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Aviation History
1958
1958 - 0301.PDF
FLIGHT, 7 March 1958 315 (T) Straight and Level I WANT to hand a small bouquet toA.W.A., which stands for Sir W. G.Armstrong Whitworth Aircraft. Several recent A.W.A. achievements deserve it, but this one is for the overall manner in which the company are handling their A.W.650 transport programme. First, they have pub- lished a detailed schedule of what will be done and when. Second, they know what their market is; they are really interested in that market; and they are not basing their design on a hunch by the board or a world-wide trip by a sales executive who stops off at every operator, sees one man and says "four engines or two?" Third, they are bring- ing everybody in on the ground floor; B.A.L.P.A., for example, really have had a finger in the pie with the 650 flight deck. Fourth, the whole Hawker Sid- deley Group are marshalling all their mighty resources to build and develop the 650; it is almost the first British aeroplane in recent years to enjoy a design and engineering strength, both in men and facilities, fully equal to that applied to comparable programmes in the U.S.A. Finally, A.W.A. are keeping every interested person fully informed. These factors add up to one thing: this is the Group's firm entry into the civil market, and they are showing every- body how such a programme should be undertaken. • All other things being equal— which, of course, they never are—it's always better to make an aeroplane pressurized, if there is any choice at all. Even DC-3s could do a far more com- petitive job if they had a pound or two of pressure differential, and pressuriza- tion even helps in the carriage of several kinds of freight—quite apart from being essential to the high-altitude transpor- tation of live animals. A typical, and unexpected, disadvantage of the un- pressurized freighter is that it cannot carry wool unless the cruising altitude is held below about 8,000ft. Exposure of bulk wool to ambient conditions above this height results in a loss of about half the weight of the shipment. • Going on from the above I have been led to wonder whether we couldn't eliminate some of our present complex pressurization systems and rely on ram pressure (obtained from simple forward- facing intakes). At 400 m.p.h. at 20,000ft a theoretical maximum pressure of 3in of mercury can be obtained by this means —i.e., about 1.5 lb/sq in. But at 600 m.p.h. the recovery can reach a ratio of almost 1.6, sufficient to maintain a cabin altitude of about 7,500ft at a true height of 19,000ft (dP greater than 4 lb/sq in), and at the present world speed record of 1,207 m.p.h. (subject to homologa- tion, as the F.A.I, says) one could hold sea-level pressure right up to 42,500ft. At sea level the theoretical ram pres- sure in the cockpit could have reached 180 lb/sqin! • Yet a further thought arising out of this is what would happen to certain fast aeroplanes if they should suddenly be deprived of their windscreens. In practice, of course, the airflow around the nose and cockpit invariably gives rise to substantial negative pressure, so that—particularly at high altitude, with the cockpit pressurized—loss of the windscreen would mean drastic reduc- tion in interior pressure. There are, however, theoretical conditions which, if met, cause the pressurizarion and ram pressure to cancel each other out. For example, an aeroplane doing Mach 1.05 at 17,500ft can generate a full-recovery ram pressure of 15in of mercury, just the same as the ambient pressure. Add- ing both together one is left with a cockpit pressure of 30—the same as at sea level. It should, therefore, be pos- sible to work out a flight-plan whereby, through increasing speed as height is gained, it is possible to maintain sea- level conditions inside and eliminate the windscreen (I think). • Do you recall my pictures of January 24 illustrating the car fin- styling cult? American car-body stylists, influenced by the aeroplane, added fins; aeroplane paint-scheme stylists promptly painted mock fins on their real fins. Now look what's happened: the Cessna 180 seen below has a mock air- intake on its flank, in imitation of the Cadillac Eldorado, whose mock side- intake was in imitation of I don't know what. Soon, Jupiter and Thor will have imitation twin-headlamps and radiator grilles as a logical follow-up to the new Pontiac convertible, seen in my other picture with rocket and shock-diamonds, all in rich gold and chrome plate. I suppose the ultimate absurdity would be a Caravelle with a third jet painted on it. Actually that wouldn't be so silly, if it led Sud-Aviation to make it real, as I feel they eventually will. They have already thought about it, as you can see in the Civil Aviation section of this issue. In the meantime, the French have really hit the short- haul jet jackpot with the Caravelle. • In our issue of June 14 last year we published an article by Alan Yates en- titled "Accuracy and Commonsense." In it he made the point, so obvious, but so often overlooked, that what usually matters in most walks of life is to get a quick approximation. Every day a mil- lion—yes, I mean that—man-hours are thrown away by people trying to get accurate answers to simple sums. House- wives working out budgets, project designers laying down the initial wing- area equations, economists studying the world's income-groups, all need a reli- able answer correct to plus or minus perhaps 20 or 30 per cent. Nine times out of ten they spend a whole day col- lecting data and another six hours try- ing to get a result correct to six places of decimals, completely overlooking the fact that half their data figures are only very rough approximations to start with. As likely as not they will make a slip somewhere and end up with ten signi- ficant figures and the decimal point in the wrong place. What one must at least try to do is to obtain a picture of what the answer is likely to be (although even this can sometimes be dangerous). The good engineer can merely look at a problem and say "the answer is between 45 and 50." The next-best man does it with a slide-rule, and takes a bit longer. Which reminds me, you have to watch those slide-rules; I just divided 68 by 17 and made the answer 3.95. This sort of thing is done every second of every day. • Most idealists mean well, but I am sure there is no place for them in a modern aircraft industry. If your in- dustry is run by practical men the result is a lot of imperfect aircraft doing a use- ful job; but if you have too many idealists the result is a lot of equally imperfect aircraft doing no useful work at all. ROGER BACON
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