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Aviation History
1963
1963 - 0628.PDF
• 602 FLIGHT International, 25 April 1963 P. 1127 Development THE EVOLUTION OF AN OUTSTANDING V/STOL TACTICAL AEROPLANE I N a paper read in Washington earlier this month, Hawker test pilot H. C. H. Merewether included a three-view drawing of the modified type of P. 1127 V/STOL aircraft which will equip the forth coming tripartite evaluation squadron. That the Ministry of Aviation have per mitted this drawing to be published is remarkable; much may be deduced from it, as will be evident later in this article. At the opening of his paper, Hugh Mere wether briefly retraced the manner in which the P. 1127 was evolved. This history has previously been recorded by several authors, notably by Pierre Young of Bristol Sid- deley Engines, and by chief test pilots Bill Bedford (Hawker) and Tom Frost (Bristol Siddeley) as recorded in this journal last October 11. The first three-view drawing reproduced here shows the original scheme conceived in 1954 by the renowned French aircraft de signer Michel Wibault. His "Gyropter" was suggested for tactical ground-attack purposes. Vertical lift and propulsive thrust was to be provided by four centri fugal blowers driven by an 8,000 h.p. Bristol Orion turboprop. In Mr Mere- wether's words, "Having failed to interest the French in this idea, Wibault submitted it to the Mutual Weapons Development Program authorities in 1956 and they in turn passed it on to Bristol Aero-Engines Ltd." Design teams at what is now Bristol Siddeley Engines Ltd under Dr Stanley Hooker and at Hawker Aircraft Ltd led by Sir Sydney Camm, thereupon began a programme of development which is today responsible for the most extensive prospects for future business anticipated by either company. Refining the Concept As an initial improvement, the engine firm evolved a more practical powerplant consisting of an Orpheus driving a large fan discharging through rotating nozzles. The hot jet was not deflected and, even with the engine set at 30c to the ground (as shown in the lower drawing), the resulting aircraft appeared to be of marginal operational value. Eventually it was decided to arrange for both the cold fan air and the hot jet to be discharged through pairs of cascade nozzles rotating in unison to provide a thrust vector in any desired direction. Early in 1958 the original three-stage fan (which had been borrowed from the low-pressure compressor of an Olympus) was rejected in favour of a new two-stage transonic fan, which not only handled the entire engine airflow but also rotated in the opposite direction to the high-pressure spool to minimize gyroscopic effects. The resulting engine became the Bristol Siddeley Pegasus, Three-view drawing of the Type 1-4-212 Gyropter proposed and patented by Michel Wibault early in / 956. The four fans run in pivoted casings discharging through nozzles which may be pointed either downwards or to the rear The next stage was to discard the four centrifugal fans in favour of a three-stage axial fan running on a shaft extending ahead of the gas generator. The fan discharged through large nozzles, one on each side of the aircraft, arranged to rotate about a transverse bearing shaft, while the hot gas at the rear issued straight aft
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