Tuesday 1 January 2019

Visibility from Tanks

"Engineer-Major L.S. Tolokonnikov
Obsevartion from Tanks

T-34 tank: the mechanic-driver observes through two mirror periscopes. The periscopes are affixed to the driver's hatch. Periscopes are made from transparent plastic. From the outside, they are covered with armoured covers, from the inside with a transparent plastic shield. The periscopes are angled towards the sides to increase the field of view. There is a backup for observing the road in front of the tank. The commander of the tank observes through the commander's panoramic sight and the telescopic sight. Two observation slits with two layers of armoured glass are located along the sides of the turret. The loader and hull gunner observe through their machinegun ball mount sights.

KV tank: the driver can observe through the observation slit, covered with armoured glass, or through a mirrored tilting periscope located to the right of it. There is a backup for observing the road in front of the tank. The commander of the tank observes through a commander's panoramic sight. There are four tilting mirror periscopes in the turret: two in the rear and two along the sides. The gunner observes through the PT and TOD sights. Two observation slits with armoured glass serve as backups for the side observation periscopes. The crew has better observation equipment than in the T-34 tank.

M3 Medium tank: the driver observes the road through one periscope. The periscope is prismatic and tilting, but it can be fixed in place. The crew in the sponson observes through the sights. There are four periscopes in the turret platform: two in the side hatches, one in the rear, and one in the front left. The machinegunner looks through the latter. The remaining three are secondary, and are only sometimes used for observation. In the turret, the gun crew observes through the sights and one periscope on the right. The commander observes from the commander's cupola through the machinegun sight and two periscopes. The tank's complicated hull shape means that, despite the large number of periscopes, there is no overlap between them, which leaves dead angles. The driver's observation is insufficient. In case of a bullet impact, the driver would be distracted from his duties in order to replace the periscope. The ability to increase the driver's vision range goes unused, since the driver cannot stop controlling the tank in order to control the periscope.

Mk.II tank: The driver has a dual observation slit and a tilting 360 degree periscope. In combat it is impossible to use the slit for observation, as it is not protected by armoured glass. As a consequence, it is only possible to observe through the periscope. The gun crew observes through the sight and a periscope. The tank commander observes through a periscope in the commander's cupola and slits. All periscopes rotate and can tilt. Special mirrors allow looking backwards without turning your head. The presence of 360 degree vision is a positive. The driver's vision is insufficient.

KV-1S tank: the KV-1S driver can observe through a vision slit protected with armoured glass or through two mirror periscopes. The gun crew observes through the sights. In addition, there are two periscopes in the turret: a front one and a rear one. Two vision slits with armoured glass allow observation to the sides. The commander is placed in an observation cupola. The commander's cupola is equipped with five mirror periscopes all around. The periscopes grant the commander 360 degree vision. The periscopes are covered with metal covers from the outside.

The KV-1S's observation devices allow the crew to observe in all directions. The driver has three methods of observation forward, in the most important direction, and the entire crew has five. The KV-1S is the most progressive tank as far as observation is concerned. A drawback of the KV-1S is the position of the mirrors, where the observer has to look upwards to survey the horizon.

T-70 tank: The driver can observe through a mirror periscope in the hatch. The periscope has an armoured cover. The commander can observe through the gun sight and the tilting periscope in a rotating observation dome. The rotating periscope allows the commander to have 360 degree vision. The driver's observation devices is insufficient.

T-60 tank: The commander has the sights and two periscopes at the sides of the turret for observation. The driver observes through a periscope in his hatch. The T-60's observation devices are satisfactory for a small tank. A lack of 360 degree vision and insufficient vision devices for the driver are drawbacks.

Mk.III tank: Two tilting periscopes with 360 degree rotation and reverse mirrors provide the driver with rather satisfactory vision. The vision slit without armoured glass cannot be used in combat. Exhaust prevents the driver from looking left, as the muffler is placed on the fender close to the front. The commander and turret gunner observe through the sights and two rotating tilting periscopes.

The installation of movable periscopes in the driver's compartment hardly improves visibility, as the periscopes are large, can easily be knocked off from their position, and require the driver's hands to fully take advantage of their rotation. It is more reasonable to have fixed periscopes for the driver.

M3 Light: The gunner and driver have mirror periscopes for observation. In the turret there are three periscopes in addition to the gun sight: one in the rear and two along the sides. The vision slits in the commander's cupola and next to the gunner and driver are not safe in combat, as they are protected with double layer glass and metal shutters. They cannot be considered full fledged observation devices. Despite the presence of a commander's cupola, the ability to observe from the M3 Light is reduced due to weak protective glass.

BT-7 tank: Observation devices, aside from the sights, consist of a slit in the driver's hatch and two side slits in the turret. All slits are protected with protective glass and armoured shutters with smaller slits. The observation is satisfactory. It is desirable to give the driver a backup observation device.

T-26 tank: Observation slits covered with protective glass and armoured covers with smaller slits make up the tank's observation devices. They serve as backups for observation through the gun sights. The driver's only method of observation is his vision slit. If the slit is hit with a bullet or fragment, the driver is distracted from driving in order to swap the glass. It is desirable to have a second observation device for the driver.

The examination of the characteristics and location of observation devices of domestic and allied tanks allows the following conclusions to be made.

The field of vision from a fixed mirrored periscope is 25 degrees. If it can be tilted, the field of vision increases to 35-40 degrees, ie by 10-15 degrees. The horizontal field of vision is 40-90 degrees. The dead zone for the driver is 2.5-4 meters for light and small tanks, 4-6 meters for medium tanks, and 6-10 for heavy tanks. Turret dead zones range from 3 to 30 meters. The smaller number applies to tilting periscopes. The amount of observation devices in addition to gun sights ranges from 2 to 12. The driver has 1-2 devices, and the commander in the turret has up to 5. Observation slits give a field of vision of 12-40 degrees vertically and 40-90 degrees horizontally.

Practice of observation through observation devices shows that external effects have an impact on visibility. For instance, the front periscope of the KV-1S observation cupola does not have its full range of vision, as it is blocked by the armoured casing of the commander's panoramic sight. On the Mk.III tank it is difficult for the driver to look to the left because of the exhaust, since the muffler is installed on the left fender. Observation devices of the Mk.III, M3 Light, and Mk.II are often not used in battle because they are not sufficiently protected. Observation is also hampered by poor placement of the observation device (the device on the left hatch on the M3 Medium), observation hatch handle, etc. Only reconciling the position of observation devices with the position of all other equipment in the tank can give the best result.

Despite its shortcomings, the KV-1S has the best observation devices of all the listed tanks. The driver's triple observation devices, reliable protection of observation devices, 360 degree vision from the commander's cupola, backup 360 degree vision from turret observation devices, a lack of dead angles, and satisfactory size of the dead zone are the positive qualities of the KV-1S observation devices.

Of the Allied tanks, the Mk.III tank has good visibility. 

In summary, when installing observation devices on a tank (mirror periscopes and observation slits), the following can be recommended:
  1. It is necessary to install two vision devices (for instance, a slit and a periscope) for the driver of a light or small tank. Medium and heavy tanks should have 2-3 observation devices.
  2. It is desirable to have the driver's dead zone no greater than 0.5 times the length of the tank (for negotiating trenches).
  3. The driver should have a horizontal observation angle of 120 degrees with dual vision devices or 180+ degrees with rotating devices.
  4. It is necessary to install armoured covers over the periscope openings.
  5. The commander of a medium or heavy tank, freed from having to service the gun, requires a rotating observation cupola, or a fixed cupola that provides 360 degree vision. A 360 degree periscope is sufficient for a light or small tank.
  6. The turret and turret platform should carry tilting periscopes to increase the angle of vision.
  7. Auxiliary observation devices should serve as a backup for 360 degree vision and coverage of dead angles.
  8. The approach to the observation device and the surrounding equipment should not hamper the range of observation.
Mirror or prismatic observation devices and observation slits are not ideal observation devices. It is necessary to work on the creation of a cheap and reliable optical observation device. Another important issue is the clearing of the devices from dust, snow, ice, rain, and condensation."

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