BARTINI STAL'-G, AND STAL'-J Stal'-8,I-240
Bartini Stal'-7 Purpose: Originally, fast passenger transport; later, long-range experimental aircraft. Design: SNII GVF; construction at GAZ (Factory) No 81, Moscow Tushino. In the winter 1933-34 the GUGVF (chief administration of the civil air fleet) issued a requirement for a fast transport aircraft to carry 10 to 12 passengers. Curiously, the two prototypes built to meet this demand were both the work of immigrant designers, the Frenchman Laville (with ZIG-1) and the Italian Bartini. The latter had already produced drawings for a transport to cruise at 400km/h (248mph), which was well in advance of what the GVF had in mind. Always captivated by speed, Stalin decreed that a bomber version should be designed in parallel. Still in charge of design at the SNII GVF, Bartini refined his study into the Stal'-7, the name reflecting its steel construction. Strongly influenced by the Stalin decree, Bartini created a transport notable for its cramped and inconvenient fuselage, highly
unsuitable for passengers but excellent for bombs, and for long-range flight. The original structure was to be typical Bartini welded steel-tube trusses with fabric covering, but the stress calculations were impossibly difficult, with 200 primary rigid welded intersections between tubes of different diameters. In late 1934 the fuselage was redesigned as a light-alloy stressed-skin structure, with simpler connections to the unchanged wing. Only one aircraft was built, in the workshops of ZOK, the factory for GVF experimental construction. The first flight was made on an unrecorded date in autumn 1936, the pilot being N P Shebanov. Performance was outstanding, and Shebanov proposed attempting a round-the-world flight. In 1937 the StaP-7 was fitted with 27 fuel tanks with a total capacity of 7,400 litres (1,628 Imperial gallons, 1,955 US gallons). A maximum-range flight was then attempted, but - possibly because of structural failure of a landing gear - the aircraft crashed on take-off. Bartini was arrested, and was in detention (but still designing, initially at OKB-4, Omsk) for 17 years.
The aircraft was repaired, and on 28th August 1939, at a slightly reduced weight, successfully made a closed-circuit flight of 5,068km (3,149 miles) in 12hrs Slmin (average speed 404.936km/h, 251.62mph), to set an FAI Class record. The route was Moscow Tushino-Maloe Brusinskoe (Sverdlovsk region)-Sevastopol-Tushino, and the crew comprised Shebanov, copilot VAMatveyev and radio/navigator N A Baikuzov. In Bartini's absence, the project was seized by his opportunist co-worker V G Yermolayev, who redesigned it into the outstanding DB-240 and Yer-2 long-range bomber. The wing was typical Bartini, with pronounced straight taper and construction from complex spars built up from multiple steel tubes, almost wholly with fabric covering. Each wing comprised a very large centre section, with depth almost as great as that of the fuselage, terminating just beyond the engine nacelles 2.8m (9ft 2/4in) from the centreline, with sharp anhedral, and thinner outer panels with dihedral. The trailing edges carried split flaps and Frise ailerons, the left aileron having
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