Tupolev Tu-4 Experimental Versions

Purpose: To use Tu-4 aircraft for various experimental purposes.

Design Bureau: OKB-156 of A N Tupolev.

In The Great Patriotic War the Soviet Union had no modern strategic bomber. Stalin cast covetous eyes on the Boeing B-29, and told Tupolev and Myasishchev to design aircraft in the same class. However, in 1944 three intact B-29s fell into Soviet hands and it was decid­ed just to copy them. Tupolev was given two years to do this immense task. The first air­craft to appear was the Tu-70 transport, which actually used the wing, engines and pro­pellers of one of the B-29s. The production bomber was designated Tu-4, and had Soviet ASh-73TK engines of2,400hp (more powerful than the B-29 engine) and a totally new defensive system with guns of 12.7mm (1st Series), 20mm (from the 8th Series) or 23mm calibre (from the 15th Series). Total produc­tion was close to 1,000. Several Tu-4 aircraft were used in air-refuelling experiments.

The Tu-4T was a single unpressurized trans­port conversion which initially was used for trials with 28 paratroops. In 1954 a small number
of 52-seat versions, again called Tu-4T, were built for the VTA (military transport aviation).

Several Tu-4K conversions were used as carrier aircraft for trials with the Mikoyan KS-1 cruise missile, for use chiefly against ships. This 3 tonne (6,614 Ib) turb ojet-engined weapon was a miniature swept-wing aero­plane with radar guidance (see page 101). The Tu-4K played a major role in the devel­opment of the entire Kompleks (electronic system) which after being cleared for pro­duction was installed in the Tu-16KS, which was the operational carrier of these missiles. Several Tu-4s were used for trials with other missiles, the earliest being with captured FilOS (so-called V-l) pulsejet cruise missiles captured in 1944-45. From March 1945 the Soviet X-10 (Kh-10) copy was on test, and numerous examples were launched from ground ramps and from Tu-2, Yer-2 and Pe-8 aircraft. In 1947 the Tu-4 became available, and several were used to test the 14Kh-l and twin-engined 16Kh, but all this work petered out by July 1955 and none of these missiles entered service.

At least 12 Tu-4s were used as engine test­
beds. Some of the early examples tested tur­boprops, of which the most startling were the three aircraft whose No 3 (starboard inner) engines were replaced by TV-12 turboprops. Take-off power ofthis single-shaft engine was initially ll,995hp, or almost six times that of the engine it replaced. The colossal thrust, which in the Tu-4 could not all be used, was transmitted by a pair of AV-60 co-axial pro­pellers each with four broad blades of 5.6m (18ft 41/2in) diameter. Later this unique pow – erplant was developed into the NK-12M of nearly 15,000hp for the Tu-95 and Tu-142. Other turboprops tested included the ex­Junkers TV-2, Klimov VK-2 (TV-4), Kuznetsov NK-2 and NK-4, and the Ivchenko AI-20, one AI-20 installation (for the Ilyushin 18) having the thrust line and jetpipe above the wing and the other (for the Antonov 10 and 12) having the thrust line and jetpipe below the wing. Jet engines tested under the fuselage of Tu-4LL aircraftincludedtheNene, AL-5,AL-7,7Fand 7P, AM-3 (RD-3), AM-5 and 5F, VD-5, VD-7, VK-2, VK-7 and VK-11.