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Aviation History
1972
1972 - 2620.PDF
FLIGHT International. 28 September 1972 441 i-:• • ?':':!s:4S::i:.;'Si'NSK;;*?;Wfcsr':':i->;ii-'•' ••• ;:i •••• ..••:••.••• • 'Flight" photograph Tour of a tank killer LAST WEEK the Sikorsky S-67 Black-i hawk prototype helicopter gunship began a month-long tour of Europe, beginning at the British Army Avia tion Centre at Middle Wallop, where it was demonstrated to the Army, RAF and Royal Navy. Flight went to see this impressively large but sleek contender in the heavy attack helicopter market in which the United States has apparently lost interest, even though perhaps temporarily. Sikorsky's approach to the US Army's requirement - as - was (the Cheyenne programme was cancelled earlier this summer, although Lock heed continues to spend a small sum of money on development of some of the aircraft's more advanced systems) has been different from that of Lock heed from the start. The Stratford company set out to build a demon strator prototype based almost en tirely on the powerplant, transmission and rotors of the S-61 series, itself holder at various times of world records and well proven in service. The target set by Sikorsky was to develop a helicopter capable of 200kt within 12 months for $3-9 million. What was achieved in the event was a 208kt aircraft in nine months for $3 million. The S-67 made its first flight on August 20, 1970, and by December 19 of the same year had set up a new world helicopter speed record of 220-8 m.p.h. over 19km. At the same time manoeuvrability was being demonstrated with split-S turns and manoeuvres pulling up to 3-3g, with rolls and loops being added to the list later. On top of the basically proven components of the S-67, certain new design concepts had to be tested. These included a cambered fin (to reduce tail-rotor loads), controllable tailplane, a 28ft-span wing, speed The S-67 Blackhawk shows off its basically aggressive nature (above left) in the otherwise peaceful British countryside round Middle Wallop. Ferry tanks are on the inner wing pylons—the turret-mounted gun is currently of 20mm calibre, although a 30mm system can as readily be accommodated. One of Sikorsky's armament tests (above) with the S-67 fitted with two 19-round 2-7Sin rocket pods, 20mm cannon and two 300gal fuel tanks. Initial tests, reports the company, showed the Blackhawk as a more stable weapon platform than they had expected brakes mounted on the wings, a new rotor-head fairing, bifilar vibration absorbers, new engine inlet fairings and swept-back rotor tips. Of these, the speed brakes and tailplane were the subject of US Army study con tracts, as were studies of the manoeuvrability and of the new arti ficial feel system. A preliminary com pany report on the Blackhawk early in 1971, when the aircraft had logged about 20hr of flight time, said that blade tip speeds of Mach 0-96 had been flown without any adverse com pressibility effects. Stability was re ported to be such that balanced turns with the rudder fixed could be made at up to 40° of bank, and the Black hawk could be flown hands-off for more than a minute between 120kt and 180kt. At that stage a speed of 239 m.p.h. had been recorded in a 5° dive with a descent rate of 2,600ft/ min. Earlier this year the US Army con ducted an evaluation of the Black hawk, which included hot and high trials in Colorado during July. The principal aims as far as the company was concerned were to support the Ultra-slim profile of a gunship, with the swept-back blade tip clearly visible. Remove those ferry tanks (which give an unrefuelled range in excess of 700 n.m) and the Blackhawk can tote a total of 152 2-75in rockets
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