicated rangefinder, but is an offensive tank designed around the Red Army's mobile "deep warfare" doctrine. A stadia rangefinder was probably the best choice as it was at least fast enough to be useful when firing from slow crawls or short halts. Therefore, optical rangefinders were understandably absent from Soviet medium and heavy tanks, but NOT from Soviet tank destroyers and assault guns. Case in point: the SU-122-54 and the experimental Obyekt. 268 both had stereoscopic rangefinders installed on the commander's cupola. Optical rangefinders only found their way into Soviet tanks with the advent of the T-64 main battle tank; the first tank to have an independently stabilized primary gunsight, and also the first tank to have an integrated optical coincidence rangefinder installed in said gunsight.
Like the TPK-1, the TPKU-2B has a target designation function. The target designation system is a rather simple one; A direction sensor is installed in the 5 o'clock position of the cupola. The direction sensor consists of a roller placed in permanent contact with the cupola race ring, a cam attached to the roller and two switches. The roller is recessed into a notch in the cupola race ring when the cupola is turned to the 0 o'clock position relative to the turret. When the cupola is turned to the right, the motion of the cupola race ring dislodges the roller from the notch and causes the roller to be deflected to the left by friction. The cam attached to the roller also rotates left, causing it to touch the switch on the right (see diagram on the top right, below). The right switch triggers the turret rotation motor to turn the turret to the right until the roller returns to the notch, which would mean that the gun is now facing the same direction as the commander's cupola. The same mechanism is repeated in reverse when the cupola turns to the left. Since the direction sensor is composed of two switches which can only be either on or off, the command to initiate turret rotation is binary. This means that the turret is either turning, or it is not. For that reason, the turret always rotates at maximum speed when the target designation system is activated.
The binary system also does not allow the commander to precisely lay the gun on target, because precision gun laying is done at the minimum turret rotation speed, which would be 0.07 degrees per second in the case of the T-55. Potentiometers would be needed in order to have a variable speed of turret rotation. However, as mentioned before, small corrections made by rotating the cupola slightly will not cause the turret to jerk onto the new aiming point, even though turret traverse is done at maximum speed by default. This is because the somewhat underpowered traverse motor will need time to accelerate the turret to its maximum speed. There is no vertical deflection sensor attached to the TPKU-2B periscope, so it is not possible for the commander to raise the cannon onto the target from his station.
As the day sights lacked any provisions for nighttime use, it was necessary to swap out the sights for the TKN-1 before commencing night operations. TKN-1 was introduced in 1951 for the T-54 obr. 1951, and continued to be used on the T-54A, T-54B, and later on in the T-55 as the TKN-1S, for the lack of a better alternative.
TKN-1 has a fixed 2.75x magnification, making it unsuitable for long range observation. TKN-1 fits in the same slot as the TPKU-2B. Older model T-54s can also use TKN-1.
Besides the usual active infrared imaging capability, the TKN-1 also sports a 1st generation image intensifier module. It is not particularly powerful. The power cable connecting the periscope to the tank's electrical system can be seen on the left side of the periscope, as seen in the photos below (Photo credit to ancientpieces from ebay). The power cable supplies power to the transformer housed in the box on top of the eyepiece, and another cable runs from the transformer to the image intensifier installed inside the optic.
Using the OU-3 in the active infrared mode will enable the commander to identify tank-type targets at a distance of only 400 meters. TKN-1 is best suited for spotting enemy tanks using IR equipment, for following the tracer of cannon shells, and for observing the fall and impact of shots.
Like the TPKU-2B, the TKN-1 can be used to designate targets by pressing the left thumb button. On the right handgrip is a thumb button to activate the OU-3 infrared searchlight on the cupola. It is not only possible for the sight to be turned to the active infrared imaging mode without turning on the searchlight, it is highly recommended. If enemy tanks have infrared searchlights as well, then the commander will be able to spot them easily without needing to turn on his own, thus remaining hidden.
Ventilation in the earlier T-54 models like the T-54-1 up til the T-54B was facilitated by a dome shaped ventilator fan installed in the roof, just in front of the loader's hatch. As you can see in the picture below (screenshot taken from this video), the dome is made from a thick piece of cast steel and welded to the turret. The heavy steel walls of the dome and the good sloping enables the dome to shrug off machine gun rounds and artillery fragments.
Here is an airflow diagram of the T-54-1. The air intake in the hull is an auxiliary respirator for the engine. It is not activated unless all of the louvers on the engine deck, including the one for the engine air intakes, are sealed to protect from air attack or napalm attack.
Here is an equivalent diagram for the T-54 obr. 1951 and the T-55. To be honest, I'm not entirely sure what the diagram for the T-55 is supposed to show. It seems that the ventilation for the fighting compartment in the T-55 is provided by drawing air from the engine air intakes, where filtration occurs.
If you have watched Nicholas "The Chieftain" Moran's "Inside the Chieftain's Hatch" episode on the T-55A, you will catch him mentioning that there is "a cylinder of some sort which overhangs the turret platform" as he sits in the commander's seat.
This cylinder is the heater for the fighting compartment. The tank does not feature any air conditioning or any circulation aids, like fans or air blowers, so it is easy to see that the T-54 is better suited for chilly or cold climates than hot climates. The heater had to be moved slightly when a rotating floor was introduced in the T-54B, in order to increase the diameter of the rotating floor (which is quite narrow. It does not reach the walls of the sides of the hull)
On a side note, it seems rather improbable that the loader or anybody else will get his leg ripped off by the heater. It overhangs the rotating floor by only an inch or two, and the loader will often be working with ammunition from the hull, so he should be very much aware of anything that might be dangerous.
Besides the general crampedness of the tank, a minor weakness of the T-54 is the scarcity of storage space. Besides the containers on the hull sponson fenders for storing tools and spare parts, there is no dedicated container for the personal effects of the crew. The abundance of external handrails and hooks for camouflage netting made it convenient for the crew to secure their canvas bags around the circumference of the turret (this is standard procedure taught to recruits), but it is not as convenient nor as secure as having proper stowage bins. One of the most common modifications of exported T-54s is the addition of external baskets for stowage.
The handrails (two large ones on either side of the turret, and two small ones at the base of the rear of the turret. See photo above) make for great footholds to help the crew mount the turret.
Models T-54 obr. 1947 and obr. 1949 featured a single MK. 4 periscope beside the telescopic main sight, which you can see in the photo above. The periscope gave the gunner unusually good situational awareness, considering that most tank gunners had only a fixed periscope, but it had few practical uses. After the numerous field exercises conducted by units equipped with the T-54, it was found out that the MK. 4 could not be used for too long when the tank was driving over rough ground, as the pitching of the tank made the gunner carsick. It was far more profitable to focus on the operating the main sight instead, and leave the MK. 4 be until it was needed, like when the tank is entering a hull down position. The gunner would then use the periscope to make sure that the cannon is clear of the ground. Later on, the MK .4 was replaced with a regular 1x periscope.
Sometime during the 50's, possibly in 1954, the T-54 gained the ability to conduct indirect fire. Laying the cannon in the horizontal plane was facilitated by a turret azimuth indicator, as seen below. The indicator works like a clock with two hands. The indicator can be seen next to the manual turret traverse handwheel in T-54 models beginning from the T-54A (1954).
A hole in the commander's cupola allows a periscope for indirect fire to be installed.
TSh-20 is a telescopic sight. Most telescopic sights from the WW2 era were fixed to the cannon, so that if the cannon elevated, the telescope went with it. This meant that the eyepiece would never be in the same spot as the gunner fiddled around trying to get a firing solution for his target. In the TSh-20, the telescopic aperture is joined to the telescope body with a hinge, optically connected by cleverly placed mirrors. With an articulated telescopic sight, the eyepiece and the main telescope body could stay fixed while only the aperture moved. This eliminated the problem of gunner fatigue and improved firing accuracy, as the gunner will always maintain optimum eye relief. This arrangement was first used in the Soviet weapons industry in the TSh-16, which was installed in the T-34-85.
The T-34's PT-4-7 sight (below, left) featured a similar system of range adjustment. The horizontal line can be moved while the vertical line remains static, unless lead is applied. The intersection point between the two lines forms the crosshair. As the horizontal line is moved down the range scales to the appropriate distance to the target for a given ammunition type, the crosshair is moved down by the same amount.
The newer TSh-16 (above, right) offered an improved viewfinder arrangement. The viewfinders on the TSh series of telescopic sights generally have a better layout as all of the "clutter" is concentrated in the top half of the sight picture where there is nothing but sky. This means that the gunner's view of everything from the ground up to the horizon is perfect, but his view of the sky is not, which is obviously not important. Insufficient magnification power of the TSh-16 aside (only 2.5x), the design of the viewfinder was considered sound, so it was carried over to the TSh-20.
One excellent feature of the TSh-20 sight is the large rubber brow pad. It is large enough to fit around the gunner's forehead and temples - even if he is wearing his helmet - and stiff enough to hold his head in place, so that even if the gunner's body is rocking about, his head will be held firm and his eyes can be glued onto the eyepiece. This is a traditional feature of almost all gun sights on Soviet and Russian tanks, including later sights present on the T-54, which we will discuss later, all the way up to the Sosna-U on the latest T-90MS.
TSh-20 offers a fixed 4x magnification with a 16° field of view. This is horrible by modern standards, but arguably within acceptable limits for a 1945 product. For example, the M71C for the Pershing had a fixed 5x magnification with a 13° field of view. The extra wide vision arc offered by the TSh-20 enabled the gunner to survey for targets at short to medium distances more easily, but severely handicapped the long range viability of the tank. Whether high magnification was necessary during that particular stage of global tank evolution is not too clear. U.S research showed that the average tank duel in the Korean war occurred at an average distance of only 450 yards (411 m) due to the abundance of natural obstacles and obscurants. In addition to that, Soviet experience and research during WWII showed that almost all tank duels fought by Red Army tanks occurred under 1 kilometer in distance. With heavy, hours-long artillery barrages usually preceding breakthrough assaults, smoke and dust in the air often reduced tank engagement distances to just a few hundred meters, with many tanks only meeting each other at "knife fight" distances (also making head-on collisions, accidental and non-accidental, surprisingly common).
If the T-54 obr. 1947 came early enough to fight in WWII, or if its sequel was conducted in much the same way, then perhaps TSh-20 is good enough. However, it was impossible not to recognize that tank warfare was evolving. Soviet strategists felt that fluid and mobile "meeting engagements" would be the primary mode of combat in a hypothetical European world war, as opposed to the frontal attack. Scoring a hit on the first round was essential, and the crews themselves complained that 4x magnification was just not good enough. The solution was simple: increase the magnification power.
TSh2-22 was introduced with the T-54 obr. 1951. Continual field trials of previous T-54 models up til this point had shown that one of the chief complaints was the limited magnification of the TSh-20. Consequently, TSh2-22 features variable magnification settings of 3.5x and 7x. By implementing variable magnification in the gun sight, the gunner could enjoy both wide vision and high power magnification, though obviously not at the same time. For an even wider field of view, the MK. 4 rotating periscope would more than suffice.
TSh2-22 is directly comparable to the Centurion's No.1 sight which had a variable magnification of 1x or 6x and the M47 Patton's M20 sight, which also had a variable magnification of 1x or 6x. The M20 sight was shared by the M48 as well.
There appears to be two variations on the TSh2-22. The early version (a) has four scales, three for main gun rounds and one for the co-axial. Listed from left to right, they are: HE (full charge), APHE (BR-412B), HE (reduced charge) and finally, the co-ax. The late version (b) has just two scales for main gun ammunition: HE (full charge) and APHE (BR-412D), plus one for the co-ax.
Much has been said about the T-54's lack of sophistication in the fire control department, but I will attempt to argue otherwise. Let us first begin by understanding what constitutes an "advanced" fire control system of that era, by taking a look at the M48, which comes with an analogue ballistic computer and a stereoscopic rangefinder.
The M48 is principally the same as the M47. The M48 has an M20 (T35) variable power periscopic primary sight, paired with the M12 stereoscopic rangefinder. In models produced before problems with the T30 ballistic computer were solved, the T24E1 ballistic drive connected the elevation mechanism of the cannon with the M20 sight and the T25 range drive, which was a simple mechanical device that converted rangefinder adjustments into vertical displacement of the reticle in the M20 sight. Once the M13 (T30) mechanical analogue ballistic computer was installed, a slightly modified T24E1, now the T24E2 ballistic drive, was used.
|M13 ballistic computer with linkage|
This system works thusly: The gunner finds the range to the target by operating the rangefinder by twisting an adjustment dial. This simultanrously causes the reticle in his M20 sight to raise or lower. By raising the reticle onto the target, the cannon elevates accordingly and thus obtains the correct ballistic solution. The fire control system of the M47 works identically. Differences are minor and mostly irrelevant as far as results are concerned. The only function of the M13 was to provide a ballistic solution given range. It could not account for other factors like wind, ambient temperature, etc. It had an input for barrel wear, but that had to be done manually (the computer did not automatically count the number of shots fired).
(Source: Camp Colt to Desert Storm: The History of U.S. Armored Forces)
(Source: Extract from publication in Forum post. Unknown publication)
If you understand the principles behind the operation of the TSh series of gun sights, then you will have noticed some similarities. The TSh2-22 sight itself performs the same basic function as the M13 ballistic computer, whose only role is to interpret range data into an appropriate superelevation angle, which it does with the spinning of wheels and the twisting of cams. The Soviet approach to the goal of interpreting range data into a ballistic solution was to pre-calculate all of the appropriate ballistic solutions for a given range of distances, and then simply print these results in the form of range scales into the gunsight for the gunner to refer to when needed. This is essentially the same as printing out the values on a dial on an external adjustment device and having the gunner refer to that instead, which is how it was done in the Centurion. On a purely technical level, the M47 and M48 are more sophisticated, but in practice, the advantage is minimal to non-existent.
By displaying all of the range scales in the viewfinder and not on an external dial, the gunner can conduct the entire target acquisition procedure without removing himself from the sight and losing visual contact with the target. This problem was solved in the Centurion in a rather creative way; they took a mirror and placed it in front of the gunner's left eye, and they angled it such that the gunner could see the range drum with his left eye as he adjusted it while the tracked the target with his right eye. This might be a source for headaches in the long run, but it works.
Rangefinding is optional, as the commander's optic is equipped for the job and the gunner is usually supposed to aim according to the commander's range reading, but if the gunner is obliged to conduct rangefinding, he can do so using a stadiametric scale imprinted into the bottom right corner of the viewfinder. To use the rangefinder, the gunner only needs to bracket the target tank between the stadia lines and read the figure corresponding to the height of the target, and then turn the range adjustment dial until the horizontal line is on the correct range scale notch for the desired ammunition type. It is also possible to use the multitude of marked mil scales that form the reticle of the TSh2-22 viewfinder and combine them with knowledge of generic tank widths and lengths to obtain a better-than-a-guess range estimate.
As mentioned before, stadia rangefinding is not very precise at long ranges, or even short ranges for that matter, if the user does not have perfect vision and concentration. However, it offers some advantages over other rangefinding methods like ranging machine guns. A learned tank crew will know to retreat immediately once they perceive tracer fire coming at them from covered and shady positions, especially from positions suspiciously abundant in foliage. It would be immediately obvious that they are being ranged by a hidden enemy. After all, what sort of idiot fires his rifle or a machine gun at a tank? Although a circumstantial one, this is a drawback that stadia rangefinders do not have.
The disadvantages to stadia rangefinding are even more numerous. For one, it is not possible to range targets other than tanks. If the target vehicle is a jeep, a SPAAG, a truck or a bunker, the stadia rangefinder is totally useless. The only practicable option at that point would be to use the burst on target technique. The sheer inaccuracy of the stadia rangefinding method is a big deal too, of course.
In an early 1970s test involving a stationary Belgian M47, the efficacy of three types of rangefinding was conducted by determining the probability of hit against a 2.3 m target. A newly developed laser rangefinder was pitted against the original M12 stereoscopic rangefinder with 7.5x magnification found on most M47s, and a stadia reticle, which, as far as I know, was retrofitted to the Belgian M47, as the vanilla tank had no such thing.
The results of the test are as follows:
|Range||Laser Rangefinder||Stereoscopic Rangefinder||Stadiametric Rangefinder|
The results may or may not be valid for the T-54, as there are a multitude of other factors to consider. For example, the M20 sight installed in the M47 has a lower magnification than TSh2B-22. Still, it is impossible to deny that stadiametric rangefinding is so inadequate that it is more of a rangefinding aid than an actual rangefinding instrument.
TSh2B-32 was first implemented in the T-54A, introduced in 1955. TSh2B-32 was practically identical to previous telescopic sights. The difference was out of sight. It was designed to connect to the new STP-1 single plane stabilizer, thus giving the sight vertical stabilization. This sight continued to be used in the T-54B despite the inclusion of the new STP-2 dual plane stabilizer since the sight had no need for horizontal stabilization anyway, as it is mounted rigidly in the already stabilized turret.
TSh2B-32 is primarily found on the T-54A and T-54B. Early model T-55s also have the TSh2B-32 installed.
In January 1965, the TSh2B-32P was installed in the T-54B and T-55. The only difference between it and the TSh2B-32 is the new range scale for 3UBM8 APDS ammunition. The "P" in "TSh2B-32P" presumably means "podkaliberniy", or "subcaliber", referring to APDS. T-54 and T-55 models from earlier batches had this sight installed during capital repairs or base overhauls to enable them to take advantage of the new ammunition.
Besides the range scale for APDS rounds, there are no other differences.
In 1974, many T-55A tanks still in active service were fitted with the new KDT-1 laser rangefinder. KDT-1 does not have a direct connection to the sight, nor is there a ballistic computer to interpret range data for the sight to process. The gunner is informed of the range via a digital readout installed in a corner. To apply the range data, he must utilize the range dial located on the underside of the sight.
T-55A tanks outfitted with KDT-1 retain the same designation. It is not known if the T-55 or if T-54 tanks were retrofitted with KDT-1, and if they were, the precise number of examples is not known. All T-54-style tanks equipped with KDT-1 display the T-55A loader's hatch with anti-aircraft machine gun, so it is likely that only T-55A tanks received the laser rangefinder.
New handgrips were fitted. They are principally identical to the old KB-4 handgrips, but with a thumb trigger to fire off the laser rangefinder.
In the year 1957, the T-54 entered its tenth year of formal service, and also the tenth year of its continuous evolution, becoming the T-54B. In that year, the T-54 became capable of night fighting with the installation of TPN-1-22-11.
TPN-1-22-11 can operate in either active infrared imaging mode or passive light intensification mode. In the active infrared imaging mode, the infrared light supplied by the L-2 "Luna" spotlight mounted co-axially to the main gun is picked up by the sight, which allows the gunner to identify a tank-type target at distance of around 800 m, which is very decent for night vision equipment from the 50's. In the passive mode, the sight employs light intensification for a nominal maximum identification distance of 400 m for a tank-type target under lighting conditions of no less than 0.005 lux.
L-2 "Luna" spotlights operate on only 200W. The advantage of infrared illumination is that it is completely unaffected by the weather, and it is possible to see through night-time fog, mist, rain and snowfall as well as windows. Light intensification imaging might work better on a moonlit night, or worse on an overcast night. It would be even worse in rain or fog. As a rule, anything that can affect visibility conditions (to the naked eye) will also affect a light intensification device.
TPN-1-22-11 has fixed 5.5x magnification, and a narrow field of view of 6 degrees. The magnification is quite reasonable for a night vision device, as the IR sight for the Chieftain only had a 3x magnification. The viewfinder is extremely simple, as you can see below. The tip of the chevron is sighted for BR-412D AP rounds for a distance of 200 m, going down to 400 m at the upper tip of the vertical reticle line below the chevron. A more comprehensive adjustment system was not included as the short range of the TPN-1-22-11 night vision system limited engagement distances to 800 meters or less anyway.
The TPN-1-22-11 has an internal lightbulb to facilitate aiming at night. It is either on or off without the option of dimming, but it can be turned on in either the day mode or the night mode as the gunner wishes. It is preferable to remain in the day mode with an illuminated reticle when operating during sunset or twilight hours.
TPN-1-22-11 is similar to its telescopic counterpart in that it is not stabilized. It is only connected to the main gun by a mechanical linkage (see the diagram below). Disregarding its night vision capabilities, the sight is otherwise quite simple.
The night vision equipment was tested in a British/Israeli assessment of the T-55, among other things. The full report is available in the Tanks and AFV News site. The relevant page of the report can be viewed here (link). According to the test, TPN-1-22-11 allowed the gunner to see:
|Chieftain (from behind)||400|
Another explanation is that the TPN-1-22-11 has lackluster performance simply because it is older than whatever the Chieftain uses by almost a decade, but then, why did the report mention that the equipment was "suspect in nature"?
Volna Fire Control System
The T-55AM deep modernization programme of 1983 involved a total overhaul of the fire control system as well as a base overhaul of the engine and other essential components.
Introduced as a complement to the Volna fire control system, TShSM-32PV is substantially more advanced than the previous telescopic sights used in the T-54 series. TShSM-32PV features a viewfinder that is very similar to the TPD-K1 in layout, especially with the removal of the range scales and its substitution with a more space efficient dial-type range indicator at the top.
The magnification of TShSM-32PV is practically identical to its predecessors; either 3.5x power magnification or 6.9x. The sight offers a field of view of 18 degrees in the low magnification setting and 9 degrees in the high magnification setting. The sight is independently stabilized in the vertical plane with a maximum accuracy of 0.3 mils, which is quite good. At 1000 m, the sight will have a maximum deviation of 0.3 meters from the point of aim.
Now that the sight is linked to an analogue ballistic computer, additional features had to be implemented in order to add more functionality. An LED tab at the bottom of the viewfinder displays the ammunition type and the range. The range dial at the top of the viewfinder spins (different dial rings spin at different rates via a differential mechanism) to display the range equivalent for different types of ammunition. In the right hand side drawing of the viewfinder above, you can see that the number "140" displayed in the range display tab, and the range dial for BK (HEAT ammunition) set to "14". This means that the target is 1400 meters away, and HEAT is selected. Switching the ammunition type will reset the range dial accordingly.
The same reticle design was retained in the TShSM-32PV, as was the method of gun laying. Once the range was automatically inputted into the sight via the BV-55 ballistic computer, the reticle drops a certain amount. The gunner must then manually raise the reticle and lay it on target. This is not as convenient as having the cannon raise automatically while the reticle remains static, as was the usual in digitized Western FCS appearing in the late 70's and early 80's.
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's active infrared imaging system is slightly improved over the TPN-1-21-11. 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 1K13-2 sight still has a viewing distance of only 800 m under ambient lighting conditions of no less than 0.005 lux. 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.
In accordance with the extended viewing distance in the active infrared mode, the sight is now equipped to adjust the superelevation of the reticle, just like the telescopic sights described before. This is to enhance firing accuracy at ranges above the reasonable range of distances for battlesighting.
|1K13-2 viewfinder in the passive light amplification mode, aimed at nothing in particular (Photo credit: Stefan Kotsch)|
POWER TRAVERSE, STABILIZERS
The original production T-54 did not have gun stabilization. The T-54-1 used the EPB-1 electromechanical turret rotation drive, also used in the IS-4 heavy tank. Later on, the 1951 model used the improved EPB-4 instead. Both had the same performance, differing only in small details. Both were reasonably precise enough that it was possible to conduct final gun laying without using the manual flywheels, but it was still not very precise, and quite underpowered to boot. EPB-4 enabled the turret to turn at a minimum speed of 0.1 degrees per second, and at a maximum of a painfully slow 10 degrees per second. Unlike the power traverse scheme on earlier tanks like the T-34-85, the turret will not continue rotating after the cessation of gunner input due to inertia, as an electric brake was installed. The electric brake will activate to reduce the speed of the turret or stop it whenever the gunner changes the degree of twist applied on the handgrips.
However, this system had a multitude of deficiencies. It took some time for the motor to accelerate, so there is "lag" when rotating the turret. Secondly, the minimum turret rotation speed of 0.1 degrees is insufficiently accurate. 0.1 degrees is equivalent to 1.778 mils, which means that at 1000 meters, the turret may be off target by as much as 1.778 meters. At ranges more than one kilometer, manual final gun laying, using the flywheels, is necessary. Consequently, the reaction time and the time to engage a target was quite long. Thirdly, EPB-4 consumed a lot of power and put extra high load on the engine and batteries. It is not possible for a T-54 obr. 1951 to operate at full capacity on batteries when its engine is off.
Control of turret rotation is done with the KB-3A handgrip (for the EPB-1), and later on the KB-4 (for the EPB-4), both of which took the form of a solitary spade grip. It is essentially a complicated rheostat. The spade grip could be rotated to varying degrees of deflection to control the speed of turret traverse. Gun elevation had to be done manually via the gun elevation handwheel. This meant that gun laying was slow, but it does not meant that it was inaccurate.
Introduced on the T-54A which arrived in 1954, the STP-1 stabilizer complex for the D-10TG made the T-54 the second postwar tank to receive a gun stabilizer, though not with full two-plane stabilization. The Centurion Mk. 3 was the first, featuring an advanced two-plane stabilization system in 1948. As mentioned before, both the primary and night sights piggyback on the cannon to benefit from the stabilization system.
The history of STP-1 dates back to research and testing efforts beginning in 1947. In accordance with a government resolution passed on the 19th of April of that year, the responsibility for the design and implementation of a stabilizer system for the then-brand new T-54 tank was assigned to Factory no.707 of the Ministry of Shipbuilding Industry, but by the end of 1948, it turned out that the factory could not fulfill this task. Renewed efforts in 1949 by TSNII of the Ministry of Armaments under the leadership of Vasiliy Grabin (designer of the ZiS-3) led to the creation of two prototypes, S-88S and S-84SA. These were single-plane (vertical plane) stabilizers. Testing on T-54 tanks was began in July 1952 and wrapped up in February 1953. Parallel work carried out by the TSNIIAG Factory no.9 in accordance with a new government resolution passed on the 29th of March, 1952, produced a single-plane (vertical) stabilizer, which was installed in three experimental T-54 tanks. These tanks underwent acceptance tests in August of that year and underwent field testing in September.
In the summer of 1954, Factory no.183 in Kharkov produced three T-54 tanks with new two-plane stabilizers from both TSNII and TSNIIAG revealed that the two-plane stabilizer improved the chance of a hit on the first shot was higher by 2 times and the overall practical rate of fire rose by 1.5 times. However, TSNII dropped out of the tank stabilizer race in 1954 due to reassignment, and TSNIIAG became the sole producer of tank stabilizers. However, issues with mass production meant that the advanced two-plane stabilizer could not be implemented on a large scale, and a stabilizer system was badly needed by the T-54 in order for it to remain competitive against the latest Western tanks like the Centurion. As a result, the less advanced but more readily available single-plane system, now developed into the STP-1, entered mass production in 1954 as a stopgap measure.
The stabilizer system is composed of multiple elements working in concert, but the focal point of our attention is the electric gun elevation control system. With a minimum elevation speed of 0.07 degrees per second, the maximum deviation is 1.24 meters at 1000 m. The maximum elevation speed is 4.5 degrees per second.
STP-1 included the new TAEN-3 electromechanical turret rotation drive, but did not include horizontal stabilization. A new EMU-5PM amplidyne amplifier was implemented, which solved the problem of excessively high power consumption. The TAEN-3 electric drive for turret traverse is located above the manual traverse handwheel. The electric motor is mounted horizontally, as opposed to the vertical mounting of the electric motor seen in the STP-2, which we will examine later. The TAEN-3 motor is quite small.
TAEN-3 was highly underpowered, as it only allowed the turret to turn at a painfully slow maximum speed of 10 degrees per second. The gun lacked horizontal stabilization, meaning that firing on the move could only be done if the tank was travelling in a straight line. The handgrip controllers were updated to the KB-4 from the KB-3A. KB-4 is colloquially known as "Cheburashka", in reference to the cartoon mouse's large ears.
Modernized versions of the tank like the T-54A, T-54B, T-55, the T-62 and even the BMP-1, all used the basic design of this controller in some form or another. along with the fire control systems of many other military vehicles.
STP-1 was decent enough, but partially by virtue of its presence alone. After all, stabilization is better than no stabilization. Various useful safety features were also implemented, including a safety device to keep the cannon under control as the tank hurdles over undulating terrain, so as to prevent the cannon from wildly swinging up and down and potentially damaging itself as well as anybody close by. A feedback system was also installed. By monitoring the load on the stabilizer motor, the stabilization system can detect if the cannon is being pushed up or down by an external force. The stabilization system will then depress or elevate the cannon in the opposite direction until the extraneous load is removed. This prevented the cannon from digging into hard objects like large rocks and concrete walls when the stabilizer was turned on.
The STP-2 stabilizer was introduced in the T-54B for the D-10T2S gun. STP-2 featured a new, more powerful electric turret drive and featured stabilization in the horizontal plane, which is an big improvement over the STP-1. Small batches of T-54B tanks were built in 1955 and 1956 for field trials and troubleshooting, and the tank officially entered service in 1956. Mass production of the T-54B with its new "Tsyklon" stabilizer began in 1957.
The amplidyne amplifier (brown cylinder) for the STP-2 can be seen in the photo below, immediately behind the turret traverse indicator and the turret traverse handwheel. The electric motor (a green cylinder to the left of the photo below) for turret traverse is located to the immediate left of the gunner, where his left shoulder should be. If you happen to be inside a T-54B or a T-55, know that the STP-2 can be distinguished from the STP-1 by the vertically placed electric motor.
The vertical stabilization system was carried over from the STP-1, but with some differences. Components such as the gyrostabilizer box, amplidyne amplifier and the mounting system for the electronics were modified and rearranged.
Unfortunately, powered traverse was still quite slow even with the improved turret drive, which was not very powerful compared to the hydraulic systems being used in Patton tanks at that time. According to a T-55 manual, the turret could spin at a measly 15 degrees per second, meaning that it would take 24 seconds to complete a full rotation. This is ever so slightly faster than the Centurion Mk. 7, which took 25 seconds to complete a full 360 degrees, but the M47 tank (no stabilizer) was faster by 14 seconds. A U.S Armor School document on the T-54B claims that the turret could complete a full rotation in 21 seconds.
The slow turret traverse speed can be lethal for the tank if it is caught in an ambush, as the crew will not be able to react quickly enough. On the upside, the lack of flammable hydraulic fluid being circulated inside the turret was beneficial towards the survival of the crew and the tank as a whole if it was hit. Moreover, the slow turret traverse speed of Israeli Sh'ot tanks during its service in various conflicts (most notably the Yom Kippur war) did not seem to be a serious detriment, as it - apparently - cut down hordes of Syrian and Egyptian tanks like wheat from a field.
The slow traverse speed can also be a handicap when the tank is neutral steering (turning on the spot) or zigzagging at a low speed, because the hull can turn faster than the turret. If this happens, the turret might not be able to catch up, making it jerky, as you can see in the video below (skip to 5:42).
The minimum speed of both gun elevation and turret traverse is 0.07 degrees per second, equating to a maximum deviation of 1.24 mils at 1000 m. The maximum speed of gun elevation is 4.5 degrees per second. The vertical stabilizer is designed to lift the cannon by about 3 degrees immediately after firing in order to improve loader access to the breech. The side effect is that the gunner's primary and secondary sights will follow, thus making it impossible for the gunner to observe the effect on the target. Mysteriously, this fact seems to be largely glossed over in the internet armour community. The most likely reason is that it has been overshadowed by the criticism of the same problem in the T-62.
A captured T-55 tested by the Israelis in 1969 yielded interesting results. The T-55 was tested on a flat sandy track at a steady speed of 15 km/h. Out of 35 shots, only 3 hit the target - a success rate of only 8.5%. This is better than the quoted value of "3% and below", but still extremely poor. Photos of the report are available on tankandafvnews. The relevant page is linked below:
Page 52 (photo)
Page 53 (photo)
Page 54 (photo)
As the report mentions, STP-2 is only suitable for stabilizing the gunner's line of sight, not firing on the move. The poor performance of STP-2 is almost certainly because of insufficient maturity of Soviet high technology industries, but the chassis itself definitely has an impact as well. The comparatively crude, unsupported suspension (which also lacked shock absorbers), could not dampen vibrations well. This translated to minute oscillations of the gun barrel, accelerated wearing of the stabilizer itself, and the oscillations were too small to be compensated by the stabilizer, thus degrading firing accuracy.
A more optimistic reviewer might suggest that the stabilizer in this case was not maintained properly, was subjected to extended periods of exposure to the extreme heat inside the tank as it baked under the hot desert sun (and cycled unhealthily between extreme heat and extreme cold). Combined with the high probability that the Arab handlers of these T-55s might not have the required specialist skills to maintain the sensitive stabilizer system, and we have a decrepit, worn-out device that cannot be expected to work at peak condition. I would not, however, go so far as to say that the stabilizer system was one of the components of the tank that was deliberately downgraded for export.
" 2) Adjustment of Fire. No difference in ease of adjustment of fire was apparent between comparable types of high explosive fired from the 20-pounder and the 90mm. Adjustment of fire with the shot APDS, on the other hand, was more difficult because of the poor observation from the Centurion III as outlined above. However, this did not prevent the Centurion III from acquitting itself favourably in initial and abbreviated ease of adjustment problems. The 20-pounder achieved 3 direct hits and one ricochet hit out of 7 rounds when firing at three 6’ x 6’ olive drab targets at ranges varying from 1,800 yards to 2,800 yards, while the 90mm firing HVAP-T and using an M83C telescope graduated for ABC obtained 2 hits out of six rounds at two similar targets 1,800 and 2,500 yards, and failed to get a hit at 2,800 yards with 5 rounds. Users and observers attributed this favourable showing to the flat trajectory of the discarding sabot ammunition which partially negated ranging errors and deflection errors due to cant."
An abridged report can be found on the World of Tanks site: http://worldoftanks.com/en/news/pc-browser/21/The_Chieftains_Hatch_Centurion_III_Pt1/
The relevant pages of the report are found here: (Link)
Six of the targets presented a broadside profile (side profile), two of the targets presented a head-on profile, and two of the targets presented an oblique broadside profile (angled profile). All of the targets were paper targets. The visible height of the target ranged from 1.45 meters to 2.45 meters, which would be representative of an average Soviet tank, but not a Western one. The Centurion is 3.01 meters tall, the M48 is 3.1 meters tall, and the M47 is an astonishing 3.35 meters tall. For the Pattons, these figures do not include the large commander's cupola.
At target distances averaging 1200 m with outlying targets at the unusually short distance of 600 m and the unusually long distance of 2140 m, the ratio of the number of hits to the number of rounds fired was obtained. The results are listed below:
|Crew||Phase||Number of Targets Engaged||Number of Rounds Fired||Hits|
This test was NOT to determined the accuracy of the gun and fire control system, unlike the test of the Centurion detailed above. This test was a simulation, with unknown and unexpected target positions, unknown distances to these targets, and so on. Another factor to consider is that these tests were held in the same extremely dusty conditions that so badly affected the crew's ability to sense the point of impact of shots. Without a doubt, this contributed to the inability of the crew to correct their fire and score hits. In fact, if we scan the details of each shot as analysed and listed in the report, we can see that literally all of the misses (including the ones involving incorrect horizontal lay) either went high or low. Therefore, the gun was almost always laid correctly on the target (credit to the horizontal stabilizer system of STP-2). The only issue was the ability of the crew to ascertain the range to the target and obtain a ballistic solution.
Out of 12 shots in phase A1, there was only one shot where the shell was off target in the horizontal plane. In phase A2, out of 11 shots, there was, again, only one shot where the shell was off target in the horizontal plane. In phase B1, out of 12 shots, we have two shots off target in the horizontal plane. In phase B2, out of 11 shots, we have one shot off target in the horizontal plane. All of the misses were due to the shot going high or low. It is very likely that in less dusty conditions, the T-55 could achieve much, much better accuracy. On a related note, the exclusive use of APDS ammunition for anti-tank purposes in the Centurion MK. 3 greatly contributed to good accuracy at all ranges, as the high velocity of APDS shells partially negated ranging errors.
From a statistics standpoint, relying on this report to generalize the performance of all T-55 tanks in all conditions will be erroneous. Therefore, I ask the reader not to take any of this data at face value. This test cannot be used to represent the majority of T-55 tanks in real battle, and certainly not T-55 tanks in Europe, where environmental conditions are very different. Take this little analysis as supplementary knowledge.
D-10T had a larger caliber than any other tank gun fielded on a medium tank at the time of the T-54's introduction, and it was a very modern weapon then. However, it was slow to receive advanced features that were common on Western tanks like fume extractors, and the barrel of the cannon was not of a quick-change design like the M3 90mm gun. The lack of a fume extractor was especially hard on the crew, as the stick propellant used in the ammunition was rather smoky. Efforts to design and install a fume extractor were combined with the ongoing STP-1 stabilization project in the mid 50's, resulting in the D-10TG stabilized cannon with a fume extractor located at the very end of the barrel. This cannon was used by the T-54A. Later on, the cannon was adapted to the "Tsyklon" dual-axis stabilization system, changing the designation to D-10T2S.
During the late 50's, nearly all T-54 obr. 1949 tanks (built and issued from 1949 to 1951) and T-54 obr. 1951 tanks (built and issued from 1952 to 1954) underwent a modernization program to improve its combat capabilities to the level of the T-54B, which was the latest iteration at the time. The technical details for the modernization of older tanks - excluding the troublesome obr. 1947 model - to the standard of the T-54B was prepared simultaneously with the development of the T-54B itself, thus ensuring that a large part of the Red Army's T-54 fleet would not be condemned to obsolescence. However, the modernized tanks were not to be fitted with a fume extractor. Instead, a counterweight was added to the end of the barrel to simulate the load of one, and to balance the cannon properly for the stabilizer to function. These unusual guns, adapted for the STP-2 "Tsyklon" but with a counterweight in lieu of a fume extractor, were designated D-10T2.
All of the guns have a gun elevation and depression of +18 to -5 degrees.
The maximum chamber pressure of all D-10T models is 289 MPa. It is directly equivalent to the M3A1 90mm and 20. pdr (84mm) cannons in that respect, but due to the longer barrel, large ammunition (100mm D-10T cases are 88mm longer than 105mm L7 cases) and large caliber, D-10T could be considered to be in a league of its own. By the late 50's, advances in cannon technology allowed the improved M36 90mm and L7 cannons to compete directly with the D-10T by using better ammunition with hotter loads. In 1958, T-55 tank was introduced with D-10T2S.
The D-10T weighs 1950 kg in its base model form. Without a fume extractor or a counterweight, that is. In contrast, the 105mm M68 weighs only 1122 kg on its own, while operating at a higher pressure, with a much more compact body. Here, the 14-year age gap between these two rivals is extremely apparent. The D-10T's outdated hydraulic recoil buffering system was one of the sources of the extraneous weight, and also the reason why the cannon extends so far into the turret.
Weight aside, however, the D-10T could be considered on par with the L7 if we use muzzle energy as a yardstick. An L28 APDS projectile weighing 5.8 kg (sabot plus subcaliber projectile) coming out of the muzzle at 1470 m/s is only slightly more powerful than 3BM8 APDS, which has a projectile weighing 5.7 kg (incl. sabot) flying at 1415 m/s at the muzzle. Generally speaking, both guns had the same power, only different ammunition technology. Western ammunition was generally more advanced, being smaller and lighter but packed with propellant with a higher energy density.
On a related note, the Israeli Defence Forces (IDF) incorporated hundreds of captured T-54 into their arsenal as Tiran tanks, and although some Tiran tanks retained the D-10T, most were refitted with the 105mm L7, which was not a small project. The breech had to be flipped 180 degrees and the recoiling mechanism had to be rearranged in order to enable loading from the left. The decision to mount the L7 had many justifications. For one, Israel did not produce 100mm ammunition. Secondly, production of the L7 and 105mm ammunition was already established. Thirdly, the L7 was more compact than the D-10T, freeing up space inside the tank. This, plus the lightweight ammunition made the loader's job noticeably easier. All of the Tiran 4 and Tiran 5 tanks operated in combat ready units by the IDF were refitted with the L7. The ones that were not were because they were sent to Lebanon as military aid for their allies there.
To replace the barrel, it is necessary to lift the turret off the turret ring and pull the entire cannon assembly out the back. The turret is designed to tilt forward and stay propped open to make this easier to do in the field, but it is still by no means a quick procedure.
Here's a scene of this procedure being carried out in the field. The cannon is being lifted by an engineering vehicle.
The D-10T was quite well known in the West, though not as a tank gun for T-54 tanks. Rather, it was known as a component of the familiar SU-100 in the form of the D-10S, and it was represented indirectly by the BS-3, a towed 100mm rifled cannon that fired the same ammunition. Captured SU-100 tank destroyers and the D-10S cannons they wielded were trialed in the UK. The results are available in the ammunition section of this article.
As a direct result of tests of the D-10S conducted in the UK, it was decided to upgrade the upper glacis armour of next production Centurions to a 127mm plate from the original 76mm. This modification was later formally accepted as the Centurion MK. 8/1, and the earlier MK.5 and MK. 7 were later upgraded with a 44mm weld-on applique armour plate. Imagine the seriousness of the threat, that the original 76mm upper glacis of the Centurion was so inadequate that the thickness needed to be boosted by 67%! Around the time the Centurion was upgraded with a thicker hide, HEAT ammunition arrived, making the added armour redundant.
The T-54 is rather short compared to the T-34, so it is quite surprising that the actual available vertical space inside the T-54 is actually quite similar to its predecessor. Measuring from floor to turret ceiling, the fighting compartment of a T-34-85 was 1.56 meters to 1.585 meters in height, depending on the exact location. The T-54, on the other hand, had a maximum internal height of 1.6 meters, even though the T-54 is 2.32 meters tall while the T-34-85 is 2.7 meters tall. This wizardry is possible because the floor of the T-34-85 is taken up by an ammunition box which stows the majority of the tank's ammunition supply. Being tall enough to stow 85mm shells three rounds deep, the box takes up a considerable portion of the tank's available vertical space. As the floor of a T-54 only needed to accommodate the torsion bars and the false floor, it could have the same internal height as the taller T-34-85.
The commander and gunner can sit down with a reasonably comfortable allotment of headroom, but 1.6 meters is not nearly enough to let a man of average height stand up straight. Only someone unusually short would be able to. A loader of average height would have to conduct his duties leaning slightly forward. As the loader's protruding cupola breaks the turret's sloping profile, he has room to stand a little straighter directly when he is directly underneath the hatch, which, conveniently, is where the breech is and where he needs to be in order to ram rounds into it. The low ceiling at the front part of the turret is not a problem, as there is no ammunition there that is stored above waist level.
The loader is furnished with an MK-4 periscope for general visibility. He is formally required to return to the MK.4 periscope immediately after loading and readying the cannon, but nobody actually does it like that. In practice, if the loader is not servicing the cannon, he is either getting another cartridge ready or rearranging the ammunition. The periscope is marginally useful when under threat of imminent contact with the enemy as it grants the tank an extra pair of eyes, but attempting to use the periscope to help spot targets is a waste of time.
The greatest value of the periscope is in the psychological benefits of giving the loader a sense of his surroundings. The extra lighting is helpful too, since the loader's station has only one dome light.
The loader's seat can be unhooked from the turret and relocated to a new position near the rear of the turret. There are two fire extinguishers underneath the position of the loader's seat closest to the rear of the turret.
Not all T-54s can carry the same load of ammunition. All T-54 variants created between 1947 and 1958 could only carry a measly 34 rounds - nearly half that of tanks like the M46 and the Centurion. To be fair, this was compensated by the significantly higher explosive and anti-armour performance of each 100mm shell compared to a 90mm or an 84mm one, but only to a certain extent.
Here is a diagram of ammunition placement in a T-54 obr. 1951. As the arrangement of ammunition in a T-54 obr. 1949 is almost identical to that of the more historically relevant T-54 obr. 1951, we will only be discussing the latter.
The 1951 upgrade that brought the new egg-shaped turret also brought improvements in the ammunition stowage scheme. Most notably, the bevelled turret rear was filled out, and this allowed an extra five rounds to be carried. You can see these racks in the photo below, empty.
The five rounds are stowed crosswise, or tip to tail. Three rounds are stowed pointing towards the commander, and two are stowed pointing to the loader. These racks can be unclipped in advance whenever the crew feels like combat is imminent. The brackets for holding up the cartridges are quite deep, so there is little fear of them accidentally falling out when the tank is driving around. Unfortunately, the racks are too shallow for the loader to avoid the recoil stroke of the cannon. It is dangerous to extract ammunition from these racks immediately after the cannon has been loaded as the loader will not know when the gunner will decide to fire.
An additional two rounds are stowed on the turret wall just behind the loader. The rounds are also mounted facing forward. This was a rather odd design decision, since this forces the loader to hold the base of the shell with his right hand and hold the nose end with his left, even though he can only ram the round in with his left hand. This prevents the loader from extracting the round, turning around and loading the round in one fluid stroke.
Four rounds are stowed with clips at shin level on the wall of the hull, on the loader's side. These are not very convenient to use in battle.
Twenty rounds are stowed in a metal skeleton frame rack at the front of the hull. The loader must squat down to access these racks, but the way they are placed is extremely convenient for him. These racks are placed underneath the flat part of the hull ceiling due to geometric incompatibility with the sloping front part of the hull. Underneath the 60 degree slope of the upper glacis plate, and in front of the ammo racks, is a large triangular fuel tank.
Here's a still from a video uploaded by Tanknut Dave showing these racks:
Here it is being used in an FSA T-54.
The T-55 introduced new front hull racks. Instead of a skeleton frame, these racks are conformal fuel tanks with slots for ammunition, but two rounds had to be sacrificed to make the arrangement work, slashing the total number of rounds stowed from 20 to 18. Amazingly, the fuel tank itself had enough room to hold 300 liters of diesel, giving the tank greatly extended range. This was a very considerable performance boost, especially since no additional internal space was used up. But despite losing stowage spots for 2 rounds, the T-55 could carry 43 rounds of ammunition, 9 more shots than the T-54. But where does all that space come from?
Contrary to the commonly held belief that the removal of the bow machine gun enabled more ammunition to be stowed (a belief repeated by The Chieftain in his video review of the T-54), the extra ammunition was not stowed anywhere near the removed bow machine gun, and it had nothing to do with it at all. The area in front of the engine compartment bulkhead/firewall, previously unoccupied in the T-54 obr. 1947 up until the T-54B, had a new rack for nine rounds installed there in the T-55. The removal of the bow machine gun in the T-55 model was simply a coincidence. The racks can be seen below (some space is being used for machine gun ammo).
|Photo credit to Jim Chandler of the Warwickshire Armour Modellers|
It is not as easy to extricate ammunition from these racks as it is from the front hull racks or from the turret racks due to the horizontal arrangement of the ammunition and the presence of the large casing deflector extending almost to the turret ring. Therefore, these racks are considered non-ready racks for reserve ammunition. Loading from them is possible in combat, but at a greatly reduced rate.
Experiences in various conflicts throughout the Cold War era have indicated that it is rare for a tank to expend more than 20 rounds of ammunition in a single engagement. Most often, the tank only needs to fire about a dozen rounds before the enemy is either destroyed or routed. This knowledge is reflected in the designs of tanks like the Pershing, M46, Centurion, and all the rest. In all of these tanks, and in the tanks that came after, ammunition stowage is divided into two types; ready and non-ready. Ready rounds are stowed in racks close to the loader, so that he can load as quickly as possible during battle. During the lulls between battles, the loader refills the ready racks with ammunition from the non-ready racks. The T-54 is no worse than any of its counterparts in this sense. The total number of rounds available in the ready racks in a T-54 is 29, whereas in the T-55, it is 27 rounds. As you may recall, another four rounds are stowed by the loader's feet at shin level, but they are not counted.
A 20-pdr-armed Centurion has 28 ready rounds, according to a U.S Army report posted in abridged form by Nicholas "The Chieftain" Moran on the World of Tanks forum. A 105mm-armed Centurion, on the other hand, has 15 rounds in various racks close to the loader. The front hull racks are quite voluminous, as they hold 25 rounds, but the loader is unable to access these rounds when the turret is pointed in a 20 degree forward arc as they are partially blocked by the bins underneath to the co-axial machine guns, as you can see below. Optimistically speaking, an L7-armed Centurion has 40 ready rounds.
The loader in a T-54 is able to reach almost all of the ammunition in the tank in both ready and non-ready racks, except for the single cartridge stowed on the floor next to the gunner's seat. The low ammunition capacity of the T-54 is not a disadvantage where modern tank combat is concerned, like in a meeting engagement. However, it can prove to be an issue when meeting engagements become pursuits as the Red Army blitzes across Europe. An adequate stream of supplies must always be maintained in order to keep up the pace of combat operations, and this overdependency can prevent tank units from exploiting gaps in the enemy's defence before reinforcements arrive. An interruption of these lifelines will badly affect the efficacy of the T-54 in combat.
A popular myth is that the Red Army was ambivalent towards the T-54's low ammunition capacity as it was believed that the tank would be sent to its doom in massed frontal attacks against well-defended NATO tanks and anti-tank weapons, so it only needed enough ammunition for one battle as entire tank fleets could be replaced within hours of its loss. However, this was never explicitly mentioned as official policy in any documents. Huge losses were expected, but that was simply the reality of warfare on such a large scale. The only reason why the T-54 has such a small stock of ammunition compared to NATO tanks is because of the paradox of having a large gun and a small tank at the same time.
The manual for the T-55A tank (a version with gun stabilization) states that the expected rate of fire when firing from a standstill is 7 rounds per minute, and that the expected rate of fire when on the move is 4 rounds per minute. Here is a copy of the relevant section of the manual:
(Red is for firing on a stop, and Yellow is for firing on the move.)
7 rounds per minute is very average for a medium tank, albeit one with a 100mm cannon. This amounts to a nominal loading speed of 8.5 seconds per shot, assuming that acquiring a target and aiming at it takes less time than that. However, keep in mind that there is a technicality in the testing procedure. The Soviet measuring criteria calls for the use of all of the ammunition in the tank, not only the rounds from the ready racks. Drawing from only the most convenient ammunition racks and containers, the loader could achieve a rate of fire higher than 8 rounds per minute. As mentioned before, the turret racks are very accessible to the loader. By unclipping all of the turret racks beforehand, the loading time can be slashed by a second or two. Using only the turret racks and the front hull racks, this optimistic greater-than-8-rounds per minute rate of fire may seem less optimistic. If the loader were obliged to only use the rounds in the racks on the engine compartment bulkhead and the side hull, he might struggle to attain a rate of fire of even 4 rounds per minute.
Consider that the very first prototype of the T-54 had a rate of fire of only 5-6 rounds per minute, and that the T-44 using the ZiS-S-53 along with the T-34-85 could attain a rate of fire of 7-8 rounds per minute.
Reloading while the tank is on the move is more difficult in the T-54 than it is in other tanks due to the lack of a rotating turret floor, even if that was counter balanced by the rather sluggish spinning speed of the turret. Unclipping the turret racks is unadvised, because otherwise there would be nothing to keep them from rolling off the racks and onto the loader if the tank suddenly dipped into a shell crater or something. Nevertheless, 4 aimed shots per minute is not too shabby, especially when compared to a Centurion tank, as you can see in the table below.
Some might feel like protest right about now, and insist that the Centurion, especially the Mk. 3 with its 20-pounder gun, most definitely shouldn't only fire 4 rounds per minute, and you'd be right. There are a lot of videos on YouTube showing L7-sporting Centurions firing once every 4 to 5 seconds, and this video shows the Centurion Mk. 3 firing once every 3 to 4 seconds (though there is some suspicion regarding the speeding-up of the footage):
However, there are three factors to consider. Travelling in a straight line like that (notice how the gun goes quiet once the tank turns), loading the gun is almost as straightforward as if it was stationary, but most importantly, the target is the same one. The Centurion in the video is displaying its maximum rate of fire, but not its maximum aimed rate of fire. If there were 10 tank targets, all spaced out at different distances, the Centurion must conduct rangefinding for each and every target before it can engage them accurately. As previously explained in the "Sights" section, this isn't so quickly done. We must also remember that the commander of a Centurion does not have any ranging equipment of his own, so he cannot help. Once the range has been determined, yes, the 20-pounder quick-firing cannon is as quick firing as its name suggests.
Being realistic, though, most gunners often simply defer to quicker and easier methods such as visual range estimation and burst on target. Any Centurion should out-shoot a T-54.
Older models of the T-54 that lack a stabilizer will have a lower rate of fire when firing on the move, as the time taken to acquire the target is much longer due to the need to halt or slow to a crawl in between shots, as opposed to the T-54 and T-54B where the gunner can scan for targets while on the move.
Limited information is available on the ammunition loadout of a typical Soviet-operated T-54. The generic loadout of a pre-APDS T-54 consists of 17 HE, 11 AP and 6 HEAT.
Two types of ammunition casings are available; D-412 steel cases, and Kh-415 brass cases. D-412 weighs 8.50 kg, whereas Kh-415 weighs 6.0 kg. Brass cases are used for AP, APDS, APFSDS and HEAT ammunition to improve firing consistency, while steel cases are used for HE-Frag ammunition as accuracy is not as important.
A tank's target is not necessarily another tank. Most of the time, it isn't. And to that end, the average T-54 tends to have a stock of HE-Frag ammunition comparable to its stock of anti-armour ammunition.
UOF-412 cartridge weighs a total of 30.2 kg. The OF-412 shell itself weighs 15.6 kg while the propellant charge contained within the steel or brass casing weighs 5.5kg. The explosive charge is TNT. The use of TNT can only be described as traditional, since RDX (also known as Hexogen) is clearly a superior choice as it is much more powerful. The only plausible explanation is that perhaps TNT was much cheaper and the expenditure of HE-Frag shells in times of war was expected to be so high that the cost efficiency of using TNT outweighed the drawbacks. Still,
A 20 pdr. HE shell, for instance, weighs 7.8 kg (according to an Unexploded Ordinance brochure) and contains an explosive charge of 0.6 to 0.75 kg of TNT or Composition B (60% RDX, 40% TNT), depending on the exact model of shell. The OF-412, on the other hand, weighs twice as much at 15.6 kg and contains twice as much explosives with a 1.46 kg TNT explosive charge. For every 100mm HE round the T-54 carries, the Centurion would need two 20 pdr. ones. The raw kinetic energy of OF-412 shells is also much higher, as it not only weighs twice as much, it also has a higher muzzle velocity of 892 m/s compared to just 602 m/s for a 20 pdr HE shell. This makes OF-412 very useful against hardened structures as it is capable of penetrating reinforced concrete bunkers and heavy field fortifications.
OF-412 is is topped off with an RGM-6 point detonating (PD) fuse. The fuze is armed only by centrifugal forces, thus making it inert until it has been fired through a rifled gun barrel. There are two fuze settings with four possible firing methods. The superquick setting is marked with an "O" and the delayed setting is marked with a "З" (a Cyrillic "Z").
The superquick setting detonates the shell 0.027 seconds after impact and the delayed setting detonates the shell 0.063 seconds after impact. 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. Keeping the (waterproof) safety cap on the fuze has a delaying effect on the fuze. Refer to the table above. Setting the fuze is the loader's job, but it is the commander who dictates which setting is used. The variety of fuzing possibilities gives OF-412 an added degree of flexibility against targets of all types, meaning that the T-54 has to use fewer rounds overall.
The delayed fuzing feature is beneficial to overall efficiency when the T-54 is used in an indirect fire role. When RGM-6 fuze is set to the delayed mode, OF-412 can be very useful against underground or dug-in positions, as the shell assumes an arcing ballistic trajectory when shooting at long range.
The fuze slot at the tip of the shell is also compatible with the V-429 variable delay fuse designed in the 60's. The V-429 fuse is point-detonating and armed by centrifugal forces, like the RGM-6. V-429 differs from the V-429E (used in the 115mm U-5TS and 125mm D-81T), which is armed by the braking effect from the unfolding of the stabilizer fins of the shell. Like the RGM-6, the V-429 has two possible settings: superquick and delayed. The main advantages of the V-429 are that it is waterproof even without a waterproofed safety cap, and it has additional safety features to prevent the detonation of the shell even if the fuze is accidentally set off.
3UOF10 is a more modern cartridge, incorporating the 3OF32 shell. This shell was introduced in 1975. 3OF32 is designed to produce a better pattern of fragmentation but also simultaneously sturdy enough that it can penetrate reinforced concrete without breaking up. The 3OF32 shell is topped off with the V-429 fuze.
Muzzle velocity: 900m/s
Complete round mass: 30.36 kg
Propellant Charge Mass: 5.6 kg
Mass of Shell: 15.96kg
Explosive Charge Mass: 1.7kg
Explosive Type: A-IX-1 (96% RDX, 4% phlegmatizing wax)
Number of Preformed Fragments and Their Mass:
With a mass of not less than 0.5 g: 1993
With a mass of 0.5 g to 2 g: 814
With a mass of 2 g to 15 g: 928
With a mass exceeding 15 g: 251
Statistical Average Mass of Fragments: 6.2 g
Velocity of Fragments and Ratio of Fragment Velocities:
100% - at least 1040 m/s
90% - 1060 m/s or more
80% - 1080 m/s or more
Interestingly, the 3OF32 was later used in the 2A70 low pressure cannon of the BMP-3. In that particular application, the low velocity of the shell further decreases the penetration of the shell into soil and snow, thus improving its fragmentation value, but the low velocity also reduced the energy of the shell and reduced the time allocation for it to penetrate hard obstacles, making it exceedingly unsuitable for bunker busting. It could, however, still be used to remove earth and log fortifications.
Armour Piercing (AP)
Before the dawn of the HEAT menace, full caliber steel armour piercing shot was the mainstream method of dealing with armour. Examples were cheap, reliably lethal, and tended to be more accurate than other types of ammunition, excepting APDS.
The battlesight range for BR-412B and BR-412D is 1200 m. This means that the gunner can set the sight at 1200 m prior to an engagement, and when an enemy tank is spotted, the gunner simply aims for the base of the target. If the target is exactly 1200 meters away, the shot will land near the lower glacis. If the target is close by, the shot may land near the turret. Either way, a hit is practically guaranteed. This is probably a more reliable way to engage targets than by relying on the results of stadiametric rangefinding. At best, the range value from stadiametric rangefinder may be used to supplement battlesighting, or to allow the T-54 to engage targets further away than 1200 meters.
When the T-54 entered service in the Red Army, there were only two types of armour piercing ammunition available for it. BR-412 AP, and BR-412B APBC. BR-412B was formally introduced sometime around 1946 (apparently, it was already in production by early 1945, but not issued) as a modified version of BR-412, featuring a blunt nose and a ballistic cap to maintain an aerodynamically pointed nose. The shape of the blunt nose is similar to the older 57mm BR-271 APHE-T shot in that it has a small bump on the tip, but the bump is completely flattened and not rounded. As the ballistic properties of the two rounds were different, chiefly due to this ballistic cap, it made little sense to keep the worst of the pair, so the early incarnations of the T-54 were stocked entirely with BR-412B.
The quality of the steel is considered high, and the hardness is respectably high as well. The hardening of the shell progresses uniformly - hardest at the tip and areas close to the surfaces, and slightly softer at the center. In contrast, wartime production 76mm BR-354B for the ZiS-3 gun ranges from 47 points Rockwell C to 38 points (451 BHN to 351 BHN) at the tip alone. Such shells were prone to shattering on impact with hard armour. A hardness of at least 600 BHN at the tip - which BR-412B achieves in excess - is necessary to prevent this from happening.
Below are two different analyses on different BR-412B samples. Both were done by the Ministry of Munitions in the U.K, but at different times. The one on the right was done in 1963 with ammunition from an unspecified recent conflict, and the one of the left was done in 1958 with ammunition taken from a captured Egyptian SU-100 from the Suez Crisis.
According to a U.S army document analyzing the Soviet 76mm BR-354B, it was mentioned that American armour piercing shots are generally hardened to approximately Rockwell C 60 (654 BHN) at the nose. By this metric, BR-412B can be considered on par with U.S ammunition.
The lethality of BR-412B is quite high, due in part to the 65-gram explosive charge of A-IX-2 at the base of the shell (assuming that armour perforation is achieved, of course). The British evaluation states that the detonation of the explosive charge has the effect of shattering the rearmost portion of the shell into five to six pieces as the shell exits the rear of an armour plate, supplementing the large spray of secondary projectile fragments and spall from the armour plate itself. These five to six large chunks of hard steel may also produce even more fragmentation as they impact the interior walls of the tank. In addition to that, the high energy of these chunks has a much greater chance of detonating ammunition inside the tank compared to smaller fragments. Contrary to how APHE shells are often perceived, the explosion will not send fragments in all 360 degrees like a grenade. It must be remembered that the walls surrounding the cavity containing the explosive charge is very, very thick. Too thick to pulverize into small fragments by such a small charge.
The killing power of the shell is augmented by the percussive effect of the blast, which has greater power than that of an F-1 fragmentation grenade (which holds 60 grams of TNT). Confined inside the small spaces of a tank, the effect of the blast is magnified, and the incendiary effect of A-IX-2 greatly increases the chance of igniting fuel and ammunition, not to mention burning the crew and internal equipment.
While 65 grams may not seem like much, A-IX-2 is a particularly useful explosive-incendiary compound, because it contains aluminium as a fuel additive. A-IX-2 consists of 73% RDX, 23% aluminium powder, and 4% phlegmatizing wax. The aluminium powder content produces an incendiary effect, because aluminium powder is pyrophoric, and aluminium can be used as a fuel additive to increase the heat of combustion (Türker 2016, p. 426).
The non-optimal aluminium content in A-IX-2 means that there will be some unburnt aluminium powder dispersed into the surrounding air, where it will burn at reduced rate due to the reduced oxygen level in the air (and also in the RDX itself. RDX is oxygen deficient) and the high concentration of byproducts from the explosion. Augmenting this effect is the fact that the burning of aluminium generates an alumina (aluminium oxide) coating over the surface of the aluminium particles. The alumina acts as an insulation layer, thus delaying the burning of the aluminium itself. Thus the efficiency of combustion is reduced. This has the effect of extending the duration of combustion, extending the release of heat energy, increasing the explosive impulse, extending the radius of the incendiary effect, and increasing the probability of igniting other flammables in the vicinity of the explosion. The unavoidable side effect of the reduced efficiency of combustion is that the explosive velocity is slightly lower (1.54 RE) compared to RDX (1.60 RE). Another reason why A-IX-2 was used in anti-tank shells is because it highly insensitive to shock, thus preventing it from detonating upon the impact of the shell with tank armour.
Muzzle velocity: 895 m/s
Mass of Complete Round: 30.1 kg
Projectile Mass: 15.88 kg
Mass of Explosive Charge: 0.065 kg
Explosive Charge Type: A-IX-2
According to the famous Yugo tests, BR-412B could only penetrate the front turret of a T-54A at a distance of 500 meters. This means (indirectly) that BR-412B can perforate 200mm of cast armour at 0 degrees at 500 meters.
Penetration at 0 Yards:
164mm at 30°
133mm at 45°
96mm at 60°
59mm at 70°
Penetration at 1000 Yards:
140mm at 30°
115mm at 45°
82-85mm at 60°
51mm at 70°
Source: British Army test document: DEFE 15/1107
"The Performance of Russian SU 100 APHE/T Shot UBR-412B Against Armour Plate"
All values are for a 50% chance of penetration.
The British use the V50 standard instead of the Soviet/Russian V80 standard. If the document were Russian, the distance where the shell would be able to penetrate the armour of the tank would be listed as shorter. Besides that, the criteria for what constitutes armour penetration differs substantially from the Russian criteria. The British and American criteria dictates that at least 50% of the projectile mass must end up on the other side of the armour plate per a certain velocity, or in more practical terms, a certain distance (as the function of distance is the derivative of velocity). This forms the basis of the V50 standard. The Russian criteria as manifested in most firing tables dictates that at least 75% of projectile mass must be found on the other side of the armour plate. In actual certification testing, though, an 80% standard is used. This is why Russian ammunition is sometimes accredited with unusually low penetration when presented in literature. But I digress.
These figures are backed up by this page of the report:
Each vertical divider on the chart represents 250 meters.
All values are in V50 standard. The hardness of the target plates is listed below.
Penetration at 0°:
100 m: 235mm
250 m: 226mm
500 m: 211mm
750 m: 197mm
1000 m: 185mm
1250 m: 172mm
1500 m: 161mm
2000 m: 141mm
2500 m: 123mm
3000 m: 108mm
(WWII Ballistics Armour and Gunnery, corroborated with Janes' Ammunition Handbook)
Zaloga gives these figures (Link):
Penetration at 0°:
100 m: 160mm
500 m: 150mm
1000 m: 135mm
1500 m: 125mm
2000 m: 105mm
Penetration at 30°:
100 m: 130mm
500 m: 120mm
1000 m: 110mm
1500 m: 100mm
2000 m: 85mm
Zaloga's values are in Soviet standard. Besides the different penetration criteria, it is interesting to note that Soviet target plates had a hardness of between 250 to 350 BHN.
BR-412B is objectively superior to 90mm M318A1 APCBC. However, the T-54 did not have access to premium ammunition like M304 HVAP, though 100mm BR-412P HVAP ammunition was built in some small quantities and considered for full issuance. Ultimately, regular steel rounds were considered adequate and BR-412P never saw the light of day. For situations where steel AP was inadequate, multipurpose HEAT ammunition could do the job better than expensive tungsten cored HVAP ammunition, while simultaneously offering anti-personnel capabilities on the side thanks to its explosive charge, which, at a hundred millimeters' caliber, was significant.
Once full armour perforation is achieved, the results are utterly devastating. (The photo on the left is actually from a BR-412D penetration, but the effect is much the same).
Because of the inefficient nature of steel ammunition, the entry channel is always larger than the actual caliber of the shell itself and the exit channel is even bigger still, given that the target plate is thick enough. If the target is made of cast steel and not rolled steel, even better. Imagine a blast of armour fragments being ejected at extremely high speed into the tank, followed by shards of the eroded shell, followed by the shell itself, which may or may not be intact. If intact, the shell will explode and annihilate everything inside the tank shortly after clearing the armour plate. The MD-8 fuse embedded in the rear of the shell has a delay to ensure that the explosive charge detonates a certain distance inside the tank past the armour, making it more deadly than if it detonated immediately after perforating the armour plate, or as it penetrates the armour plate.
Although it was originally designed for German steel, BR-412B does not discriminate when it comes to targets. The M26 Pershing, and by extension the M46, both have a 100mm-thick cast steel upper glacis angled at 46 degrees. Factoring in the lower efficiency of cast armour compared to rolled armour and the information from the British tests, it should be vulnerable to BR-412B at in excess of 1.5 km. As for the M47, the famous Yugo tests mention that the 100mm cast steel upper glacis with a slope of 60 degrees can be perforated by BR-412B at a distance of 750 meters. This is rather close for comfort, but at least the T-54 would still outrange the M47.
So that's three Pattons covered so far. What about the M48? The upper glacis of the M48 is cast steel, 110mm thick sloped at 60 degrees, which more formidable than what the M47 has: 110mm of cast steel should be equivalent to something just under 100mm of rolled steel, making the upper glacis of the M48 nearly on par with the T-54 itself. A detailed report on the performance of BR-412B against the M48 is detailed in this Tank Archives post, courtesy of Peter Samsonov. Soviet testing revealed that BR-412B is not capable of penetrating the upper glacis of the M48 even at point blank range, which should not be surprising, since the Yugo test report mentions that BR-412B is not capable of perforating the upper glacis of a T-54A. The lower glacis can be perforated at 2500 meters, though.
The turret of the M48 is much weaker than the upper glacis, mostly because it is not nearly as sloped as the upper glacis, but it is still very well rounded. The thickness of the front turret face at the gun mantlet region varies from 178mm to 100mm, with sloping that ranges from 14 degrees at the very bottom edge of the turret where it is thickest to 56 degrees near the turret roof, where it is much thinner, but no matter what the thickness or slope is, the thickness on the front turret face invariably measures up to exactly 7 inches, or 178mm. The thickness reduces considerably beyond the immediate front turret face, but this is somewhat compensated by additional horizontal slope, although the final LOS thickness is still less than the front turret face. By referring to the penetration values given earlier, we can see that the front turret face cannot be considered well protected.
The gun shield overlaps the front turret face slightly, but the area of overlap is very small and the gun shield itself is negligibly thin. The most significant portion of the gun shield is 110mm thick, sloped at 30 degrees, which comes out to 127mm in LOS thickness. This should be vulnerable to BR-412B at a distance of more than 1200 meters.
Overall, BR-412B should be able to perforate the area near the base of the turret at distances in excess of 1250 meters, while the area near the roof should be highly vulnerable at a distance of at least 800 meters. This was inexcusable, since BR-412B was by no means new. It was replaced by the superior BR-412D in the same year that the M48 was introduced.
Steel shell with a soft steel armour piercing cap. This shell formally replaced the BR-412B as the standard anti-armour round in 1953, but it came as early as 1951 as an component of the loadout of the T-54 obr. 1951 (the brand new TSh2-22 sight for the T-54 obr. 1951 had a range scale for BR-412D). Both BR-412B and BR-412D continued to be used side by side for some time. Some former Soviet satellite states were still using BR-412B into the 2000's until they eventually scrapped their T-54 tanks completely.
The armour piercing cap prevents the shell from breaking up when it impacts high hardness steel plate at high velocities, particularly when the plate in question is highly sloped. Controlled fracturing of the nose of the shell is beneficial towards penetration on sloped targets, but shattering of the shell will neutralize it completely. This shell is superior to the BR-412B on both low and high obliquity targets, but the difference is most noticeable at high obliquities.
Muzzle Velocity: 887 m/s
Complete Mass of Round: 30.4 kg
Projectile Mass: 15.88 kg
Mass of Explosive Charge: 0.061 kg
Explosive Charge Type: A-IX-2
Zaloga gives these figures (Link):
Penetration at 0°:
100 m: 200mm
500 m: 185mm
1000 m: 170mm
1500 m: 155mm
2000 m: 125mm
Penetration at 30°:
100 m: 150mm
500 m: 140mm
1000 m: 130mm
1500 m: 120mm
2000 m: 100mm
These values are in Soviet standard. Soviet target plates had a hardness of between 250 to 350 BHN.
Penetration at 0°:
100 m: 250mm
1.0 km: 185mm
1.5 km: 170mm
The CIA report "TECHNICAL INFORMATION ON THE 100-MM GUN AND OTHER ARMAMENT ON THE T-54 TANK", which you can view here (link), has this penetration table for the BR-412D:
Comparing these figures to Zaloga's, we can see a huge discrepancy. The CIA's figures are much higher, especially when we go up to and beyond 2000 meters. At 500 m and 1000 m, the CIA's figures are 10mm higher for a 30-degree impact and 15mm higher for a 0 degree impact. At 2000 meters, the CIA's figures are 20mm (!) higher for a 30-degree impact and a 30mm (!) higher for a 0-degree impact. Such a big difference can only be explained by different target steel hardness and the difference in the V50 and V80 certification criteria.
According to these figures, BR-412D should be more than capable of perforating the front hull armour of a Leopard 1 at distances in excess of 1500 meters. The Panther's 82mm upper glacis sloped at 55 degrees, was found to be penetrable at a distance of 1500 meters. As for the M48, the BR-412D should have an effective range of several hundred meters more than the BR-412B when attacking the turret, but the most noticeable advantage is that BR-412D should be able to perforate the upper glacis of the M48 at a distance of around 500 meters.
APDS shell introduced in 1967. BM8 had good performance on vertical plate, possibly as good as 105mm L28 APDS, but its effectiveness on heavily sloped plate is highly unremarkable. We do not need firing tables to know this. MK. 3 and the more advanced L28 are similar in that they both have an unsecured cap. The MK.3 has a steel one, and the L28 has a tungsten one. BM8, on the other hand, is similar to an APCR shell, which are traditionally poor performers on sloped armour plate. There is no armour piercing cap, only a wall of mild steel in front of the core, and the hollow tip is partially filled with some lightweight metal. Besides that, the tungsten carbide core in BM8 is smaller and lighter than the one in MK. 3 and also lighter to the one in the L28. From left to right: BM8, MK.3, L28.
The same design of core contained within the 3BM8 projectile is shared by the 122mm 3BM11. The development of the 3BM8 is directly related to the 3BM11, as they were both born out of the same set of requirements. The shared heritage can be seen in their identical designs. 3BM11 appears to be larger than 3BM8, but that is mostly due to an increase in the thickness of the steel sheath over the core, leading to an increase in the overall diameter of the projectile but not in the diameter in the core itself. The sabot has a distinctly larger diameter. 3BM11 penetrates 320mm at 0 degrees and 110mm at 60 degrees, but this is purely due to the higher power of the cannon that fires it.
Muzzle Velocity: 1415 m/s
Maximum Chamber Pressure: 3000 kg/sq.cm
Mass of Complete Round: 20.9 kg
Projectile Length (incl. sabot): 240mm
Projectile Mass (incl. sabot): 5.7 kg
Subprojectile Diameter: 55mm
Subprojectile Length: 223mm
Subprojectile Mass: 4.13 kg
Source for dimensions: (Link)
Core Material: Tungsten carbide
Core Diameter: 48mm
Core Length: 115mm
Core Mass: 3 kg
For a target height of 2.0 m - 1680 m
For a target height of 2.7 m - 1930 m
For a target height of 3.0 m - 2020 m
Penetration at 2000 m
190mm at 0°
80mm at 60°
As you saw in the viewfinder of the TShSM-32P sight, APDS ammunition was a huge improvement over the old full-caliber steel AP rounds. According to According to V.A Grigoryan in "Защита танков" (Download), BM8 has a muzzle velocity of 1415 m/s and a velocity of 1202 m/s at 2 km. This comes out to a rate of speed loss of 106.5 m/s per kilometer of travel.
The main benefit of BM8 was the improved probability of achieving a hit on long distance targets, but knocking out the target is a different matter entirely. If the T-54 hoped to defeat an M60 or a Chieftain in the 1961-1975 time frame, it could only do so with HEAT ammunition. This confirms that the commonly held belief that the 115mm gun on the T-62 was made redundant by APDS ammunition for the D-10T is nothing more than a myth.
3BM19 is a pure steel projectile. Its torpedo shape is indistinguishable from contemporary APFSDS rounds in the 115mm and 125mm calibers. The increased speed of the shell compared to even 3BM8 APDS enables the T-55 to engage targets with much greater confidence. With a battlesighting range of 1690 meters against a 2-meter high target, it is possible for the gunner to lay his gunsights on the bottom part of the silhouette of an enemy tank and expect a successful hit at any range within 1700 meters.
The three piece sabot differed significantly from the usual "ring" type sabot for the smoothbore 115mm and 125mm guns. It was purpose-built for the D-10 family of guns, and had some special features to ensure that round could operate normally with rifling.
The back end of the sabot was lined with a sheet of rubber. When the projectile assembly is being propelled through the barrel, the high energy gasses pushing on the back of the sabot causes the rubber to expand and form a gasket to seal the gap between the rifling lands and grooves. This prevents the propellant gasses from exiting the barrel before the projectile.
The single copper driving band on the sabot is loosely connected to the rest of the sabot. It is meant to engage the rifling on the barrel, but the friction between it and the sabot is not great enough to cause the sabot to spin. The driving band supplements the rubber gasket in sealing the bore to prevent the escape of propellant gasses ahead of the projectile.
There is only one copper driving band on the sabot, but make no mistake, there are two contact points with the barrel. This is proven by the lack of copper bearings on the ends of the stabilizer fins. Therefore, the two contact points must be on the sabot itself. The second contact point is the band-less segment of the sabot. It only contacts the lands of the rifling, never with the grooves. This is not optimal, as aluminium alloy is very soft but still harder than pure copper.
Weight of Complete Cartridge: 19.5 kg
Projectile Mass: 4.58 kg
Odd as it might seem, 3UBM7 APFSDS is lighter than 3UBM6 APDS. The reduction in weight further lightened the loader's burden and increased the fire rate of the T-55.
3BM20 is broadly similar to the 3BM19, but it has a tungsten alloy core in the same configuration as the 115mm 3BM3. The design of the armour piercing cap of 3BM20 gives it far superior performance on sloped targets compared to the obsolete 3BM8 APDS round.
Penetrator Mass: 0.17 kg
Projectile Mass: 4.58 kg
Projectile Diameter: 38mm
Projectile Length: 496mm
Core Material: Tungsten alloy
Penetration at 0 degrees:
240mm at 2000 m
The penetration power of 3BM20 is practically identical to 3BM8 on a flat target at two kilometers, but 3BM20 performs much better on sloped targets at all ranges. Most importantly, 3BM20 uses only 170 grams of tungsten alloy - only 5.7% the amount used in the 3BM8. In economic terms, 3BM20 is a war winning design.
3UBM11 was formally introduced in 1978, but mass production had been underway since around 1975 or 1976. The order for the modernization of anti-tank munitions for anti-tank guns of the 100mm to 125mm calibers was issued in 1972, and led to the creation of 3BM25 "Izomer" alongside 3BM21 "Zastup for the 115mm U-5TS and 3BM22 "Zakolka" for the 125mm D-81T.
The three-piece sabot was carried over from the 3BM-19.
Total Length: 978mm
Total Mass: 20.7 kg
Projectile Mass: 5.2 kg
Muzzle velocity: 1430 m/s
Information from "Оружие России (2001-2002)", or "Russia's Arms (2001-2002)".
The change in muzzle velocity of the shell with temperature is tabulated here:
|1430 m/s||+15° C|
|1466 m/s||+40° C|
|1364 m/s||-40° C|
|Photo credit to PzGr40 of the wk2ammo site|
The advantage of 3BK5 over typical AP rounds is slightly offset when taking the poorer ballistic properties of the shell into consideration. Although the shell has a muzzle velocity that is essentially equal to BR-412D, it was significantly lighter so the shell had less kinetic energy behind it. This means that it takes less time to slow down from aerodynamic drag, which is compounded by the higher drag from the stabilization fins, leading to a larger drop in velocity over distance. Evidence of this is marked on the range scales on the TSh2B-32 sight. Over long distances, 3BK5 will also be less accurate than normal AP ammunition.
There are two variants of the shell. One is the basic 3BK5, which had a steel liner, and the other is the 3BK5M, which had a wave shaper and a copper liner. The wave shaper was a block of inert material that controlled the propagation of the blast wave to optimize the formation of the cumulative jet of the shaped charge. 3BK5M had improved penetration power.
3BK5 is interesting as its shaped charge cone had a square apex, as you can see above (photo shows 3BK5M with a copper liner). This was to increase the diameter of the cumulative jet, thus increasing the size of the hole in the target armour, and thus increasing the post-penetration effects. This practice was later abandoned in order to optimize penetration as serious anti-HEAT measures began to appear on tanks.
Fuse: GPV-2 PIBD
Penetration (at all ranges):
180mm RHA at 60 degrees
390mm RHA at 0 degrees
With each cartridge weighing in at just 25.5 kg, 3BK5 was easier to load than either AP and HE, but not APFSDS. This contributes to a slightly higher rate of fire. It is interesting to note that during the famous Yugo tests, 90mm M431 HEAT failed to fuze on the upper glacis of the target T-54 if the tank had a side angle of more than 20 degrees, but there were no such remarks to the same effect regarding the 3BK5. It can be inferred with reasonable confidence that 3BK5 with the GPV-2 fuze can handle steep slopes.
Total Length: 1093mm
Total Mass: 21.9kg
Muzzle velocity: 1075m/s
Projectile Mass: 10kg
CO-AXIAL MACHINE GUN
The T-54 mounts the SGMT on the right side of the main gun as a co-axial weapon. It has a cyclic rate of fire of 600 rounds per minute, and it is fed from a 250-round box. Sometime in the 60's, the SGMT was replaced by the PKT machine gun for standardization reasons.
BOW MACHINE GUN
The T-54 has a fixed bow SGMT machine gun, mounted just to the right of the driver (pictured). This was not unusual in any way, especially considering the T-54's World War II roots. However, what is unique to the T-54 is that there is a bow machine gun, but no dedicated bow machine gunner! In this sense, the T-54 was a more forward-thinking design than tanks like the M46 while simultaneously being a more silly one.
Ammunition is supplied by a 250-round box to the right of the gun (the machine gun is mounted sideways, rotated 90 degrees counterclockwise), and stripped ammo belts and spent casings are collected in a canvas bag placed just below the machine gun. There is a tinny metal casing deflector to prevent the machine gun from pelting the driver with spent casings. Reloading it is the driver's duty (obviously). The machine gun is fired using a solenoid thumb trigger on the end of the right steering tiller, but there is no way to aim it at all other than by steering the tank. It doesn't take much imagination to figure out how effective this would have been in combat. In practice, the ammunition allocated to the bow machine gun would be used up by the co-axial instead, and if it isn't, then it should be.
ANTI-AIRCRAFT MACHINE GUN
The original T-54-1 was a departure from usual Soviet tank practice in that it had a DShK anti-aircraft machine gun installed on its roof. Prior to the T-54, only IS-1 and IS-2 heavy tanks had one. Medium and light tanks generally did not have external machine guns of any kind, unless field modifications were performed.
as translated by Peter Samsonov from archiveawareness.com, are:
1. Determine the armour that will protect the hull and turret from 75 mm and 88 mm shells with the muzzle velocity of 1000 m/s.
2. Improve the shape of the hull from the point of view of robustness and shell resistance.
3. Improve the armour of the turret to the point that it resists shells as well as the front of the hull.
4. Develop armour screens for the T-54 to protect it from HEAT shells up to 105 mm in caliber inclusive and Faust type anti-tank rockets.
5. Develop a robust track and track pin (increase track life to 3000 km).
6. Investigate the optimal location for ammunition in the tank.
T-54-1 (T-54 obr. 1947)
As a result of these requirements, the T-54-1 prototype tank had an upper glacis plate measuring 120mm thick, angled at 60 degrees. This was equal to the armour of the prototype of the IS-2, and thicker in total than the upper glacis of a King Tiger! The lower glacis plate was no joke, as it was equally thick as the upper glacis but less well angled at 45 degrees, and the side armour was 90mm thick. In the end, though, the tank became too heavy for the engine and the transmission to handle.
The turret has a very distinct out-of-this-world appearance, but in reality, it is merely a rounded-off reimagination of the hexagonal design of the T-34-85 and T-44 turrets. The overhead photo shown below clearly displays the six sides of the turret, analogous to the T-44 turret. Unlike the later turrets, this design retained a mantlet/gunshield, where the gunsight and co-axial machine gun fitted.
|Photo credit to Vladimir of Urban3p|
The ballistic shaping of this turret was better than the previous versions, but the problem of the large shot traps around the turret ring area was a huge liability. Other than that, the good angling of the side cheeks of the turret in combination with the well-rounded mantlet provided good protection. See the photo below, kindly provided by Vladimir of Urban3p. Urban3p is a community of adventurists. Their members travel all around Russia, taking photos and experiencing the abandoned ruins of man-made structures. One example is this abandoned T-54-1 pillbox turret.
The photo shows the gunner's station. The hole at the end is for the TSh-20 telescopic gunsight. By comparing the angle of the wall of the turret to the cannon breech, we can see that the horizontal slope of the turret is quite steep. There is not much in the way of vertical slope, but the turret is rounded.
T-54-2 (T-54 obr. 1949)
In 1949, the revised T-54-2 arrived, sporting a new turret. Its shape had familiar curves, but it was not quite the same as the final version. The shot traps were reduced, but still extant around the rear of the turret. The hull was finally reduced to 100mm front, making it the same thickness as the production model of the IS-2 mod. 1944. The sides were reduced to 80mm.
T-54-3 (T-54 obr. 1951 and onwards)
In the year 1951, the T-54 finally gained its iconic rounded turret. The turret has been described in many ways, from "overturned soup bowl" to "hemispherical". In truth, it is a unique shape with complex angles that cannot be summarized easily. From above, it is distinctly egg shaped. From the side, it is more oblong than round. Only from the front does it resemble a perfectly rounded overturned soup bowl.
Production turrets were manufactured by chill casting, but there was an issue with casting the entire roof along with the rest of the turret in one piece. To fill in the gap, the roof had to be built from two D-shaped rolled steel plates, welded onto the cast walls in an automated procedure done by a machine rig. This results in a marginally weaker turret than one that is all-cast, as the plates might be ripped off at the weld seams if struck by cannon fire even at its highly oblique angle, or the plates might collapse due to reduced structural integrity. However, using rolled steel plates in this location has the benefit of increasing the chance of a ricochet when struck, as the rolled steel plate is significantly harder than the cast turret.
The welds joining the hull roof to the side hull, and the welds joining that to the glacis plates and to the floor and all the welds in between were strengthened in the T-54-3 compared to the T-54-2. The geometry of the fittings between the armour plates was changed to increase the surface area and thus improve the strength of the joint. This helped to improve the armour integrity of the hull and thus improve protection without changing the thickness of the plates.
The hull and turret were evaluated against anti-tank guns of a myriad of calibers of both domestic and foreign make. The frontal aspect of the tank had to be proofed against common tank guns like the 90mm M3 of the M26 Pershing and the M46, but it was also tested against the tank's own D-10T and the 85mm S-53 of the T-34-85.
As the post war reality showed that American 90mm guns would be the main threat to Soviet armour amd not German 88mm guns, the basic requirements for the ability to resist 88mm shells "with a muzzle velocity of 1000 m/s" (referring to PzGr. 39-1 fired from the 88mm KwK 43 L/71) became very convenient. M82 APCBC/HE-T was obtained via lend-lease, and became one of many foreign-made munitions for use in testing.
The photos below show the armour of a T-54-3 pattern model tested against anti-tank weapons of various calibers. Note that the roadwheels are of the spoked type, indicating that the test vehicle is indeed a T-54 obr. 1951 and not a T-54A or T-54B, which were fitted with "star" type roadwheels.
The sides of the tank turret and hull were shot up just as thoroughly as the front, and with weapons of the same variety. Besides large caliber tank shells, the vulnerability of the sides of the tank to large caliber anti-aircraft cannons like the Red Army's own 57mm S-60 was also investigated. It is unknown if the widely used Bofors 40mm L/70 was tested.
Both the upper and lower glacis plates and the side hull plates are constructed from 42 SM armour grade steel. The rear armour plate and the roof plate was made from 49 S armour grade steel, and the belly of the tank was made from 43 PSM armour grade steel. The cast steel turret was made from 74L CrNiMo armour grade steel, while the two-piece roof welded onto the cast turret was made from 43 PSM steel. The 49 S and 43 PSM steel plates installed in the roof and belly of the tank was quite thin - only 20mm, so it is quite surprising that these steels are rather soft for their thickness. This table states that 49 S and 43 PSM have a hardness of only 180-250 BHN. The rule of thumb is that thinner plates are easier to harden than thicker plates, so the plates used in the tank are definitely closer to latter than the former, but even so, that is really quite soft for such thin plates. 42 SM and 74L, on the other hand, are medium hardness steels with a hardness of 270-340 BHN and still quite thick. This information comes from the famous "Техника и Вооружение" (Tekhnika i Vooruzhenie) magazine.
Foreign appraisals of the steel for the armour of the tank were consistently positive. In the (translated) famous Yugo tests document, for example, it was noted that "T-54A cast parts were 270 BHN (rolled plates were 290 BHN) and were judged to be of excellent quality". From this, we know that 74L cast armour steel has a hardness of 270 BHN, while 42 SM has an average hardness of 290 BHN when combining the softer glacis with the harder side armour.
Strictly speaking, the T-54 does not really have a gun mantlet. What it has is more of a gun collar. The collar is mostly useful for preventing autocannon fire from damaging or jamming the trunnion, as it is not large and thick enough enough to actually stop a shell on its own. If it is struck by a tank shell, what will happen is the shell will be deflected, perhaps into the turret face. Only the upper part of the gun collar is thick enough and properly sloped to deflect a cannon shell, though still not without potentially damaging the gun barrel.
A serious disadvantage to the lack of a gun mantlet is that a tall slit has to be cut into the armour to accommodate the vertical movement of the co-axial machine gun and the aperture of a telescopic gun sight. As long as a telescopic sight is used, there must be a hole in the armour, but as a gun mantlet moves with the cannon, a gun sight aperture embedded in the mantlet only needs a single, small hole. The relatively large slit in the turret of the T-54 increases the size of the weakened zone. Examples of tanks that possess this weakness besides the T-54 include the Chieftain tank, which has a tall vertical slit in the front of the turret for the co-axial machine gun. The Chieftain bypasses the need for a slit for the gun sights by using a periscopic sight.
The optic slit in the left turret cheek is about the size of a child's forearm, while the machine gun slit in the right turret cheek is a bit shorter and a bit higher up.
As you can see in the photo above, the turret (which we will define as the area just next to the machine gun and gun sight ports) has a more or less uniform thickness (which we know to be 203mm) around the bottom half, thinning down to 70mm at 68 degrees at the highest point of the cheeks similar to the T-54-2 turret. This means that the LOS thickness goes down to 186mm, but the curvature of the turret actually improves the protection value as we move up the turret. This is because the performance of full caliber AP shot as well as early APDS degrades drastically on sloped armour plate.
The sides of the turret slope inwards at 60 degrees and converge at the gun mantlet, giving it a rounded needle-nose shape. This shape is excellent for an all-steel turret from a ballistic point of view, but the effect on internal space in the turret is somewhat negative, which is compounded by the fact that the turret of the T-54-3 is also dome-shaped. The sides of the turret that slope inwards to form the needle-nose shape are 150mm to 170mm thick, thickest as it transitions from the turret front and thinner as it curves round to the back. The rear part of the turret sides, at the commander's and loader's areas, are around 100mm to 120mm thick, thickest at the bottom and thinner as the steel curves towards the top.
If we take a close look at the turret wall behind the gunner's primary gunsight, we can see very plainly how the turret immediately assumes a side slope after the gunsight port.
The photo above also shows that the flat part of the front of the turret is shaped like a right angled triangle. This is the weakest part of the T-54 turret, as it is only sloped in the vertical plane. Aside from the flat triangle, the turret is sloped in three dimensions.
As you can see in the photo, the area behind the gunner's MK.4 periscope is distinctly more curved than the rest of the commander's station. In other words, the flat part of the turret is much narrower than it appears in exterior photos.
VERSUS SPECIFIC AMMUNITION
Penetrating just 147mm at 0 degrees at a thousand meters' distance, M82 was simply inadequate against the T-54. A large portion of the side of the turret has the potential to shrug off a hit from M82 at close range, and the side hull is largely immune at most angles, unless it is struck straight on.
Much later on, the M36 gun became available as well, as nearby Yugoslavia operated 319 M47 Patton tanks. Accroding to the famous Yugoslavian tests, the front of the turret could only be perforated by PzGr. 39-1 APCBC fired from the KwK 43 at a dangerously close distance of 600 m. The upper glacis was totally immune, even from a hundred meters, but the sides of the turret can be defeated at a distance of up to 1750 m.
Fired from the 90mm M3A1, T33 APBC rounds totally fail to defeat the front of the T-54's turret at any range. Shot perpendicularly from the side, the front part of the turret sides can only be defeated at a suicidal range of 250 m. When hot loaded T33 is fired from the higher pressure M36 cannon, the chances improve a bit. The shell is still not capable of getting through the glacis even at a hundred meters, but the front of the turret can now be perforated at 350 m. The frontal part of the side turret can be perforated at 850 m, which is much better. M304 APDS is mandatory when fighting the T-54, as the front turret can be perforated at 750 m.
M431 HEAT works well at any range on any part of the T-54, but the killing power is low, and the shell has fuzing problems on angled parts of the armour. It has a high probability of failing to detonate if it strikes the upper glacis when the tank is angled 20 degrees sideways. The shell may not work properly on the well rounded shape of the turret, especially the top half. Also, M431 was not introduced until the late 50's. Details on the M431 are available here: (Link)
The M82 APCBC/HE-T round packs a lethal 200 grams of RDX, but it is almost useless against the T-54 unless you aimed for the side hull or rear hull and turret. M82 was not included in the Yugo tests, but it is not difficult to predict its performance. According to U.S Army tests detailed here (link), T33 fired from the M3 cannon is capable of defeating the upper glacis (82mm at 55 degrees) of a Panther at a range of up to 1100 yards, but M82 fired from the same cannon cannot repeat the same feat, despite having a capped penetrator. At most, it could deal with the lower glacis - which measured 60mm thick at 55 degrees - at a maximum range of something over 950 yards.
The T-54 offered the next best chance against itself, behind the 88mm KwK 43 as BR-412B is capable of perforating the front of the turret at 500 m, and the front part of the side turret at 1000m. With BR-412D, there is no doubt that a better result may be obtained.
The M48 will find itself in a rather bad situation in comparison to the T-54 where hull armour is concerned. It is well known that cast armour is significantly weaker than rolled armour, but to what extent is not often grasped by many. In the Yugo tests, testing of domestic M47s have shown that the upper glacis, a 100mm cast steel plate sloped at 60 degrees, can be defeated by BR-412B at a distance of 750 m, even though BR-412B is technically only rated to penetrate 96mm of rolled steel angled at 60 degrees at a point blank distance according to a British evaluation using the same metrics of penetration. The 100mm rolled steel upper glacis of the T-54A is unsurprisingly immune to BR-412B from all ranges. The T-54 can be considered arguably on par with the M60 tank in terms of hull armour protection.
There is much more information that can be gleaned from the results of those tests, but only if we pay close attention to detail. The tests involved shooting at the side of the turret from a right angle, but as we know, the turret is sloped inward. If the turret is attacked at a perfectly perpendicular side angle, the front part of the sides of the turret will have a horizontal slope of 30 degrees, thus making the LOS thickness 196mm to 173mm. We know that T33 fired from the M36 cannon is capable of defeating this at 850 m.
However, a shot coming at the turret from a forward 30 degree angle would also have to face between 173mm to 196mm of LOS armour, because the 60 degree inward angle of the turret sides is reduced to just 30 degrees. This means that if the turret is attacked from its forward arc, it may only be as strong as its side in certain parts. In general, the turret becomes more vulnerable as the incident angle increases from 0 degrees to 30 degrees to 50 degrees and so on, up til a point at 90 degrees where it is as vulnerable as it is at 30 degrees. This is a peculiarity of this type of ballistic shaping, and it is not limited to the T-54. The turret of the M60A1 has the same problem, only it is even further amplified because the cheeks of the M60A1's turret are thinner - only 140mm thick. The T-54's turret can be considered to be extremely resilient to anti-tank guns of its time, but it is not without its weaknesses.
VS 20 pdr
According to British tests, Centurion's MK.3 APDS for the 20 pdr. gun would fail to defeat its own upper glacis (76mm at 57 degrees) at a minimum distance of 4400 yards, or 4023 meters. After the addition of a 44mm weld-on applique armour plate, the distance of immunity was decreased to just 850 yards, or 777 meters. This means that MK. 3 APDS can penetrate less than 120mm RHA angled at 57 degrees at 777 meters, and less than 76mm at 57 degrees at 4023 meters.
According to Swedish archive documents shared by renhanxue, owner and administrator of the Swedish Tank Archives website (tanks.mod16), 20 pdr. APDS (most likely MK. 3) can penetrate 240mm of vertical plate at 500 m, and 95mm at 60 degrees at 1000 yards (914 m), and it fails to penetrate 122mm angled at 60 degrees at 500 m. This is congruous with the aforementioned tests. The hardness of the plate used is unknown. However, the drop in penetration performance is between 4400 yards and 1000 yards is suspiciously small for an APDS round. It is possible that the Centurion's rolled steel plates are softer than the test plates used during the Swedish tests.
Taken all together, this means that using MK. 3 APDS, a Centurion Mk. 3 should have the ability to defeat the upper glacis plate of a T-54 only from below 900 meters. This makes the Centurion the best performer among all of its Western peers in a hypothetical face-off against Soviet T-54s.
Let's see how MK. 3 does against shallowly sloped plates:
So, MK. 3 can confidently defeat 150mm RHA angled at 30 degrees at about 1750 yards, and pierce 120mm RHA angled at 25 degrees at up to 2250 yards. This is all bad news for the T-54's turret.
According to Swedish test data provided by renhanxue, 105mm L28 penetrates 200mm RHA at 30 degrees at 1500 m, and 140mm RHA at 55 degrees at 900 m. On TankNet, renhanxue states that the British give a penetration value of 120mm RHA at 60 degrees at 1000 yards for L28. This means that the turret of the T-54 is vulnerable from combat ranges of 1500 meters, and beyond.
Additionally, any evaluation of the T-54's survivability is not complete without also reviewing the value of its relatively small silhouette. Being quite small for a tank, the T-54 is easy to conceal in vegetated areas. The small surface area of the tank also makes it less time consuming to camouflage it.
Unfortunately, the low mounting of the telescopic gunner's sight is not conducive to certain practices. For example, it is not possible to do "berm drills" with a T-54, as the gunner is not able to see the target when the tank is in turret defilade. It would be possible if the gunner switches over to the auxiliary sight, which is periscopic, but it is not an optimal solution. Whether this is a fatal flaw, a minuscule annoyance or something totally irrelevant to the tank's combat potential is debatable.
Moreover, the merits of extreme hull down positions are somewhat ambiguous. If the tank was so far hull down that the barrel barely clears the crest of whatever hill it is behind, imagine the cloud of dust that will be kicked up when the gun fires? This has already proven to be a huge issue in legacy tanks like the T-54 as it prevents the application of the burst on target method, which we have already established to be a critical tool for fire correction.
|An Israeli Tiran tank in a partially obscured position|
A BRIEF AND GENERAL ANALYSIS OF T-54 COMBAT LOSSES
Compared to some other tanks, the T-54 might seem to have a rather spotty combat history, particularly in major wars like in Vietnam, but all too often, a short analysis of the circumstances can reveal why. Generally speaking, T-54s have performed well as long as they have been used well. Below is a photo of a destroyed T-54 featured in the January issue of Armor Magazine, 1973, along with an excerpt.
So as it turns out, driving slowly down a highway in a column is not the best idea. Just like that, six or eight T-54s were destroyed. Can you blame the tank? Here's another case:
A T-54 destroyed due to the air superiority enjoyed by U.S forces. Below, you can see a T-54 knocked out by two armour piercing shots to the rear, plus what appears to be a single HEP shell. It was powerful enough to rip off part of the rear plate from the floor and the side hull.
What sort of armoured unit lets themselves get shot in the rear by large caliber cannons?
The photos below shows three tanks knocked out in an ambush at the Lang Cha Ca intersection by the 81st Airborn Ranger Battalion of Vietnamese Rangers, a light infantry force trained and assisted by U.S special forces. There is no trace of doubt that they were knocked out with M72 rocket launchers.
You can see in the photos that the tanks were flanked by shop houses on one side. The rearmost tank is pointing its gun into one of them. Evidently, two of the tanks were put out of commission by a barrage of rocket launchers from within the shop houses, and the last tank had just enough time to slew the turret before getting knocked out as well. The last tank burned up (photo). Here is a colour photo (link).
Here's another case:
Five tanks, one of them captured in the photo above, were eliminated by air power as they were crossing a river.
T-54s were destroyed as they drove down Saigon's streets in columns, parade-style. According to the 81st Airborne Ranger Group and Vietnamese Special Forces Association website (link), several more tanks were destroyed in the last day of the war as NVA forces roamed the streets of Saigon.
At 6:00 A.M., five T-54 tanks and a column of accompanying VC infantry advancing into Saigon were stopped in front of the gate to Tan Son Nhat Airbase by resistance from elements of the Airborne Division and the 81st Airborne Rangers. Four VC tanks were destroyed, and the last one turned around and retreated. The Airborne Ranger companies that fought to defend the front gate of the JGS were the 817th Company, commanded by First Lieutenant Le Van Loi, and the 818th Company, commanded by Captain Nguyen Anh.
At 7:00 A.M., another column of Viet Cong armor headed toward the main gate into the JGS compound. A team from the 81st Airborne Rangers fighting in a tall building destroyed the lead vehicle with an M-72 rocket. The second tank fired its main turret gun into the building, neutralizing the defensive position there, but this vehicle was then destroyed by soldiers from 1st Lt. Le Van Loi’s 817th Company in front of the gate into the JGS.
From the huge haul of information gathered during my research, of which only a fraction is presented here, it appears that the vast majority of T-54s in Vietnam were lost to rocket launcher and recoiless rifle fire, the majority of which can be attributed to the M72 LAW. The T-54 held up as well as could be expected, considering that they were often poorly handled and blundered into ambushes. A significant number of tanks were destroyed by air power or forces aided by air power, though this is often downplayed or not mentioned at all like in Wikipedia:
"The NVA and ARVN engaged each other with tanks for the first time during Operation Lam Son 719, in February 1971. During that battle, 17 M41 light tanks of the ARVN 1st Armored Brigade destroyed 22 NVA-tanks, 6 T-54 and 16 PT-76, at no loss to themselves,[full citation needed] but the friendly units lost 5 M41s and 25 APCs."
This summary of the battle is incomplete. The truth is that the ARVN 1st Armored Brigade was supported by gunships armed with a pair of anti-tank rocket pods on each wing which strafed the NVA tanks. This is mentioned in "Vietnam War: The New Legion, Volume 2 by Vinh Truong. The author has provided a method of reading his work for free via this forum topic here: (Link). The relevant post is post #12, copied out below:
"Some troop elements had done conspicuously better than others. The ARVN armored units had been especially early in the operation the 1st Squadron, 11th Armored Cavalry had encountered NVA elements in a fight at southern Fire Base 31 and performed brilliantly, destroying six enemy T-54 tanks and sixteen PT-76s without any friendly losses in the first major tank-to-tank engagement of the war, but of course with our gunship air cover supported joint-strafing with the both flank-sides [of our helicopters] equipped [with] two 19-shot 2.75-inch antitank rocket pods. Today by chance we got the record shooting into the POL pipe-line at random burned all of them for a while right after NVA shut-off the pipes."
By "2.75-inch antitank rocket pods", the author is, of course, referring to Hydra 70 rockets. 70mm M247 HEDP rockets have a shaped charge warhead that can penetrate 145mm of steel armour. This might not seem a lot compared to the 66mm warhead of an M72 LAW, which can penetrate up to 200mm of armour, but 145mm of penetration is already more than enough to punch through the sides and rear of a T-54 tank. Even if HE rockets were used instead of HEDP ones, the tanks' observation equipment can still be destroyed, rendering them blind. Either way, it is clear why the battle was so one-sided.
Besides Hydra rockets, TOW guided anti-tank missiles fired from helicopters as well as ground mounts were responsible for a sizable portion of T-54 losses during the closing stages of the war. The TOW was especially successful when it was first used in April 1972 on Huey UH-1B gunships. Here are two excerpts from "History Of The TOW Missile System", page 168.
Here is a photo of one of the Huey gunships.
The TOW missile system was extremely deadly to T-54 tanks by the virtue of its accurate SACLOS guidance system and the large 5-inch warhead, which had greatly overmatching penetration against the basic steel armour of the T-54 and thus produced very powerful beyond-armour effects.
Additionally, when tanks of any technical capabilities compared, it is nearly impossible to form any accurate conclusions from their performance in battle without also taking into account the competence of the army fielding them, besides also taking into consideration the individual peculiarities of the local combats where the tank was involved. Here, I would like to use the example of the Chinese incursion into Vietnam in 1979.
When the Chinese intervened in response to the Hanoi regime's hostility towards Pol Pot and the Khmer Rouge - both Chinese affiliates - they brought with them an initial invasion force of more than 80,000 soldiers and the best tanks available in the PLA across the border, including the Type 59 medium tank, Type 62 light tank and a number of Type 63 armoured personnel carriers, with a smattering of Type 63 amphibious tanks. Despite all this, the Chinese failed to penetrate deeply into Vietnamese territory and were repulsed after sustaining 50% more losses than the Vietnamese, in defiance of all expectations. It would be asinine to refer to this incident to claim that the T-34 is better than the Chinese Type 59, and by extension, the T-54, so what went wrong? As usual, the reason is because the Chinese invasion was atrociously deficient on all levels, from planning to execution. The battle-hardened and well motivated Vietnamese army, now evolved into a de jure conventional army, bested their totally inexperienced Chinese counterparts in every way.
Besides tanks, the Chinese invasion force were largely equipped with the same weapons and gear as their Vietnamese counterparts. Soviet-designed artillery, anti-aircraft guns, mortars, machine guns and small arms were the primary weapons on both sides, with the Vietnamese army being supplemented with captured South Vietnamese arms.
Similarly, the poor performance of the T-54 in Arab hands against the Israelis during the Yom Kippur war of 1973 has left an extremely misleading impression. Hundreds of T-54s were lost to the heavily outnumbered Israelis in that infamous war, but hundreds of American tanks fell to the Israelis in preceding conflicts as well. Using mostly M50 and M51 Shermans, also known as Super Shermans, the Israelis felled Jordanian M48, M48A1 and M47 tanks and captured (!) about 100 M48 tanks - more than half of Jordan's fleet of 170. Jordan had none of the same success with the Centurion as the Israelis did with theirs during the Six Day war, and later on, the Yom Kippur war. For us, the Yom Kippur war deserves special mention because it featured the use of the T-54 is a truly mammoth scale, and also because T-54s were lost in equally appalling numbers.
This famous photo of knocked out Syrian T-54 and T-62 tanks on the Golan Heights has sometimes been shown as "proof" of the inferiority of Soviet tanks, but in reality, it is quite the opposite.
Take a closer look. All of the vehicles in the photo have been abandoned, including the two trucks, but most importantly, all of the tanks (except one) have their guns aimed behind them. The tank that fell off the bridge in the foreground was moving from left to right (based on the assumption that no idiot driver is going to reverse a tank over a narrow scissor bridge), and that tells us that that was the direction of the advance or retreat. So why do all of the tanks have their rears pointed in the direction of advance/retreat and their turrets pointed in the opposite direction? The photo below is a close up of the scene, showing two of the knocked out tanks. They were clearly not destroyed or disabled by enemy fire, but by crew incompetence.
In all probability, this scene had nothing to do with combat. Most likely, these tanks were abandoned when the dismounted crew was ambushed by infantry or tank fire while they were restocking ammunition (this explains the presence of unarmoured trucks). This is most likely a case of insufficient reconnaissance, leading to the failure to anticipate enemy movements.
One of the most storied accounts from that war is that of Zvi Greengold, which has become something of a crowd-pleaser. Although the events undoubtedly occurred and were hugely impressive, the unfortunate reality is that the story has been exaggerated and distorted. It is not necessary for me to elaborate too much, as there are already very good publications on the subject, including this article here (Link). Zvi Greengold's story has less to do with the superiority of certain tanks, and more to do with the superhuman endurance and fighting spirit and quick thinking of Israeli tankers.
Zvi Greengold's story was not the only one where Arab tanks were lost. Many tanks were knocked out while travelling in columns, unaware that they were being targeted (which we can blame on the lack of forward reconnaissance). More importantly, however, the vast majority of Egyptian and Syrian tanks were not destroyed, but captured. According to this article (link), the Israelis had 1000 captured T-54 and T-62 tanks in their arsenal, and had 444 of them in active service in the form of modified "Tiran" tanks. The number of captured tanks is especially shocking when considering the fact that most estimates place the number of tanks in the Syrian invasion force at the Golan Heights at around 1300 to 1400 tanks, while the Egyptians crossed the Suez Canal with as many as 1000 tanks. As a rule, if the tank is burned out, it is no longer usable in any capacity. Therefore, it can be reasonably inferred that a majority of Arab losses were in fact due to their crews abandoning their tanks even though their tanks were still serviceable, or at least in repairable condition. This dispels the widespread impression that Soviet-built tanks are hopeless deathtraps, and it also shows that the Egyptian and Syrian armies lacked the tactical capacity to consolidate territorial gains and lacked a mature support system to recover battlefield losses. It also shows that Egyptian and Syrian tank crews lacked discipline, as they neglected to scuttle their (functional) tanks as they fled the field of battle - a double act of cowardice and negligence.
The T-54's performance in the Middle East is intrinsically linked to Israeli competence and Arab incompetence. In those conflicts, as in any, the tool does not matter as much as how the workman wields it. One is reminded of the atrocious performance of advanced Chieftain tanks in Iranian hands when facing off against Iraqi T-54s, Type 59s, T-62s and Type 69s. And yet, there can be no reasonable doubt that the Chieftain is the superior tank in every respect. If we go even further back, the example of Char B-1 tanks is particularly appropriate. Even though the Char B1 was quite clearly a superior tank to the more numerous German ones at the time of the invasion of France, a plethora of mitigating factors completely negated whatever advantages the tank might have had to the point where these supposedly superior tanks became practically useless. The only logical explanation for these apparent inconsistencies is that in no way do any of these conflicts truly represent the T-54's capacity for war. In many of these cases, one of the belligerents was totally outmatched in skill and motivation by the other.
Of course, there is no excuse if the T-54 has displayed consistently poor performance throughout its life, but it does not need to be said that the T-54 does not have the monopoly on poor tactical leadership and poor crew training. The Pakistani M48 and Sherman pictured below, destroyed at Asal Uttar, illustrates that perfectly.
We have examined the T-54's armour, and we have seen that it was very well protected from common Western arms of the era. But what good is your thick frontal armour when the enemy has the opportunity to shoot at you from the flanks? In some rare cases, exposing your vulnerable sides is unavoidable, but if it becomes a habit, then there is a deep rooted problem.
Speaking of deep rooted problems, it is not wise to ignore religion as a factor. Read this Indian Defence News article for more. Here is an excerpt from the article.
"The Pakistanis would abandon a tank soon after it was hit, fearing that it would catch fire and they would be charred in flames—not the best way to die for a Muslim." So many Patton tanks recovered were brand new. They had just done 30 to 35 miles. Pakistani Army had far superior equipment, but weren't trained to use them," says Brigadier JP Singh."
According to Islamic teachings, cremation is strictly forbidden as it is considered a sin. It is customary for a Muslim to be buried with his body intact, wrapped in white cloth. Before learning that their Abrams tanks were mostly immune to RPGs, Iraqi tankers had an unspoken policy of ditching the tank immediately after it was hit. It is not uncommon to see U.S Army soldiers and training staff and active servicemen lamenting the poor discipline of Iraqi and Afghan soldiers on social media and forums. Bottom line: Arab Muslim tank crews are to blame, not the T-54.
Now that we have covered the Middle East, let's take a look at a less well known example: The South African Border War.
In September of 1987, the first tank battle between the Angolan and South African forces occured at the Lomba river, involing FAPLA T-54/55s and SADF Olifants. A wide variety of factors affected the course of the battle, with the final result being that the Angolans were beaten badly into a retreat. Throughout the much of the conflict, the Angolan experience was appreciably worse than the South Africans'. Much of this can be attributed not to the superiority of South African armour, but to the superiority of South African artillery and air power. I recommend reading 'Bush War: The Road to Cuito Cuanavale: Soviet Soldiers' Accounts of the Angolan War' to better understand the situation. Angolan artillery was often outranged by SADF artillery, as the SADF had G6 (155mm) howitzers while the Angolans usually only had smaller caliber artillery pieces like the D-30 (122mm) and BM-21 "Grad" (122mm). Virtually all of the anecdotes told in the book mention constant bombardment by artillery, sometimes by rocket-assisted shells, while they (the Angolans) had their hands tied by the limitations of their own equipment. Air defence systems like the Osa and Strela-10 were often destroyed, not by SEAD ops, but by artillery fire. Furthermore, systems like the ZU-23-2 were inoperable during an artillery barrage due to the open nature of the rig. All this seriously compromised what meager air defence the Angolans were afforded, leaving them vulnerable to air strikes. Mobility was occasionally hampered as shrapnel filled the air almost every hour of the day, puncturing both the thin sheet metal skin and the tyres of the trucks that served as Angolan APCs. All this meant that even when T-54 tanks were available to spearhead assaults on SADF positions, those tanks were themselves not protected from South African rocket launchers. It's absurd to single out the T-54 as the root cause of all the failures of FAPLA forces when it is the other way around.
In the right hands, the T-54 was easily capable of success. Cuban T-54/55s and Cuban-guided Angolan T-54/55s proved themselves in Cuito Cuanavale against South African forces (SADF) in late 1987 and early 1988. On 14 February 1988, three battalions of SADF troops, reinforced by a six battalions of UNITA guerilla fighters and 100 armoured vehicles including 40 Olifant tanks, launched their second attack on Cuito Cuanavale, breaking the already severely demoralized 59th FAPLA Motorized Infantry Brigade. To plug the gap in the defence, a tank company comprising of 8 Cuban T-55s, commanded by Lt. Col. Hector Aguilar, was quickly deployed. This modest tank force successfully repelled the offensive, destroying 10 Olifants and 4 Ratel 90s in the process, effecting a South African rout. On the Cuban side, 6 of the 8 T-55 tanks were knocked out, three by RPG fire and three by Olifants. Of the 39 Cuban soldiers and tank crewmen involved, 14 died.
Interestingly, the generally undisciplined FAPLA forces floundered under the leadership of Soviet advisors, but Cuban commanders managed to handle them better, and needless to say, Cuban units were far superior to their Angolan counterparts. Also, 'Bush War: The Road to Cuito Cuanavale' mentions that the Cubans conducted their own reconnaissance. The result was that Cuban forces were usually equipped with good information on SADF troop movements and were better able to plan operations.
The Cuban military is not known for being particularly elite, so it might seem strange that they performed so well in the war, but this is probably due to the 13 years of prior experience with the Angolans. The Cubans had intervened in Angola in 1975 and a sizable contingent of officers had stayed there ever since. The involvement of bona fide Cuban tank crews and soldiers made quite a difference as well. The Soviets themselves were never actually involved in direct combat. The Cubans likely had a better grasp of South African tactics as well as the limitations of Angolan forces, having had extensive exposure to the local environment. Cuito Cuanavale proves that the equipment matters less than the crew when there is no clear technological advantage, and where the T-54/55 is concerned, that needs to be fully understood.
"Brow armour" has already been covered in Tankograd's T-62 article. It would be pointless to repeat it all here, so please head over to the T-62 article to read more. However, the unique geometry of the turret of the T-54 means that the spacing between the turret and the add-on armour blocks is not the same as on the T-62, which is worth talking about.
The photograph below comes from Paul Lakowski's "Modern Armour", and is apparently taken by an individual named Georg Stark. "Modern Armour" uses very old estimates and figures, but some of the information - like the photo and sketch below - is accurate.
As you can see from the sketch, the air gap between the "Brow" armour block and the turret ranges from 50-60mm at the bottom to around 200mm at the top. The presence of an air gap behind the armour array gives room for KE projectiles to break apart as the buildup of internal stresses from the penetration of the steel front plate and the moving internal plates is suddenly released, thus magnifying the effect of the armour. For shaped charge jets, the air gap may give room for disturbed jet particles to disperse radially outward, such that they do not contribute to the total penetration depth from the residual jet tip.
In the wake of the Hiroshima and Nagasaki atomic bombings, the first priority in the Soviet Union was to develop their own nuclear weapons and the means to deliver them, but as time went on and new battle theories were formed, the question arose; what place will the tank have in a nuclear war? As the T-54 was designed during the closing years of WW2 and was finalized only after its conclusion, no considerations were made for the effects of nuclear destruction. As part of tests carried out between 1952 and 1953 to determine the effects of nuclear weapons on various ground equipment, including tanks, the T-54 tank was exposed to a nuclear explosion from various distances. As it turned out, even at large distances, the turret could be displaced by the sheer power of the nuclear winds even when the turret was locked in the travelling position, causing the gear teeth around the turret ring to break and render the tank unserviceable. As a result of these tests, the turret locking mechanism was strengthened, so that even at around 300 meters' distance from the detonation of a 2 to 15 kiloton bomb, the tank remained serviceable.
However, it was discovered in subsequent tests that at distances of up to 700 meters, animals (rabbits, dogs) standing in for the tank crew died immediately from the shock wave and overpressure of the blast. As a result of these findings, the requirements for a comprehensive anti-nuclear protection suite for the T-54 were drawn up, and in 1956, the KB-60 design bureau from Kharkov finalized the "PAZ" (Nuclear Protection System) complex and sent the technical documentation to the Uralvagonzavod tank factory for implementation.
PAZ was first implemented on the T-55. It was an advanced collective type system. A gamma radiation sensor was used to detect the detonation of a nuclear bomb and initiate countermeasures before the shockwave could reach the tank. The system could react 0.3 seconds after detecting a spike in gamma radiation. All openings in the tank would be automatically sealed by heavy steel wedges activated by explosive squibs. The engine and the cooling fan would be stopped, and the armoured louvers over the engine deck would be closed, all done automatically.
The old dome ventilator was insufficiently powerful to create an overpressure inside the tank and it only provided low level filtration of dust and smoke, so it was replaced by a new ventilator system. The ventilator drum is placed right beside the co-axial machine gun, in front of the loader. Not only was it capable of producing an overpressure inside the tank to prevent foreign particles from seeping in, the filtration system could also remove chemical and biological agents, though only when activated, either manually or automatically. In normal operation, the powerful compressor fans are not used, and the ventilation system performs the same basic function as the old dome ventilator.
A tiny slit was created at the rear of the turret at the 2 o'clock position to let air out and control the flow of air to prevent the internal pressure from building to excessively high levels.
The T-55A obr. 1967 can be differentiated from the T-55 by an extra layer of anti-radiation lining of the anti-radiation material. The material and the lining are both known colloquially as "Podboi" - fiber-reinforced sheets made from borated polyethylene. It is designed for absorbing neutrons, but it also performs admirably as a spall liner when present in sufficient thickness.
|Photo credit goes to Marcel Jussen from Primeportal.|
The external circumference of the cupolas also received a new bolt-on anti-neutron shell. The photos below show the shell over the loader's hatch.
And here is the shell over the commander's hatch.
The T-54 has an escape hatch. It is located behind the driver's seat. It is held in place by four locks. Once all four have been disengaged, the hatch drops down, allowing the crew to crawl out. It is much easier said than done, and it will be nearly impossible to do a quick escape from a hatch of such small size, but having a hatch presents unique tactical opportunities, as the crew can exit the tank without being seen by the enemy.
We have already examined most of the components of the driver's station in Tankograd's T-62 article. As the driver's station in a T-62 is almost identical to one from a T-55, there is no point to repeat it here. Please head over to the T-62 article. However, there are some small historical details that uniquely belong to the T-54. One of them was the periscopes.
Originally, destroyed periscopes were almost impossible to remove if a powerful shell struck the armour in front of it, as the mounting piece would usually be damaged in a most inconvenient way. This was solved in 1953 by using a heat-treated mounting piece of a higher grade of steel, increasing the strength of the welds and by thickening certain components.
In 1951, the TVN-1 infrared nightvision driving periscope was introduced along with the infrared headlight. This nightvision periscope was carried over to the T-62, and you should too.
A superior gearbox enabled the tank to get more out of its 520 hp V-12 piston engine, designated the V-54, and the new super-compact dry plate clutch transmission made the T-54 just as quick and agile as the T-34 despite having a worse power-to-weight ratio. The top speed when travelling in a straight line was slightly worse compared to its legendary predecessor, but the new mechanical synchromesh transmission enabled the driver of a T-54 to shift gears more easily and accelerate quicker.
The T-34-85 had a top speed of 56 kph on paper, while the T-44 had a top speed of 51.1 kph. The T-54-1, with its heavy upper glacis armour plate and sides, chugged along at 43.5 kph. The definitive T-54 base model, the T-54 obr. 1951, had a top speed of 50 kph. The T-55 had a higher top speed of 55 kph. The rate of acceleration is not known, but it is presumed with high confidence to be superior to the T-34 and T-44 due to thr improved transmission.
The T-55 utilized an improved air filter and an improved V-55 engine. The V-55 produced 580 hp. The added power comes from a better optimized compression ratio and an improved fuel injection system. The improved air filter also helped by reducing the power loss in extremely dusty environments.
The T-54 used a dual epicyclic geared steering system. This steering system is functionally the same as the one used IS-1 heavy tank. Steering is achieved by having two separate final drives with separate gear boxes for each track, connected by a central transmission assembly. Steering is accomplished by stepping down the gear ratio of the inside track to a lower gear, thus reducing the speed of that track. By manipulating the gear ratio instead of applying a brake like in the clutch-and-brake system used in the T-34, the tracks can be slowed down incrementally rather than braked for smoother and more precise steering. However, geared steering does not work on first gear, because there is no gear lower than first gear except neutral, so the T-54 is fitted with an auxiliary clutch-and-brake system as well. The driving tillers (or levers) each control the track on its side. Each tiller has three positions, the first (1) for full forward, the second (2) for engaging the planetary mechanism to reduce speed to that track, and the third (3) to engage the clutch and brake system for really tight turns, for turning in first gear or for pivot turning in neutral. But what is a clutch-and-brake system? In a T-34, steering is accomplished by locking one of the tracks by disengaging the clutch and applying the brake. This can create very tight turns, but it has the effect of slowing down the tank significantly when making small course adjustments.
The geared steering system is a regenerative steering system, meaning that it supplies full power to both tracks so there is minimal energy loss when turning. This means that the T-54 is much more energy efficient than the simple clutch-and-brake type steering system present in many WWII era tanks (including the T-34 and KV-1), allowing the T-54 to preserve most of its speed while turning, and even more so in muddy or swampy ground. The energy efficiency of the geared steering system is roughly comparable to contemporary double and triple differential systems in use by Western tanks of the same era, with the caveat that the T-54 still used tillers to steer. This directly relates to the tank's speed in real world conditions. After all, there are not many paved highways on the battlefield, and zigzagging is a better tactic for survival than travelling in a straight line. In other words, the T-54 can be as fast as a T-34-85 in actual combat conditions, or maybe faster. One big selling point of the geared steering system is its hardiness and extremely reliability. It is one of the reasons why the T-54 is still used (with minimal maintenance) in third world armies to this day. The photo above shows the transmission casing, the power take-off block atop it, and the finals drives and brake drums behind it.
The power take-off block is the box at the top right of corner of the photo below. The block connects directly to the master drive shaft from the engine as a mini gear box of its own, so the amount of power supplied to the block changes only when the output of the engine itself changes. The block splits the power between three smaller drive shafts. One goes to the AK-150 air compressor (we will examine that later), seen attached to the block to the right side of the photo above. The second connects to the centrifugal radiator fan, as seen here (link). The third connects to the radiator coolant pump.
The three crane-like protrusions on the transmission casing are part of the steering system. These work the gear boxes to bring about the changes in gear ratio. They connect to control rods that are operated by the tillers. The three loops on the corners of the transmission casing are lifting eyes, to be used with a small crane to lift the whole thing out of the tank's engine compartment.
Like many tanks preceding it, the T-54 has the option of using compressed air to start its engine. Two 5-liter air tanks mounted in the driver's station inject air into the cylinders of the engine, forcing the pistons into motion. This method is harsh on the engine, but dependable. Starting the engine in the summer is usually done electrically, but in the wintertime, the electric starting system may not be reliable due to piston lockup, so using air is necessary. In the harshest weather conditions, with the most poorly maintained T-54, starting the engine will require a combination of both methods simultaneously.
However, like the T-34, the compressed air tanks in a T-54 are not refilled automatically, so the reserves of compressed air is limited. This was changed in the T-55, which was equipped with an AK-150 V-shaped air compressor, powered by the engine. AK-150 is a typical V-shaped reciprocating compressor. It runs on an input shaft from the engine and uses pistons (operating essentially like a reverse order piston engine) to compress air drawn from the engine compartment, which it then routes directly to the air tanks. The AK-150 compressor can be seen in the photo of the exposed engine compartment above, partially obscured. The photo below shows the compressor on its own. On a related note, AK-150 compressors seem to be rather popular in the civilian market as a cheap, extremely durable and extremely reliable high pressure air compressor for miscellaneous commercial uses.
It must also be said that the T-54 is extraordinarily light compared to its foreign counterparts. Weighing in at only metric 36 tons dry, it is lighter than a generic Centurion tank (52 metric tons) by an entire 16 tons, and lighter than an M48 tank (45 metric tons) by 9 tons, and despite this, it is comparable in most respects and manages to achieve superiority in others. The light weight of the tank enables it to not only exploit bridges intended for light loads, but to also use pontoon bridges and scissor bridges with impunity, as there will be a large load surplus. A large convoy of T-54 tanks may cross a pontoon bridge without needing to take turns.
The T-54 exerted a ground pressure of 0.8 kg/sq.cm, whereas the newer and heavier T-55 exerted a ground pressure of 0.81 kg/sq.cm.
Like the T-44 before it, the T-54 used torsion bars instead of Christie spring suspension. This saved internal space, but by retaining the same unsupported Christie live track concept (no return rollers), there was no space for traditional shock absorbers. See the tanks below - the M47, M48 and M48, in descending order.
Note that all of these tanks have three large shock absorbers, two for each of the two frontmost roadwheels and one for the rearmost roadwheel. From reading the testimonies of ex crewmen, one can safely assume that these worked quite well and made these tanks easy to drive and comfortable to ride. On the T-54, there is no room for this type of shock absorber, as you can see below.
In order to overcome this limitation, a special compact hydraulic shock absorber was invented and installed.
These shock absorbers were installed on the first and last roadwheels on either side. However, two on either side isn't quite as good as having three, resulting in more vibrations when travelling over uneven ground. This affects both the efficiency of the crew in the long run and weapon accuracy when firing on the move.
The torsion bars were swapped out for better ones in the T-55AM modernization, and in any variant of this modification including the T-55AM2, T-55AM2B, and others. This was mainly due to added weight of the tank, although the improved driving experience was a welcome bonus. The author has conversed with many armour enthusiasts and a handful of amateur restorers, and the ones which have driven a T-55AM have noted that it traverses bumpy roads more smoothly than either the T-55 or the T-54. Mr. John from War For Slow Readers has noted the same in this 2012 blog entry: "We're heading for the treeline across a muddy field. The T55 takes bumps in it's stride - it was surprisingly well sprung - and mud poses no problem - as you'd expect from a Russian design". Of course, part of the credit for the reduced oscillations should also be attributed to the dampening effect from the added weight of the "Brow" armour.
As with earlier Soviet tank tracks, OMSh is held together by pins. The pins are only secured in on the inner end of the track by an oversized head. There are no clips or fasteners to hold it on the other end of the track, so when the tank moves, the pins are allowed to come loose and worm its way out of its slot, but only in the direction of the hull. A raised chunk of steel is placed just next to the drive sprocket to knock these loose pins back into the track.
OMSh tracks can be easily identified by the distinctive loop at the end of each track link.
Starting in the mid to late 70's, T-55s became the subjects of a modernization program that gave them new sighting equipment (as detailed before). Another improvement was the retrofitting of RMSh tracks to these tanks. RMSh tracks were originally developed for the T-72. These tracks were designed for the sort of dynamic loads expected from a heavier tank, so they were built heavier and much sturdier. These tracks were also heavier by a ton, so it was something of a burden on its own, but the added off-road mobility must have been worth it. However, the biggest improvement offered by RMSh tracks is the increased service life, which is exactly twice that of the OMSh tracks. Due to the weight and sturdiness of RMSh tracks, it would be impossible to throw a track in a T-55 equipped with it. These tracks are standard on T-55AM (1983) tanks.
Rare type of tracks designed for operations in swampy terrain. Not much is known about them, except that they are very wide.
One important drawback to the design of the T-54's powerpack is the barely-adequate cooling system. The system works on simple principles. The engine is water cooled, and the radiator is located on the rearmost half of the engine deck. A large centrifugal fan at the very rear of the engine compartment draws air through the radiator and into the engine compartment from the outside, and then ejects the hot air out through a port. The centrifugal fan can be seen in the photo below.
As mentioned before, the fan is driven at very high speed by a shaft from the gearbox. Along with the compressor, the fan comprises one of the parasitic elements reducing the amount of power that is ends up in the drive sprockets.
The radiator pack is rather large. Inside it is a maze of tubes and heat sinks to maximize the loss of heat. The radiator pack is protected from above by an armoured cover, complete with armoured louvers. The armoured louvers can be closed to protect the radiator and the gear box under it from air attack and molotov cocktails, but the consequence of closing them is that the airflow into the radiator is severely restricted, so that less heat is removed from the coolant.
The armoured cover is hinged and can be lifted up and away, as seen in the photo above. The radiator pack can be lifted up and away in the same manner, and it even has two rubber padded handles for this purpose, as seen in this photo. It would presumably take two men two lift the armoured cover and radiator pack. Once out of the way, the gear box, transmission, brakes, radiator pump and coolant reservoir can all be accessed easily.
Unfortunately, the cooling system is not effective in high ambient temperatures. As a result, engine performance tends to be worse than normal when operating in hot climates, such as in the Middle East, especially when the tank has been running for long periods of time, or when it has been parked under the open sun for hours. In hot weather of 30° or more, the T-54 may have to stop every few dozen or so miles of continuous driving to prevent the radiator from boiling over.
A common remedy for this issue is to simply open up the armoured radiator access hatch, so that airflow is maximized. Unless the tank is operating in urbanized areas, nearly all T-54-type tanks seen fighting in hot climate countries like Syria and Iraq can be found with the radiator access hatch open.
In the photo of an SAA T-55 below, the armoured radiator cover is seen open as the tank fires on rebel positions from afar. Keeping the armoured cover open maximizes airflow over the radiator pack and helps keep it cool.
Chinese T-54s, or Type 59s, share the same troubles. Here is a Type 59 participating in an exercise with its armoured radiator cover opened up.
One other disadvantage of the cooling system is that the ejected air is blown out of the centrifugal fan at a high velocity that air kicked up by the tracks gets sucked into the air stream, and the effect is that there is a "rooster tail" of dust about 15 feet in the air. If you happen to be a NATO scout conducting forward observation in a very dry area, this would be a dead giveaway that T-54 tanks are coming your way.
Swapping out the engine was not an easy procedure. I do not know how long it would take on average, but it has to be more than an hour.
By the way, requirement no. 5 was fulfilled in full. Recall that the T-54 was developed under a set of six requirements, or orders, the fifth being: "Develop a robust track and track pin (increase track life to 3000 km)". In testing in 1946, the T-54 prototype drove 20,000 kilometers and wore out 6 pairs of tracks, equating to an average lifespan of 3,333 kilometers per track, thus exceeding the original requirements by a statistical average of 11.1%.
Many armour historians have observed that, among other things, one of the main factor behind the T-54's longevity is its automotive reliability and simplicity of maintenance. This is an understatement. Quoting from Stefan Kotsch's website (link), which uses Russian sources including Uralvagonzavod's official works on the T-54:
"For example, in the period from October to November 1956, service station no. 20 was tasked to repair 188 tanks T-54. Of these, 18 had tanks, covered with the meantime the engine has change, a driving distance of around 8,000 km. Another 56 tanks reached an average of 6,031 km. The engines on 15 tanks achieved an average operating hours of 600 Mh, an even 696 Mh. Constructor Kartzev presented in 1956 found the tank T-54 can be used without major repair, for replacement of individual modules, certainly achieve a mileage of up to 10,000 km. Thus, the T-54 can be described as one of the most reliable tanks in the world."
According to Pat Ware and Brian Delf in "The Centurion Tank", the engine life of the Rolls-Royce Meteor was reported in service to be only around 3,000 miles (4828 km) before a base overhaul was required. Many other tanks have been deemed "satisfactory" or "perfectly sound", but not many tanks have the same legendary reputation of toughness as the T-54.
In 1958, the T-54 received the OPVT snorkel, thus gaining the ability to cross water obstacles as deep as 5 meters.
When not in use, the OPVT snorkel is stowed away at the back of the tank, underneath the wooden log.
As you may have noticed in the diagram above, the external fuel tanks are not connected with the fuel lines of the internal fuel tanks. Both the internal and external fuel tanks are connected to the main fuel tank in the engine compartment. Fuel supply can be switched between internal fuel tanks or external fuel tanks or switched off entirely from a dial located in the driver's compartment. It is recommended to use up the internal fuel supply first, so that the only fuel left in the tank will be located in the engine compartment and the external tanks, thus eliminating a fire hazard.
One of the big selling point of the T-54 is its good fuel economy and long cruising range. This is further enhanced by two removable 200-liter fuel tanks mounted at the very rear of the tank. The quick release mechanism can be studied in the diagram below. The driver can pull a lever to release the drums, but they will not jettison on their own. Someone must get out of the tank and kick them off. These fuel drums are connected to the fuel network, so that the tank can continue driving as long as possible without needing to be refueled manually be siphoning from these drums, as was the case with the T-34.
In the absence of tank transporter lorries or appropriate rail transport, the T-54 could cover 500 km on a road under its own power. If the two external 200-liter fuel drums were fitted, the road range increases to 600 km. Travelling across unpaved roads and cross country terrain will reduce the travelling range by approximately half, as a rule of thumb.
The Centurion, in comparison, consumed fuel at an eye-watering rate of just 0.27 to 0.52 miles to the gallon, giving a range of just 33 to 62 miles. When Stalin closed down all avenues of entry to West Berlin in 1948 (nearly starting WWIII in the process), it became clear that Centurions would not be able to reach the city from their bases in West Germany without needing to refuel en route and waste precious time. This problem was only solved in 1963 with the installation of a bolt-on 109-gallon fuel tank at the rear of the tank, but the T-54 still maintained a huge - only now slightly smaller - advantage in road range and more importantly, fighting endurance.
It is impossible to discuss the T-54/55 without mentioning that it is the most widely produced tank design in the history of tanks. About 60,000 examples have been produced in the USSR alone, and thousands more have been produced in satellite states. Copies and derivatives of the design, including the Chinese Type 59 and Type 69 boost the total number of tanks even further.
According to Simon Dunstan, production of the Centurion Mk. 3/5 medium tank ran from 1946 to 1958, during which 2,833 Mk. 3 tanks (1946-56) and 221 Mk. 5 tanks (1955-58) were manufactured. Three facilities were responsible for Centurion final assembly: Vickers Armstrong and the Royal Ordnance Factories at Leeds and Dalmuir.
The T-54 is in service in Russia as targets on the firing range. A few examples are were serving in the Far East as coastal defence as recent 2012, but since then, all existing T-54 tanks have dismantled and melted down for their steel. Almost all of the tanks that served in the Far East were T-55As equipped with KDT-1 laser rangefinders.
T-54 technical manual (Link)
T-55 technical manual (Link)
TM 9-718A 90-mm Gun Tank M47 1952 (Link)
British/Israeli Assessment of the T-55
ТЕХНИКА И ВООРУЖЕНИЕ вчера, сегодня, завтра (Август 2011 г.)
(Equipment and Weapons magazine, August 2011 edition)
ТЕХНИКА И ВООРУЖЕНИЕ вчера, сегодня, завтра (Апрель 2000 г.)
(Equipment and Weapons magazine, April 2000 edition)
Handbook on Soviet Ground Forces
Red Armor, by Paul Hofrichter
M60 vs T-62: Cold War Combatants 1956–92, by Lon Nordeen, David Isby
M48 Patton vs Centurion: Indo-Pakistani War 1965, by David R. Higgins
BrochuresДегтяревец, Еженедельная производственно-экономическая газета ОАО «ЗиД»
Degtyarevets, Weekly Production and Economics Newspaper of "ZiD" (Degtyarev Weapons Factory)