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Aviation History
1953
1953 - 0361.PDF
FLIGHT, 20 March 195 3 359 then Vickers' chief test pilot, eased the prototype 630 off the ground at Wisley, and remained airborne for approximately 20 uneventful minutes. He said afterwards, with enthusiasm, that the Viscount was "the smoothest and best" aircraft he had ever flown. This flight was particularly noteworthy in that it was the very first by an aircraft powered with four turboprops and, fur thermore, the engines concerned had been designed from the out set for civil and not for military operation : singularly few others built in this country have gone into civil production without first being tried out extensively in the military sphere. Less than 15 airborne hours later, the aircraft—G-AHRF—very con vincingly "showed the flag" at the Farnborough display. A comprehensive programme of test flights was put in hand when the Show was over, and as part of this programme the machine visited Villacoublay, near Paris, on September 20th—in the circumstances, surely a very early foreign debut. In Decem ber of the same year the Press had their first opportunity to sample travel by the new medium, albeit under very adverse weather conditions, which were such as to prevent true presentation of the vibration-fret characteristics of the aircraft. They were, however, able to form some idea of its high cruising speed and the low noise-level that existed in—at any rate—the rear cabin. Noise in the smaller, front cabin was found to be less than in conventional aircraft, but perhaps not quite so low as had been anticipated in view of the low r.p.m. of the airscrews (Dart reduc tion gear is approximately 10: 1 and maximum engine r.p.m. is of the order of 14,000.) Further soundproofing in this area is in fact now being incorporated on production aircraft. Accommodatioii in the prototype had been limited to 32 seats, as already stated; but it was realized that, by removing the cen tral pantry, a larger number of passengers could be carried, so arrangements for 36 (and even 43) seats were worked out. At about this time, however, it became clear that the Rolls-Royce R Da 3 Darts that were to be fitted to future aircraft would develop 1,400 s.h.p., and that there was therefore scope for an enlarged version of the aircraft, combining longer range with increased payload—a much more attractive proposition to potential operators. Thus the concept of the Viscount 700 series first came into being, for which Mr. Edwards was so largely responsible. Fuse lage length was to be increased by 6ft 8in, and span by 5ft. Maxi mum take-off weight was to rise from 45,000 lb to 48,000 lb, wing loading would drop fractionally to 49.8 lb/sq ft, and under carriage track and wheelbase were to be increased very slightly. Two variants were originally projected—the model 40 with 40 seats, and the model 52 with (curiously) 53 seats. By June 1949, the first prototype had completed the first stage of its trials and was having the pressurizing system fitted. The second prototype was well advanced in construction, and—at the desire of the Ministry of Supply—was being fitted with two Rolls-Royce Tay turbojets (the Tay, a development of the Nene, was scheduled to be built by both Pratt and Whitney and Hispano Suiza). This aircraft was intended purely for research, and that in fact has been its role. Soon, rumours began to circulate that B.E.A. were so im pressed with the design-performance data of the new 700 that they were considering making a complete about-face and placing a substantial order. Confirmation came in late August when, at a luncheon held to celebrate the thirtieth anniversary of the first regular London-Paris service, it was announced that both B.E.A. and B.O.A.C. were to order the type—the latter with a view to operating them in the Caribbean area through their subsidiary company, British West Indian Airways. This decision must have promoted a great sense of relief and well-being at Vickers, and there was further elation a few weeks later, on September 15th, when the prototype was granted a Cer tificate of Airworthiness. At this stage 290 hours had been logged, including no fewer than 320 take-offs and landings. The C. of A. did not cover use of the pressurizing system or operation in icing conditions, but in January 1950, highly successful de- and anti- icing trials were carried out off the coast of Ireland where—not without difficulty—suitably severe icing conditions were located. These operations were based on Shannon Airport. It was found that the aircraft flew well when heavily and deliberately iced up; that the thermal de-icers were remarkably effective in removing existing ice; and that no ice formed at all if the hot-air flow was turned on before entering a dangerous region. The behaviour of the Darts was also exemplary; which was as expected, since Rolls-Royce had already carried out icing ground-tests with success. Nevertheless, later Darts were scheduled to have heated intakes, thereby avoiding risk of increased fuel consumption due to partial intake blockage. Airscrew de-icing was by fluid over shoes, but an electric blade-heating system was planned for the 700 series. The only device which proved not entirely adequate was the windscreen fluid-type de-icer—a fact, incidentally, which completely vindicated Vickers' faith in a thermal system for wings and tailplane. An improved pump is being fitted to production aircraft as a result. During March and April 1950, an extensive demonstration tour of Europe was undertaken, during which eight capitals were visited and 4,400 miles covered. Capt. Wakelin of B.E.A. was the pilot, and Sir Hew Kilner (deputy chairman of Vickers- Armstrongs, aircraft division) and Capt. Summers were among the passengers. The deliberate fuel-saving use of two engines only (for descents and airport "stand-offs") was tried out, and found entirely practicable. The next stage of prototype development started in June, when the aircraft was flown to Khartoum and Nairobi for tropical trials. Capt. R. Rymer (B.E.A.) captained the machine in transit, Mr. G. R. Bryce (later Vickers' chief test pilot) carried out the The prototype 630, now in B.E.A. markings, at Schiphol airport—0 scene typical of the interest aroused by the aircraft.
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