- Yes
- No
TL;DR:
Light bomber, fast tandem prop bomber with small load.
Overview:
During the late interwar period the Soviet Air Force was looking for a new light attack aircraft, beginning with the “Ivanov” competition that resulted in the Su-2 and Niemen R-10. During this time, Professor Viktor Bolkhovitinov designed the “S” high-speed bomber, standing variably for Sparka (“twined”) or Skorostniyi (“fast one”). It doesn’t appear to have received any official military designation, though some alternate names like “S 2M-103”, “BBS-1”, and “LB-S” exist.
One of the main design goals of the “S” was to substantially increase engine power without a large increase in drag. In order to accomplish this the “S” was fitted with two engines in a tandem configuration, driving 2 contra-rotating propellers. This in theory would allow the aircraft to have a very high top speed, though the engine shaft was large and heavy, and the tandem operation complicated, flaws that would eventually lead to its downfall. Its structure was all-metal, with the fuselage and wings covered with large panels (the fuselage made with only 4). Uniquely of the smaller light bomber designs it also featured a twin tail with variable gear ratio controls for the elevator. The twin tail allowed the gunner a wide field of view for defensive firing. The bomb load was a light 400kg, made up of 4 100kg bombs in a bay in the fuselage dropped by the rear navigator via bombsight, and armament was a single defensive 7.62mm MG, with no forward armament, though there were plans to fit it with two 7.62mm MGs in the wings and also to replace the defensive gun with a twin 12.7mm MG. The “S” design was finished in 1937 and construction of a prototype began the next year, with both being completed in late 1939. During the early design process there were also proposals for reconnaissance and bomber interceptor variants.
The prototype first flew in the summer of 1939, and state tests began in 1940. Unfortunately they gave very disappointing results. The tandem configuration was inefficient, with the rear engine especially, losing a big chunk of its engine power through the tandem propeller shaft. The load on the wings was found to be very high at speeds faster than 300km/h, while at the same time it had slow acceleration while climbing, and finally was difficult to land. It reached a respectable max speed of 570km/h, though that was still considerably slower than the projected 640km/h. Afterwards, Bolkhovitinov would modify the prototype, refitted the wings, strengthening the wings and changing the shape, while also fitting slats to help its manoeuvrability. The rear engine was removed and the remaining one replaced with an M-105P. Unfortunately, the performance of the simplified “S” was also poor and with the much more successful Pe-2 already in production (at the same factory that would’ve produced the “S”), the “S” was cancelled in 1941. Additionally a fighter-bomber based on the “S” design, called “I”, was also created after. It had stronger engines and was heavily armed, but construction of the prototype was stopped with the German invasion, and Bolkhovitinov’s design bureau refocused on rocket-powered aircraft.
Specifications:
Weight:
Empty: 3400kg
Take-off: 5652kg (reduced to 5150kg in 1940)Dimensions:
Length: 13.2m
Wing Span: 11.38m
Wing Area: 22.9m²
Height: unknownEngine:
2x Klimov M-103P inline V-12 engines
960 hp
Max Fuel: 660L
Liquid cooledPerformance:
Max Speed:
570km/h at 4600m
Ceiling: unknown
Range: 700km
Rate of Climb: unknownCrew: 2
Armament:
1x1 7.62mm ShKAS in rear turretOrdnance:
400 kg of bombs (4x1 100kg like in the Yak-9B)
Images:
Sources:
Gordon, Y. and Gunston B. (2000). Soviet X-Planes (pp. 46-50). Midland.
Nemecek, V. (1986). The History of Soviet Aircraft from 1918 (pp. 197, 422-423). Collins Willow.
Shavrov, V. B. (2002). Istoriya Konstruktsiy Samoletov v SSSR 1938-1950 gg. (pp. 53-56). Mashinostroenie.