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Aviation History
1947
1947 - 2076.PDF
6o8 FLIGHT November 7.7th, 1947 FLIGHT PILOTS A JET. . . m.p.h. At around 60 m.p.h. a slight stick-back movement lifted the nosewheel off the ground, and at 90 to 100 the Vampire (with 30 deg. flap and about | fuel load) fairly popped off the ground in answer to a further small stick movement. Reflecting on the first take-off, which was made in rather poor light and a rainstorm, I must confess to one short blank in my memory. Things happened quickly, and although I remember selecting wheels-up (their retraction is quickly confirmed by a pronounced thud and a momen- tary twinkle of red indicator lights), followed by flaps-up and throttling back, I was not conscious of flying the machine until I had reached about 800ft and the speed was building up to about 200 m.p.h. Almost automatically I turned gently to port before making a check-up around the cockpit. I expected to read about 9,500 r.p.m. on the rev counter, which is of the two-needle sensitive altimeter type, but at first glance all the dial registered to me was about three minutes past six! I worked it out quickly enough, but since then two things have become apparent to me: one, that if a familiar dial is re- graduated for another purpose it may be- come confusing, and, two, that a small movement of a "jet" throttle produces (a) a relatively large change in r.p.m., and (b) if it is at the wide-open end, a very large change in power. These points are, of course, no discovery, but one has to fly and control an aircraft with a turbo-jet to appreciate them fully. The throttHng-back movement, which I had made by force of habit when the wheels were up, had been quite small, but had, neverthe- less, over-reduced revs and thrust. Speed .had increased to just over the 200 m.p.h. mark, and the height was only 1,500ft by the time I had worked things out and completed a down-wind leg, so opening up to a cruising r.p.m. of 8,700 with a very small throttle movement, I saw rather than felt the speed begin slowly to build up as I flew around to get the feel of things gener- ally. Best climbing speed is about 260 m.p.h. and correct r.p.m. are 9,700, but wishing to gain height and still having a vague idea of rocket-like ascent and enormous -thrust, and also because I had decided to take things easily for a start, I pulled up into a medium climb with speed and r.p.m. as they were, and was puzzled to see the speed drop off quite rapidly within a thousand-or-so feet. Levelling out under the clouds at about 4,000ft I quickly analysed tkis manifestation, as it seemed, of jet perversity. A olear sky lie ahead of me, and so this time I carefully opened-up to 9,700 r.p.m., the correct climbing revs, and allowed the speed to build up to rather more than 260 m.p.h. Again I pulled up the nose, holding correct climb- ing speed and enjoyed the marvellous sensation of rising up past the edges of cloud layers at well over 4,000 ft/min, almost as if in a lift, and of seeing the altimeter needle counting off the thousands of feet like an elevator floor- indicator at the Rockefeller Centre. When I next fly 5 Vampire I shall have in my mind a picture of the Goblin V r.p.m. /thrust curve—particularly the steep bit at the top At high speed I shall also be more conscious of the effet of ram and the " 95 per cent efficient, high-velocity ductec air intake." In some ways I went up expecting too much, but in others I got more than I bargained for. Three thousand pound' of thrust cannot be expected to raise a 10,000-lb aircraft vertically, nor to accelerate it like a rocket, but it can and does provide a thrilling performance. On reaching a little over 12,000ft I levelled off, as I was not wearing an oxygen mask, and throttled back to an engine cruising speed of 8,700 r.p.m., which gave around 320 m.p.h. indicated. At 10,oooft, 10,000 r.p.m. and 300 m.p.h., the Goblin II gives a fraction under 1,900 lb thrust, but at 8,000 r.p.m. and the same speed the thrust is only 900 lb. If air speed is increased to 500 m.p.h. these powers D.H. 100 VAMPIRE Mk 111 Goblin II- Span Length* H Service Still air range at 350 m.p.h. Patrol duration Full load takeoff to 50ft... Landing from 50ft (8,5001b) Max. all-up weight Total fuel capacity Ib Static Thrust ... 40ft ... 30ft 9in ... 6ft 3in ... 45.8 1b/sqft r ,.. 4,350 ft/min ... 531 m.p.h. ... 43,500ft 590 miles S.L. 1,145 miles 30,000ft 2.35 hr at 30,000ft 1,180 yd 1,100 yd 12,170 Ib 530 gallons become approximately 1,920 lb and 840 lb. It is at about this speed that ram effect proves beneficial, and in the case of the Vampire installation, thrust, after falling off, begins to increase again with speed at about 480 m.p.h. While still getting accustomed to the feel of the Vampire at higher altitude and speed, I tried the cockpit pressur- izing equipment, which is operated by one small tap. The effect was instantaneous, and the gauge showed about 1 lb differential pressure at this height. The compressor fan could be heard plainly above the whistling of the wind. I also tested the effect of the cockpit seal and was surprised at the tremendous increase in noise when "unsealed." Even so, the turbine could scarcely be heard and was so smooth in operation that it could not be felt. In fact, one of my outstanding impressions was of the incredible silence as I cruised along high above the cloud. The sensation suggested skating through space in a transparent egg. The inability to see any of the Vampire except, with an effort, its wingtips, and the magnificent view afforded down- wards to the sides, and all around at eye level and above, emphasized this illusion. Extraordinary as it may seem, there was a suggestion also of the balloon there: no appar- ent motion, no visible means of support, and silence except for the wind. Accurate visual flying was at first something of a prob- lem. There is no prominent nose or wingtip to hold on the horizon, and none of the ordinary noises to tell of the The Vampire offers spirited performance at high speed but doJlitf and potitive obedience to control for approach and landing,
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