- TsKB-50: In accordance with the tactical-technical characteristics approved by the Committee of Defense of the SNK on December 11th, 1940, an experimental armoured aerosan must be developed, similar to the Tunguska sleds.
- NKVD factory #5:
- Assemble a full sized model in parallel with the design process, due on December 25th, 1940.
- Assemble a prototype by January 25th, 1941.
The assigned due dates for the model and prototype were met.
The experimental armoured aerosan consists of a Tunguska style two-skid sled 7.7 meters in length, 1.9 meters wide, with 0.4 meter wide skids (in the middle). The skis are wooden and the lower part is covered by 2 mm thick stainless steel. The skids are connected with a welded frame made from thin aircraft pipes. The frame cross-section resembled an arc with 400 mm clearance.
- The armoured aerosan hull can be split into three main parts:
- The armoured cabin with a T-40 type turret that contains the crew, armament, ammunition, and equipment. The hull and turret armour is 7 mm thick, the roof is 5 mm thick.
- The engine compartment. The sides are 7 mm thick and the roof is 5 mm thick.
- The front armoured compartment for fuel tanks and unarmored compartment for instruments and equipment.
- The propeller and engine group of the armoured aerosan consists of the M-103-A motor positioned in the rear section of the hull, covered by an armoured cap.
Water and oil radiators are installed under the motor for cooling.
- The armament of the armoured aerosan consists of an MP-6 23 mm gun with a coaxial DT machinegun and a TMFP sight.
The aerosan is also equipped with a PPD submachinegun to fire from the hatches (the horizontal traverse of the main gun is 280 degrees).
- The ammunition capacity of the aerosan is 308 shells for the MP-6 gun, 1890 rounds for the DT machinegun, 568 rounds for the PPD, and 20 hand grenades.
- The aerosan is controlled by the driver using brake levers and the steering wheel etc, positioned in the front of the cabin.
- Communication and observation: the aerosan is equipped with a KRSTB radio. Observation is performed through Izhor factory observation devices. The cabin and turret have five pistol ports for firing the PPD.
- The electrical equipment of the aerosan is done in the one-wire layout.
Electric devices are powered by batteries, which are charged by a generator attached to the M-103-A engine.
During the draft process and subsequent review of the project and the model building, several changes compared to the initial requirements were approved:
- Increased armour for the fuel tank.
- Crew of two instead of three.
- Mass of 4.7 tons as opposed to 3.5 tons in the requirements.
The prototype was presented with the following deviations:
- The mass was 5360 kg instead of 4700 kg, approved by the Model Commission.
- Instead of a combat ready MP-6 gun, a used one was sent by OKB-16.
- The TMFP sight is absent (not sent by the People's Commissariat of Armament).
- 37 magazines for the MP-6 are absent.
As a result of official trials carried out between February 10th and February 18th at various temperatures, the need to increase the cooling surface of the water radiator and a series of other changes were requested. Factory #5 began working on the requested changes on February 18th, 1941, with a deadline of February 23rd, 1941. After completion of work, factory trials resumed on February 24th. Trials were completed by March 3rd.
During the final factory trials on March 3rd, the aerosan traveled 60 km at an outside temperature of +3 degrees.
- Total engine runtime: 2 hours
- Temperature range: normal
- Fuel pressure: normal
- Oil pressure: normal
During March 3rd trials, the aerosan could start without assistance from 2000-2200 RPM.
Official trials continued on March 4th. During official trials, the motor worked nonstop for 3 hours and 35 minutes. Travel distance: 140 km.
Speeds with a 2.8 meter diameter propeller:
- February 18th trials: 44 kph at 2350 RPM, air temperature of -7 degrees.
- March 4th trials, air temperature between -1 and +1 degrees:
- At 1700 RPM: 45 kph
- At 2000 RPM: 65 kph
The speed at 2400 RPM was not recorded as the aerosan left the measurement strip.
The aerosan engine worked the following amount during all trials:
- February 16th: 100 km, nonstop work, 3 hours 35 mins
- February 26th: 45 km, nonstop work, 1 hour 30 mins
- March 3rd: 60 km, nonstop work, 2 hours
- March 4th: 140 km, nonstop work, 3 hours 35 mins
Further off-road trials will be performed on March 6th, 1941.
NKVD Factory #5 Chief, Intendant 2nd Class, Lokshin
Chief of TsKB-50, Engineer Ponomarev: