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Aviation History
1944
1944 - 0552.PDF
284 Indicator Discusses Topics o) the Day FLIGHT Mathem atical MARCH ICTH, 1944 yopia Blinding by Science : Theoretical Perfections Against Practical Values : Qliding Speeds and Distances : More Muddled Thinking C'iG ago 1 regretfully came to the conclusion that people in general were far too easily blinded by science and, m particular, by formula; and statistical figures. Anybody can prove almost anything by reference to statis tics—mostly phoney—and the sight of a lot of mathe matical formula; in a book, or an article, or a letter in the correspondence pages, reduces the average person to over awed silence. An enormous amount of nonsense is let past by otherwise intelligent people who have this '' figure complex." Anybody can try it out quite easilyand with huge success on a bunch of people engaged^Jfk^L general conversation. Let there be disagreement, for instance, on the subject of flying training or medical research; all you have to do in clinching an argument is to say: "Do you know that 72.37^^>*atemerrtsv per cent, of the flying accidents in this country are duff to overshooting ? " or: " Are you aware that no fewer than 38.69 per cent, of the deaths from disease in this country last year were the result of initially incorrect diagnoses? " and all your opponents fade out immediately. The two ligurps after the decimal point are the telling^ usVsaying, "about thirty per cent." or "a* Of course, the trick shouldn't be used too olp very professional people, or unless one own essential Tightness. If the trick is becomes suspect; amongst experts there is least one who knows the right answer; an sure of yourself you cannot possibly give the right degree of emphasis and conviction. . _s* Because of this human weakness I think the greatest danger to which the race is subject is that of being dominated by the so-convincing theorists and consequently being moulded into a new and unhappy shape, or that of having the social aifd industrial structure re-made so " per fectly " that nojrtocly will ever again be happy. Building to Formula The danger can be seen everywhere. Just look at all the "world's best aircraft" nonsense. One day the Powers That Be may get hold of a formula which strikes their fancy, and so decide to build only those military or civil aircraft which reach top figures. Ajad in nine cases out of ten the decision would be an utterly wrong one, because no allowance would be made for the opinions and prefer ences of the crews who have: to fly them, or of the passen gers who are to be carried. It would not be too much to say that the success of certain military types in this war has been the result rather of good inherent characteristics than- of sheer performance as such. If the Spitfire or the Hurricane, for instance, had t>een less good as fighting machines, their pilots would still have done well if they'd liked flying them and been confi dent in their structural strength. The pilots would, in fact, have done better even with inferior types than with uncomfortable aud dangerous devices with a startling per formance. At least one remarkable day bomber is likely to disappear from use because its take-off and near-ground handling characteristics are more than can be reliably coped with by the average pilot. Nobody imagines that the British heavy bomber would have done such good work if the load- carrying capacity had been obtained at the expense of good handling qualities or ease of operation or simplicity of maintenance—all qualities which cannot jre given a fair figure in any formula. Wing loading, for instance, offers no criterion of manceuvreability; there are bad aircraft with low wing-loadings and good aircraft with quite phenomenally high loadings. Formula figures would have to be included for control weight, the crew's move-about- ability, stability in cloud-flying .conditions, and a host of other things if any sort of fair comparison was to be made —and the test pilot and / or the squadron pilot would scrub the whole thing if he just happened not to like the machine very much! In just the same way figures can be used to support the most cock-and-bull statements about aircraft handling— and some shocking faux pas are made daily by people who should know better—myself no doubt included from time to time. I hadn't been following very closely the corre spondence in Flight a jew weeks ago about gliding speeds and distances, but ]r did see one or two extraordinary ime and Distance ' it the time, appear to me to be anything abstruse about the problem, whatever it aijrcraft has its most "economical" gliding atteVs of time and distance, and this speed Cording to the all-up weight. Obviously a heavfly- aircraf,f has a higher stalling speed, a higher " sink- peed/ and, consequently, a higher "economical" spe€d. Other things being equal, an aircraft with -will stay in the air longer because its wing-loading lower and its gliding angle flatter. The faster it is flown above the optimum figure, the greater will be the necessary drag and the sooner it will reach the ground. If the mass of air in which one is flying happens to be moving at, say, 30 m.p.h. in the same direction, it will obviously pay one to keep as near as possible to the best figure; if it is moving in the opposite direction then, after a series of calculations in time and distance, it might be found to pay to be prepared to reach the ground a little sooner (the result of increased drag in the ordinary way), but, consequent on the increased ground speed, a little farther 011. One can so easily quote the extreme case of the light aircraft in which the best gliding speed happens to be the speed at which the air, on that day, is moving; in order to land anywhere but on a spot immediately under neath, it will be necessary to fly faster and to lose flying time but gain distance. It's all rather like the old handicapping problems in peacetime air racing. Unless the handicappers allowed for the average strength of the wind on the day of the' race, and there happened to be half a gale blowing, the slower machines would be right out of the race—simply because they spend so much longer (at a low ground speed) covering the up-wind legs of the course, while not spending proportionately longer on the down-wind legs. The Moving Medium The great thing is not to consider whether an aircraft is flying, up-wind or down-wind, but to treat it as flying quite normally, at its usual speed, in a mass of air which happens to be crossing the country at a certain speed. Unless it is near the ground—and consequently affected by gusts and ground-deflected masses of air—wind speed and direction haven't the slightest effect on an aircraft's flying characteristics or its various "economical" speeds except in so far as the time factor enters into the problem. Perhaps it would be better still for the " argifiers" to imagine the aircraft flying along while some strong and important chap shifts the earth bodily along while t&e pilot isn't looking; that's all that happens in effect, and it becomes a nuisance and a matter for furious calculations
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