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Aviation History
1964
1964 - 2166.PDF
183 FLIGHT International, 30 July 1964 Westland's All-British Helicopters By JAMES HAY STEVENS, AFRAes IT is now eight years since the P.531 helicopter was conceivedin the form of preliminary design studies by Saunders-Roe'sHelicopter Division at Eastleigh Airport, near Southampton. In 1960 the division was bought by Westland Aircraft Ltd, and the P.531 has now grown in power and weight and is the prerogative of Westland's Fairey Aviation Division at Hayes and White Waltham. The leader of the team is Dipl Ing T. L. Ciastula, MiMechE, FRAes, Westland's chief designer—light helicopters, while overall policy is controlled by Dr G. S. Hislop, phD, BSC, ARCST, MiMechE, FRAes, FRSA, the company's technical director (development). The pro- duction P.531 is called the Scout in the British Army and the Wasp in the Royal Navy. Before describing the aircraft, a brief note on its history will help to give its background. The P.531 originated as a private venture, and much of the development work continued on a PV basis while the Ministry of Supply and the two Services were evolving their ideas. In 1956 the Army was using the Saro Skeeter, a 2,3501b two- seater with the 215 h.p. DH Gipsy Major. Fairey Aviation was working hard under Dr Hislop to persuade the authorities to adopt the Ultra-Light Helicopter, which had tip-jet drive from a Palouste air compressor. In contrast, Saunders-Roe investigated a direct development from the Skeeter; and this is what the original P.531 was, since it had a rotor composed of four (instead of three) Skeeter blades, a similar tail boom, transmission and tail rotor. The main difference, however, lay in the substitution of a gas turbine for the piston engine. Powerplant choice had initially been a major problem, for at that time there was nothing suitable in Britain. However, Blackburn Engines had a Turbomeca licence and could offer the 400 h.p. Turmo, which was well suited to the original size of the P.531 as a 3,4001b five-seater. Choice of this engine was prompted by the immediate success of the Sud Alouette II with the Turbomeca Artouste, but the Turmo went a step further in having a free power turbine, which eliminates the need for a centrifugal rotor clutch and overcomes the power lag characteristic of gas turbines. The original P.531 was fully described in this journal on August 8, 1958. Having obtained some lead on what would be acceptable to the Army and the Navy as a light helicopter for general-purpose and small-ship duties, respectively, the company went ahead with two P.531 prototypes powered by the Turmo derated to 325 s.h.p. This took nine months, the first aircraft flying at Eastleigh on July 20, 1958, and the second on September 30. A brief evaluation at the A&AEE by Army and Navy pilots showed the need for development aircraft—designated P.531-0/N—for trials on small ships. These had the minimum of modifications, the major one being a special skid undercarriage in place of a neat four-wheel gear. The three 0/Ns were worked hard by the RAE Bedford and the RN, and deck- securing devices were evaluated in the course of some hundreds of day and night flights from frigates. In parallel, the Army and Navy worked out their needs and arrived at an aircraft 50 per cent heavier and of double the power. This characteristic situation had been foreseen by both Saunders- Roe and Blackburn, and the latter had developed the 1,000 s.h.p. A.]29, later named the Nimbus. The Army asked for a 5,0001b vehicle of 650 h.p. capable of maintaining full performance to 7,000ft under tropical conditions; the Navy needed one of 5,200/5,5001b, with 710 h.p. and maintaining performance to ISA + 25°C at sea level. The aircraft to satisfy both these requirements, the P.531-2, was designed rapidly (and at company expense) and flew on August 9, 1959. On May 3, 1960, another prototype was flown with a derated Gnome (T58), to flight-test the engine and compare performance with the Nimbus. Both engines are now products of Bristol Siddeley Engines Ltd. The first Scout AH Mk 1 for the Army flew on August 4, 1960, and deliveries started in the spring of 1963. The first Scout with powered controls flew on March 6, 1961. As well as making "substantial quantities" for the Army, Westland has delivered two to the Royal Australian Navy for use from survey ships, and three to the Royal Arab Air Force, one of which is for King Hussein's personal use. In the Navy, the alighting problem continued to be investigated; 19 schemes were examined and five were actually tested. Finally, the Wasp HAS Mk 1 was ordered in September 1961. This is essentially a Scout AH.l fitted with a folding tail and special alight- Heading picture: Scout AH.I of 10 Flight, 6S6 Squadron, Army Air Corps, operating in South Johore, Malaysia
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