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Aviation History
1946
1946 - 0754.PDF
388 FLIGHT "Indicator" Discusses Topics of the Day APRIL ISTH, 1940 In Praise of Ourselves; The Air Speed Record Situation : What We Have in Hand : The Jet Fuel Question A SOMEWHAT uneasy silence appears to have fallenon the American air-speed record experiments.Presumably development work is still proceeding, . while technicians do their best to find some means of super- ficial re-design which'will put up the Mach number on the P-80 and permit it to make use of the available thrust. Certainly, judging from all that one hears, the Shooting Star appears to be quite an exceptionally good aircraft up to its natural limiting speed—which is probably in the region of 570 m.p.h. with its present intake arrangements and general shape. The few British pilots who have flown it are enthusiastic about its handling qualities at all speeds up to this limit, whatever it may be, and certainly about the technical perfections of its various electrical and other installations. But there seems to be no doubt that, unless the various "shapes" can be suitably re-designed, there is not much hope that speeds of the record-breaking order will be possible, whatever thrust may be available. Apart from any control peculiarities at high Mach numbers, the standard P-80 appears to run into a '' wall'' soon after the critical number has been reached. In the meantime—and so that our friends across the Atlantic may not feel less than the appropriate amount of despondency to match our own in matters of immediate civil aircraft production—it might be as well to say a word or two about our own high-speed position. One way or another the basically five-year-old Meteor appears to be very much more than holding its own in the matter of sheer performance. Even at the time of the record attempt at Herne Bay, the pilots certainly seemed to be quite confident that the record could have been safely broken by a very much greater margin had more thrust been laid on. Develop- ment flying by Glosters appears to have effectively shown that, even if the Americans were to be successful in jump- ing our record claim by the requisite amount, we could ourselves go right ahead and improve at least on any reasonable figure which may be set up. And unreasonable speeds can hardly be expected at this stage of aircraft development. Present Prospects Iii fact, were it not for the considerable amount of expen- sive and time-wasting organization required before any intermediate attempt on the record, this could now be handsomely re-broken—and at a figure which, it is reason- able to suppose, would considerably exceed that so pleasant round figure of 1,000 kilometres an hour. This after all, is only a matter of 621.4 m.p.h., and casual gossip puts the Meteor's possible level maximum at 630 m.p.h. or more. It would certainly be rash to make a guess at the handle- able maximum of which the Meteor is capable, but Mach numbers up to and over an order of 0.84 have already been reached on test with everthing in fairly good order. And there does not appear to be any shortage of available thrust from existing power units. This particular Mach figure, if •the conversions produced by ray guesiing Stick are not too wildly inaccurate, gives a sea level speed of 640 m.p.h. Curiously enough, the Meteor's critical Mach number— 1hat at which local airflow reaches the speed of sound— is about 6.76, yet no drag rise occurs even at a level speed figure equivalent to 0.80, and the introduction of the lengthened nacelles has also considerably improved the high-speed handling qualities. From all that one hears, there is no tendency for this particular aircraft to become nose-heavy, in the usual way, at high Mach numbers—in fact, the tendency appears to be rather the other way—and as a matter of interest even the production Meteor has the very high "official" design limitations of 600 m.p.h. for indicated air speed and 0.85 for the Mach number. Of course, though all recorded high-speed figures are J& immensely useful from the propaganda point of view, the real value of the enormous thrusts which are now available for fighters lies in the very considerable increases which are possible in rates of climb for interception purposes. The ability of an aircraft to reach really high speeds and to remain under comfortable control at these speeds will always be vitally important in air warfare, but rate of climb appears now to be the priority target in fighter design. The highest fighter climb figure which has so far been publicly given is, in fact, that of the Meteor IV, which has a sea-level rate of 8,300 ft/min, and reaches 30,000ft in rather less than five minutes. According to calculations, the height at which a rate of climb of 500 ft/min can still be maintained is 53,000ft—which is not too bad for the time being. The expression "according to calculations," in this case,brings one to another point in the fighter development story. Needless to say, nobody has been to 53,000ft inthe Meteor or any other standard fighter; altitudes of such an order will not be practicable in normal operationalflying until high-pressure cabins can be organized. Inci- dentally, I believe that the P-80, amongst its other in-genious and technically exciting features, has a device in the pressurization system by which this pressure is whollyor partly released when the gun buttons are set for " fire." The idea being to prepare the interior for any possible"strike" damage and too-sudden de-pressurization. Fireworthiaess . While on the subject of jet aircraft, there seems to be atendency nowadays towards the idea of returning to the use of low-octane petrol rather than kerosene. Though Iconfess to partial ignorance of the various pros and cons, this does seem to me, as a superficial observer, to be apainfully retrograde step. In one fell swoop we seem to be throwing away the chance both of making aircraft alittle less fireworthy and of improving consumption figures. On the side of the supporters of the change-over there are,no doubt, a number of temporarily important advantages to be gained. We all know that trouble is being experi-enced with carburation—if it can so be called—at high altitudes, and that there is a tendency for the "fires" togo out in the consequent rich-mixture conditions. Fur- thermore, any re-lighting is problematical until the air- fcraft, has returned to much lower altitudes—by which time the units are likely to be stone-cold and re-lighting isstill not easy. The use of low-octane petrol would no doubt deal effectively with such faults. It may eventually be decided that high-altitude com-bustion difficulties with kerosene cannot easily be over- come, and that the loss of fire-safety, and the increasedconsumption are ivorth while, in balance, for the advan tages gained. But, on the face of it, there are surely soimobvious ways out of the impasse. Experiments might be made, for instance, with a slightly mpre volatile fuel whichcould be carried in a separate tank and fed when nece* sary to the jets, with the normal fuel, under suitable baro- ;metric control. Again, a small petrol supplv might h carried solely for relighting purposes. Nobody is going t<>tell me that our technicians are likely to be defeated bv this or any other difficulty, and I certainly feel that weshould stick to kerosene if it is at all possible to do so.
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