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Aviation History
1951
1951 - 2179.PDF
554 FLIGHT DEMONSTRATIVE Display Flying : Some Factors which the High-speed Pilot Must Keep in Mind By JOHN DERRY THANKS to the brillian<flying of the pilots at the S.B.A.C.Display last September, public interest in demonstration flying has undoubtedly reached a new high level, and wehave sensed a keen curiosity as to "how it is done." Test and demonstration pilots are almost notoriously modest, butwe have persuaded John Derry, D.F.C., de Havilland experimental test pilot, to reveal here at least a few of theguiding principles of the art. WHEN one is asked to make a demonstration flight therequest may imply one of a long list of possibilities,depending upon who makes the request. To pick out a few, it may imply a highly spectacular and dangerous beat-up, an exhibition of classic aerobatics, the making of as much noise as possible, or, of course, a genuine demon- stration of the capabilities of the aircraft. Ironically, the last-mentioned, although most often the excuse for requesting a show, is seldom what is really required; and is hardly ever really possible, except for aircraft designed for short take-offs and landings and slow flying, e.g., helicopters. Here, how- ever, it is my intention to discuss, mainly, demonstration flights on fighter types of aircraft. It is quite impossible to demonstrate stability or control- feel to someone on the ground and, moreover, an aircraft that is very bad from this point of view can be made to look (by a strong pilot with good reflexes) like the answer to the aerodynamiscist's dream. Equally, a demonstration of climb by a jet aircraft at its best climbing speed will appear very fiat; and the climbs actually made at demonstrations, although often spectacular, are well below the best rate of climb. In speed, too, the same applies. Even people accus- tomed to watching high-speed runs can be completely misled as to the fastest aircraft by such tricks as banking during the run or appearing from a bund spot. There are many such examples of the inadequacy of a demonstration as seen by watchers on the ground. For the demonstration pilot, then, the natural decision is to provide some sort of compromise between the genuine attempt at A typical Derry demonstration: the occasion, Farnborough, 1948; the aircraft, one of the first de Havilland Vampire 5 fighter/bombers. With their small radii of turn and general handiness, the D.H. jet fighters are ideal media for the author's technique. an honest demonstration and the purely spectacular show. Depending on the reason for the show, the compromise may be biased more in one direction than the other. Thus, if the show is for a non-technical audience, it can legitimately be made of a more startling nature than when critical eyes are watching, say, the acceleration to top speed, or the touch-down attitude. It would, of course, be wrong to suppose that the technical spectator does not enjoy a good display of aerobatics and general evolutions. Moreover, during a technical demonstration in which many other air- craft are performing there is, perhaps, strong justification for drawing attention to the aircraft by the performance of an unusual or exciting manoeuvre which may not serve any other purpose. Healthy and responsible competition between pilots is thoroughly desirable and results in more variation—always an important aspect of demonstration flying. But it is, of course, essential that such competition should not be allowed to go too far ! This requires particularly careful watching when identical, or similar, aircraft are performing. Aeroplanes can perform only a fairly limited number of completely separate manoeuvres and, therefore, with one or two notable exceptions, any original manoeuvre must be a variation on or combination of one or more of these classic aerobatics. Bearing in mind our earlier thoughts on a com- promise between demonstration and spectacle, the pilot's first consideration must be to make his show as original as possible At least he must make it look original. Many hours of careful work have been spent in perfecting a difficult sequence which, while completely new to the pilot, appears dull and ordinary to those watching. The question of how best to practise for one or a series of aerobatics is not easy to answer. But one point is quite clear. A very thorough work-out must take place at a good height (depending on the type) with a close watch kept on the average height-loss, if any, over a score of attempts. Except in manoeuvres which involve temporary loss of control, e.g., a spin, I always feel that no height-loss should be permitted. While a margin of safety must always be kept in hand, the pilot must never use up any of this margin; and, if all manoeuvres are worked out as though without margins, a safer show results. Fortunately, during aerobatics one usually feels nearer the ground than is, in fact, the case. Although one hesitates to encourage lower aerobatics there have been cases where the confidence bred of height or climb has resulted in sloppy manoeuvres, sometimes with fatal results. Low-level aerobatics must be accurate, and a pilot who has practised them over thin cloud and at a safe height first will be safer (and, most important, will look safer) than the non- practised and over-confident pilot at l,oooft. . , While there can be no doubt of the value of practising each individual manoeuvre (and, even when familiar with ltj keeping in practice) the value of an actual run through one s complete show is less obvious. Personally, I always nna when I try this that it is almost impossible to get into the swing of it, and often feel dissatisfied, rather than encouraged, by such rehearsals. Probably the fact of doing it over a different location, coupled with the absence of spectators ana with no strict timing, gives a dull atmosphere not in ^eeP^ with the actual show. For this reason the arrangement ot tn S.B.A.C. Display, whereby there is a full-scale programme
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