Air International 1979-04
B.Burns - VTO for combat aircraft /Fundamentals of design/ (2)
The latest derivative of the original Hawker P.1127, the world's first and to date only completely successful V/STOL combat aircraft, is the AV-8B, developed by McDonnell Douglas for the US Marine Corps and first flown on 9 November 1978.
Another Yak-36MP being readied for take-off. This photograph show clearly the dorsal spine enclosing the ram intake cooling the rear avionics bay. An IR warning sensor is believed to be accommodated in the fuselage tailcone.
The Yakovlev 36 is capable of supersonic level flight but lacks the Harrier‘s ability to make rolling take-offs.
The VFW VAK 191B with two RB.162 lift engines and one RB.193 vectored thrust engine in the fuselage, producing a total of 21.300 lb st (9670 kgp) to lift 19.480 lb (8844 kg).
The British Aerospace Harrier, to date the most successful operational VTO aircraft, is a progressive development from the original P.1127 prototype by way of the Kestrel (on photo). Over a decade, operational take-off weights for VTO and STO have been raised from 12.400 lb (5 630 kg) and 15.500 lb (7037 kg) to 17.250 lb (7832 kg) and 25,000 lb (11350 kg) respectively.
Several VTO aircraft have been flown over the past 20 years but have fallen by the wayside for political or technical reasons. The VJ 101C shown here had six RB145 engines - two for pure lift in the fuselage and two pairs (with reheat) in swivelling pods at the wing tips. The tip nacelles featured translating intakes, with sharp lips for high speed flight and rounded lips with intakes in the up position for VTOL.
The Dassault Mirage IIIV (the second prototype of which is illustrated) featured a single propulsive engine and eight lift engines. Flight testing showed that it suffered high jet-induced lift losses because of the battery of engines mounted in the centre of the large wing.
Another of the VTOL prototypes that did not succeed: the Lockheed XV-4A Hummingbird with two 3,300 lb st (1500 kgp) thrust engines feeding 20 rows of multiple, rearwards-inclined nozzles which, with ejector augmentation, produced total jet lift in excess of the 7.200-lb (3269 kg) weight of the aircraft. The use of ejectors involved complex plumbing but gave a cool "foot print'' and extra thrust, and the system is again being studied for future US naval fighters.