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Aviation History
1963
1963 - 0448.PDF
426 AIR COMMERCE . . . altitude of 25,000ft; a flight at Mach 0.895 at that altitude was planned for the same afternoon. The high-speed programme at 10,000ft had been completed. It was possible, he said, for the VC10 to do 0.9 in level flight though the nose had to be pushed down a little to achieve 0.92. Measurements had been made against Boscombe Down's calibrated Javelin, flying past this aircraft up to speeds of 0.9. Handling characteristics had been "right on prediction"—at 0.88 a nose-down tendency, followed by a nose-up at 0.91, obviating the need for a Mach trimmer. There was no buffet up to just over 0.88, with just a little tremor at 0.9. He personally wanted the lateral control lightened a little at high speed. There was no doubt that the low-speed characteristics were "the real feature" of the aircraft, and the one which had made "the biggest impact" on the pilots who had flown it. The approach and threshold speed during the demonstration flight that morning had been 120kt even though the aircraft was 14,0001b above the maximum permissible landing weight for normal operations (as opposed to manufacturer's testing). Rotation and take-off safety speeds were also low. Stalls in all flap configurations had been made; following the addition of a fairing along the slats they felt they were about 80 per cent "along the road" in the full-flap case and the other con figurations looked good so far. Stalling behaviour was in accor dance with requirements. He was "extremely pleased" with the autopilot so far as tests had gone. Autoflare and autoland instal lations would be provided for in all aircraft delivered by Vickers. Capt Peter Cane, BOAC's special duties pilot assigned to the VC10, said it was unique in BOAC's experience to get their pilots on a new aircraft at such an early stage. Two of the corporation's captains, himself and Capt Field, had been assigned to the pro gramme together with three flight engineers, one permanently based at Wisley and the other two onanaif hoc basis. In Capt Cane's view the VClO's behaviour in the circuit, approach and landing was "its most remarkable characteristic." For 30 years landing speeds had gone up and up, ten miles an hour at a time. Then, said Capt Cane amid laughter, came the change to knots. Pilots had said that landing speeds must be cut. The Boeing 707's threshold speed at 7,0001b over max landing weight, 207,0001b, was 138kt according to the book. Add 7,0001b to that to compare it with the 14,0001b overweight condition of the VC10 that had landed that morning and the threshold speed would have been up to 141kt—or 149kt taking into account the ARB's additional margin, compared with the VClO's 120kt. "Ask anybody in BOAC," said Capt Cane, "if they would care to put down a 707 on a 6,600ft runway at 14,0001b overweight and stop the aircraft half way, and I hate to think what sort of a reply you'd get." The VC10 was, in his opinion, "a very great step forward in the general safety of aviation." He also said that the aircraft had "one of the softest gears I've come across—it is almost impossib'j to put it down hard." He liked the flight deck very much—"the first reasonable-sized cockpit we've had. You can take a deep breath without knocking somebody's hat off." The VC10 was "a most encouraging aircraft—a pilot's aircraft, simple and easy to fly, and nowadays that really means something." Asked by the Press to give a measure to the VClO's lower land ing speed compared with the 707, Capt Cane said that it seemed to be 15 or 20kt less for a comparable weight. It seemed to give the pilot longer to look at the runway on the approach. Compar ative Vj speeds at full weight (299,0001b for the VC10 and 310,0001b for the 707) were 140kt and 165kt. Take-off distance was in broad terms about 2,000ft better than the 707. Mr G. F. H. Hemsley, Vicker's chief engineer, said that drag had been "our serious problem." It was unfortunate that the wind tunnel had not given any indication of the deficiency, which could only be put down to changes in Reynolds Number or to the effects of downwash and boundary layer. At first, buffet at the back end had been quite severe, and they had been worried about flutter. But it turned out to be a nacelle flow problem. By a series of modifi cations the fairing aft of the jet pipes had been altered and this (which he described as a beaver-tail), had got rid of the buffet and had reduced the drag. Two or three different configurations were being flown; *VB for example had had the "Mk 2 beaver tail" which had been revised to the Mk 1 shape. There had also been other flow problems, for example around the gulley or strut joining the engine nacelles to the fuselage. There FLIGHT International, 28 March 1963 had been a tendency for a shock wave to form underneath the gulley. It had been decided to rotate the engines three degrees nose up. At present the engine nacelles were horizontal, contributing a little to trimming by carrying a down load. In addition the width of the struts was being increased by 11 in each side. Tests in the wind tunnel had shown a significant potential reduction in drag, This modification, a fairly major one, was being applied to the fif :h aircraft, 'VE, due to fly in mid-April. Already, said Mr Hemsley, the drag discrepancy had been reduced by more than 50 per cent: and the mods on 'VE promised to get rid of the other "half. Another cause of excess drag had been due to the build-up of a pressure field ahead of the engines in the cruise condition where cruising speed was higher than intake speed, causing a reduction of lift in that particular part of the wing. Where intake speed was higher than cruising speed a marked reduction in drag resulted. Penalty of the new beam, according to Mr Hemsley, would be about 3001b but the aircraft had been within 2501b of the 1957 weight estimate so there was no problem there. There had also. he said, been some "fairly difficult trouble" with the slats, the design "step-down" of which had not lifted as estimated in flight: but this drag problem was being overcome. So far as BOAC'b request for London-Los Angeles range was concerned this would require a further 5 per cent improvement in drag beyond the reductions to be achieved by the fixes outlined. Other ideas were being tested in the wind tunnel, including a change in the shape of the rear fuselage to reduce suction. Mr Hemsley declined to give a measure to the excess of the VClO's drag above estimates but he pointed out that even a one per cent increase in drag could on a long range flight mean something like 1,4001b of fuel. Asked whether Vickers were aware of any similar rear-engine drag problems with the Caravelle Mr Hemsley said he had hoped to get an invitation to go over to Sud but this had not so far been forthcoming. (Although Sud are building parts of the VC10 it seems that One-Eleven/Baby Caravelle rivalry has so far precluded design co-operation.) In-flight impressions of VC10 cabin-quietness had to be "factored" considerably to make allowance for the fact that only a small section of G-ARVA's cabin was soundproofed and furnished, most of the rest being occupied by test recorders. Even so, take-off and cruising noise-levels were low, and it really sounds as though the fully furnished cabin will, as 707 and DC-8 competitors may well fear, be something quite new in the market. There seems to be a fraction more noise—or rather, less quietness—on the flight deck compared with the 707; but how much of this is due to aerodynamics and how much to an underfloor fan (which is being dealt with) could not be assessed. The cabin, certainly by Comet and Caravelle standards and even by Britannia standards, seems vast. Although cabin-width is the same as that of the 707, head room is about a foot more. The three Zantop brothers sign the contract with Whitworth Gloster for two Argosy 100s (see last week's issue). The brothers, seated, are, left to right, Duane, vice-president of Zantop Air Transport Inc; Howard, president of the company; and Lloyd Zantop, vice-president. Standing, left to right, are Messrs Arthur V. Norden, Whitworth Gloster's US representative; R. E. belong, Whitworth Gloster's general sales manager, and J. Duguid, Whitworth Gloster contracts
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