The T-62 is undeniably the least memorable among all of its world-famous post war era brothers. When we think of a Soviet tank, we think of the T-54/55, T-64, T-72, T-80 and T-90, and the T-62 is usually sidelined as an oddity. The T-62 is also arguably the least historically significant among them all, but it was, nonetheless, a step in the evolutionary path to the modern T-14 we know today, and its relevance on the battlefield was certainly undeniable for the better part of two decades.
The sentiment among the few amateur academic-enthusiasts that haven't forgotten the T-62's existence is that it was a highly mediocre design with a whopping gun, and that is perfectly true in many ways from a technological standpoint, but there is also a myriad of differences that distinguish the T-62 from the T-54. The enlarged turret, now completely round, is the most major external difference between the two tanks, but the hull was also changed, as you can see in the diagram below.
The widened turret ring did not affect the width of the hull, as the overhanging portions of the turret ring are supported by supporting platforms welded to the hull. However, the length of the hull had to be changed by no small amount in order to accommodate the exceptionally wide turret ring and the revised engine compartment. The arrangement of the roadwheels (and the torsion bar suspension) was also revised in accordance with the redistribution of weight.
Although woefully obsolete at present, it could at least boast of having the one of the most powerful tank cannons in the world for the better part of the 1960's before being usurped by the T-64A. Indeed, the sole reason of the T-62's existence was its pioneering smoothbore cannon. Tactically speaking, there were very few differences between it and its predecessor the T-54 in the mobility and armour protection departments, and indeed, the T-62 inherited much of its internal equipment from the T-54, thus simplifying both production and logistics to a certain extent. Even many of the newer devices were functionally similar, making the transition from the T-54/55 to the T-62 wonderfully seamless for the crew. That said, commonality was not entirely positive, because this meant that there was an unacceptable stagnation in armour technology.
Being a mere evolutionary stepping stone, though, we can observe the way Soviet school of thought on mechanized warfare evolved with it. In the early 60's, tank riding infantry was still considered a core part of mechanized warfare. The armoured APC had arrived on the scene in the form of the wheeled BTR-152 and tracked BTR-50, but infantry were sometimes obliged to move and fight as one with a tank, and so to that end, the T-62 had handrails over the circumference of the turret for tank riders to hold on to. When the BMP-1 was introduced in 1966, it drove a major revision of contemporary tank tactics, and the shift in paradigm can be very well seen in the T-62's successors. The T-64A did not have any handrails, nor did the T-72, and the T-62M introduced in the 80's abolished them too.
The changes to the T-62 dutifully followed international trends as well, most notably the global shift to jet power in the aviation industry. Too fast to be harmed by machine gun fire, the ground attack jet rendered the normally obligatory DShKM machine gun obsolete. The birth of the AH-1 Huey Cobra and the subsequent heavy use of helicopters for fire support and landing missions during the American intervention (or invasion, if you prefer) in Vietnam permanently shifted the conventional ideals of armoured warfare, and the men and women at Uralvagonzavod obeyed; the DShKM was back by 1972.
In the Soviet Union, the T-62 was produced from 1963 to 1975, with the first pre-production models appearing in 1961. After 1975, all "new" T-62s are actually simply upgraded, modified, or otherwise overhauled versions from the original production run. By then, production at the Uralvagonzavod factory had irreversibly shifted to T-72 production.
Table of Contents
- Commander's Station
- TKN-2 "Karmin"
- TKN-3 "Kristal"
- Gunner's Station
- Laser Rangefinder
- Volna Fire Control System
- 1K13-2 Sight
- Loader's Station
- Ammunition Stowage
- Rate of Fire
- Secondary Weapon
- Tertiary Weapon
- Side Skirts
- Yom Kippur
- Ilyich's Eyebrows
- Belly Armour
- Slat Armour
- Mine Clearance
- NBC Protection
- Fire Fighting
- Driver-Mechanic's Station
- Engine Deck
- Road Endurance
- Water Obstacles
The commander is seated on the port side of the turret, directly behind the gunner, and to his left is the R-113 radio station, created just as the T-62 first entered service in 1961.
The R-113 radio operates in the 20.00 to 22.375 MHz range and has a range of 10 to 20 km with its 4 m-long antenna. It could be tuned into 96 frequencies within the limits of its frequency range.
In 1965, the radio was swapped out for a newer and much more advanced R-123 radio. The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could instantly switch between four preset frequencies for communications within a platoon. It had a range of between 16km to 50km. The R-123 had a novel, but rather redundant frosted glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had a modular design that enabled it to be repaired quickly by simply swapping out individual modules.
Although the T-62 superficially resembles the T-54 from many angles, the dome-shaped turret is significantly larger and noticeably more spacious, even with the larger cannon. This can be largely attributed to the 2.245-meter diameter turret ring, a big improvement over the 1.825-meter one of the T-54 family. The T-62's turret ring is bigger than the one on the M48 and M60, which had the widest turret ring (2.16 m) among all Western tanks in service at the time. This is partially offset by the much larger cannon breech, whereas the M48 used a smaller 90mm gun and the 105mm M68 cannon used by the M60 was unusually compact, but the turret of the T-62 got rid of the needle-nose ballistic shaping of the T-54. This contributed to a modest increase in the amount of habitable room inside the turret.
Unique to the rest of this dome-shaped turret, the area around the commander's station was cast to be devoid of any vertical sloping or rounding whatsoever, which was necessary to enable his rotating cupola to be installed. This also meant that any debilitating effects of the shaping of turret (lack of headroom, for instance) do not apply on him. The crew stations in the T-55 tank were compromised by the egg shape of the turret, a shape optimized for ballistic protection, not comfort.
The commander's cupola cupola is secured to the turret by screws rather than bolts like on the T-54. The cupola is mounted on a race ring. The fixed part constitutes half of the total size of the cupola, while the other half is occupied by the semicircular hatch. The hatch opens forward, which is quite convenient for when the commander wants to survey the landscape from outside - perhaps with a pair of binoculars - because being as thick as it is, the hatch is a superb bulletproof shield to protect the commander from sniper fire.
There is also a small porthole in the hatch. It is meant for a panoramic periscope tube for indirect fire.
As befitting his tactical role, the commander's general visibility is facilitated by two TNPO-170 periscopes on either side of the primary surveillance periscope in the fixed forward half of the cupola, further augmented by two more 54-36-318-R periscopes embedded in the hatch, aimed to either side for additional situational awareness. Overall, this scheme could be considered more than adequate, but it was clearly deficient if compared to the much more generous allowance of periscopes and vision ports found on NATO tanks.
The TNPO-170 periscope has a total range of vision of 94° in the horizontal plane and 23° in the vertical plane. The four periscopes in addition to the TKN-type periscope aimed directly forward gives the commander a good view of the battlefield in an arc spanning the 4 o'clock position to the 8 o'clock position. There is no rearward-facing periscope, but the commander can look backward by simply turning the cupola to one side and looking back through one of the 54-36-318-R periscopes. The use of periscopes instead of direct glass vision blocks presents pros and cons - for one, the lack of any direct vision means that the viewer's eyes is protected from machine gun fire or glass specks if the device is destroyed, but a bank of periscopes offer a much more limited panorama than vision blocks like the type found in the commander's cupola on the M60 tank.
The TKN-2 was the first combined periscope to be installed in a Soviet tank. Work on "Karmin" first began in 1956 at the Zagorsk Optical and Mechanical Plant. In 1957, the TKN-2 was tested in an experimental T-55 test bed at the testing grounds of factory No. 183, better known as Uralvagonzavod. TKN-2 later went on to be installed on the original T-62 upon its introduction in 1961.
Due to the combination of nightvision equipment with regular daytime functionality, the optical paths from the two eyepiece lenses had to be merged to form a single aperture lens. This means that the periscope is no truly binocular, but pseudo-binocular. Compare the two photos below, TKN-3B on the left and TPKU-2B on the right:
With only one aperture, the user has very little depth perception. This makes it rather difficult to estimate the distance to a target by eye, but the commander has a stadia rangefinder for that anyway.
The TKN-2 had an active night channel relying on the infrared light emitted from the OU-3 IR spotlight attached to the periscope aperture to provide a limited degree of night vision to the commander. With a nominal viewing range of only about 300 to 400 m, the TKN-2 was all but useless for serious target acquisition at night, serving only to give away the tank's position the moment the spotlight was turned on. Performance could be improved with mortar-delivered IR flares, of course, but that doesn't count as an intrinsic merit of the device itself.
It is not known what the TKN-2 looks like, but this unidentified periscope could be it. Photo from apexgunparts.com. The best evidence that this is the TKN-2 is shape of the housing, which bears a striking resemblance to the TKN-3, the power cables, and the single aperture lens, seen in this photo. All of these evidences point to the unidentified periscope being a combined day/night optic, and we already know for sure what the TKN-1 and TKN-3 look like. Therefore, it must be a TKN-2.
Due to the fact that the periscope is unstabilized, identifying a tank type target at a distance is very difficult while on the move over very rough terrain. However, the commander is meant to bear down and brace against the handles of the periscope for a modicum of improvised stabilization, which is adequate for when cruising at a moderate speed (about 20 km/h to 30 km/h) over a dirt road, but not when traversing over rougher ground.
The left handle has a thumb button for activating the OU-3 spotlight. The thumb button must be held to keep the light on. This allows the commander to illuminate his target intermittently or to flash friendly forces. To toggle the spotlight on or off, the commander must flip a toggle switch on the cupola race ring.
The OU-3 is a high-powered xenon arc lamp with an IR filter. The filter isn't totally opaque, though, and the spotlight will glow faintly red. It is linked to the periscope by a pushrod, enabling it to elevate with the TKN-2.
|OU-3 IR spotlight with the IR filter removed to transform it into a regular white light spotlight|
The OU-3 spotlight operates on 110 W of power.
In 1964, new batches of T-62 tanks began to be equipped with the new TKN-3 combined periscope, a direct descendant of the TKN-2. Like TKN-2, the "Kristal" is a pseudo-binocular periscope, so the commander still has very poor depth perception. One of the biggest improvements of the TKN-3 over the TKN-2 is the use of superior glass prisms with two times more light transmittance. This substantially improved the brightness and sharpness of the image.
The periscope has a fixed 5x magnification in the day channel with an angular field of view of 10°, and a fixed 3x magnification in the night channel with an angular field of view of 8°. The periscope can be manipulated up and down for elevation, and the commander's cupola must be turned for horizontal viewing.
The TKN-3 was a sufficiently modern observation device of its time. It featured target cuing, was very compact, and had a relatively advanced passive light intensification system, but it wasn't stabilised, and featured only rudimentary rangefinding capabilities as a cost saving measure.
TKN-3 offered night vision in two flavours; passive light intensification or active infrared. In the passive mode of operation, the TKN-3 intensifies ambient light to produce a more legible image. This mode is useful down to ambient lighting conditions of at least 0.005 lux, which would be equivalent to an overcast, moonless and starless night. In these conditions, the TKN-3 can be used to identify a tank-type target at a nominal distance of 400m, but as the amount of ambient light increases such as on starlit or moonlit nights, the distance at which a tank-sized target is discernible can be extended to up to 800m in dark twilight hours. Any brighter, though, and the image will be oversaturated and unintelligible.
The active mode requires the use of the OU-3K IR spotlight, which is practically identical to the OU-3 in many respects. Activating the OU-3 is done the same way as with the TKN-2. With active infrared imaging, the commander can identify a tank at 800m, or potentially more if the opposing side is also using IR spotlights, in which case, the TKN-3 can be set to the active mode but without turning on the IR spotlight. This way, the commander can see enemy tanks from many kilometers away at night.
To switch between the day and night channels, the user simply rotates a dial on the right side of the periscope housing by 90 degrees. This flips an internal mirror by 90 degrees, thus changing the optical path between the night vision unit and the regular daytime optic. The diagram below shows the two choices. Diagram (a) on the left shows the path of the light from the aperture through the night vision system and into the eyepiece, while diagram (b) on the right shows the mirror flipped 90 degrees and the light from the aperture passing through the normal optical channel for daytime use.
Rangefinding is accomplished through the use of a stadiametric scale calibrated for a target with a height of 2.7 m, which is the average height of the average NATO tank. The ranging error margin is negligible at distances of around a kilometer, but at distances exceeding approximately 1.6 km, it becomes difficult to accurately find the range of the target due to a multitude of factors, including weather conditions, limited magnification power, mirages (a big problem in deserts), and obstruction of parts of the tank (tall grass can hide the lower part of the hull). At long distances, contrast between the target tank and the background is also often very poor, since there is usually some modicum of camouflage to conceal the tank.
It is also possible to find the distance to the target tank by using the horizontal and vertical mil scales printed on either side of the reticle. Knowing the width of a Patton tank to be around 3.6 meters, the commander will know that the distance to the tank is exactly 1000 meters if the tank can be slotted exactly between the reticle, which has a width of 3.6 mils. Depending on how exact the fit is, the commander can roughly estimate the range.
Like the TKN-2 and other previous binocular sights for the commander, the TKN-3 is unstabilized, making it exceedingly difficult to reliably identify enemy tanks or other vehicles at extended distances while the tank is travelling over rough terrain, let alone determine the range. On a related note, the lack of stabilization would have made it equally difficult to operate an optical coincidence or stereoscopic rangefinder, especially one with 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 could 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-62, on the other hand, is an offensive tank designed around the Red Army's mobile "deep warfare" doctrine. Optical rangefinders were therefore 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 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; 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.
The left thumb button initiates turret traverse for target cuing, and the right thumb button turns the OU-3K spotlight on or off, but the button must be held to keep the spotlight on. The spotlight should not be turned on for more than 20 seconds, as it will overheat without periodic cooling. A toggle switch on the race ring of the cupola enables the commander to keep the spotlight on or off. The range of elevation is +10° to -5°. The OU-3K spotlight is mechanically linked to the TKN-3 by a pushrod to enable it to elevate and depress with the periscope.
Target cuing is done by placing the crosshair in the viewfinder of the TKN-3 over the intended target and pressing the left thumb button. The system only accounts for the cupola's orientation, and not the periscope's elevation, so the the turret will traverse to meet the target, but not the cannon. This was not an issue, since the gunner needs to manually elevate the cannon to place the crosshair on target anyway (explained later in the Sights segment). The wide field of view offered by the gunner's sight made it impossible for the gunner to miss a target even if the turret was imperfectly aligned with the commander's periscope.
The target designation system is practically the same as the one used in the T-54. A direction sensor is installed at around the 3 o'clock position of the cupola, and has the function of determining the deflection of the TKN-3 relative to the longitudinal axis of the turret. 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 - refer to the diagram in the middle.
When the cupola is turned to the right (see diagram on 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, but no action is taken until the target designator button is pressed. When the target designator button is pressed, and electric signal is sent from the button to the direction sensor via a conductor track on the cupola race ring. The depression of the right switch by the cam then triggers the turret rotation motor to turn the turret to the right until the roller returns to the notch, whereby the cam is no longer in contact with the right switch and no action is taken even if the commander keeps his thumb on the target designator button. 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. This ensures that the gunner is cued to the target as quickly as possible. The the gun-laying precision of the turret at its maximum traverse speed is low, but that is irrelevant as the final lay is conducted by the gunner.
Because the cupola does not counter rotate as turret traverse is initiated, it may spin along with the turret as it rotates to meet the target cued by the commander, potentially causing him to lose his bearings. To prevent this, there is a simple U-shaped steel rung for him to brace with his right arm as he uses his left hand to designate the target. This wasn't as convenient as a counter rotating motor, of course, but it was better than nothing. The photo below shows the steel rung, as well as the toggle switch for the cupola's electrical systems (turns on power to TKN-3 and OU-3K) next to the right part of the steel rung. The direction sensor is visible next to the left part of the steel ring.
Overall, the commander's facilities, furnished with the TKN-3, might be considered better than most Western tanks when it comes to target finding. As far as the knows, the M60A1 and the Leopard 1 to 1A2 didn't have anything even approaching the TKN-3. In 1973, the TKN-3 was soundly outmatched by the new and quite excellent TRP 2A sight installed on Leopard 1A3s, and by the highly advanced PERI-R12 panoramic sighting system for the Leopard 1A4 in 1974. However, it should be mentioned that the Leopard 1A3 was only produced from between May 1973 and November 1973, and that only 110 examples were built, and only 250 units of the Leopard 1A4 model were produced. The Leopard 1A4 was the last major Leopard 1 variant and the most advanced operated by the Bundeswehr until the end of the Cold War. The rest of the Leopard fleet was less advanced.
The close proximity between the commander and the gunner makes the internal climate hot and humid, contributing to the overall discomfort. This is compounded by the fact that the crew isn't provided with any local ventilators such as fans or directed air vents, so it can get quite stuffy inside. However, the commander seems to be the most well off, since he sits right in front of the ventilator air outlet in the turret. Besides the roomy loader's station, it is clear that the commander's seat is one of the best places to be in the very spartan T-62.
Here in the photo above (credit to Aleksey Kotov), you can see the backrest of his seat and a few pieces of equipment. He has access to a communications control box that enables him to switch between the radio and intercom. There are a few metal loops for strapping on personal effects, his binoculars (in its pouch), his pistol (in its holster), and anything else that might need to be secured. He also has access to the turret traverse lock. Underneath his seat is the tank's heater unit.
One of the considerations made for the comfort of the commander was the removal of the shoulder guard that separated him from the cannon. In the T-62, only a piece of triangular metal is placed between him and the cannon. It is very likely that the shoulder guard was removed because there was no longer any danger of shell casings bouncing into him, thanks to the automatic casing ejector in the T-62.
Sometime during the 70's, a select few T-62s received a shield of sorts over the commander's hatch. It is a sheet steel face shield with a canvas skirt draping down. Being so thin, the face shield is not bulletproof.
Since it doesn't really do very well as ballistic protection, the main function of the shield appears to be to conceal the opening of the commander's hatch to disguise his exit from the prying eyes of snipers, and to shield the commander from dust and bugs if he feels like sitting outside during road marches. Either way, not many T-62s received the addition, though almost all T-72s did. The reason for the bias is unknown.
As was, and still is common among manually loaded tanks, the gunner doesn't have a hatch of his own. Instead, he must ingress and egress through the commander's hatch. The biggest flaw with this layout is that if the commander is unconscious, incapacitated or killed, then the gunner will suddenly find it extremely difficult to leave the tank unless the commander was somehow completely vaporized. Even worse, if the tank has been struck, there is a very distinct possibility that the interior is catching fire.
Another flaw with the layout is if the turret was perforated through the front on the port side cheek, both the gunner and commander would be killed, effectively rendering the tank useless in combat. If the tank was perforated on the upper glacis near the turret ring, the driver, commander and gunner would all be killed in one go. Quite morbid.
Nevertheless, Nicholas "The Chieftain" Moran has commented that the gunner's station in the T-55 is very well laid out, and overall quite satisfactory. The T-62 should offer a similar experience, and slightly better thanks to the more voluminous turret.
For extra visibility, the gunner has a single TNP-165 periscope pointed forward and slightly to the right, though for what exact purpose this lone periscope is meant for is unknown, since the field of view from it is so small that the gunner can't really see very much, nor can the commander seated behind him. It is more useful for the commander for checking directly in front of the tank. The gunner can also use it to check the clearance of the gun when approaching a berm or when entering a tank hole, but that's about it.
In addition to all of the necessary switches and toggle buttons to activate this and that, there are also some other odds and ends at his station, including a turret azimuth indicator, which is used to orient the turret for indirect fire. It is akin to a clock, having two hands - the hour hand for general indication measured in 6000 mils, and the minute hand in 100 mil increments for precise turret traverse. Combined with the gunner's quadrant and the range card on the arm guard of the cannon breech near his right shoulder, the T-62 can conduct indirect fire.
The azimuth indicator has an internal bulb that can be turned on to allow the gunner to read it at night.
|TSh2B-41 sight aperture port, with nuclear attack seal in place|
The gunner is provided with either a monocular TSh2B-41 or a TSh2B-41U (in later models) primary sight and a TPN-1-41-11 night sight, which also functions as a backup sight in the event of the failure or destruction of the primary sight.
The TSh2B-41 is a monocular telescopic sight, functioning as the gunner's primary sight for direct fire purposes. It has two magnification settings, x3.5 or x7, and an angular field of view of 18° in the former setting and 9° in the latter setting. It comes with a small wiper on the aperture to clean off moisture and dust, and it comes with an integrated heater for defrosting. The sight has an internal light bulb that when turned on, illuminates the reticle for easier aiming in poor lighting conditions such as during twilight hours or dawn. There is an anti-glare filter inside the telescope housing that can be toggled. The anti-glare filter should only be used when looking directly at the sun, otherwise the filter washes out most of the colour and contrast, and darkens the image considerably, thus making it much harder to make out the shape of a camouflaged tank at long distance. All of these features are activated manually by the gunner via toggle switches on the telescope itself.
Like most other tanks of its time, the T-62 lacked a ballistic computer. It had no FCS, only this sight. As the tank lacked a stereoscopic rangefinder like the M48, it was also deficient in the rangefinding department. For rangefinding, the gunner had to make use of a stadiametric ranging scale embossed on the sight aperture. Compared to optical coincidence rangefinders, stadia rangefinding was terribly imprecise, but also much simpler in both production and employment, and much more economical than, say, optical coincidence rangefinding. The savings made from the exclusion of an optical coincidence rangefinder were enormous, amounting to many thousands of rubles. However, by sticking with the stadia rangefinder, ranging errors of up to several hundred meters was often the norm, especially if some of the lower part of the target vehicle is obscured behind vegetation or other terrain features. It isn't uncommon for the first shot on faraway tank-sized targets to fall woefully short or fly clear over when using low velocity ammunition like HEAT rounds.
Below is the sight picture:
|Range scales from left to right: APFSDS, HEAT, HE-Frag, Co-Axial Machine Gun|
When the gunner has obtained range data, he manually enters the necessary correction into the sighting system by turning a dial. The dial adjusts the sight to calibrate it for that range.
Calibration is when the chevron is elevated or depressed to account for range. If the target is very far away, for example, then the chevron will be dropped significantly, forcing the gunner to sharply elevate the gun to line up the target with the chevron, thus forming a ballistic solution. If the target is closer, the chevron will only drop a little. Because APFSDS, HEAT and HE-Frag shells all have different ballistic characteristics, the gunner must refer to a set of range scales drawn on the upper half of the sight in order to get the proper gun elevation. For instance, if the target is 1.6 km away, and the gunner wishes to engage it with high explosive shells, then he must turn the dial so that the notch marked "16" on the range scale for "OF" (refer to diagram above) lines up with the fixed horizontal line (all of the range scales will drop, so HEAT rounds will also be calibrated at 1.6 km and the co-axial will be calibrated for 2.0 km (refer to diagram), but the gunner ignores that). The chevron will drop by the same amount as the range scale, the gunner will then lay the chevron on the target and open fire. If the gunner wishes to use APFSDS instead, then he need only line up the horizontal bar with the "16" notch on the "BR" scale. The chevron will drop a little, and the ballistic solution for APFSDS at 1.6 km will be obtained. The gunner will then lay the chevron on the target and open fire.
It is more difficult hitting targets with lower velocity ammunition like HE-Frag and HEAT shells, and even harder for moving targets. However, the inclusion of near-hypersonic APFSDS ammunition in the loadout of the T-62 greatly helped counterbalance this issue, making it markedly easier for the gunner to hit both stationary and moving tank-type targets, while most targets requiring HE-Frag shells like machine gun nests and pillboxes and other fortifications would be stationary anyway, thus making pinpoint accuracy much less of a priority. On account of the extremely high speed of the APFSDS rounds fired from the 2A20 gun, the sight can be battlesighted at a very generous 1000 m, allowing the gunner to confidently hit a tank of NATO-type dimensions in the open at any distance between 200 to 1600 m by aiming at center mass without needing to ascertain the range beforehand. If the target is closer to 200 meters, the shot will land above center mass, i.e the turret. If the target is closer to 1600 meters, the shot will land below center mass, i.e the lower hull.
However, one inescapable flaw of the TSh2B-41 was that it lacked independent vertical stabilization. The movable aperture assembly of the sight is directly linked to the 2A20 cannon via a pair of rods. Due to the "loader assist" function of the "Meteor" stabilizer, the aperture of the sight will raise along with the cannon when the loading procedure is underway. This can cause the gunner to (very annoyingly) lose sight of anything he is aiming at at the moment, thereby making the commander's the only pair of eyes to observe the 'splash' and give corrections or search for new targets. However, this can be bypassed if the gunner switched to the 3.5x magnification mode, whereby he will still be able to observe the 'splash' at the bottom part of the sight picture. He might also be able to get a glimpse at the bottom edge of his sight at 7x magnification, but this depends on the elevation of the cannon. On flat ground, this might be possible, but this will be impossible if the tank is peeking over a reverse slope. These complications led to the development of the independently stabilized TSh2B-41U.
But since we are on this topic, we cannot neglect to mention that it is very difficult to observe the fall of a shot when high velocity APFSDS rounds are being used. For one, the flash, smoke and fumes from ejected from the gun barrel will immediately block out any attempts to find the point of impact. Secondly, the shock and vibration from firing the cannon does not leave enough time for the gunner to recover and visually reacquire the target. These two factors are extremely relevant for any tank, but the T-62 suffers since the sight aperture is very close to the ground when the tank is hull down, so dust from the ground is an even bigger issue. Even if a tank had a thermal sight, it is not possible to escape this phenomenon.
The video below shows a Chieftain tank firing at a target on what appears to be sheep grazing on a grassy field. Due to the clean environment, the amount of dust kicked up by the muzzle blast is very minimal. The target is visible in a mere two seconds after firing.
|Video from here (link)|
The GIF below shows the view from the thermal sight of an Iraqi Abrams firing at ISIS fighters. The dusty environment obscures the gunner's vision for around five to six seconds immediately after firing. See the difference between this and the clean, grassy environment of the Chieftain before. Both examples show the difficulty of maintaining visual contact with the target immediately after firing, and a comparison between the examples show the importance of the dustiness of the environment.
|Video from here (link)|
Nevertheless, even if the gunner's view is not obstructed by dust or sand, it is still possible to see the target through the TSh2B-41 at the bottom part of the viewfinder. When on flat ground, the 9° field of view of the sight on 7x magnification is almost always sufficient to maintain visual contact with a target. Assuming that the target is placed near the center of the viewfinder where the aiming chevron would be, the raising of the cannon by 3° after firing. This is immediately apparent if we split the 9° field of view into two parts: 4.5° degrees above the center point, and 4.5° below. Raising the sight by 3° leaves 1.5° for the gunner to see the target with. If the 7x magnification setting is too high, the gunner can simply switch to the 3.5x setting with its 18° field of view.
In the 1972 modification of the T-62, it was given the upgraded TSh2B-41U sight with independent vertical stabilization as a transient solution. It lacks the usual components of a true stabilization system, like its own gyrostabilizer system, so its performance is highly unimpressive. The sight has a mean vertical stabilization accuracy of 3 mils - meaning that it has an accuracy of 3 meters at 1000 m, or a maximum deviation of up to 1.5 m, which would incredibly inadequate for anything other than just general observation. Fortunately enough, that's all that it is meant for, as the sight is only stabilized when the cannon is elevated during the loading procedure. When the cannon elevates, the sight does not follow, allowing the gunner to use his handgrips to manipulate the elevation of the sight. Once the cannon is ready to fire again, the "Meteor" stabilizer reengages and "catches up" to the sight, whereby the sight's stabilizer deactivates and defers its work to Meteor once again. This is different from true independent stabilization where the sight's stabilizer can be as precise or more precise than the stabilizer for thecannon, and the stabilizer for the cannon is perpetually slaved to the sight.
One tangible benefit of the independent vertical stabilization of the sight is that the gunner will be able to survey the landscape if the tank is on the move after firing from a short halt or crawl, or if the tank is firing on the move.
The stabilization system of the sight enabled the aperture lens to elevate as high as the cannon, but it could only depress by -5 degrees. Because of this, T-62s from 1972 and onwards have a reduced gun depression of -5 degrees, as compared to the -6 degrees afforded by the original TSh2B-41.
Another modification was the addition of a range scale for the new and improved 3UOF18 HE-Frag shell, and the separation of it from the scale of the older 3UOF11. The aiming distance of HEAT ammunition was increased to 3.7 km and the aiming distance for OF-18 and OF-11 shells are listed as 4.8 km and 3.6 km respectively.
TSh2B-41U suffered from poor performance. Even if it did offer a modicum of independent vertical stabilization, it was not useful enough. TSh2B-41U was was not installed on many tanks.
Because the sight aperture is just left of the gun barrel, there is a very high likelihood that it will be rendered inoperable if the turret takes a hit anywhere near it. A very close miss may create a big enough shock to knock the sight out of alignment or even crack the lenses, not to mention the disastrous effects of a direct hit on the aperture itself. But for all of its inherent flaws, the TSh-2B-41 should not be seen as anything less than an extremely high quality product of its time. Lack of independent vertical stabilization notwithstanding, the glass was of superb quality and the insulation and shockproofing of the sight unit was sturdy enough to survive the blast wave of a nuclear explosion and ambient temperatures of over 200° C. Nevertheless, whereupon the TSh2B-41 is out of service, the gunner will have no choice but to rely on the TPN-1-41-11 backup night sight.
The TPN-1-41-11 is a monocular periscopic night or backup sight located on the turret roof just in front of the commander's cupola. The TPN-1-41-11 has a fixed magnification of x5.5 and a field of view of 6° in the daytime mode. It could operate in either passive or active modes, but it must be powered on to be used at night. This is done by flipping a toggle switch on the BT-6-26 power supply unit on the turret wall, above the manual traverse flywheel. In the active mode, it must work in tandem with the L-2 Luna IR spotlight which moves along with the cannon though a mechanical linkage. The infrared light supplied by the spotlight is picked up by the sight, which allows the gunner to identify a tank-type target at distance of around 800m, which is only just decent, but not worse than its immediate counterparts'. In the passive mode, it employs light intensification for a nominal maximum identification distance of 400m for a tank-type target under lighting conditions of no less than 0.005 lux. The intensity of the image can be adjusted by changing the voltage, which can be done by turning a dial on the sight. When in use, the gunner turns the dial until the image he sees has maximum contrast. As with the TKN-3, and indeed any optronics using light intensification, the viewing distance and resolution increases as ambient light intensity increases, but only up to a certain point before the sight is oversaturated and can no longer produce a legible image.
The diagram below, taken from the U.S Army Operator's Manual for the T-62, shows the reticle for TPN-1-41-11. Note that the tip of the top vertical bar is calibrated for 800 meters for APFSDS (marked 'APDS' in the diagram) This is the nominal maximum viewing distance afforded by the sight in the active infrared mode, and is also a convenient battlesight distance. The gunner can use this aiming point to engage any target he sees through this sight in the active infrared mode and be assured that the shot will definitely hit.
Turning on the L-2 IR spotlight will also turn on a red tinted light bulb near the roof of the turret. This gives the gunner's station an ominous red glow, which is great. The sight has an internal lightbulb which facilitates aiming at night.
TPN-1-41-11 is mechanically linked to the TSh2B-41, and does not have independent stabilization. As such, just like the TSh2B-41, its range of vertical motion is limited and depends on the range of elevation afforded by the cannon, which is -6° to +16°. The picture below shows the system of linkages that connect the sight to the TSh2B-41, which in turn is connected to the cannon.
|T-62 with KDT-1|
The KTD-1 had a maximum measuring distance of 4000 m and a minimum of 400 m. The maximum margin of error in the measurement was 20 m.
KTD-1 does not directly interface with the existing fire control systems, except for the handgrips. There is a laser rangefinder control panel mounted in its own special corner, but the handgrips are replaced with one that had an additional trigger button for firing off the rangefinder. Range data is displayed on a digital readout. Now knowing the range, the gunner will then have to manually apply the data into the TSh2B-41/U sight by adjusting the range dial appropriately, and then continue the firing procedure in the normal manner.
Having a laser rangefinder in 1974 was quite a big deal at the time. The best that the Leopard 1 had at the time was the EMES 12A1 with a stereoscopic rangefinder, which could be found on the Leopard 1A4 model built in 1974. But it is understood - this does not mean that the shortcomings of the T-62's fire control system (or lack thereof) vanish into thin air. Rangefinding with the KTD-1 is fast, but the additional hassle of inputting the range data is a cumbersome chore that takes valuable seconds. The presence of the rangefinder is most helpful when firing on non-tank targets like bunkers and machine gun nests, as these targets cannot be ranged with stadiametric rangefinders. Additionally, the T-62's APFSDS ammunition makes up for the lack of rangefinder in the fire control system at short to medium ranges, but not so much at long ranges. The presence of a laser rangefinder further improves medium distance accuracy, and greatly fortifies long range accuracy.
The T-62M introduced in 1983 came with an entirely new "Volna" fire control system. "Volna" is a comprehensive fire control system overhaul. All of the original components of the T-62's fire control system have been replaced, and some new technology has been added, including the KTD-2 laser rangefinder, the BV-62 analog ballistic computer, and the new TShS-41U sight, purpose-built for "Volna", plus all of the necessary electrical equipment like the 9S831 transformer to adapt the new technology to the tank's electrical system.
Overall, "Volna" cannot be considered a cutting edge product for the 80's. Rather, it was an extremely cost effective modernization to raise the fighting capabilities of an old and outdated tank up to the level of the T-64B and maintain a sufficiently large fleet of tanks.
TShS-41U can be described as a transition model in terms of capabilities, as it is superior to TSh2B-41U, yet it does not quite reach the level of the 1A40 sighting complex used in the T-72 since 1976. The new vertical stabilizer has an accuracy of up to 0.3 mrad, translating to an error margin of 0.15 meters at 1000 m. This is good by 80's standards. However, the sight-gun stabilizer interface was still mechanical, and the sight was still slaved to the gun.
Laser rangefinding had become standard worldwide by 1983, so it was only natural that TShS was fully adapted to the new add-on rangefinder system.
The KTD-2 laser rangefinder has a minimum measuring distance of 500 meters and a maximum of 4000 meters under perfect meteorological conditions, namely a visibility distance of 10 kilometers. The principal difference, though, is the installation of a viewfinder directly routed over to the gunner's sight. Through this viewfinder, the gunner can observe the battlefield within an angular field of view of 2.5° under a 7x magnification, and select and range up to 3 targets simultaneously.
The gun laying system is of an automatic type, similar to the TPD-K1. KTD-2 sends range information to the BV-62 analog ballistic computer, which then calculates a firing solution and adjusts elevation of the cannon accordingly. The ammunition type is selected by the gunner, and the selection will influence the elevation of the cannon to match the ballistic profile of the ammunition selected. The aiming chevron always remains static. All the gunner must do then is to simply lay the chevron on the target and open fire.
The aiming point for the laser rangefinder is just slightly above the aiming chevron, which is a little inconvenient. Besides the laser rangefinder interface and the overhauled viewfinder picture, TShS-41U features a greatly improved vertical stabilizer, much more precise than the vertical stabilizer of the Meteor-M.
TShSM-41U features an electronic interface with the updated Meteor-M1. With Meteor-M1, the gun stabilization arrangement was changed from a sight-slaved-to-gun regime to a gun-slaved-to-sight one. This promoted better firing accuracy. The sight could now be moved vertically using the gunner's handgrips with total independence.
TShSM-41U also introduced a simple target leading system. A secondary chevron (secondary chevrons are the small chevrons on either side of the center chevron) paired with the central chevron to allows lateral lead to be calculated as long as the distance to the target is between 800 m and 1800 m. Beginning with the center chevron, the time it takes for the target to reach the first secondary chevron is recorded by the gunner, done by pressing the button on an integrated digital stopwatch. Using the range data from the laser rangefinder, the sight will then calculate the lateral velocity of the target, and then display the required amount of lateral displacement that the gunner needs to apply in mils. The gunner will then choose one of the secondary chevrons and adopt that as the new aiming point.
This system is inferior to the already questionable UVBU lead calculator featured in the 1A40-1. The "stopwatch calculator" system was convoluted and was presumably largely ignored in favour of finely honed gunnery skills. Even if we ignore the complicated procedure for its operation, the time needed for the system to calculate lead is quite long. It is totally impractical to use the system in actual combat.
All T-62Ms received the 1K13-2 to replace the TPN-1-41-11, but as the 1K13-2 operates independently from the "Volna" FCS, it should not be placed under the same banner. For the sake of convenience, however, that is what we will do.
The 1K13-2 is a combined monocular auxiliary sight which introduced the ability to guide new 115mm GLATGMs like the 9K116-1 "Sheksna", among other things.
The sight has a nominal maximum identification range of 5000 m on a tank-type target in the daytime mode under a maximum 8x magnification, though the actual distance depends on meteorological and geographical conditions more than anything. Like with the previous auxiliary sighting complexes, the 1K13-2 has two modes; passive and active, both of which operate under a 5x magnification. The sight enables the gunner to detect a tank-type target at nominal maximum range of 800 m in the passive mode under lighting conditions of no less than 0.005 lux. Alternatively, the identification distance can be as high as 1100 m in the active mode under illumination from the L-2G IR spotlight. The sight has an internal lightbulb that illuminates the reticle to facilitate aiming at night.
In contrast to all of the previous sighting complexes, the 1K13-2 sight has two-plane stabilization. The accuracy of stabilization while the tank is on the move at 15 km/h is 0.15 mrad in the vertical plane and 0.2 mrad in the horizontal plane, translating to a stabilization accuracy of 0.02 m at 1000 m vertically and 0.03 m horizontally. which is a level of accuracy so high that it is practically the same as if the tank was not moving at all.
The sight can only be used to guide GLATGMs in the daytime mode.
From 1961 to 1971, the loader's hatch was large and perfectly circular. It was slanted so that it followed the curving contours of the turret roof. In 1972, the installation of the DShK anti-aircraft machine gun required a level circular ring mount to operate, and so the loader's part of the turret was renovated completely. Now, he had his own rotatable cupola, and the area of the turret around his station lost its dome shape. His new hatch shrank by half and became an irregular semicircle, making it half as easy to ingress and egress, especially with bulky winter clothing.
There are two variations of the same type of cupola. Early model T-62s upgraded to obr. 1972 standard have a separately cast cupola welded onto the original turret, while T-62s produced in 1972 and after have the cupola cast as part of the turret.
For general observation purposes, the loader is provided with a single MK-4S periscope with a rear view feature. It can be elevated and depressed, or rotated 360 degrees for all-round vision, though the geometry of the turret and the L-2 spotlight block out a large portion of the loader's leftward vision. It's not very useful in combat, since the loader must concentrate on his loading duties, but it may be intermittently useful under certain circumstances. For instance, the periscope gives the tank an extra pair of eyes to help ascertain the direction of enemy fire in an ambush during the first few seconds of the attack, which can prove critical to the tank's survival and prompt destruction of hostile forces - in theory.
The loader has his own seat, but he performs his duties standing. The seat is the same type used in the T-54. It can be folded up and out of the way, or detached from the turret ring and moved to a different position, so that the loader can choose to either be facing forward or facing the cannon breech. The former option is the most comfortable, as the loader can stretch his legs for long journeys, and the latter option allows him to load or service the cannon while seated. The seat can be detached from the turret ring and stowed away if the loader desires even more room.
When not seated, the loader stands on the rotating floor, which is rather narrow, as you can see in the photo above and in the diagram below. Practically speaking, the loader may not always have both of his feet planted on the rotating floor while carrying out his duties.
One of the biggest drawbacks of the dome-shaped turret is that the loader hardly has any headroom while standing, whereas some contemporary Western tanks allow their comparatively tall loaders to stand completely straight. The loader's station in the T-62 has 1.6 m, or 5'4" of vertical space from the rotating turret floor to the loader's hatch . This is the same as the T-54, which is a bit surprising since the T-62 appears squatter than a T-54. That is evidently an optical illusion caused by the much, much wider turret. The vertical space was increased in the 1972 model of the T-62 by raising the ceiling by adding new cupola to the loader's side of the turret. Now, a loader of average height could stand up straighter when ramming shells into the breech, and a shorter loader could stand completely straight.
On the whole, the loader does not have very much room to work with, but he does have a bit more shoulder room than the loader of a T-54, as the turret of the T-62 is much wider. Below the waist, however, the working space is the same as in the T-54 because the width of the hull is practically identical.
Besides the size of the loader's station, it is also necessary to take the ammunition itself into consideration and not just the amount of working space, and having said that, it will be surprising to many to know that 115mm cartridges are surprisingly lightweight. The T-62 has taken a lot of flak for its lack of amenities, especially for the loader, and there is even an apocryphal story about an Israeli loader being hospitalized for spinal injuries while evaluating a captured T-62. The truth is, the Soviet 115mm caliber is remarkably efficient compared to previous artillery and tank gun calibers. 115mm APFSDS rounds weigh only around 22 kg, lighter than 100mm steel AP rounds by an entire 8 kg, and the 115mm 3UOF1 HE-Frag rounds are lighter than 100mm UOF-412 by 2kg, but fires a shell of similar mass at a similar velocity muzzle. The HEAT ammunition for both calibers weigh the same, but 115mm HEAT shells are much more powerful and possess significantly better armour penetration. Only 100mm APDS and APFSDS is lighter than 115mm APFSDS ammunition.
In terms of size, 115mm ammunition is not significantly larger or more difficult to handle than 100mm ammunition within the confines of a tank turret, despite being wider. Shell casings for the 115mm caliber are larger, of course. To be more specific, 115mm caliber casings have a length of 727mm and a maximum diameter of 165mm, and 100mm caliber casings are 692mm in length and have a maximum diameter of 147.32mm. However, 100mm casings are 147mm in diameter for most of its length and only neck down to around 100mm near the very end of the case, whereas 115mm casings are only 165mm in diameter at the lower half of the case, so being wider does not necessarily make them harder to handle. Case in point:
Also, the fact that the shell casings of 115mm ammo are longer than the ones for 100mm ammo does not really matter, because 115mm ammunition is still shorter overall. The 3UBM-5 APFSDS cartridge, for instance, has a total length of only 950mm. The UBR-412B APHE cartridge measures 962mm in length, and the 3UBM-11 APFSDS cartridge is 978mm in length, so generic 115mm APFSDS ammunition is actually shorter than its generic 100mm counterparts, but what about HEAT? The 100mm UBK-4M HEAT cartridge measures 1094mm in length, and the 115mm UBK-3M measures 1052mm in length, so once again, the 115mm caliber shows its merits. It is same for HE-Frag ammunition. Overall, 115mm ammunition is not only shorter than 100mm ammunition, but also much lighter, and the larger case diameter makes little difference.
Compared to 105mm ammunition, however, a generic 115mm APFSDS round weighs about 4 kg more than a generic 105mm APDS or APFSDS round, and all 115mm ammunition types are longer and wider than their 105mm counterpats. Still, the 115mm rounds are more powerful than their 105mm counterparts, so there is at least a good excuse for the added bulk. In the same working space, a loader should be able to load a U-5TS faster than a D-10T, but slower than an L7, with all else being equal.
Loading the U-5TS is no different than loading any other tank gun. The auto-ejector mechanism does not interfere with the loader in any way, as it is quite far from the cannon breech and is in a slightly lower position (to compensate for gravity as shell casings are extracted after firing), so it is completely out of the way when the loader is ramming a shell into the chamber. In fact, the ergonomics of the T-62 is greatly superior to the T-54 in this regard, because there is much more space between the cannon breech and the rear wall of the turret, so there is plenty of room for the loader. In addition to that, the unusually long neck of 115mm cartridges makes it easier for the loader to insert them into the cannon chamber, as it allows him to insert them with a sideways angle.
If the stabilizer is used, the loader assist function prompts the cannon to automatically elevate by +3°30' immediately after firing in order to allow the loader to load the cannon quicker when travelling on the move. This feature is almost always misunderstood and comes across as self-defeating, but it is a known method of improving the rate of fire. The Leopard 2 has the same feature, as demonstrated in this video clip (link). In the video, you can clearly see the breech rising slightly after the loader presses the loader's safety button, which deactivates the safety measures and the loader's assist function, and clears the gunner to open fire. Some other tanks like the Abrams do not have this feature, making it more difficult for the loader to insert rounds into the chamber while the tank is on the move, as the position of the cannon breech is constantly being adjusted by the vertical stabilizer, as demonstrated in this video clip (link). Having a loader's assist function is particularly important when firing on the move, because advancing tanks usually slow to a crawl or halt to fire in order to maximize accuracy, and then immediately accelerate to a high speed to perform evasive maneuvers in between shots to minimize vulnerability to counter fire. The stressful period between shots would be when the loader is obligated to perform, and the loader's assist function is meant to aid him. It is worth mentioning that the T-55A has the same feature, and should not be a factor when comparing the rates of fire between it and the T-62.
The T-62 can carry a total of 40 rounds of ammunition. The two sets of front hull stowage racks (both are conformal fuel tanks) hold 8 rounds each, for a total of 16 rounds of ammunition. These racks are pictured below. Another 20 rounds are stowed in the very back of the hull on the partition between the engine compartment and the fighting compartment. The loader has 2 rounds in a ready rack on the turret wall directly behind him for convenient loading, and single round secured by tension latches in a rack near his feet on the floor of the hull side wall. There is another round stowed in the same way near the commander's feet.
The 16 rounds in the front hull racks are the most convenient for the loader, second to the rack of two behind him. The rounds are held in place by simple hinged handles, which can be easily flicked up to let the loader pull the round out, as you can see below:
The loader must squat down to access these rounds. These racks are principally identical to the ones found on the T-54, only slightly modified for the different dimensions of 115mm rounds. These racks are one of the most convenient ones for the loader, second only to the rack on the turret wall. Once the loader has pulled a cartridge out of its slot, he can stand up and immediately ram the round into the chamber. There is no need to manhandle or maneuver the shells around to fit them into breech. The loader can be expected to load within 6 seconds using these racks.
As mentioned before, there are 20 rounds stowed in the rear of the fighting compartment, just ahead of the fireproof bulkhead that separates the fighting compartment from the engine compartment. These rounds are stowed crosswise to make the most out of the limited space. The two illustrations below (taken from what I assume is an Osprey book) show the location of these rounds.
The cartridges are held in that position by rubber cups holding the base of each shell casing and metal frames to prop them up. The photo below shows the rubber coasters for the right side of the racks.
This diagram from the T-62 technical manual gives a better idea of how the metal frames are supposed to look like supposed to look. It only shows the rubber coasters for the left side of the racks. The loader can extract cartridges from these racks by first unclipping the tension latch on the metal rack before carrying it up to the cannon breech. Since the rounds are stowed in a double stack, it is only possible to access the rounds at the back after depleting the rounds in the front and after folding the metal frame away (you can see the hinge, marked 14 at the bottom of the diagram below).
The photo below shows the same rubber coasters seen in the diagram above. The metal frame has been dismantled entirely.
The loader is not able to easily access the rear hull racks compared to the other racks in the tank. It is particularly difficult to access the ammunition stowed at the very back of the racks. Despite this, it appears that a good loader can be expected to load a round in a respectably short time even from the rear hull racks from what we see in this video (link). As the video shows, a motivated loader can pick up a shell from the bottom of the rear racks and pass it out of the hatch within 5 seconds after passing out the first one. Taking this as a surrogate for the loading procedure, we can say that the loader in a T-62 can load the cannon once every 7 seconds from the least convenient ammo racks.
Last but not least is the ready rack just behind the loader. It holds two rounds, mounted crosswise. Being located directly behind the loader (if he was to face the breech), these are the most easily accessible. To load, he must unlatch a round from a rack first, grab it and turn to face the cannon breech, then ram it in. This can be easily done in 4 seconds or less. The ready rack can be seen in the photo below.
The theoretical absolute maximum rate of fire should be around 8 to 10 rounds per minute using the front shell racks and the ready racks only, which is very reasonable. In reality, the gunner typically takes longer to find a target and acquire a firing solution than it does for the loader to load. In an extremely target-rich environment where the cannon will be fired as quickly as the loader can load it, then the maximum rate of fire can potentially be as high as 10 rounds per minute. The T-62 might be able to achieve something close to its theoretical maximum rate of fire if the commander and gunner forego the range finding procedure altogether and instead engage using battlesighting, as mentioned in the "Sighting Complexes" section of this article. This is a big advantage to the T-62, as the margin of error using battlesighting is negligible thanks to the high velocity of its APFSDS ammunition. In the average Central European battlefield, the gunner will only need to point, and shoot.
The T-62 technical manual lists the aimed rate of fire of the tank while stationary as 4 rounds per minute, but this figure is not to be taken at face value because the testing committee usually presents the loading rate as an average when using all ammunition stores, including the least convenient ones. Evidence of this practice is provided by Peter Samsonov in his article here (link). In other words, the listed rate of fire is the average sustained rate of fire, and not the practical or maximum rate.
In addition to that, the commander or gunner is obliged to carry out the entire formalized firing procedure - including rangefinding - during such tests. In real life, the gunner will most probably forego this procedure as the trajectory of the T-62's APFSDS shells is flat enough that there is a big likelihood of achieving a hit by battlesighting. It is very likely that a competent crew can fire the gun at a much higher rate than 4 rounds per minute.
With that said, this also raises an important question. If 115mm ammunition is lighter than 100mm ammunition and both the T-62 and T-54/55 are Soviet tanks that were evaluated by the same standards, why does the T-55A manual state that the rate of fire of the T-55A is 7 rounds per minute when stationary? There are a few explanations. One important factor to consider is that the T-55A carries 25 ready rounds, out of a total capacity of 43 rounds. There are 18 ready rounds in the front hull racks, and 7 ready rounds in the turret. For the T-62, there are only 18 ready rounds - 2 in the turret and 16 in the front hull racks - out of a total capacity of 40 rounds. Expressed as a percentage, ready ammunition makes up 58% of the ammunition in a T-55A and 45% of the ammunition in a T-62. Additionally, the T-55A stores another 4 rounds on the side wall of the hull on the loader's side. These rounds are easier to access than the ones in the racks at the back of the fighting compartment, next to the engine compartment bulkhead.
A reasonable estimate of the T-62's maximum average rate of fire in combat while firing on short halts or on a crawl should be around 4 rounds per minute, as the loader is inconvenienced whenever the turret needs to turn when the tank is moving because of the narrow turret floor and the potential loss of access to his most convenient store of ammunition. How long the loader can maintain his speed under the most optimal conditions, fatigue notwithstanding, is a different matter entirely, of course, and this is a universal issue with all manually loaded tanks. The T-62 loses out in pure loading speed since the ammunition is far inferior to contemporaries that have a bustle, as the bustle stays put when the turret spins, unlike ammo in the hull like the T-62's front hull racks, but even though it's not the most optimal configuration, it is still acceptable. The loader has access to all of the ammunition in the tank from his station regardless of the turret orientation. Plus, the ability to access all of the tank's ammunition from the loader's station counts for something during lulls in combat, namely that the commander can continue to do his duties on standby.
In terms of ammunition sustainability, the T-62 cannot hold a candle to its NATO counterparts. Counting the turret ready racks and the front hull racks, the T-62 has 18 ready rounds. The Leopard 1 must be considered excellent in that all of its 50+ ammunition is in convenient reach of the loader. The M60A1 is also quite good, as the loader has access to up to 37 rounds in the turret. With only 18 ready rounds, the T-62 should not be able to stay in continuous combat for as long as these tanks - only if we assume that tanks regularly expend dozens of rounds in most engagements, and fortunately they do not. After all, tanks with even fewer ready rounds than the T-62 have never been singled out for this weakness.
Besides the ammunition for the main gun, the loader is also responsible for reloading the co-axial machine gun. Three ammunition boxes are stowed in simple sheet metal containers mounted on the turret ring bulge recess, and two more boxes are mounted on the turret rear. More boxes can be tucked away on the hull floor.
The chief justification for the T-62's existence was the 2A20 "Rapira" smoothbore cannon, also known as the U-5TS "Molot" as per its internal designation.
Compared to its predecessor the D-10T, the U-5TS is much, much more powerful, and also heavier. The U-5TS weighs 2350 kg, compared to just 1950 kg for the D-10T, but the U-5TS also had a maximum chamber pressure of 366 MPa, compared to just 289 MPA for the D-10T.
The 2A20 has all-round decent durability. It has an EFC rating of 450 shots. This means that the cannon should be able to safely shoot off at least 450 lower pressure rounds like HE-Frag and HEAT, or perhaps around 200 to 150 APFSDS rounds, which operate at a much higher pressure. With a standard mix of HE-Frag, HEAT and APFSDS, around 300 shots can be safely fired through the barrel. After the 450 mark, the danger of a catastrophic failure from excessive wear increases exponentially, which can result in the self destruction of the barrel.
The cannon has a recoil stroke of between 350 mm and 415 mm, depending on the power of the ammunition used. The recoiling mechanism has a hard stop at 430 mm.
The cannon has three triggers - the electric button trigger on the gunner's right hand grip, the solenoid button on the manual elevation flywheel, and the manual trigger on the breech itself.
The cannon can be elevated to
The diagram above shows all of the components related to "Meteor".
Even as the first pre-production T-62s rolled off the factory gates in 1961, it was already fitted with the advanced 2E15 "Meteor" 2-plane stabilizer. This was not a common practice in the West at the time. Case in point, the M60A1, which was essentially the nemesis to the T-62, had just powered traverse and only received a serious two-plane stabilizer in 1972 in the form of the AOS (Add-On Stabilizer) system retrofit, which even then was not noticeably more useful (reading Tank-Net, it seems that the AOS system had a range of issues, including the tendency to sometimes spin the turret uncontrollably), though it was more advanced. The Leopard 1 caught up in 1970 with the Leopard 1A1 upgrade, when it received a new Cadillac-Gage 2-plane stabilizer.
"Meteor" was not a new development at the time. It was assembled and adapted for the T-62 from two previous stabilizer projects; the STP-2 "Tsyklon" from the T-54B and 2E12 "Liven" from the T-10M. To be specific, "Meteor" used This greatly reduced the financial and time costs. "Meteor" gave the T-62 a modicum of a fire-on-the-move capability which is excellent for the era, granting it a necessary advantage over contemporary Western tanks in highly mobile meeting engagements, which was considered the main format of tank combat by Soviet and Western experts. This also meant that the T-62 was more flexible on the dynamic battlefield, being nearly equally adept on the defensive as on the offensive.
"Meteor" has two modes of operation: Automatic and Semi-automatic. In the automatic mode, the stabilizers operate at full capacity and work to keep the gun oriented at the point of aim set by the gunner using his sight. In the Semi-automatic mode, the stabilizer system suspends operation, but not the horizontal and vertical drives. In effect, the gunner is left with power traverse and elevation but no stabilization. The Semi-automatic mode is used when the tank is used defensively in a fixed position and when travelling in anticipation of imminent combat, the reasons being that keeping the system in the Semi-automatic mode greatly improves the lifespan of the stabilizer system, and switching from Semi-automatic to Automatic is very quick, and is done with the flick of a switch on the gunner's handgrips.
Control of gun elevation and turret traverse is conducted using the Meteor control handgrips. The right thumb trigger fires the main cannon and the left thumb trigger fires the co-axial.
In case of a failure of the electrical systems or some other malfunction, the gunner must use hand cranked flywheels located directly behind the handgrips. The gearbox on the manual elevation and traverse mechanisms both have buttons for disengaging the powered actuators and engaging the manual drive gears. The elevation flywheel handle has a solenoid trigger for firing the cannon.
As the years went by, the T-62 received continuously updated versions of the Meteor. The 1964 version received the "Meteor-M", which was functionally identical to the Meteor, but replaced its vacuum tubes with transistors. The "Meteor-M1" was installed on the 1967 variant, and brought only minor modifications without changing the operating characteristics of the original "Meteor". With this in mind, only the original variant will be discussed in detail.
2E15 "Meteor" Hydroelectric Stabilizer
Turret traverse at the maximum rate is quite slow. It takes around 22.5 seconds to make a full revolution, or 16° per second. This is slow compared to NATO tanks which tended to be about twice as fast. The underwhelming turret rotation speed is broadly inconsequential during long to medium range engagements, but the T-62 suffers in non-linear combat where targets may appear suddenly from unexpected directions. The slow reaction time of the T-62 is typical of Soviet tanks, and is partially remedied when the tank is deployed as part of a platoon.
Minimum Traverse Speed: 0.07 deg/sec
Maximum Traverse Speed: 16 deg/sec
Minimum Gun Elevation Speed: 0.07 deg/sec
Maximum Gun Elevation Speed: 4.5 deg/sec
"Meteor" is not precise enough to be used for engaging targets on the move at long distances, but it must be reinforced that it was still quite advanced for its time. The mean deviation in the vertical plane is 1 mil and the mean deviation in the horizontal plane is 3 mils when the tank is in motion, meaning that the cannon shifts by an average of 1 meter at 1 km from the aiming point in the vertical plane, and 3 meters at 1 km in the vertical plane. Firing while stationary is much more accurate, of course. According to the T-62 manual, the system is accurate enough for a stationary T-62 to achieve a greater than 70% hit rate at 1000 m on a tank-type target moving at 20 km/h at a relative angle of approach of 30°, according to a U.S TRADOC bulletin, pictured below.
"Meteor" was quite good for 1963, but by 1972, it was technically outclassed by the M60A1 stabilizer from the M60A1 AOS (Add-On Stabilizer). According to Direct support and general support maintenance manual: turret for tank, combat, full-tracked, 105-mm gun, M60A1 (2350-00-756-8497) and M60A1 (AOS) (2350-01-058-9487), the AOS stabilizer offered better gun laying precision, having a minimum traverse speed of 0.5 mils per second, or 0.028 degrees per second, and an equal minimum elevation speed. The AOS stabilizer also offered a vastly superior maximum turret traverse speed. The accuracy of stabilization was also somewhat better when the tank was in motion.
There are various methods to improve firing accuracy when firing on the move. The crew is primarily trained to fire on short halts and on slow crawls, which is a process that must be coordinated by the commander. For either methods, the process is as follows: The commander spots a target, designates it for the gunner and cues the loader to load an appropriate round, while simultaneously using the stadia rangefinder in his periscope to determine the distance to the target as accurately as he can. The gunner then inputs the range data from the commander, lays the gun on target, and the driver is ordered to either stop or slow down the tank. Once stopped or slowed down, the gunner fires. If at all possible, the tank approaches the target straight ahead. This minimizes the stabilization error in the horizontal plane, which is very high.
However, that is not to say that the stabilization system was insufficiently accurate for firing on the move. With a mean vertical deviation of 1 mil, a T-62 could aim at the center mass of an M60A1 and expect to hit it at 1 km if the tank is moving straight towards it, as the body of the M60A1 measures around 2.5 meters tall, not including ground clearance or the large commander's cupola. The shot could be fall short by 1 meter and still hit the lower glacis, or go over by 1 meter and still hit the upper part of the gun mantlet. On the other hand, the low accuracy of the horizontal stabilizer makes it highly improbable for the T-62 to score a hit at long range while moving at an angle to the target, or while performing zig-zagging maneuvers.
As mentioned before in the "Sighting complexes" section, "Meteor" features a Loader Assist function where it raises the cannon by about 3 degrees, or rather, lowers the breech by 3 degrees, thus making it easier for the loader to ram a shell in. Turret traverse is also suspended, so that the loader is not caught off balance if the gunner suddenly decides to turn the turret. Pressing the "Ready" button on the loader's safety control box will arm the cannon and end the Loader Assist sequence. This system is integral to "Meteor". The auto-ejector works independently of the Loader Assist system, so turning off either one will not affect the other. The Loader Assist function is intended to help the loader carry out his duties while the tank is on the move, as fixing the breech of the gun at a lowered position makes it much easier for the loader to ram a shell into the chamber while the tank is moving. The loader will find it rather difficult to place a shell into the chamber if the chamber is undulating up and down from the vertical stabilizer.
There is an amplidyne amplifier for the turret traverse motor located at the very rear of the turret, immediately behind the commander. It takes an electrical current and amplifies its voltage to produce the immense power needed to rotate the heavy turret at an acceptable pace.
There is a gyroscopic tachometer for measuring the angular velocity of the turret and tank in relation to the intended target. The tachometer is installed at the very front of the gunner's station, behind the sighting complexes. The gyro-tachometer was taken from the STP-2 two-plane stabilizer system for the T-54B.
|Gyroscopic tachometer for Meteor-M1|
Underneath the loader's handgrip is the ejection system control box. The ejection mechanism can be set to either the automatic mode or the manual mode by flipping a toggle switch. Two push-buttons on the control box are used to open and close the ejection port. The ejection port can be opened and closed independently of the rest of the ejection system. If the tank is fighting in an NBC-contaminated environment, then the auto-ejection system should be set to manual mode.
Before the ejection cycle even starts, its springs are cocked by the recoil of the cannon. Refer to the picture below. As the cannon recoils, a push rod (Yellow) connected to the recoiling part of the cannon pushes a octant-shaped lever arm (Green), which hinges (Blue) backwards and pulls the ejector spring; a tension coil spring (Red). This cocks the ejector spring. When the ejection cycle is in its last stage to eject the spent shell casing, this ejector spring
When the shell casing is ejected from the breech from the recoiling cycle, it is caught by the lifting tray, which is a shallow 'U'-shaped tray affixed to the lifting mechanism. The shell casing is held in place by the rim of the casing by two spring-loaded grippers on either side of the tray, which you can see in the photo below. A rubber-padded plate on the arm guard placed just behind the lifting tray prevents the casing from hitting the rear wall of the turret and helps to soften the noise. The ejector mechanism is triggered by the recoil of the cannon and by the base of the spent shell casing striking a switch located above the rear plate behind the lifting tray. The act of ejection itself is done by a pair of ejectors striking the rim of the shell casing (refer to picture below).
Then, the ejector mechanism lifts up to the ejection port, the ejection port is opened briefly, and the shell casing is thrown out very forcefully. As you can see in the photo below, the ejection port is operated by a servo motor, and there is a handle to lock it and unlock it on the left side.
The ejection process is explained in exquisite detail in the T-62 technical manual. Here are translated paragraphs from the manual (pp. 89-90):
"When the base of the spent shell casing strikes against the rear wall of the lifting tray, the casing trips a start button for the electrical circuit. The ejection port is opened and the frame is lifted to the ejection position. When the frame is lifted, the leaf is disengaged from the hook, which returns to its original position.
The lifting frame with the spent casing occurs until the cam touches the copier plane and presses the frame lifting limit switches. The switches are in the position with the shell casing against the ejection port in the tower. With the pressing of the switch, voltage is applied to the reset solenoid, which releases the rim of the shell casing from the hold of its latch. With the force of the cocked torsion bar and springs, the shell casing is thrown through the ejection port to the outside.
After the ejection of the casing the lifting frame is lowered to its original position and the ejection port in the turret is closed. When lowering the frame, it acts against the bevel of the hook and is locked in place. After the frame is lowered and the ejection hatch is closed, all of the ejection mechanism will be in its original positions."
"При ударе фланцем о заднюю стенку ограждения гильза включает кнопку запуска электрической схемы. Происходит открывание люка в башне и подъем рамки на линию выброса. При подъеме рамки створка выходит из зацепления с зацепом, который возвратиться в исходное положение.
Подъем рамки с гильзой происходит до тех пор, пока кулачок не коснется плоскости копира и не включить переключатели ограничения подъема рамки. Переключатели включается в положении рамки с гильзой против люка в башне. С включением переключателя подается напряжение на электромагнит сброса, который пальцем освобождает захват с зацепами от удержания его защелкой. Силой взведенного торсиона и пружин гильза выбрасывается через люк наружу.
После выброса гильзы рамка опускается в исходное положение и закрывается люк в башне. При опускании рамка воздействует на скос зацепа и входит с ним в зацепление. После опускания рамки и закрытия люка все механизма выброса занимают исходное положение. "
The diagram below shows the sequence of ejection. The order of the sequence goes clockwise from the top left. Viewing the diagram in its original size is recommended.
The entire ejection cycle takes 3 seconds in total, including the firing of the cannon and its recoiling cycle. Without including the firing of the cannon and its recovery from recoil, the ejection cycle takes only 2.1 seconds. Proof of this comes from this video of a Vietnamese T-62 with a working ejector (link). You can tell when the ejection cycle starts by the opening of the ejection port. The extremely quick work of the ejector mechanism means that the loader will never have to wait for it to finish before loading the cannon, so the system does not interfere with the loading procedure in any way. In fact, the two seconds spent by the autoejector should be over before a loader is even able to retrieve a round from the front hull racks. By the time the lifting frame has lowered, the loader should be ready or just about ready to ram a fresh shell in. The system brings the long term benefit of removing spent shell casings from the floor of the fighting compartment and also the fumes emanating from the unburnt propellant residue inside the casings, so in that way, it indirectly improves the rate of fire.
Contrary to popular belief, shell casings can never bounce off the back of the turret and injure crew members because of "misalignment". The lifting frame elevates right up to the ejection port, and even if by pure chance a shell casing does somehow miss the gaping ejection port opening, it will not bounce back and hit anyone, because there is no space for a shell casing to go between the lifting tray and the ejection port; the casing can only go forward and slide down the tray and drop to the floor (the grippers that hold on to the rim are disengaged during the ejection). This redundancy feature also means that if the ejection mechanism were to fail mid-cycle, the loader can simply pick up the shell casing and throw it away by hand.
The entire system is centered on the KV2 control box, which coordinates the timing and execution of all of the actions of the autoejector.
Inside the KV2 control box are five relays. One relay controls the raising of the autoejector to the ejection position, one controls the lowering of the autoejector to the original position, one controls the opening of the ejection port hatch, and one controls the closing of the hatch. These four relays are coordinated by a time delay relay.
Using the toggle switch labeled (6) on the diagram above, the loader can either set the system to the "Automatic" mode or the "hatch control" mode, which is essentially the manual mode. When the toggle switch is set to the "Automatic" mode, the autoejection system works automatically as we have already examined. When set to the "hatch control" mode, the loader can press the "Open" button to manually open the ejection port. Pressing the "Close" button closes the ejection port. As the opening and closing of the ejection port hatch is no longer controlled by the system, autoejection is therefore suspended. This mode is used in NBC conditions to prevent contaminated particles from entering through the ejection port. However, it has never been used for that purpose. The ability to open the ejection port hatch is sometimes exploited by leaving it open for for extra ventilation, or to turn the ejection port into convenient loading hatch if needed, as demonstrated in the two photos below.
When the autoejector system is suspended in the "hatch control" mode, the loader must manually remove shells from the lifting tray at the back of the ejector. He will then place it into its original slot in the ammo rack, and then retrieve a fresh round from the same ammo rack. This conveniently solves the issue of empty shell casings rolling around the floor of the tank.
115mm VS 120mm
The size difference between 115mm cartridges and 120mm cartridges is minimal. In terms of heft and dimensions, 115mm ammunition was bigger than NATO 105mm and Soviet 100mm ammuniton, but essentially identical to NATO 120mm ammunition (not British 120mm). In order to truly appreciate the burden on the loader, here's a photo comparison between a 120mm cartridge and a 115mm equivalent:
|M829 compared to 3UB56|
The similarities in the sizes of 115mm and 120mm ammunition can be proven by the T-62AG variant, a modernization package offered by the KMDB, which you can read about here (link). Looking past the fact that they managed to fit a 120mm tank gun (in reality a domestic production version of the French CN120 called the KBM2) into the T-62, it must be noted that the total amount of ammunition carried by the tank did not change. The T-62AG carries a total of 40 rounds of 120mm ammunition, stowed in the same positions as the 115mm cartridges it replaced, with only minor modifications to better fit the new ammunition.
115mm rounds are simply much bigger than 105mm rounds. Even though they are both given approximately the same width of space, the T-62 loader is fatigued more easily than an M60 loader, even more so since a ride in the T-62 isn't quite as smooth.
And of course, a T-62 loader didn't have nearly the same amount of space that loaders in NATO tanks sporting 120mm guns did. Here's another photo, this time of a 115mm cartridge container held up by what appears to be a Siberian tanker.
However, it must be reiterated that loading the U-5TS was still an easier task than loading the D-10T in a T-54.
The two biggest assets of the U-5TS cannon were the 3UBM3 shell, the first ever serial APFSDS tank shell to enter service, and the 3UBK-4 HEAT shell, which benefited from the lack of rifling on the cannon.
Shell casings had an atypical form, identifiable by a greatly elongated bottlenecked front section, which was necessary for properly seating the APFSDS shells for which the casings were specially designed for. There are two types of casings; steel 4G9 cases and brass 4G10A cases. Steel 4G9 cases cost less to manufacture, while the brass 4G10A cases cost more but improve overall performance. Steel cases were used HE-Frag ammunition, for which accuracy was of less importance while the higher quality brass cases were used for APFSDS and HEAT-FS.
The "default" loadout for a T-62 for a breakthrough assault would be 12 APFSDS shells, 6 HEAT-FS shells and 22 HE-Frag shells. As usual, the loadout changes based on necessity, but generally speaking, APFSDS was preferred over HEAT.
High-explosive fragmentation shells are arguably the most important ammunition type for the T-62, given the expected tactical contributions of a Soviet tank to combined arms combat. Though tanks are obviously a major threat, the vast majority of the vehicular targets that a tank would encounter on the battlefield are thin-skinned APCs, IFVs and utility trucks, and the tank will always be called upon by infantry for fire support against bunkers, machine gun nests, and other garrisoned troops. HE-Frag shells may be used as a last resort against enemy tanks as well, serving to knock out various essential components for anything from a mobility kill to a firepower kill (though obviously rooting for the latter). The 2A20's selection of HE-Frag shells are characterized by very thick steel walls and a relatively high muzzle velocity. However, the stabilizer fins are a major source of drag. This means that 115mm HE-Frag shells tend to slow down considerably at long range.
First HE-Frag shell available to the 2A20 cannon in 1961. The body of the shell has a polygonal shape. Its thin steel walls are suitable for fragmentation and splintering, but the bulk of the damage done by this shell is caused by blast. The propellant charge used is 4AD11 stick powder. The explosive compound used 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.
Muzzle Velocity: 905 m/s
Maximum Direct Fire Range: 3600 m
Mass of Complete Round: 28.1 kg
Total Mass of Projectile: 14.86 kg
Mass of Explosive Charge: 2.695 kg
Improved shell with an ogived nose and much thicker shell body for greater fragmentation mass and volume as well as a better optimized spray pattern for increased casualties. The shell also boasts an extended firing range despite a 20.1% increase in mass over the OF-11 thanks to better ballistic properties and a more powerful propellant charge taken from the 3UBK3 HEAT cartridge. The new 4AD20 stick powder propellant boosts the muzzle velocity of the shell to 940 m/s, at the cost of increased chamber pressure and also a slightly higher rate of barrel wear. Because of the increased muzzle velocity, this shell is slightly more accurate than the 3OF11 at all distances. The explosive charge is still TNT.
The V-429E variable sensitivity fuse was available later on.
Muzzle Velocity: 940 m/s
Maximum Direct Fire Range: 4800 m
Mass of Complete Round: 30.8 kg
Total mass of Projectile: 17.86 kg
Mass of Explosive Charge: 2.8 kg
Newer shell that is largely similar to the 3OF18, but with an A-IX-2 explosive charge replacing the traditional TNT. Like the 3UOF6, 4AD20 propellant is used. The reason why the mass of the A-IX-2 explosive charge is greater than the mass of TNT available in previous shells although the walls of the 3OF27 shell are only slightly thinner is because A-IX-2 is slightly more dense. Why they decided to use A-IX-2 in this shell is not clear.
Muzzle Velocity: 940 m/s
Maximum Direct Fire Range: 4800 m
Mass of Complete Round: 30.75 kg
Total mass of Projectile: 17.82 kg
Mass of Explosive Charge: 3.13 kg
Being widely considered to be a pioneer on the introduction APFSDS technology into widespread service, the T-62 essentially relies on it as its main selling point, and for good reason. Because of the remarkably high velocity of the T-62's APFSDS ammunition, their ballistic trajectory was essentially flat up to 1600m - quite different from APDS shells. This meant that in typical tank-on-tank combat scenarios, the T-62 gunner would only need to put the sight chevron on target and fire without even needing to determine the range. The extremely high velocity also meant that engaging moving targets was a lot easier, since it would tend to take less than a second for the shell to reach its target in normal European battlefields where combat distances typically don't exceed 1500m. This almost entirely negated the need for calculated target leading, even against relatively fast-moving vehicles. APFSDS shells would also be very useful against vehicles moving at irregular speeds, again because the gunner does not need to apply much lead. This greatly helped offset the retarded engagement time caused by limitations of the targeting system and increased first-round hit probability significantly.
According to this TRADOC graph, a stationary T-62 had a 50% chance to hit an exposed stationary M60A1 tank with its APFSDS rounds on the first try at 1500 m. The shots were conducted using 3UBM5 rounds - pure steel rounds.
It must be noted that the large, bore-riding stabilizing fins at the tail end of the projectile produced a great deal of aerodynamic drag. According to V.A Grigoryan in "Защита танков" (Download), 115mm fin stabilized projectiles had a muzzle velocity of 1615 m/s, and a velocity of 1358 m/s at 2 kilometers. This translates to a rate of speed loss of up to 128.5 m/s per kilometer of travel. BM8 APDS, on the other hand, loses 106.5 m/s per kilometer of travel.
The 2A20 "Molot" cannot be considered a "bad" gun, but it had one major drawback related to the Iranian Chieftain in the photo below.
Steel was cheap, plentiful, easy to handle and reasonably strong, but is intrinsically inferior to heavy metals like tungsten and depleted uranium. The high elongation of the steel rod is absolutely critical in counteracting this. In the photo above, an eagle-eyed observer will note that the impact crater on the left shows evidence of deflection. It cannot be part of the channel made by a cumulative jet, because the photograph was taken at eye level with the turret, not at a downward angle, and a cumulative jet does not leave such huge entry holes, so the crater must have been left by an APFSDS round. However, despite whatever deflection occurred on impact, the APFSDS round perforated the turret all the same.
This report provided by Tank-Net and Otvaga2004 member Wiedzmin tells us that Iranian Chieftain tanks were vulnerable to both 115mm APFSDS and HEAT, and that the majority of the hits were achieved by APFSDS rounds. The report notes that:
"of the eighty eight strikes, seventy one penetrated, many on the relatively vulnerable hull but some in the areas of highest protection on the turret front. The consequences of penetration were:
a. A 'fireball' of low duration but high intensity surging through the penetrated compartment. The turret padding and any cloth, such as crew clothing, was badly singed and paint was blistered. In many cases the singeing of the padding and its foam lining had caused dense smoke and the production of a noxious gas.
b. A 20° high energy cone of spall was discharged from the point of penetration. Four feet from the penetration the cone was some 600mm in diameter. The internal diameter of the penetration was normally 60 to 80mm."
The report also notes that "by far the majority of the damaged tanks (70%) had been hit by the 115mm long rod penetrator APDSFS T62 tank gun round", proving that APFSDS rounds were the preferred anti-tank round. From what we see here, it is clear that 115mm APFSDS is highly effective against the Chieftain, providing that penetration occurs. The post-penetration effects of this type of ammunition is proven to be effective at either killing the crew and damaging internal components or at least smoking the crew out of the tank. Unfortunately, the ranges of engagement for any of the damaged Chieftains was not given, and they did not provide a definition for "battle range", so we cannot know the limits of the capabilities of 115mm APFSDS by reading this part of the report. We can, however, make good guesses by taking an in-depth look at 115mm APFSDS ammunition:
|Photo Credit: Stefan Kotsch|
Original APFSDS shell made for the 2A20 cannon, first introduced in 1961. It had a tungsten carbide slug in the bulbous region of the projectile at the tip, topped off with a flat steel armour piercing cap to prevent the slug from shattering outright on impact and to improve performance on sloped armour.
In 1961 terms, the BM3 was vastly superior to contemporary 105mm APDS ammunition such as the L28 and L36A1 and the American M392 derived from it, having at least 35% better penetration values at the same distance, accounting for different certification standards and different target steel strength and hardness. BM3 can be placed between 100mm 3BM8 APDS for the D-10T (T-55) and the 122mm 3BM11 APDS for the M-62 (T-10M) in "power" ranking. These two contemporaries were introduced quite a while after BM3 - in 1967 and 1968 respectively. 3BM8 penetrates 190mm at 0 degrees at 1 km, and 3BM11 penetrates 320mm at 0 degrees at 2 km. BM3 is also superior to the L15 APDS shell in terms of penetration on both sloped and unsloped armour, and generates more lethal after-armour effects on significantly overmatched armour as a result of its less optimal design; being much less efficient than a single solid tungsten carbide slug, it would produce a much more massive fragmentation pattern post penetration.
A small part of this is simple extrapolation, since the author hasn't seen any documents pertaining to this matter, but based after-armour lethality reports on extremely similar 125mm tungsten-cored APFSDS, there can be very little doubt about it. This article by Peter Samsonov is mandatory reading. The document featured in the article pertains to a lethality analysis done on 3BM-9, 3BM-15, 3BM-22 and 3BM-26 APFSDS rounds. 3BM-9 is an all-steel "torpedo" APFSDS round. 3BM-15 is the closest representation of BM-3, as both have a tungsten carbide core at the front of the projectile, as opposed to one at the rear, as in 3BM-22 and 3BM-26. All of the shots were for a 60 degree obliquity impact, and the velocity of all of the shells corresponds to their velocities at 2 km.
Assuming that the round overmatches the armour plate by 100mm to 200mm (LOS), then a penetrating 3BM-15 shell will produce 150 to 200 pieces of fragmentation capable of penetrating 3-6mm of aluminium sheeting in a 110 degree cone.
According to graph (b):
The number of lethal fragments increases as the armour overmatch increases. The curve of this graph was drawn based on calculations from the tabulated data of all four APFSDS rounds, so it does not exactly represent any of them, but we know that the late model APFSDS designs with the core at the rear have a greatly improved fragmentation pattern and quantity compared to the earlier designs, so we can assume that 3BM-15 - and by extension, the BM3 - produces somewhat less fragments than listed in graph (b) per 100mm of overmatched armour. If we take 3BM-15 as a surrogate for BM-3, then when BM-3 is fired at the side of an M60A1 (74mm cast side armour) at 60 degrees, it will overmatch by 112mm. This means that it will generate slightly less than 80 lethal fragments (according to graph (b)), but it will also generate around a hundred other fragments that will badly injure the crew, cut electrical wiring, sever hydraulic fluid lines, and so on. Adding on to that, remember that the APFSDS rounds fired in the test had an impact velocity corresponding to their velocity at a distance of 2 km.
Fragments that are capable of penetrating at least 30mm of aluminium are few and far in between; most of the fragments are only capable of penetrating less than that. While fragments that can penetrate 30mm of aluminium would not be more useful than smaller fragments at harming or killing the crew, they will be capable of detonating ammunition on a direct hit, which is something that the low penetration, low energy fragments cannot readily do.
This would make the BM3 incredibly potent against relatively lightly armoured tanks like the Leopard 1 and AMX-30 appearing in the late 60's. Additional evidence of the high lethality of BM3 comes from U.S Army evaluations, which assign a very high Pk (probability of kill) to BM6 rounds on an M60A1 - 71% - according to the TRADOC bulletin. As shown in the report above, 3BM-9 steel APFSDS produces more fragments post-armour penetration than 3BM-15 cored APFSDS. This relationship should not be different for the BM3 and its all-steel counterparts.
Muzzle Velocity: 1615 m/s
Mass of Complete Round: 22 kg
Projectile Mass: 5.5 kg
Certified Penetration at 1000m:
300mm @ 0°
130mm @ 60°
Certified Penetration at 2000m:
270mm @ 0°
115mm @ 60°
With what we currently know about the armour of the M60A1, BM3 would have been more than sufficient at combat ranges. The cast upper glacis of the M60A1 measures 109mm in thickness, angled at 65 degrees, making for a more formidable target than even the sloped turret cheeks, but even so, most parts of the M60A1 should be vulnerable to BM3 at combat ranges, and that is without taking into account the differences in ballistic standards. The Soviets use V80 ballistic limit, as opposed to V50, meaning that given a data sample of 'x' number of rounds, 80% must penetrate a certain amount of armour within a reasonable range of velocities. Also, the American criteria of what constitutes full armour perforation is based on the recovery of 50% of projectile mass behind the armour plate. The Soviet criteria uses 75%, but 80% is also used. Taken together, all this means that if BM3 can penetrate 300mm at 1 km according to the Soviet penetration criteria, then it could penetrate around 324mm when expressed in the Western penetration criteria, and for every successful armour perforation, the behind-armour effect would also be much stronger.
Knowing the armour thickness of the Chieftain Mk.5 tank from ultrasound measurements, it can be reasonably surmised that the 3BM3 is capable of reliably perforating the turret on any point from at least 1000 m, but probably more, because the Chieftain has cast steel armour and not rolled armour, and we are basing our estimations on Soviet penetration values based on Soviet penetration criteria. The weak lower front plate of the hull can be penetrated from any conceivable distance, but the highly sloped upper front plate is a tougher target than even the turret, since 115mm APFSDS does not handle extreme slope well. It is fortunate for the T-62, then, that the upper front plate of the Chieftain occupies only a very small portion of the total frontal profile of the tank.
The true ingenuity behind the 3UBM3 round wasn't that it was radically more powerful than anything on the planet - it wasn't. The innovation of the BM3 projectile was that the tungsten carbide slug within only only weighed about 300 grams, but could punch through more armour than the 2.82 kg slug in the 100mm BM-8 APDS shell for the T-55. For every BM-8, they could have made almost ten 3BM3 shells that were more powerful and more accurate. This would have been a huge incentive to prioritize the T-62 if a major conflict erupted. Recall that tungsten was very scarce in Nazi Germany in the late war period, making it extremely difficult for the Wehrmacht to procure APCR rounds as the war drew to a close and heavier and heavier Allied tanks started to appear on the frontlines. A similar scenario would be disastrous for the Soviet Union, as the technology for producing depleted uranium ammunition was still decades away, and the only alternative was steel ammunition, which would struggle against the heavily armoured M60A1. For this reason alone, the 3UBM3 round deserves nothing but praise. But let's take a look at that steel ammunition:
Introduced in 1963 as an even cheaper alternative to the 3UBM3, presumably having the secondary function of a training round. It was basic in construction; It was all-steel, was torpedo-shaped and very cheap to manufacture, but most importantly this shell clocked in at an unheard-of 1650 m/s at the muzzle, just a fraction above a mile a second.
The entire projectile functions as the penetrator. There is no internal core, only an armour piercing cap at the tip. It is made entirely of solid 60KhNM tool steel with a hardness of around 310 BHN. It had 6 steel fins, which were of a bore riding type that worked alongside the sabot to stabilize the shell as it travels down the barrel. The ends of the fins have copper lugs embedded in them to minimize abrasive damage to the much tougher chrome lining of the gun barrel. The soft armour piercing cap is made of 35KhGSA steel, built with a flat tip to decrease the likelihood of a ricochet on sloped armour as well as to protect the projectile from shattering upon impact.
Furthermore, the presence of the armour piercing cap protects the round from the effects of single plate light spaced armour, such as the type present on upgraded Leopard 1 turrets. The spaced plate will successfully destroy the armour piercing cap, but the penetrator will be intact, and it will continue to pass through the turret armour with extreme ease even at high obliquities.
Moreover, the after armour effects of BM4 are even greater than BM3, as shown in the comparison between pure-steel BM-9 and BM-15.
The main factors contributing to the penetrating performance of the shell is the relatively high length-to-diameter ratio of 13:1 and the fantastic speed of the projectile, but because it was made entirely from steel, its performance falls short of the BM3. However, that is not the point of the 3UBM4. If the 100mm BM-8 APDS projectile penetrates around 264mm of RHA steel at 0 degrees at 1 km using a 3 kg tungsten carbide slug, then the BM4 projectile can be considered a reasonable alternative, as it is capable of penetrating about 228mm RHA at the same distance, without needing any tungsten or special manufacturing techniques to build. Furthermore, the performance of BM-8 APDS was very underwhelming on sloped targets. As all Cold War era NATO tanks featured heavily sloped armour, BM4 would have been much more useful than BM-8 in practice.
Mass of Complete Round: 22 kg
Projectile Total Mass: 5.5 kg
Penetrator Mass (Without Sabot): 3.196 kg
Armour Piercing Cap Mass: 0.187 kg
Certified Penetration at 1000 m:
228mm RHA @ 0°
110mm RHA @ 60°
Certified penetration at 2000 m:
200mm RHA @ 0°
100mm RHA @ 60°
Alternate Russian source lists the penetration at 1000 m as:
250mm RHA @ 0°
130mm RHA @ 60°
However, there must be something wrong here. The astute reader will notice that this all-steel APFSDS round can penetrate more armour at 60 degrees than it can at 0 degrees. This is not possible.
With this shell, the T-62 had a respectable (but by no means dependable) chance of defeating tougher customers like the M48 or M60 frontally out to more than 2000 meters, and no trouble at all defeating an AMX 30, Leopard 1 or Centurion frontally out to 2000m. The Chieftain's turret is generally immune to this shell at any range, but the prominent lower hull is vulnerable at a distance of up to 1000 m, but no more.
Introduced in service in 1970 as a slightly more advanced but similarly cheap alternative to the 3UBM4, although in reality production had already switched over to 3UBM5 from the 3UBM4 between 1966 to 1968.
The stabilizing fins are made from 40KhFA steel alloy with high thermal resilience. The fin assembly weighs a total of 0.651 kg.
Externally identical, the BM6 projectile can be distinguished from the 3BM4 by the presence of "teeth" on the edge of the sabot, which are absent from the one on the 3BM4 projectile. Internally, they are quite different. The penetrator is made from 35KhZNM tool steel with a hardness of around 600 BHN - a huge step forward over the previous standard, although it is nothing special as 100mm BR-412B rounds for the D-10T/S had already achieved this standard of hardness in the late 40's. The penetrator now had a rounded nose, and it had an armour piercing cap made from softer 35KhGS steel. Although still made entirely of steel, this shell offers appreciably higher performance, but still far from being comparable to the BM3.
Here is what the penetrator without the armour piercing cap and the windscreen (ballistic cap) looks like:
Projectile Maximum Diameter: 42mm
Diameter of Stabilization Fins: 114mm
Total Projectile Length: 550mm
Total Cartridge Length: 950mm
Mass of Complete Round: 21.66 kg
Total Projectile Mass: 5.34 kg
Projectile Mass In Flight: 4.00 kg
Mass of Penetrator: 3.009 kg
Mass of Armour Piercing Cap: 0.167 kg
Muzzle Velocity: 1680 m/s
Certified Penetration at 1000 m:
280mm RHA @ 0°
135mm RHA @ 60°
Certified Penetration at 2000 m:
240mm RHA @ 0°
110mm RHA @ 60°
This shell deserves special attention for the huge improvement over the BM4. The new armour piercing cap appears to have improved the performance of the projectile on sloped armour to the point where it is superior to the BM3, making this shell even more useful than its predecessor on the heavily sloped armour of contemporary NATO tanks like the Chieftain and the M60A1.
Despite lacking any tungsten component whatsoever, 3BM-6 was already enough to defeat the Chieftain at typical combat distances. According to a Soviet analysis of an Iranian Chieftain captured by the Iraqi army during the early part of the Iran-Iraq war, available here on Andrei Tarasenko's btvt.info, the frontal armour of the Chieftain Mk.5 could be defeated at a distance of 1600 m. The frontal cheeks of the turret could be pierced at 1600 m, and the base of the turret could be pierced at 2300 m. The upper front plate, an 85mm cast armour plate sloped at 70 degrees, could be defeated at 1600 m, while the lower front plate could be defeated at more than 3 km. The table says 3 kilometers, since they did not bother to conduct testing past that distance, but the projectile velocity is listed as 1000 m/s, which corresponds to a distance of 5 km. For an all-steel tank shell, these are excellent results.
It must also be noted that the all-steel projectile offers better performance than the L28 or M392 APDS shells for the L7 cannon. The L28/M392 had a very substantial tungsten carbide core, larger than the 3 kg slug in the 100mm BM-8, in fact, but they achieved less penetration (than both the BM-8 and 3BM6) at the same distances; at 1 km distance, the L28/M392 could penetrate 252mm at 0 degrees, and 117mm at 60 degrees. To add insult to injury, combat experience in the 1973 Yom Kippur conflict apparently revealed that these shells could not perform reliably on heavily sloped armour, which was quickly solved with a tungsten tilting cap on the M392A2. However, this upgraded version is still inferior to the 3BM6 in performance on sloped armour.
This round made up the bulk of ammunition exported to client states, making it the most numerous type of APFSDS ammunition available to Egyptian and Syrian tank crews during the Yom Kippur war.
Like with the previous designs, an armour piercing cap with a flat tip is present to reduce the likelihood of a ricochet, and in this case, to protect the tungsten core from shattering upon impact. The difference between 3BM21 and previous models is that this cap is now much bigger. The enlarged cap effectively neutralized any difference in performance on sloped targets compared to flat targets. Here, the armour piercing cap and the tungsten carbide core are clearly visible.
Mass of Complete Round: 23.50 kg
Projectile Mass: 6.26 kg
Muzzle Velocity: 1600 m/s
Certified Penetration at 1000 m: (Extrapolated from values at 2 km)
360mm RHA @ 0°
175mm RHA @ 60°
Certified Penetration at 2000 m:
330mm RHA @ 0° *
165mm RHA @ 60° (Inferred)
* From Andrei Tarasenko's site (link), MV Pavlov, IV Pavlov "Domestic armored vehicles 1945-1965". Tiv №9 2008.
Most advanced 115mm APFSDS round of Soviet origin, and also the last APFSDS round developed for the T-62 before it was withdrawn from service. 3BM28 has a sheathed monobloc depleted uranium penetrator with a flat AM6 light alloy armour piercing cap at the tip. The penetrator is made from UTsN uranium-zinc-nickel alloy.
Muzzle Velocity: 1650 m/s
Mass of Penetrator: 4.36 kg
Mass of Armour Piercing Cap: 0.1 kg
Penetration at 2000 m:
380mm @ 0° *
200mm @ 60° (Inferred)
* From Andrei Tarasenko's site (link), quoted from MV Pavlov, IV Pavlov "Domestic armored vehicles 1945-1965". Tiv №9 2008.
Between the mid-50's to late 60's, shaped charge warheads was widely appraised as being the 'great equalizer' of tank warfare. Tube-launched HEAT warheads were decently popular, being tremendously useful in a variety of roles, from general tank-killing to bunker busting or simply as a more flexible alternative to HE-Frag or HEP shells thanks to their thick steel bodies, but because of the immaturity of shaped charge technology in those days, manufacturing a HEAT warhead tended to be costlier than manufacturing a kinetic energy one. Still, the typical HEAT shell on both sides of the Iron Curtain was so powerful that they rendered all contemporary tank armour essentially useless in the event of a direct hit, but the problem was exactly that - scoring a direct hit. Because of the vastly lower velocity - even lower than contemporary 105mm HEAT shells - the 2A20's selection of shaped charge ammunition can be generally characterized by subpar accuracy but excellent armour penetration and external fragmentation effects. Unfortunately, the post-penetration effects of HEAT rounds do not hold a candle to the power of APFSDS rounds. The report provided by Wiedzmin has this to say about the relationship between HEAT rounds and Iranian Chieftains:
"There had been forty hour HEAT strikes from both 115mm T62 tank gun rounds and TOW [only one TOW strike was recorded]. All but five had achieved some penetration; two Sagger warheads had achieved penetration; seven RPG 7 had struck but none had penetrated. The internal diameter of the 115 and TOW penetration was normally 35mm; penetration led to much less damage than APDSFS and seldom led to fires"
So despite the comparatively high penetration power of HEAT ammunition, HEAT is still no substitute for a good AP round.
Basic HEAT shell entering service alongside the T-62 in 1961. It had a cone-shaped nose and generally unremarkable ballistic properties. The warhead uses a steel shaped charge liner with a squared apex. The explosive compound used in the warhead is A-IX-1, a composition of 96% RDX and 4% paraffin wax. The walls of the shell are unusually thick compared to other HEAT shell designs. This is probably to enhance the fragmentation value the shell.
In shells produced from 1961 to 1964, there was a small 20-25 gram charge of A-IX-2 inside the tailboom, between the tracer and the warhead. It has no fuze or detonator - it is detonated by the explosion of the main warhead. The purpose of the small A-IX-2 charge was to increase the total fragmentation effect of the shell, but after several cases of the tailboom rupturing in the cannon barrel when fired, this feature was deleted. 3BK-4 shells produced after 1964 have a perforated hollow tailboom.
The penetration of 3BK-4 is roughly equal to the 105mm M456 HEAT round, despite the use of a copper liner in the M456. 3BK-4 greatly overmatches any NATO armour it meets, especially more lightly armoured tanks like the Leopard 1 or even slightly older tanks like the M48. The higher the level of overmatch, the more powerful the post-penetration effect will be.
Though extremely capable of knocking out an M60A1-type tank on the first hit, the chances of scoring a hit are extremely low. At 1500 m, the chances of hitting an M60-sized target is only 20%, and though this rises to about 48% at 1000 m, this still only means that just one out of two shots will connect. See the diagram below, taken from a TRADOC bulletin.
This is partially related to the design of the shell itself. 3BK-4 depends entirely on its stabilizer fins for accuracy, whereas M431 (90mm) and M456 (105mm) make use of shape stabilization; the shape of the shell is designed in such a way that the airflow around it keeps it very stable in flight. Additional factors that contribute to the lower accuracy of 3BK-4 are the lower velocity of the shell and the lack of precise rangefinding equipment on the T-62 itself. After all, the TRADOC bulletin gives its accuracy figure in the context of the T-62 engaging an M60A1 tank, so in other words, it gives the true practical accuracy of the shell.
The warhead uses the GPV-2 fuse. It is the same fuse used in the 100mm 3BK-5 HEAT round for the D-10T.
Mass of Complete Round: 26.00 kg
Projectile Mass: 12.97 kg
Diameter of Shaped Charge: 85mm
Mass of Explosive Charge: 1.55 kgExplosive Charge Type: RDX
Muzzle Velocity: 950 m/s
440mm @ 0°
200mm @ 60°
It is strange that 3BK-4 has 440mm of penetration at 0 degrees when the 125mm 3BK-12 has a penetration of only 420mm at the same angle. Given the increased caliber, one would expect the penetration to rise accordingly. In fact, the difference in the caliber of the shaped charges inside the warheads is more significant than the external calibers would lead you to believe; the shaped charge liner in the 3BK-4 has a diameter of 85mm, whereas the shaped charge liner in the 3BK-14 has a diameter of 105mm. The 3BK-4 was introduced in 1961 and the 3BK-12 was introduced experimentally in 1962, so there is no technology gap between them. One possible explanation is that the 0 degree penetration figure for 3BK-12 was created by someone simply converting the 60 degree penetration figure. If that were the case, 3BK-12 would have 210mm penetration at 60 degrees, and more penetration at 0 degrees as well.
Improved variant of the 3BK-4 replacing the steel liner with a copper one, yielding better penetration power. The copper liner was slightlu more elongated, which reduced the mass of the explosive filling slightly, but the overall effect was positive. Using
The shell uses the GPV-2 point-initiating base detonating (PIBD) piezoelectric fuse.
Mass of Complete Round: 26.00 kg
Projectile Mass: 12.97 kg
Diameter of Shaped Charge: 85mm
Mass of Explosive Charge: 1.478 kg
Explosive Charge Type: RDX
Muzzle Velocity: 950 m/s
>440mm @ 0°
>200mm @ 60°
The replacement of the steel liner with a copper one was not considered sensitive technology, as there is evidence that these shells were freely exported to the Syrians and Egyptians. It is difficult to imagine that this shell was less prolific in the Red Army.
The 3BK-15 had a greatly improved warhead design compared to its predecessors, doing away with the traditional conical or ogived aerodynamic fairings in exchange for a a flat-sided cylindrical body and a spike nose carried over from contemporary 125mm HEAT shells. The Engineer's Handbook from the U.S Army Materiel Command provides us with a more esoteric examination of spike noses: link.
The pictures below, taken from page 4-11, show the different airflow characteristics with different lengths of the standoff probe (referred to as the "spike nose") and at different mach numbers.
The handbook remarks under subheading "4-7.8.1 Spike-Nosed Projectiles" in page 4-10 that: "These spike-nosed projectiles had higher drag coefficients than the corresponding projectiles with ogival heads", indicating that 3BK-15 probably has a higher drag coefficient than the rounds it was designed to replace, trading velocity for some other desirable trait of the ballistic shape. Further down the paragraph, the handbook details a phenomenon called "dual flow":
"Examination of spark photographs showed that the low drag coefficients were associated with rounds on which the airflow separated from the spike at its tip, while on the high-drag rounds the flow separated at a point about half-way down the spike. This phenomenon was called "dual flow"; its existence was a function of the geometry of the spike. In order to avoid the occurrence of dual flow, with its serious effect on accuracy, modern spike-nosed rounds arc furnished with a small ring near the tip of the nose which insures the early separation of the flow."
In other words, a mach cone forms at the tip of the spike, and sometimes separates down the middle of the spike to form a second cone. Projectiles with two mach cones; one at the tip of the spike and one down the middle of the spike experienced higher drag, whereas projectiles with a single mach cone at the tip experienced low drag. A projectile with a simple straight spike could experience both flow configurations, resulting in some shots experiencing higher drag and landing low on the target, while others experience lower drag and land high. The purpose of the ring is to ensure the separation of flow at the tip of the spike, thus ensuring that the second cone down the spike is consistently eliminated leaving a single mach cone at the tip of the spike.
The effects of dual flow on accuracy are further explained in a Ballistics Research Laboratory study on this topic in the paper "THE EFFECT ON DRAG OF TWO STABLE FLOW CONFIGURATIONS OVER THE NOSE SPIKE OF THE 90MM T316 PROJECTILE" from 1954. Here is an excerpt:
"Since the occurrence of either type of flow appears to be of a statistical nature, caused by unknown conditions, a given group of rounds fired on a target might contain both species. With markedly different drag characteristics, the two groups will gradually separate, principally in a vertical plane, by as much as three mils at 2000 yards. The vertical target will then contain both high and low rounds thus jeopardizing what otherwise might be a good dispersion pattern. Clearly, it is desirable to fix the flow over the spike in such a way that only one type of flow occurred and preferably of a lower drag type."
The lack of a ring similar to the type present on Western spike noses might be because a truncated cone nose already had acceptably low drag, as suggested in the BRL paper. The paper showed that a truncated cone spike nose could reliably achieve stable low drag flow with almost as low of a drag coefficient as that achieved by a ringed spike, with no dual flow. See the table graph below:
The research conducted by the BRL resulted in engineers settling on the now common Western-style spike, with a square spike nose and a small ring. The 90mm M431, for example, perfectly matches this description, having a squared-headed fuse and a small protruding ring around the spike. We can infer that truncated nose cones were perhaps not quite as effective, but then why did Soviet HEAT shells have pronounced conical noses?
A plausible reason could be because the Soviet conical fuse had other, perhaps more important advantages. bojan from TankNet stated the 100mm BK-5M HEAT shell (with the GPV-2 PIBD fuse, pictured below) worked at slope angles of 65 to 70 degrees, whereas the square-headed (M509A1) fuse on the 90mm M431 HEAT only worked up to 60 degrees.
|Photo credit to PzGr40 of the wk2ammo site|
Therefore, the decision to not use a square-headed fuse might have been a deliberate compromise to trade ballistic performance for more reliable fuzing on very steeply sloped armour plate. Indeed, during the famous Yugo tests, the 90mm M431 had high probability of failing to detonate when it struck the upper glacis of the target (a T-54A tank) when the tank was angled 20 degrees sideways. It would not have been acceptable for a Soviet HEAT shell to exhibit similar limitations, as the upper glacis of an M60A1 tank was already more sloped than 60 degrees (it was sloped at 65 degrees) and the upper glacis of the Chieftain was even more sloped (72 degrees). This might explain why Soviet HEAT shells remained with conical noses despite the USSR obtaining some quantities of captured Western HEAT rounds over the course of the Cold War.
The spike nose of 3BK-15 had a length of 1.4 calibers and a maximum diameter of 0.38 calibers. The warhead also implemented some new old technologies to improve jet formation characteristics, including the use of a slightly tapered cylindrical wave shaper to optimize the direction of the blast wave from the explosive filling. 3BK-15 also has more precisely drawn shaped charge liner cones, and uses compressed explosives to increase the density of the explosive filling for more punch per volume.
The use of more energetic 12/7 stick powder boosted the shell's muzzle velocity to 1060 m/s, or Mach 3.11, yielding significantly better accuracy at longer distances, though the shell would still be less accurate than 105mm HEAT shells at longer ranges.
Mass of Complete Round: 26.3 kg
Total Projectile Mass: 12.2 kg
Muzzle Velocity: 1060 m/s
Penetration: (Unknown, estimated)
450mm @ 0° (?)
225mm @ 60° (?)
For some reason, the tracer was not placed at the base of the shell assembly. Instead, it is embedded into the wall of the warhead at the very front. My guess is that this created a more distinct tracer signature and helped the crew track the fall of the shot more easily.
Improved warhead using a copper liner instead of steel for improved penetration power. All other properties remain identical.
Mass of Complete Round: 26.3 kg
Total Projectile Mass: 12.2 kg
Muzzle Velocity: 1060 m/s
480mm @ 0° (?)
240mm @ 60° (?)
The original 1961 preproduction model T-62 was armed with the SGMT machine gun chambered for the 7.62x54mmR cartridge as a co-axial machine gun. It had a cyclic rate of fire of 600 rounds per minute, and it is fed from a 250-round box, of which ten more are stowed inside the tank for a total of 2750 rounds of ammunition. The SGMT could be fired with the left trigger button on the gunner's handgrip, or with the solenoid trigger button attached to the machine gun in case of a total failure of the tank's electrical systems.
In 1964, the SGMT was swapped out for the then-new PKT machine gun. Performance-wise, the two were practically indistinguishable, though the PKT does fire faster at 800 rounds per minute, so the true impetus for the change was not to have a better machine gun, but to standardize the PK general purpose machine gun among the entire armed forces.
The PKT machine gun is fed from proprietary 250-round boxes, of which 10 more are stowed, exactly as with the SGMT. Like the SGMT, the PKT can be fired from the left trigger button on the gunner's handgrips, or with the inclusive solenoid trigger button if the situation calls for it.
Because both machine guns use the same ammunition and have similar barrel lengths and rifling twists, the ballistic trajectory of the shots fired are essentially identical, so there was no need to modify the sights to accommodate the new machine gun. The nominal maximum effective range of both machine guns is around 1500 m, while the effective range against a running target is around 650m. Ball and tracer ammunition are usually linked in a 2:1 ratio, but sometimes tracers are used exclusively. Spent casings and emptied links are collected in a metal bin to the left of the machine gun.
The exact use of the co-axial machine gun is dependent on the gunner more than anything. It is usually used instead of cannon rounds to engage enemy personnel to save ammunition. It is useful for when excessive destruction is undesirable; when friendly forces intend to occupy an evicted foe's garrison, for instance.
The installation of the DShKM necessitated that the loader was given a more developed cupola with a race ring and a mount to place the machine gun. Elevating and depressing the machine gun cradle is done with a flywheel, and slewing the cupola side-to-side is done by moving it with body weight.
The DShKM has a rate of fire of around 600 rounds per minute, but it is characterized by somewhat mediocre accuracy in comparison with the later NSV and KORD machine guns.
It is fed with 50-round boxes, with another five strapped close to the side of the turret (see photo above) for easy access by the loader, who needs only to bend down to reach them.
Aiming can be done with either the K-10T anti-aircraft collimator sight kept in the raised box mounted to the cradle, or the classic leaf-type iron sights on the machine gun. The K-10T facilitates accurate aiming at both ground level and high altitude targets, though the leaf sights on the DShK would be more appropriate for aiming at ground targets. The collimator sight has a tinted screen in front of the holographic screen to reduce glare.
The K-10T is electrically powered by the tank's electrical systems. When not in use, the protective cover is closed, mainly to shelter it from the weather.
The DShKM was technically sufficient against attack helicopters of its day, given that common examples like the AH-1 Cobra did not have enough cockpit armour to protect the pilot from 12.7mm shots, and the windscreen was only a thin polycarbonate sheet. The rest of the fuselage lacked any meaningful armour protection.
The T-62's hull retains the same general layout as the T-54, differing only in dimensions. Armour thickness remains unchanged from its predecessor, which was a perpetual liability for the T-62 since the beginning of its service life, in contrast to the T-54 which enjoyed a high level of immunity from contemporary anti-tank guns when it achieved IOC in the early 50's. Like the T-55 before it, the hull of the T-62 was essentially immune to American 90mm shot and somewhat resistant to 20 pdr. APDS (at ranges of 1 km or more). The front hull armour is composed of upper and lower glacis plates. The upper glacis measures 100mm at a 60° slope for a LOS thickness of 200mm, and the lower glacis is the same thickness but with a 55° for a LOS thickness of 178mm. Regardless, the lower glacis can be considered a weak point of sorts, though it is mostly inconsequential since the lower glacis is only a third of the height of the upper glacis.
It must be noted that the glacis armour is stronger than the LOS thickness may suggest due to the inherent positive qualities of rolled armour in combination with the high hardness of the plate compared to the typical hardness of the plates used by NATO to certify their ammunition. Both of these factors boost the glacis' ability to deflect armour-piercing ammunition. Overall, the steel used in the T-62 was of a higher quality and of a higher hardness than the steel used in the American Patton series of tanks, though that would not mean much if the difference in thickness is big enough. Still, the glacis should have some chances of resisting M392 at distances of 1.5 km and more, keeping in mind that M392 can penetrate 117mm at 60 degrees at 1 km.
The hull side is 80mm thick, thinning down slightly to 70mm over the engine compartment, while the rounded hull side "collars" for mounting the turret are cast steel with a thickness of 45mm, angled at 60°.
The steel used for the all-welded RHA hull is 42SM armour steel, which has a hardness of 280 to 340 BHN, harder for the thinner plates (i.e side hull) and softer for thicker plates (glacis). Though the glacis armour of the T-62 is nominally thinner than that of, say, an M60 (252mm LOS), the T-62 uses RHA steel instead of cast steel, and not only that, the hardness of said RHA steel was significantly harder than that of American cast steel at the time. The M60's cast glacis, for example, was unusually soft at 220 BHN, and because of its cast nature, it wasn't as effective as the rolled steel on the T-62. One very excellent demonstration of this difference can be found in Yugoslavian testing of T-54A tanks and their own M47s. Both tanks had 100mm of steel glacis armour sloped at 60 degrees. The only difference being that the M47 had a cast hull, and the T-54 had a rolled and welded hull. It was found that BR-412B fired from a D-10TG could penetrate the upper glacis of the M47 at 750 m, while the T-54 was fully immune from any distance down to point blank range. The thicker armour of the M60 does not give it superiority to the T-62, only parity. Therefore, although the T-62 had a thinner glacis, it cannot be considered less well armoured.
Now for the turret:
The T-62 uses MBL-1 armour grade cast steel for the turret, which has a hardness of 270 to 290 BHN. The original production turret had an effective thickness of 214mm throughout the front facing. Only the base of the turret near the turret ring was physically 214mm thick - the rest of the front turret wall thinned down to as little as 95mm as the front turret transitioned into the roof, but the effective thickness of 214mm was maintained due to vertical sloping. 1972 saw the appearance of the up-armoured T-62 obr. 1972 with a new 242mm cast turret. Again, only the base of the turret is physically so thick. A close look at the shape of the front turret wall is available from the T-62 technical manual, on page 560.
The top part of the front turret is as thin as 112mm, but the much higher slope at this part increases the effective thickness to somewhere approaching 200mm. The discrepancy in effective thickness compared to the physical thickness at the base of the turret is compensated by the lower effectiveness of APDS ammunition on sloped plate. Different ammunition will have different behaviour at certain slopes, so the effective thickness of the sloped portions of the front turret differs from one instance to the next. Using basic trigonometry, the slope of the turret where it is 112mm thick appears to be 33 degrees. If a particular shell is able to penetrate around 115mm at 30 degrees obliquity, then it should be able to defeat that particular part of the turret.
The sloped roof above front turret face is quite resilient despite the much lower thickness, chiefly thanks to the steep angling of the roof. The area of the roof above the cannon a maximum thickness of 58mm sloped at an angle of 80° at the edge of the roof, thinning down very slightly to 54mm at the same angle as it goes further towards the back, and then transitions to 30mm sloped at 83° over the middle and rear portions of the turret roof.
Beginning from the zone just next to the mantlet, the front turret wall gently thins down until it reaches the side of the turret at the commander's cupola, where it is only 122.5mm thick. The photo below shows part of the left side of the turret of an early model T-62 (pre-AA machine gun cupola). The cut-up hull in the background is of a T-64.
From the area around the commander's cupola, the steel sharply declines to only about 65mm at the lower half of the rear of the turret, and only about 55mm at the upper half where it just begins to form the roof, below the ejection port and ventilator housing. The turret hatches themselves are respectably thick, the commander's being around 30mm thick and the loader's being just under 20mm. The roof armour is 30mm thick. This is better illustrated by the diagram below.
Overall, the turret armour is completely insufficient against M392 and L28A1 105mm APDS at even at distances exceeding 2 km. These APDS rounds, introduced at the turn of the decade to complement the upgunned Centurion and the new M60, could penetrate armour plate far in excess of the thickness of the turret at any location. Combining that with the fact that the T-62's turret was made of cast steel, and the situation is very dire indeed. For all intents and purposes, the T-62 was no better armoured than the T-54, and would have to rely on getting the first shot off to ensure its own survival.
While the T-62 was not originally equipped with side skirts, most T-62s were retrofitted with steel-reinforced plastic ones (interwoven textile skirt), similar to that of the T-72.
The main function of the side skirts was to reduce the amount of dust kicked up by the tank while travelling, which was highly undesirable because the dust clouds could give away the tank's position, not to mention blinding the vehicles following it, if the T-62 was travelling in a convoy. And of course, they acted as spaced armour for the hull. They are about 10mm thick and quite stiff; enough to ensure that an RPG grenade fuse activates reliably, but not thick enough or strong enough to be of much use against kinetic energy penetrators. The skirts were mounted 610mm away from the hull.
But let us not forget that the protection scheme of a tank is not solely dependent on raw armour thickness. The crampedness of the interior was very well justified by a seemingly impossibly small frontal silhouette, if the tank were to be compared to foreign analogues of the time.
Although similarly wide and similarly long compared to its NATO counterparts at 3.30 m and 6.63 m respectively, it is significantly shorter at just 2.40 meters tall, which is 0.50 m shorter than the Chieftain, 0.80 m shorter than the M60 pictured above, and slightly shorter still compared to the French AMX-30 and German Leopard 1. This is an extremely important aspect to the T-62's survivability. Getting hit and shrugging it off is one thing, but not getting hit in the first place is crucial, so in this sense, the T-62 is arguably on par with NATO tanks in the defensive role, while having a distinct, if small advantage in the offensive one chiefly due to its relatively small size.
The advent of mass produced thermal imaging equipment practical for combat use in tanks, the advantage of size as a concealment factor became largely immaterial, and new technologies such as superior sabot designs, highly precise stabilizers and ballistic computer made hitting even small targets so easy that you couldn't argue for that either. However, those innovations only came in the late 70's and early 80's, years after the T-62 arrived.
The T-62 had quite a hard time in the 1973 Arab-Israeli war, known to the Syrians and Egyptians as the Ramadan war and to the West as the Yom Kippur war. Hundreds were knocked out in combat, mostly by Israeli Magach (M60A1) and Sh'ot (Centurions) tanks. However, I contend that the T-62 cannot be blamed for its poor showing. One of the more famous tank-on-tank engagements involving the T-62 was the the Battle of The Chinese Farm in October 17.
See this excerpt from Zaloga's "T-62 Main Battle Tank 1965–2005":
"Egyptian tank column was spotted in advance by the Israelis, and elements of the 217th Armored Brigade were assigned to lay an ambush. The 25th Armored Brigade advanced northward with the Great Bitter Lake on their Western flank.
Centurion Sh'ot tanks suddenly emerged over the sand dunes of their Eastern flank, initiating a violent engagement around 1445 hours. The Egyptian tank battalions were caught by surprise due to a lack of flank security and began taking heavy losses. The Egyptian column was hemmed in by a large Israeli minefield that had been laid in 1970 during the "War of Attrition". Although the T-62 companies tried to rally and attack the advancing Israeli wave, they were unprepared for the ferocity of the attack and the brigade was decimated.
In his account of the battle, Lieutenant-General Saad el Shazly later wrote: "When our tanks rolled north into the killing ground, they were attacked from three sides and trapped against the lake on the fourth. Our crews fought desperately against the odds. But when night came there were only a few survivors to pull back to the Third Army bridgehead. It was an utter waste."
About 50 to 60 T-62 tanks were destroyed in the attack by the 217th Armored Brigade, and others were lost in the neighboring skirmishes. By day's end, only 10 of 25th Armored Brigade's original 96 T-62 tanks survived; Israeli losses were only four tanks."
An ambush by hidden and hull-down tanks, from three directions! On a column of tanks with no flank protection! Trapped by a minefield! Now, this isn't the whole story. The initial ambush was conducted by Sh'ot tanks, but later on, Magach tanks joined the fight. This is only a short anecdote, and I recommend doing some serious reading of your own. I am confident that you will reach the same conclusions that I have: There was nothing wrong with Arab equipment. They were simply incompetent fighters, and the Israelis were exceedingly competent.
All T-62Ms are equipped with applique BDD armour, and older T-62s may be retrofitted. BDD armour is more popularly known as "Ilyich's Eyebrows" in humorous reference to Soviet Premier Leonid Ilyich Brezhnev's bushy facial features:
BDD armour covers the hull glacis and the turret front on either side of the gun, but not the lower hull area nor the turret top. It is a form of NERA armour, composed of a laminate of alternating steel plates and a solid polyurethane filling. First entering inventories in 1980, BDD armour boosted the T-62's protection level close to that of the T-64's or T-72 Ural's, giving it the ability to intermittently resist widespread 105mm APDS ammunition from the upper boundaries of typical combat ranges as well immunity from lightweight portable anti-tank rockets like the LAW and RPG-7 families.
Method Of Operation
BDD armour most likely operates on the transfer of kinetic energy from impacting projectiles to the thermoplastic polyurethane (TPU) layer, which is violently displaced out of the projectile's path like a fluid due to its elastomeric properties. The TPU layer thus impart all of the energy to the first steel plate, which then deforms inwards and moves into the projectile's path laterally. When the projectile enters the layer of TPU behind the first steel plate, that layer expands like the first layer, pushing the first steel plate outwards and pushing the second steel plate inwards, thus imparting energy onto the penetrating projectile in two different lateral directions. This is repeated again in the third plate, for a total of at least three "reactions" - hence the 'R' in NERA; Non-Explosive Reactive Armour. This lateral motion would have the effect of either disturbing the delicate flow of cumulative jets or eroding and destabilizing a kinetic energy penetrator.
The single hull block is 150mm thick - or 300mm thick taking into account the hull sloping - complete with an array of steel plates within. Each internal steel plate is just 5mm thick, and the polyurethane layer fills the gaps in between. The front wall is 30mm thick, or when angled at 60° as the glacis is, 60mm thick. The internal steel plates are angled at 65°.
The turret blocks are uniformly 296mm thick, but the front plate becomes thinner as it curves upwards. The front plate itself is cast steel, 71mm thick at the top half and 85mm down the bottom half. The added thickness compared to the glacis plate is intended to compensate for the relative weakness of cast steel, which is only about 90% as effective as generic rolled steel, and the positive influences of the slope on the glacis. The internal steel plates in the turret array are angled at 50° instead of 65°.
|Notice the thickness of the front wall of the turret BDD modules|
The BDD blocks give uncompromising coverage of the upper glacis, but the turret front is not protected over the mantlet and the immediate sides. Only the turret cheeks are protected. The two "brows" weigh 1.8 tons together, and the upper glacis block weighs about 1.5 tons. Equipped with BDD armour, the T-62M bloated to 41.5 tons, 3 tons greater than the vanilla T-62, and about the same as a T-72 Ural.
A Hungarian test at the end of the Cold War showed that the side of the turret of a T-54 equipped with "Brow" armour (taken from a modernized T-55) could not resist a Fagot missile. The results of the test are detailed on this TankNet post. This effectively means that the "Brow" armour for the turret, plus 120mm of cast steel, cannot resist a shaped charge warhead with 400mm of penetration. However, the front of the turret of a T-62 has much more than the side of the turret of a T-54 (242mm vs 120mm), so there is no reason why it cannot resist a Fagot missile or something similar.
The video cannot affirm or disprove anything, as the missile struck the turret approximately where the gun breech is. There is no way to know if the missile defeated the side armour or not, because even though the loader is fine, this could be because he was seated below his hatch, meaning that he would not have been in the line of fire had the missile perforated the base armour. If the missile did not manage to get through, it is still more than possible that the crew bailed as a matter of principle.
The T-62M can be considered on par with or even superior to the T-72A, but much inferior to the T-72B in armour protection against both KE and CE threats. "Brow" armour leaves the mantlet area uncovered by the NERA armour array, but at least the thick steel wall of the BDD blocks forms spaced armour over the machine gun and gunsight ports. With the applique armour, the maximum total thickness of the turret armour of the T-62M is 512mm (296mm BDD block plus ~70mm air gap plus 200mm turret) over the areas covered by the NERA armour. The total amount of steel is less than in the T-72A turret, but needless to say, it should be self evident that the NERA array and airspace combo is more effective than "Kvartz".
Judging by the configuration of the BDD blocks, 105mm M735 APFSDS would not be sufficient against a T-62M from the front where the NERA array is present, not to mention M392 and L28 APDS. The area over the machine gun and gunsight ports is definitely resistant against M392 or L28 as the 71-85mm spaced plate should effectively de-cap the tungsten carbide core and fracture the core, whereby it is broken up inside the nonmetallic filler before it reaches the ~242mm turret front. Even without the spacing, the added thickness of steel is likely to be enough to defeat the shell.
Even when totally expended by multiple hits, the thick front wall of the blocks can still perform as simple spaced armour. In effect, the armour still provide a respectable amount of protection even if it is hit in the same area twice in a row, certainly still enough to immunize the T-62 from the shaped charge warhead of the less advanced versions of LAW rockets to the frontal arc. Going by steel thickness alone, an expended block and the main armour will still be too thick to be defeated by an M72A3 LAW from 1977.
Overall, "Brow" armour on the T-62M can be viewed as a case of "too little, too late". Portable threats such as the 105mm M40 recoilless rifle (400mm penetration), LAW, Carl Gustav (400mm penetration), and the anaemic M47 Dragon (450mm of penetration) were effectively neutered, and "brow" armour can be considered very successful as a low cost equalizer of the status quo in that context. However, the ITOW was just around the corner by the time the T-62M was introduced, and it would have been able to defeat this new armour with relative ease from the front. "Brow" armour could not change the status quo of the T-62 against opposing tanks given the relatively recent introduction of 105mm APFSDS ammunition, so even if it could offer full protection from 105mm M456 HEAT and M392A2 APDS and possibly M735 APFSDS, the T-62 could still never truly achieve the level of protection of the latest T-72, T-64 and T-80 tanks. This, combined with the general obsolescence of the chassis itself, meant that any further potential for the T-62 was exhausted. Nevertheless, these obsolete tanks reigned supreme in Afghanistan in the absence of a serious anti-tank threat, and it was there that "brow" armour proved to be the difference between life and death.
"Brow" armour was not exclusive to Volna-equipped T-62Ms, or even to the T-62M in general. Many T-62s have been seen in Afghanistan with "Brow" armour and sideskirts, but no other upgrades. The lack of a laser rangefinder is a dead giveaway for the tanks below:
This is expected, as "Brow" armour is an applique armour kit that is intrinsically compatible with the T-62. There is nothing to limit the installation of it to older versions of the T-62. In fact, it was not uncommon to see a pre-1972 model T-62 equipped with "Brow" armour in Afghanistan, as field technicians did the best they could to armour up the army's valuable armoured assets with whatever they had. The photo below shows an early model T-62 (distinguished by the loader's hatch) equipped with "Brow" armour leading what appears to be a tank platoon. The second tank in the line is a T-62M, as we can see by the smoke launchers on the right side of the turret.
The photo below shows another early model T-62 with "Brow" armour.
And the photo below shows another one in a partially hull down position.
But besides the (lack of) additional protection from new NATO weapons, the BDD armour also came with added belly armour for extra mine protection in light of the tactical situation in Afghanistan at the time. The applique belly armour is quite simple in construction, composed of a large spacer frame with many reinforcing ribs, and twelve steel plates individually welded on to it, as you can see in the photo above. The escape hatch received an extra welded armour plate as well.
The total thickness of the armour is 20mm. The new armour reduced the ground clearance of the T-62M from the original 430mm to 397mm. This affected its ability to drive over some of the larger tree stumps, large rocks and overcome vertical obstacles, but the otherwise, it was business as usual.
Slat armour was often used to cover areas unprotected by BDD armour. This was a not an uncommon combination during the Soviet campaign in Afghanistan, where it proved more useful than the basic rubber side skirts originally installed onto the T-62M. The full slat armour set weighs 0.55 tons.
|Photo from Andrei Tarasenko's website|
When Kontakt-1 became available in the early 80's, some T-62s were formally equipped with the armour, but only on an evaluatory capacity. Instead of Kontakt-1, T-62s were invariably given slat armour instead, which could not be often seen on tanks that used Kontakt-1 like the T-64 and T-72. They both had the same basic function, but slat armour was much cheaper and easier to install, and since the T-62 became more or less obsolete by that era, it was only ever given slat armour instead of more effective ERA kits. However, some units in Afghanistan ignored the official regime and retrofitted their T-62s with Kontakt-1 anyway.
Mounting the blocks are easy. Each one is bolted onto a spacer bolted to the surface of the hull and turret. The ease of installing and replacing the blocks meant that the entire modification could be done as part of regular scheduled maintenance. However, simplicity comes at a price in this case. The ERA boxes are somewhat fragile, and can be quite easily knocked off when the tank is travelling through densely wooded areas, or perhaps traversing obstacles in urban sprawl. A great many Syrian T-72s lost their side skirts and all of the Kontakt-1 blocks on them from reckless driving.
Each Kontakt-1 block consists of two 4S20 explosive elements - plastic explosives packed into a flat steel plates. Each plate of plastic explosive weighs 260 grams, and have an explosive power equivalent to 280 grams of TNT. The plastic explosives have a very low sensitivity to ensure that they can survive being hit by machine gun fire and even autocannon fire without detonating. The weight of each block is 5.3kg, and a full set covering the entire tank weighs approximately 1.2 tons, meaning that there are around 220 blocks of Kontakt-1.
A full examination of Kontakt-1 is available on the T-72 article. View it here.
The entire tank is covered in all areas except for the rear half of the side skirts, and rear of the hull and turret, and the turret ring is left exposed. Each Kontakt-1 block can reportedly reduce the penetrating effects of cumulative jets by up to 55% at 0 degrees obliquity, and up to 80% when angled at 60 degrees. The addition of Kontakt-1 would have made the T-62 immune to all handheld anti-tank weaponry, and the vast majority of anti-tank missiles without a tandem warhead.
|Photo from Andrei Tarasenko's website|
Each Kontakt-1 block consists of two 4S20 explosive elements - plastic explosives packed into a flat steel plates. Each plate of plastic explosive weighs 260 grams, and have an explosive power equivalent to 280 grams of TNT. The plastic explosives have a very low sensitivity to ensure that they can survive being hit by machine gun fire and even autocannon fire without detonating. The weight of each block is 5.3kg, and a full set covering the entire tank weighs approximately 1.2 tons, meaning that there are around 220 blocks of Kontakt-1.
Method of Operation
A full examination of Kontakt-1 is available on the T-72 article. View it here.
The entire tank is covered in all areas except for the rear half of the side skirts, and rear of the hull and turret, and the turret ring is left exposed. Each Kontakt-1 block can reportedly reduce the penetrating effects of cumulative jets by up to 55% at 0 degrees obliquity, and up to 80% when angled at 60 degrees. The addition of Kontakt-1 would have made the T-62 immune to all handheld anti-tank weaponry, and the vast majority of anti-tank missiles without a tandem warhead.
PT-55 Mine Rollers
Mine rollers meant to detonate anti-tank mines before the tracks do. Main disadvantage of mine rollers is that it is not safe for the cannon barrel to be pointing forward, due to the negative effects of the blast on its integrity. They weigh in at a hefty 8.8 tons, and quickly wear out the front suspension of the tank.
Later on, the improved and progressively lighter PT-54M and PT-55 could be mounted. They could not clear as wide a path as the original PT-54, but are more sustainable because of their weight.
KMT-4 Mine Ploughs
Mine ploughs that dig up and shove anti-tank mines out of the way, creating a path just wide enough for the tracks to pass through They weigh 1.2 tons, and are lowered with a hydraulic piston powered by the tank's electrical system. The tank can move at normal speeds with the plough raised, but must slow down to 12 km/h with the plough lowered. The plough is light enough that it will not affect the frontmost torsion bars, which is helped by the better optimized arrangement of roadwheels on the T-62. The large gap between the first and second pair of roadwheels in the T-54 and T-55 designs meant that they would have been placed under excessive strain, possibly breaking them.
Neither of these devices could remove or safely detonate tilt-rod mines, but tank crews could tie a piece of steel wire or cable across the two plows or rollers for a makeshift standoff detonator. Later mine clearance devices like the KMT-5 combined rollers with a plough while weighing less than the original PT-54-type rollers. Later on, the T-62 could mount more sophisticated KMT-6, 7 and 8 devices capable of detonating both tilt-rod mines as well as electromagnetically fused ones. This is mostly thanks to the completely standardized mounting system used for all Soviet mine clearance devices.
Like any other tank, the T-62 can be decontaminated swiftly by being blasted with jets of hot air to remove chemical and biological agents, which is what is happening to the T-62 below:
Before external decontamination can begin, it must be made sure that NBC contaminants cannot slip through gaps in the tank's armour to incapacitate or even kill the crew, and the effects of a nuclear blast may cause severe illnesses in the long run. To combat all of these effects, the T-62 was furnished with a comprehensive NBC protection suite, something which no other tank in the world save its predecessor had at that time.
With the need for nuclear protection firmly established with the appearance of tube artillery-delivered tactical nukes, the requirement for such a system remained the same for the T-62 as it did for the T-55, which had the most advanced nuclear protection scheme in the world of tanks, being the only tank that had one. For simplicity's sake, the T-62 was equipped with the same ERB-1M system as the T-55. ERB-1M could detect a nuclear explosion through a gamma radiation sensor located in the middle of the hull, just beside the commander's seat (red box), and activate the tank's collective protection suite.
When gamma radiation was detected and determined to be at or above a dosage indicative of a nuclear explosion or leak, all portholes would be automatically sealed to prevent contamination, as the tank was not actually airtight. The seals were applied via small pyrotechnic squibs detonated through an electric impulse sent from the main control unit of the ERB-1M system. The engine would be immediately stopped and the radiator cooling fan suspended. The radiator louvers would be automatically shut closed, and to fully assure the impenetrability of the fighting compartment from radioactive particles, the compressor in the ventilator would be powered up to create a slight overpressure. The driver has manual switches for activating the defensive systems.
The sealing mechanism for the gunner's telescopic optic is illustrated in the diagram below. The diagram is taken from the T-62 technical manual, page 560. As you can see, the area around the gunner's telescopic sight is a weakened zone due to space concessions required for the fitting of the sight. Based on the diagram at the top left, the thickness of the turret around the optic port was reduced by around 60% at the area above the port, and around 20% below it. The aperture of the telescopic sight peers out from behind a small porthole, under which the seal is installed.
The optic port itself is thinly armoured compared to even the weakened region. By scaling it with the base of the turret wall as depicted in the diagram, it is apparent that the armour is only 67.4mm thick. Note that it is a separate piece of armour made from rolled plate rather than cast steel. This would be enough for virtually any machine gun or autocannon fire, but nothing more. While tall, it is some consolation that the weakened zone is rather narrow, based on the drawing at the lower left corner of the diagram above. The thickness of the optic port armour is shown below:
A sealed optic aperture is shown in the photo below. The red box indicates the location of the seal when retracted. The entirety of the weakened zone is shown by the yellow box.
Ventilation for the crew is facilitated by the KUV-3 ventilator, identifiable on the rear of the turret as a large, overturned frying pan-shaped tumor on the rear of the turret. The "frying pan" is quite thick.
A centrifugal fan inside the ventilator housing sucks in air and performs some low level filtration, ejecting dust and larger particles out of a small slit at the base of the housing (refer to photo above). The filtered air is then released into the crew compartment, passing through a drum-shaped NBC filter unit inside the tank proper. The air can be optionally cleaned of chemical and biological contaminants by the filter in contaminated environments where the centrifugal fan is simply not enough. The filter unit also contains a supercharger to increase the positive pressure inside the tank to produce an overpressure, preventing chemical and biological agents from seeping into the tank. A diagram from the T-62 technical manual may make this information easier to visualize:
When activated, whether it be automatically or manually by the driver, the system generates an overpressure of 0.0015 kg/sq.cm, thus preventing irradiated particles or chemical and biological contaminants from entering the tank.
Although the T-62 did not have equipment capable of detecting chemical and biological agents, the supercharged filter-ventilator can be manually activated from a control box near the shell casing ejection port. The control box is easily within the loader's reach (red box below in the photo below). If the crew notices clouds of suspicious smoke or have been informed of contaminated sectors, they have the opportunity to safeguard themselves on their own initiative by activating the supercharged filter-ventilator to produce an overpressure to prevent the ingress of any such contaminants.
Compared to a plug-in system where crew members must plug in their gas masks into the tank's air filter unit - a system that is very commonly found in American armoured vehicles - the collective-type protection suite of the T-62 is ergonomically superior by far. The crew does not need to wear masks that obturates their vision, and they can breath without restrictions.
Like the T-54, the T-62 has an on-board smokescreen generation system. Diesel fuel is injected into the exhaust manifolds, vaporizing it with the heat which produces wonderful plumes of white, opaque smoke. One of the most positive aspects of this system is that smoke produced with this method will be the exact same temperature as the exhaust manifold would be. This makes it impossible to differentiate the heat signature of the tank from the heat of the smoke, giving the T-62 a reliable way of self-concealment from NATO thermal imaging sights appearing in the mid-80's.
902V "Tucha" Smoke Grenade System
The T-62M was outfitted with the Tucha smoke grenade system for instant concealment. Since the T-62M was introduced rather late into the Cold War in 1983, they skipped ahead of the early 3D6 and would (or could) be straightaway equipped with the more advanced 3D17 IR-obscuring smoke grenades.
The 3D17 is an advanced IR-blocking aerosol smoke grenade. It completely obturates the passage of IR signatures or IR-based light as well as light in the visible spectrum. It is effective at concealment from FLIR sights and cameras as well as at blocking and scattering laser beams for tank rangefinders and laser-homing missiles. Unlike the 3D6, the 3D17 grenade detonates just 1 second after launch, allowing it to produce a complete smoke barrier in 3 seconds flat. The drawback to this is that the lingering time of the smokescreen is only about 20 seconds, depending on environmental factors and the number of grenades detonated. This is enough for the tank to hastily shift its position, but not much more. This grenade detonates in mid air about 50m away from the tank. It has a caseless design with a propulsion method identical to that of the VOG 30mm and 40mm grenades which came later.
The system can operate in either 'automatic' or 'semi-automatic' modes. In the 'automatic' mode, the system alerts the driver of the source of the fire and immediately closes all of the radiator louvers, shuts off the engine, cuts off the engine air intake and shuts down the radiator fan to deprive the fire of air. Then, the fire extinguishers are activated and the entire compartment is flooded with the extinguishing agent.
In the 'semi-automatic' mode, the system alerts the driver of the presence of a fire via an alarm and a signal light, but takes no action on its own. The driver can then choose whatever action he deems most suitable at the moment. He can control the deployment of the fire extinguishers from his station, and the commander has a master switch for deploying the fire extinguishers as well.
In addition to the automatic fire extinguishing system, the driver is supplied with a single manual OU-2 carbon dioxide fire extinguisher. Carbon dioxide is suitable against Class B and C fires, namely fuel and electrical fires, which are the predominant causes of fire in a tank. The OU-2 is the only means of extinguishing fires in the fighting compartment.
The T-62 mounts an escape hatch for the crew to use in the very worst of emergencies. It is located directly behind the driver's seat and in front of the gunner. All of the turret's inhabitants can (relatively) easily swing down and out, but for the driver to exit, he must first fold his seat backwards, enter the turret, and then fold his seat forwards (the driver must fold as well) before he can egress.
|(The one at the bottom of the photo)|
Though small as always, the hatch has one highly redeeming feature, and that is that it is opened inwards on a hinge as opposed to being a drop out-type. Not only does this practically eliminate any potential concerns of the hatch dropping out on its own accord from bad securings, it means that it can be opened if the tank is submerged.
The driver's station is practically identical to the one in the T-54, with only very minor differences. It is located at the front left quadrant of the hull, and the driver absconds through an elliptical hatch. When swung open, the turret cannot be turned owing to a built-in safety mechanism to prevent the driver's head from being lopped off, and there is a small indicator light that alerts the driver that the gun is over the hatch.
The driver's station is exactly identical to the one in the T-55. Steering is accomplished using the obligatory pair of tiller levers. To save legroom for the driver, the instrument panel is moved to the right. The speedometer is placed on a pedestal to the driver's left, and the gear shift is placed to his right. The driver is also in charge of the tank's automatic firefighting system. Two 5-liter compressed air tanks for cold weather engine starting are located just behind the driver on the left wall. They are replenished by an engine-driven AK-150SV air compressor. The compressed air reserves are also used for the pneumatic clutch assist, but the air compressor can be used with a pneumatic hose and used as a pneumatic washer for detailed cleaning of the more sensitive parts of the tank. The driver's left periscope also has an air nozzle to blast away dirt and debris, which is around as effective as a traditional wiper. It takes about an hour to refill both air tanks using the AK-150SV air compressor if the tanks are empty. The AK-150SV is powered by the engine, so that a continuous supply of air is provided the moment the engine is started.
Starting the engine is done with the VB 404 ignition device. You can find out how it works by watching Nicholas "The Chieftain" Moran's video on the T-55.
For daytime driving, the driver is provided with two 54-36-317-R periscopes. To remove them, the driver can loosen its clamp by turning a nut on the side of the periscope and pull it straight down by its handle. This causes spring-loaded armoured shutters to flip down and shut the periscope port from gunfire and irradiated particles. The 54-36-317-R periscope has 1 x magnification. The periscopes have special K-108 windows infused with cerium. When the windows are blasted with gamma radiation from a nuclear explosion, they will begin to darken to protect the driver's eyes from the intensity of the visible light and infrared and UV radiation emitted from the explosion. They will return to their original undarkened state under daylight within several hours, depending on the time of day (intensity of sunlight). Just like the periscopes everywhere else on the tank, the 54-36-317-R periscopes are heated through the RTS electrical heating system to prevent fogging. The cable for the internal heater can be found on the bottom right of the periscope.
Visibility from the 54-36-317-R periscopes is best described as "average". There is absolutely nothing wrong with it, but also nothing exceptional. The periscopes are slightly larger than the direct vision blocks on the T-34, but the field of vision offered by the 54-36-317 periscope is the same, due to the tunnel effect from the distance between the eyepiece mirror and the aperture mirror. By being one periscope short, the driver of a T-62 has inferior visibility compared to the driver of any Patton tank or a Leopard 1. The GIF below (taken from this video) shows the view from the left periscope. Unfortunately, the view to the right side is partially obscured by a canvas bag, possibly a sandbag.
For nighttime driving, the driver is equipped with the TVN-2 binocular infrared nightvision periscope. It has a fixed 1x magnification and a 30° field of view. The left periscope can be replaced with the TVN-2. The driver must then connect the TVN-2 to a special cable from BT-6-26 power supply box. Infrared light is sourced from the single IR headlamp on the hull glacis and another similar lamp on the turret, installed just underneath the L-2G Luna spotlight. The driver can only see about 60 m in front of him, and the field of view is rather constricted compared to the daytime periscope, so the speed of the tank must be carefully controlled when driving in unpaved or otherwise unfamiliar terrain. It is not possible to navigate at night using only the TVN-2, as the driver will be unable to see the landscape and recognize landmarks.
This picture, taken from the U.S Army Operator's Manual for the T-62, shows the TVN-2 as it looks when installed in the tank:
Navigation is facilitated by a simple GPK-48 gyrocompass located near the driver's feet. The main function of the gyrocompass is of course to let the crew know which direction they are travelling in, but it is particularly useful when driving underwater or when driving at night. With the GPK-48, it is possible for the driver to perform maneuvers when driving underwater (provided that certain conditions are met, including riverbed integrity and so on) and at night, with assistance from the commander.
|Photo credit: mashpriborintorg from flikr|
In 1966, the T-62 received the GPK-59 gyrocompass, which had more knobs and dials.
The use of gyrocompasses can perhaps be labeled as a rudimentary form of an Inertial Navigation System (INS), advanced versions of which are often present in modern combat vehicles due to their independence from outside input contrary to a GPS-based navigation system.
The tactical mobility of the T-62 - that is, its ability to maneuver under its own initiative as opposed to piggybacking on transporters like by lorry, rail, by plane or by ship - is very average. One of the T-62's main grievances, though minor, is that it is just slightly underpowered compared to its predecessor the T-55, mainly because it uses the same V-55V diesel engine and the same transmission of the T-55, but weighs over a ton more than it, bringing its mobility characteristics down to the level of the T-54.
The five-speed transmission is of a planetary type, with dry friction clutches. There is one reverse gear. The transmission and the mechanical linkages linking it to the gear stick can be seen in the picture above, taken from the T-62 technical manual. According to the technical manual, the speed of the tank for each gear at 1800 RPM is as follows:
- 1st Gear: 6.85 km/h
- 2nd Gear: 14.66 km/h
- 3rd Gear: 20.21 km/h
- 4th Gear: 28.99 km/h
- 5th Gear: 45.48 km/h
- Reverse: 6.85 km/h
The T-62 uses an dual epicyclic geared steering system - otherwise simply known as a geared steering system - of the exact same design as the T-55, with an auxiliary clutch and brake system for tight turns at any gear and in neutral. A similar steering system was employed on the IS-1 heavy tank. Steering is achieved by having two separate final drives with separate gear boxes connected to a common transmission. This design is extremely compact and highly durable. Unlike a (very outdated) single differential or a clutch and brake steering system, full power is sent to both tracks while steering. By manipulating the gear ratio, either the left or right track can be slowed down incrementally rather than braked for smoother and more precise steering. This is done by stepping down the gear box of the inside track to a higher gear ratio (more torque, less speed), thus creating a difference in speed, causing the tank to turn. However, this system will have the same fixed turning radius regardless of which gear you are in when driving.
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 for that track, and the third (3) to engage the brake. Each gear had a fixed (but not the same) turn radius, except the first gear, where steering can only be done by clutch and brake. The T-62's geared steering system was capable of a form of neutral steering called pivot turning, but not true neutral steering. The turning radius when pivoting the tank on the spot in neutral is 2.64 m.
By the early 1960's, this method of steering could still be considered modern, but it had been surpassed by more advanced Western designs. Western tanks generally had double differential or triple differential transmissions that were capable of true neutral steering and were additive in addition to being regenerative. Something also worth mentioning is that while the geared steering system of the T-62 was a regenerative system and just as efficient as the triple and double differential steering systems used by the M60A1 and Leopard 1 respectively, it was not additive, and this is important. It means that in addition to being regenerative, the outside track of an M60A1 or Leopard 1 will gain power. The steering systems for the M60A1 and Leopard 1 also have multiple turn radii, so that steering precision is even better. It does not need to be said that the Leopard 1 is faster and more agile than the T-62, of course, but when comparing the M60A1 with the T-62, the additive feature of the steering system of the M60A1 be enough to nullify what few advantages the T-62 may have with its higher power-to-weight ratio.
The V-55V engine puts out 580 hp at 2000 rpm with a maximum torque of 240 kgm at 1200 to 1250 rpm. It has a specific fuel consumption of 180 g/hph, which is reasonable for an engine of its size. The average fuel consumption per 100 km of travel is 190-210 liters on paved roads, and 300-330 liters on dirt roads. Mounting the this engine, a production model T-62 weighing in at up to 37.5 tons combat loaded would have a nominal power to weight ratio of just 15.46 hp/ton. This placed the T-62 firmly in the category of contemporary medium tanks like the M48 Patton and the Centurion and better than the then-brand new Chieftain, and only slightly better than the M60A1. The T-62 could attain a top speed of 50 km/h on paved roads, and the average speed when going cross country was around half of that at 25 km/h, which was more or less the same as the M60A1. The reverse speed, however, was quite bad by Western standards at just 6.8 km/h.
The T-62 could traverse difficult terrain as well as any other tank. It could climb vertical obstacles up to 0.8m tall, climb a 32° upward slope and drive on a side slope of 30°. The tank can cross trenches 2.85m wide at slow speeds, but it is possible to jump the tank over much wider trenches provided that it travels fast enough.
The engine could be started either electrically, pneumatically or by a combination of air pressure and electricity in extremely cold weather, as mentioned before. Electric starting is done with the ST-16M electric starter and the air is supplied by the compressed air tanks.
The engine powers the F-6.5 alternator with a maximum output of 6.5 kW for the tank's power supply.
This engine was fitted to the T-62M. Thanks to a more optimized direct fuel injection system, it had a slightly increased output of 620 hp to compensate for the added weight of "Brow" armour on the T-62M, but was identical to the V-55V in every other way. The small increase in power does not adequately balance out the gain in weight, so the T-62M has noticeably poorer acceleration.
Instead of the F-6.5 alternator, the V-46-5M is equipped with the G-6.5 model with the same output, differing only in the method of installation and the input capacity.
The T-62 has the exact same powertrain and steering system as the T-55, which in turn is exactly the same as the one from the T-54. It is not known if the gearboxes were changed when the V-46-5M was installed.
Like the T-55 before it, the T-62 had individual torsion bar suspension and five hollow die-cast aluminium alloy roadwheels with a thick rubber rim. The T-62's suspension is aesthetically similar to that of the T-54 and T-55, but it can be differentiated by the even spacing between the three roadwheels at the front of the tank and the wider space between the two at the rear. This was done due to the shifted center of gravity of the tank due to the new enlarged turret, making it more front heavy than the T-55, thus necessitating more suspension elements at the front to ensure better load distribution for a longer lasting suspension as well as a smoother ride across bumpy terrain. The diameter of the roadwheels is 810 mm. They have a standard layout with a central channel for guide horns on the tracks to pass through. The same 5-spoked wheel was kept throughout the T-62's service life. The tank had 430mm of ground clearance.
The frontmost and rearmost roadwheels were fitted with rotary shock absorbers, identical to the type installed in the T-54.
The T-62 used OMSh single pin tracks, carried over from the T-54/55. A full set of 96 links weighs 1386 kg. The tracks are of a simple hinged type, with no inner rubber padding or rubber bushings, nor were there any rubber track pads available for this type of track during the T-62's years of service, so travelling on paved roads was not very good for the asphalt. The tracks are 488mm wide, with standard centered guide horns.
The idler wheel is of a skeletal design with 10 spokes. The drive sprocket has 4 spokes.
The increase in weight from the T-55 to the T-62 did not result in an equivalent increase to the ground pressure, because the T-62 had a longer hull and a longer track, and therefore longer ground contact length. Rather, the ground pressure of the T-62 (0.75 kg/sq.cm) was actually considerably less than the T-55 (0.81 kg/sq.cm). In fact, the T-62 exerted lower ground pressure than any foreign tank of the time.
Exerting a ground pressure of only 0.75 kg/sq.cm, the T-62 was very slightly better off than the M60A1 (0.76 kg/sq.cm) which was heavier by 12 tons, but it was definitely better than the common M48A1/A2 (0.83 kg/sq.cm). The T-62 was rather light-footed compared to tanks like the Centurions (around 0.95 kg/sq.cm for Mk. 3 and above) and the Chieftain (0.90 kg/sq.cm), both of which are considered to be on the heavier side of the spectrum.
During the 70's, the T-62 along with the T-54/55 series was retrofitted with RMSh single-pin tracks from the T-72, which are wider by 92mm and considerably more durable thanks to larger and tougher connecting pins and a reduced rate of wearing thanks to internal rubber bushings. A full set of 97 links weighs 1655 kg. All T-62Ms are fitted with the RMSh track. The installation of RMSh tracks increased the ground pressure to 0.77 kg/sq.cm and decreased the power-to-weight ratio of the tank to 15.4 hp/ton.
The easiest way to tell apart an OMSh track from an RMSh track is to observe the ends of a track link. An OMSh-type track has an open loop at the ends of the track links whereas an RMSh track doesn't (check the photos above to confirm).
The engine deck was renovated twice since the original iteration in 1961. The original engine deck had maintenance hatches to allow easier inspection of the engine and air cleaner without removal of the engine deck. The hatches aren't very large, though, so doing any sort of detailed repairs will be difficult.
Replacing the engine or doing more extensive maintenance can only be done with the removal of the entire deck.
The T-62M brought with it a revised deck design with a large T-72-style engine access hatch, giving a clear, unobstructed view of the innards of the engine compartment.
|Photo credit: Andrei Tarasenko's website|
None of the engine deck designs have enough armour to resist 30mm DU rounds from the legendary A-10 Warthog's GAU-8 cannon, but it is still strong enough stop the extremely anaemic 20x102mm cartridge, which isn't saying much, but very relevant given that the A-10 did not even exist until the T-62 was already well on its way out of Soviet frontline units.
The radiator is located directly behind the engine. It can be accessed by lifting the protective radiator access panel, which is hinged. Directly underneath the radiator unit is the cooling pack into which coolant carries heat from the engine to be dissipated by air sucked in through the radiator unit and out the rear of the engine compartment via a centrifugal fan.
The fan is powered by the engine via a drive shaft connected to the gearbox, thus allowing the fan to meet the engine's cooling needs following its power output, which is proportional to its heat output. The fan housing has its own armoured cover, which has rubber seals to prevent water ingress while the tank is driving under water.
The radiator air intakes are protected by a set of armoured louvers to protect from air burst artillery and mortar shells or even molotov incendiary bombs. These are further augmented by auxiliary armoured covers, which must be manually closed, but can be sprung open with the press of a button in the driver's station. They are too thin to be of much use against air attack, so their main function is to seal the radiator from the ingress of water.
|Engine air intake (Credit: Alex Chung)|
The VTI-4 engine air intake filter is located the beside the engine, just under the air intake grille. It is a dual-stage fabric-type filter, good for many hours of operation under highly dusty conditions. Dust is filtered out from the air to ensure that the engine is not clogged up and has sufficient oxygen to run at normal rates. Larger particles of pollutants are ejected from the filters using the dust ejector, via compressed air.
When the engine air intake is sealed and the vehicle is underwater, the engine draws air from inside the hull via a respirator fan located just behind the commander's seat, on the partition between the engine compartment and fighting compartment. There is no filter in this channel, because the air in the fighting compartment is already filtered.
|(Notice the fan duct at the top of the photo)|
There is an electric air heater just in front of the fan duct and under the commander's seat (cylindrical tank in photo below). It supplies hot air to warm up the engine during cold weather, and it also functions as the heater for the crew compartment.
The tank's electrical supply needs are handled by four 6-STAN-140 accumulators located at the front of the hull, adjacent to the driver's station. These are simple lead acid batteries connected in series. They supply 24 volts when the engine is turned off, and 27 volts when the engine is on.
Fuel storage is divided between 3 internal tanks and 3 external tanks for a sum total of 960 liters. Two of the internal fuel tanks are also the two front hull shell stowage racks (as seen previously) and the other fuel tank is located at the starboard side of the hull, at the very rear of the fighting compartment, right next to the partition between the engine compartment and the fighting one. The two front hull fuel tanks hold 280 liters each, and the solitary fuel tank at the rear of the fighting compartment in front of the engine compartment partition holds 115 liters
Since all of the fuel tanks are interconnected, the driver-mechanic only has to top up the tank from one fuel filler port. There is one at the rear of the hull leading to the rear fuel tank:
(Photo credit: Evgeny Starobinets)
And another two for the pair of conformal front hull fuel tanks at the front of the hull:
The three external fuel tanks are mounted atop the starboard fenders, each with their own fuel filler caps. These external fuel tanks are part of the fuel system.
|Here you can see how the fuel tanks are connected|
Total internal fuel capacity is 675 liters, plus another 285 liters carried on the external fender tanks. An additional 400 liters of fuel is carried in two 200-liter auxiliary fuel tanks mounted on brackets at the rear of the tank to augment the tank's operational range. With all fuel tanks filled, the tank carries a sum total of 1360 liters of fuel. With auxiliary fuel tanks, the T-62 has a highway cruising range of about 650 km, or 450 km without. The cruising range on dirt roads with auxiliary fuel tanks is 450 km, and 320 km without.
As mentioned before, all of the fuel tanks are interconnected. The driver has a control knob located beside the right steering lever to select which set of fuel tanks he wants to draw from, choosing between the internal fuel tanks only, external and the auxiliary drums only, or all together, or the driver may cut off all fuel flow entirely. This is quite helpful if one of the tanks were to be compromised, because by shutting off a set of fuel tanks, the rate of leakage can be greatly reduced and this may even help control a potentially catastrophic internal fire if the driver reacts promptly.
There are certain procedures that need to be followed prior to snorkeling, however. In order to prevent water from entering the engine air intake and radiators, they must all be sealed by locking their armoured covers down, and the bilge pump should be activated, which can be done with a switch on the driver's instrument panel. It is only necessary to close the armoured louvers for both the radiators and the air intakes when fording. Once the engine air intake is shut off, however, the engine must draw air from inside the tank through a respirator fan located just behind the commander's seat.
When snorkeling, it is also necessary for the exhaust outlet to be sealed with a valve bank, which is a bolt-on cover for the exhaust outlet equipped with four spring-loaded circular exhaust ports that prevents exhaust gasses from being released until they can build enough pressure to blow out forcefully enough that water will not have a chance to leak in.
If the tank is to be snorkeling deeper than three meters, the last step is to seal all of the hatch gaps with a waterproof paste, which has the consistency of clay. The entire preparation process takes around 30 minutes for snorkeling, but the tank can readily ford across any stream without any preparations whatsoever.
The air supply for both the crew and engine is provided by the single snorkel erected from the turret roof.
The snorkel is broken down into three parts and latched onto the rear of the turret and under the auxiliary fuel tanks for convenient stowage during road marches and combat. The snorkel must be assembled on site by the crew before it can be used. It is possible to install only one or two of the three parts depending on the depth of the body of water to be crossed. The snorkel is installed in a small port in the turret roof, just in front of the loader's hatch. Once the tank resurfaces and drives off, it is not necessary to remove any of the snorkeling accessories except the snorkel (for obvious reasons), which can be simply cast away by pushing on it from the inside.
The porthole plug has a thick rubber seal to prevent rainwater from dripping into the tank, as do all of the hatches.
A wider type of snorkel is used during training. This type of snorkel fits over the commander's hatch, and is large enough to allow crew members to escape from the tank via an internal ladder. This is to help ensure that the crew does not drown underwater. These snorkels are not used in combat.