Tanks and Autoloaders – MSI Turkish Defence Review / MSI TDR Reference Magazine of Turkish Defence and Aviation Industry

Tanks and Autoloaders

30 Nisan 2017
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Alper Çalık, analysed Autoloaders Utilised on Tanks, in the 34th issue of MSI Turkish Defence Review.

You can reach the full text of the article titled “HÜRKUŞ: Is Ten Years Really a Long Time?” below.

 

Its main gun armament that makes the tank the formidable vehicle it is. As such, the loading mechanism of a tank is a crucial factor which significantly affects its design and tactical capabilities. Although tank guns were initially loaded manually, developments since World War Two have offered a new option. Nowadays, certain countries prefer using autoloaders in their main battle tanks, while others still continue to rely on the conventional method of using loading personnel. However, despite present-day advances in technology, many modern tanks still assign a personnel to reload the main armament. The reason for this is that this method offers its own set of advantages.

Looking at the different approaches adopted in various countries, it can be seen that countries following the old Soviet approach, such as Russia, Poland, and People’s Republic of China, as well as Japan, generally use autoloaders; while Western countries such as the United States, Germany and the United Kingdom prefer using a human loader in the tank.

 

History of Autoloaders

Efforts at developing autoloaders first began during World War Two. The first fully functional system was developed in 1945 by the United States, for use in the 75 mm gun of T22E1 medium tank. However, just as the other members of the T20 family, these T22E1 medium tanks designed with autoloaders never entered into serial production. Nevertheless, work of developing autoloaders continued into the 1940s and 1950s. The biggest next step on this subject came with the production of a semi-automatic loader for use in the 75 mm gun of the AMX-13 light tank’s the oscillating turret (Picture 1). Following this, there was very little further progress until the launch of the turretless Stridsvagn 103 Tank (or S-Tank) developed by Sweden in 1961 (Picture 2). This tank became the first to enter service with a fully automatic loader. In 1960s, the MBT-70 main battle tank developed by the United States and West Germany was designed to feature an autoloader, and the first prototypes were produced accordingly. However, despite the promises it seemed to hold and having been designed as a tank far ahead of its times, serial production for the MBT-70 was never initiated. The main reason for this was the failure to solve the problems caused by the application of too many new systems at the same time on the platform, such as an adjustable hydropneumatic suspension, the placement of the driver in the turret, and a concealable 20 mm anti-aircraft gun in the turret, which together led the project to exceed the estimated costs.

 

The first tanks with autoloaders in their conventional turrets that passed the prototype stage and entered into service were the T-64 and T-72 produced by Soviet Russia in the 1970s.

 

 

Types of Autoloaders

Autoloaders which have been developed until now employ different operation principles, which can be organised into three main categories depending on the freedom of movement between the gun and the magazine (i.e. ammunition racks).

 

1. Systems without Freedom of Movement

In these systems, there is no freedom of movement between the breech (base of the gun) and the magazine. In other words, these two are in fixed positions relative to each other. This is the simplest one among the alternative loading systems, and the fact that it maintains the lowest movement distance for the ammunition, results in a high rate of fire. However, this system can only be used in tanks with a certain configuration, and their use also engenders a number of limitations. For instance, although this type of autoloader was used on the turretless Swedish S-Tank, this was only possible because the tank’s gun was kept in a fixed position on the hull. Since the tank lacked a turret, an adjustable suspension had to be used to elevate and depress the barrel, while changing the direction of the barrel horizontally, required the entire hull to turn right or left.

Another platform in which this category of autoloaders was used was the French AMX-13 light tank. In this tank, the magazine is located on the rear side of an oscillating turret, whose upper section rotates together with the gun on the vertical axis (in other words, leans completely backwards to elevate the gun).

Another way in which autoloaders of this category are used involves attaching an ammunition magazine to the breech of the gun. This method, which could be effectively applied for low calibre guns, was used in the 57 mm Bofors gun of the German Begleitpanzer, enabling a fire rate of 200 rounds per minute. However, due to the limited space within the tank turrets, the magazine capacity of this configuration only allowed a few rounds in case high calibre guns were employed.

 

2. Systems with Partial Freedom of Movement

Another class of autoloaders are the systems which have freedom of movement between the gun and the magazine in a single direction, such as elevation. These system are further sub-divided into two groups.

 

2.1. Systems in which Magazine Is Located in the Turret Bustle

As in the MBT-70 tank of joint American and German design, these systems have the ammunition magazine positioned in the rear section of the turret. The loading of the ammunition requires the gun barrel to first decouple from the elevation system, and to then align itself with the magazine loading arm. As a result, the loading system temporarily assumes the same configuration as the first category of autoloaders described above. In this process, the barrel will be slightly elevated by an angle of generally two or three degrees, although the exact angle varies from tank to tank. However, once the ammunition is fed into the barrel, the barrel reattaches itself to the elevation system, returning to its previous angle setting. In addition to its relative simplicity, this type of system also keeps ammunition stored in a compartment behind the turret, thus offering the advantage of keeping the personnel completely separated from the ammunition.

 

2.2. System in which Magazine Is Located at the Turret Basket

In these systems, ammunition is stored beneath the turret at its base (turret basket). Two main configurations have become widespread, which differ with respect to either using complete rounds or two-part ammunition with separate shell and propellant:

  1. The fixed ammunition (complete round) are lined up either in an upright position or in circular way, in a manner reminiscent of the arrangement of bullets in a revolver. An example of this system is the American T22E1 tank.
  2. Separate loading ammunition are arrayed radially inside a carousel magazine. This arrangement can be compared to the way petals surround the centre of a flower. This approach permits the storage of many ammunition inside the constricted and narrow turret basket; however, it does not allow the use of fixed ammunition, due to their length. Using separate loading ammunition instead is thus mandatory. There are also two different practices in use, concerning this approach:
    1. In the Russian T-72 and T-90 tanks, propellant charges and shells are stacked horizontally in an alternating fashion inside a drum-shaped magazine, with a propellant charge positioned on top of each shell. The ammunition hoist will pick up a suitable combination from the magazine. When the hoist is aligned with the barrel, the rammer will first load the shell at the bottom into the barrel, after which the hoist will slightly lower itself to allow the propellant charged to be loaded next. The loading process thus consists of two steps.
    2. On the other hand, Russian T-64 and T-80 tanks feature L-shaped carrier casettes, in which the propellant charge is lined up vertically, while the shell is in horizontal position. This L-shape carrier has a hinge at its midpoint junction. As the hoist lifts the carrier upwards, it also causes the carrier to become horizontal by opening it up at this hinge. The carrier becomes fully horizontal by the time it is aligned with the barrel, and the rammer then pushes forward the two-part ammunition into the barrel. In this system, the loading process is executed as a single step.

 

3. Systems with Full Freedom of Movement

Systems in this third category have freedom of movement between the gun and the magazine in both axes. In the 1970s, an example of these systems was recommended for the NKPz tank project conducted in Switzerland. In this design, ammunition was placed at the rear of the tank hull, and each ammunition was fed into the barrel by means of a rotating arm, after being carried, one at a time, to the base of the turret, and then being aligned with the barrel.

Another example of this type of system was planned for the UDES-19 tank concept of Swedish design. In this system, the gun rotates on a pedestal located outside the tank, while ammunition is kept inside a magazine positioned externally at the rear of the tank hull, with every single ammunition being carried from the magazine to the gun base by moving on the outside. A mechanical arm then takes the ammunition, rotating it around the pedestal until it is aligned with the gun, and then feeding it into the gun by raising itself upwards. One of the biggest problems with this system is that the ammunition is located outside the tank, where it is exposed to broad range of threats, and has to cover a long distance before reaching the barrel.

 

Comparison of the Two Approaches

Tanks with Autoloaders

These systems, generally preferred by former East Bloc countries, offer numerous advantages. Main battle tank using these systems generally have three crew: commander, gunner and driver. The advantages of the system can be listed as follows:

Weight: Tanks with autoloaders have smaller turret volumes, which reduces the turret’s surface area and, by extension, the amount of armour it requires. This considerably decreases the overall weight of the vehicle, such that these types of tanks generally weigh between 45 to 55 tons, while classical tanks mostly weight between 55 to 70 tons. Undoubtedly, this difference in weight also has to so with the level of protection and the sub-systems being used. In the end, the lighter weight afforded by the smaller turret not only increases the vehicle’s speed and agility, but also enhances its operational range owing to reduced fuel consumption.


Table 1.
Weight, Height and Loading Method of Various Tanks

Autoloader Country Tank Unit Average
Weight Height Weight Height
Yes Russia T-90 47.5 t 2.2 m 52.6 t 2.4 m
China Type 99 58.0 t 2.4 m
Japan Type 10 48.0 t 2.3 m
France Lecrerc 57.0 t 2.5 m
No United States M1 62.0 t 2.4 m 61.0 t 2.8 m
United States M60 57.3 t 3.3 m
Germany Leopard 2 62.3 t 3.0 m
United Kingdom Challenger 2 62.5 t 2.5 m

 

Low profile: In these type of tanks, the turret houses only the commander and the gunner, while the autoloader always requires less space than crew members. As a result, turrets with autoloaders can be flatter, thus having a thinner and more compact profile. As such, the turrets of these tanks can be nearly half as high as those of classical tanks. This feature gives the tank a lower profile, allowing it to present a smaller target. Such a lower profile considerably enhances the tank’s survivability.

 

Rate of reload: The ability to fire more shells in a brief window of time is an important tactical advantage in armoured warfare, where events transpire rapidly and suddenly. For this reason, the high rate of fire of autoloaders, which are considered as one of their strongest advantages, has been drawing the attention of tank designers from the very beginning. For instance, the Swedish S-Tank’s autoloader enables its 105 mm gun to reload at a rate of 15 shots per minute. To compare two tanks which are more conventional and also more similar to each other: personnel in an M1 Abrams series tanks with a 120 mm gun can reload ammunition six times per minutes, while in T-72 series tanks, the reload time is eight ammunition per minute.

 

Rate of fire in difficult terrain: Unlike humans, autoloaders do not lose effectiveness when the tank travels through difficult and rugged terrain. Although personnel can use safety belts to fasten themselves to their seats inside tank, they cannot avoid the vibrations and shocks caused by travelling through on terrain, or the centrifugal forces resulting from sudden turns. For this reason, these types of situation will cause the human crew to lose their effectiveness in executing tasks. In contrast, autoloaders retain their effectiveness in every type of terrain; they can constantly keep operating at the same pace, and load any desired type of ammunition into the barrel

 

No training requirements: Since tanks with autoloaders require less crew in total, training requirements for these tanks will also be lower. This has the indirect effect of reducing the need for trainer personnel. Consequently, there is a notable decrease in the need for personnel in total, which in turn reduces the operating costs associated with tank personnel.

 

No risk of injury: The guns of present-day main battle tanks are designed to fire repeatedly while on the move. To prevent the gun from changing direction or orientation between two shots, a tank needs to have a highly effective recoil system. To this end, gun mounts are equipped with hydraulic or spring shock absorbers. After the gun fires, the barrel and breech, whose combined weight exceeds a ton, moves backwards inside the turret at very high speeds. During this process, loader personnel have to be very careful and keep away from the breech; otherwise, they might suffer serious injury due to the high kinetic energy transferred by the gun mount.

 

Classical Tanks

Resistance to Explosion: In most tanks with autoloaders, ammunition is found in a separate section – a turret basket, so to speak – located inside the tank, and specifically reserved for this purpose. In contrast, ammunition in classical tanks is generally stored in a special compartment located at the rear of the turret. The difference between these two approaches especially manifests itself in the way stored ammunition can explode (or cook off) when the tank is hit. In tanks with autoloaders, where ammunition is stored inside the hull, the explosion of the stored ammunition creates more than enough pressure to detach the turret and propel it far into the air. The strength of the explosion is such that the turret may sometimes be launched tens of metres away from the hull. The term “Jack in the Box Effect” is even used to describe this event, in reference to the classical children’s toy in which a figure hidden inside a box suddenly jumps out, under the effect of a released spring, when a crank on the side is turned.

On the other hand, in classical tanks where ammunition is carried inside the turret, various measures can be taken against this kind of explosion risk. For example, in the American M1 Abrams tank, the compartment housing the ammunition is separated from the rest of the turret by armoured blowout panels, which open and close very rapidly when loading ammunition. At the same time, there are also panels located at the roof of this compartment, designed to easily open when there is pressure from the inside (i.e. due to ammunition cook off), and to protect the inside of the compartment from external effects.

 

Greater range of movement for gun; increased variety of positions for the tank: The gun is the main weapon, as well as the reason for being, of a tank. To operate normally, the gun requires a certain amount of space within the turret that allow for upwards and downwards movement. This is because the breech – the part where ammunition is loaded into the gun and the empty case is ejected – is situated inside the turret. Since classical tank turrets have a higher roof and greater internal volume, they may take aim at relatively greater angles below the horizon line.

This angular difference between the two types of tanks is approximately five degrees. Tanks with autoloaders can at most aim 5 degrees (-50) below horizon, while classical tanks may aim as much as 10 degrees (-100) below horizon. This difference may seem minor at first, but when considered together with the battle doctrine for tanks, it becomes apparent that the ability to take aim five degrees lower offers a significant tactical advantage.

The main reason for this has to do with way tanks take position of the battlefield. Just as infantry, tanks also take positions during combat, open fire from behind them. However, these massive vehicles lack the flexibility of humans, which move around in foot and can crouch or lay down when necessary to present a smaller target. For this reason, tanks require special terrain features for taking position on the battlefield, positioning themselves as shown in Figure 3. The tank first has to find terrain with a sufficient slope, where it can conceal itself from its target. It then moves towards the target, which means that it has to climb upwards on inclined terrain. The tank advances until the commander periscope, and then the gun, can visualise the target (in this process, it transitions from hide position to turret-down position, and then to hull-down position). If the target is at the same height as the tank, by the time the gun points towards the target, it will be parallel to the ground, while being inclined relative to the hull of the tank. Consequently, there will be a negative inclination between the tank’s gun and hull, equal to the inclination of the field in which the tank finds itself. This incline should not exceed the minimum depression angle of the tank gun. Otherwise, the tank will not be able to open fire at its target from its position.

The angle to which the tank gun can be lowered below the horizon directly affects the variety of positions the tank can enter; for this reason, classical tanks will have a higher chance of finding positions on the battlefield suitable for firing.

 

Substitute personnel: Although every crew on board a tank specialises in his own task, personnel can also be prepared to fulfil every type of task by receiving cross-training. Thus, the loader may acts as either the driver or gunner whenever necessary; this means that whenever a tank personnel on board becomes incapable of performing a certain task, there will always be a substitute.

 

Reduced logistic requirements: Less mechanical parts inside the tank also means less parts that can possibly malfunction. As a result, tanks will have less need for maintenance, consequently having to spend less time inactive. Similarly, the number of maintenance and repair personnel will decrease, along with the costs associated with their training. Moreover, the costs allocated for procuring spare parts, the duration of procurement, and the storage costs associated with the spare parts being kept will all be reduced.

 

References

  • Macksey, Kenneth, Tank Versus Tank, London: Grub Street, 1999.
  • Miller, David, Tanks Of The World, London, Salamander Books, 2004.
  • Ogorkiewicz, Richard M. Technology of Tanks I, Jane’s Information Group, 1991.
  • Tucker, Spencer C., TANKS: An Illustrated History of Their Impact, Santa Barbara, California, ABC CLIO, 2004.
  • Worldwide Equipment Guide, TRADOC DCSINT Threat Support Directorate.
  • Zaloga, Steven J. M1 Abrams vs T-72 Ural: Operation Desert Storm 1991, Oxford, Osprey Publishing, 2009.

 

To reach the original article as it was published in our magazine:

http://www.milscint.com/en/files/2017/04/70_79_msi_TDR34_OtomatikDoldurucu.pdf

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