Aircraft jet propulsion

911,652. Vertical or short take-off and landing aircraft. BRISTOL SIDDELEY ENGINES Ltd. June 29, 1961 [July 6, 1960], No. 23654/60. Class 4. An aircraft is equipped with a main jet propulsion unit 11 for providing lift and normal forward propulsion, and also with an auxiliary jet propulsion gas turbine engine 12 including an air intake duct 16, this auxiliary engine 12 providing additional forward propulsion and being arranged behind the main propulsion unit 11 which comprises a gas turbine engine 19, discharge nozzles 21 fed with compressed air from a ducted fan or low pressure compressor driven by engine and a jet pipe 23 comprising a straight upstream portion 40 and a forked downstream portion 41 terminating in discharge nozzles 25 fed with exhaust gases from engine 19, and means for selectively orienting the discharges of nozzles 21, 25 downwards to obtain lift or rearwards to obtain forward propulsion, the air intake duct 16 of auxiliary engine 12 extending from a point off the axis of the straight portion 40 of jet pipe 23 through a point directly behind portion 40 to reach the auxiliary engine. Duct 16 leads rearwardly from an opening in the air intake duct 13 for engine 19, and a flap 18 controls the air flow to engine 12. Both pairs of nozzles 21, 25 are rotatable about axes which intersect at right angles the centre line of engine 19. In an alternative embodiment, the air intake duct for the auxiliary engine is separate from the intake duct for the main engine and extends from an opening in the top of the fuselage downwardly and rearwardly behind the main engine to the auxiliary engine. Specification 881,662 is referred to.