From "Observation from Modern Tanks"
Engineer-Major L.S. Tolokonnikov
Vestnik Tankovoy Promyshlennosti (Tank Industry Herald) 1944 #10
"Presently, tanks use simple observation devices
- Observation slits with protective glass and without.
- Mirror observation devices (periscopes).
- Commander's cupolas with observation slits or periscopes.
- Observation ports.
Optical (aside from sights) and mechanical observation devices are completely absent. until a new type of tank observation device is discovered, further improvement of observation from tanks, protection of the observer, and convenience of observation can only be increased by improving the design of existing devices, increasing their quality, positioning them more rationally, and improving their attachment inside the tank.
This article will examine only a portion of the issue, that is the position, amount, and observation angle of modern tanks, domestic, captured, and allied (25 in all).
The basic observation device in this tank is a simple mirror periscope. There are three periscopes in the tank. One is installed in front of the driver in an observation hatch. Two periscopes are located along the sides of the turret. The location of the periscopes and their range is shown in figure 1.
The amount of observation devices is limited. There is no all-round vision. The driver cannot see to the sides. The design of the periscope and its attachment to the armour do not provide protection for the observer.
Figure 1: T-60 tank. Dead zones: driver's periscope - 4.5 meters, turret left and right - 9 meters.
The T-70 light tank has mirror periscopes for observation. One periscope is installed in the entrance hatch in front of the driver. A tilting and rotating periscope is installed in the turret. The tank has all-round observation. The tilting periscope increases the observation range. The process of switching out periscopes is quick. A lack of a backup periscope for the driver forces him to stop driving the tank if he has to replace the periscope. The ranges of observation and dead zones are given in figure 2.
Figure 2: the T-70 tank. Dead zones: driver - 9 m, commander's observation device - 7.5 m (turret corners - 16.6 m).
In addition to the sights, observation slits are used for observation. The slits are protected with glass blocks and shutters with small slits. One slit is located in the driver's hatch, the other two are on the sides of the turret. The location of the sights and observation angles are given in figure 3.
The observation from the tank is marginal. There is no all-round observation. The slits are easily packed with mud or snow. The ease of replacing the devices depends on how well the glass is matched to the cartridge.
Figure 3: BT-7 tank. Dead zones: driver- 4 m (large slit) or 5.5 m (small slit). Turret left and right - 3.8 m (large slit) or 7.5 m (small slit.
The T-26 is equipped with the same devices as the BT-7. There is one observation slit in front of the driver and two along the turret sides protected by protective glass and armoured shutters with small slits.
Drawback: a lack of backup observation device for the driver and all-round vision. The observation range is shown in figure 4. A feature of the T-26 is that the observation devices are interchangeable, the same device is used for the driver and in the turret.
Figure 4: T-26 tank. Dead zones: driver - 3 m (large slit) or 4.4 m (small slit). Turret left and right - 4.6 m (large slit) or 6 m (small slit).
The T-34 tank has two periscopes in the driver's compartment. The periscopes are installed at an angle in the driver's hatch. The periscope openings can be closed with shutters. The periscopes are protected with a layer of plastic. The radio operator can only see through the machine gun sight.
The turret crew mostly observes through the gun sights. Two slits in the turret can be used to look to the sides. The slits are protected with two layers of protective glass.
The driver has the best observation. The rest of the crew, especially radio operator and turret gunner, have limited observation. The position of the sights and their range is shown in figure 5.
[Note - the article author leaves out the periscopic gun sight that also doubled as a rotating periscope for observation]
Figure 5: the T-34 tank. Dead zones: driver - 6.8 m. Turret slits - 22 m.
T-34 modernized [the author likely means the T-34-85]
The driver has the same means of observation as on the earlier T-34. The driver looks through two periscopes in the entrance hatch.
The observation from the turret were improved. An immobile commander's cupola was installed on the main turret. The cupola has five slits that are protected with two layers of protective glass. Two slits protected by two layers of glass are located on the sides of the turret.
The radio operator and turret gunner still look only through their gun sights.
The tank has all-round vision. Observation through the cupola has a backup in the form of slits in the turret. The driver has a dual and reliable means to observe the road. Observation from the tank is definitely improved.
The angles of observation and location of devices is shown in figure 6.
Figure 6: the T-34 tank. Dead zone: driver - 5.7 m, turret left and right - 17 m, commander's cupola - 21 m.
The heavy KV tank has its observation devices gathered in the turret platform in front of the driver and in the turret. The driver's observation devices consist of an observation hatch, a slit protected with protective glass, and a tilting mirror periscope. The driver has a backup for observing the road.
Four tilting periscopes are installed in the turret: two along the sides and two in the rear. The observation sideways also has a backup in the form of two slits. The slits are closed off with protective glass.
A positive quality is that there are backup observation devices in the main directions of observation. The number of devices is sufficient, but their location does not permit all-round observation. The placement and range of the devices is shown in figure 7.
Figure 7: the KV tank. Dead zones: driver's vision slit - 3.6 m (large slit), 6.7 m (small slit), or 6 m (mirror periscope). Turret left and right 6.5 m (slit) or 4 m (periscope).
The driver observes the road through an observation hatch, a slit with protective glass, and two mirror periscopes. In addition to the gun sights, there are two mirror periscopes in the turret: one to the front right and one to the rear. Two slits with protective glass are placed along the sides of the turret.
The tank has a commander's cupola. Five observation devices are installed in it. The entrances to the pericope openings can be closed off with shutters.
The diagram showing the placement and range of observation devices (figure 8) shows that the crew has visibility in all directions. The driver has three ways to look forward. There is all-around vision.
The advantages of the placement of the devices are marred by the design of the mirror periscope.
Figure 8: KV-1S tank. Dead zones: driver - 9 m (large slit), 12 m (small slit), 7.5 m (mirror periscope). Turret: left and right slits - 23 m, mirror periscopes: 17 m, commander's cupola: slit 1 - 28 m, slit 2 - 18 m, slit 3 - 14 m, slit 4 - 9 m.
On light tanks, the driver has, as a rule, one observation device. On medium tanks, there are two, and on heavy tanks there are two-three. The driver cannot look to the side on any tank. All observation devices installed in the turret platform are given to the driver. The radio operator has no observation devices.
Most vehicles have observation slits with protective glass in the side of the turret. Heavy tanks have backup observation devices for looking to the sides.
Heavy tanks have visibility backwards. Latest tanks are equipped with commander's cupolas. Rotating periscopes are installed in the entrance hatch. The commander's cupolas have periscopes or observation slits for vision.
The KV-1S and modernized T-34 have reliable observation devices. Their placement allows for all-round vision. The location of the observation devices is reasonable. Drawbacks: the KV-1S tank has the commander's panoramic sight impede forward observation through the cupola, and in the T-34 the vision to the right is constricted by the entrance hatch handle. The location of the observation periscope in the entrance hatch is not rational. The periscope can be damaged when the hatch is closed and impedes exiting and entering the tank."