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Aviation History
1938
1938 - 0352.PDF
-122 FLIGHT. FEBRUARY IO, 1938. fighters and bombers "for the duration." It has not even seemed verv keen to have Army officers trained as air pilots, and when the number was increased a few years ago the initiative came from the Air Ministry. The seriousness of the situation is this. If war broke out and the Army had to move overseas, as in 1914, it would, of course, take with it the army co-operation squadrons which have been trained to work with it. Leav- ing aside for the moment the question of whether there are enough of these squadrons for the Army's needs, it is quite certain that co-operation squadrons would not be able to do all the classes of air work which the Army would require. They are merely reconnaissance squadrons —eyes in the air. They are not prepared to carry out ground attacks on troops, which they regard as the func- tion of fighter squadrons, and their powers as bombers are not extensive. To use them as fighters or bombers would, in fact, run the risk of depriving the Army of reconnaissance, which is quite vital. It would seem that the War Office hopes that the Air Ministry will lend it some squadrons of fighters and bombers as it has always done for manoeuvres. But is that hope well founded? If heavy air attacks were being made by the enemy on Great Britain, it is. unthinkable that the Fighter Com- mand or the Bomber Command would agree to part with any of their squadrons. The prospect of such a refusal would create a very serious situation, and might result in the Army's defeat. Until such an impasse has been made impossible we cannot say that our defences are in a healthy condition. Optimum AltitudeS OME of the fantastic theories which have been ad- vanced on the subject of sub-stratosphere flying are ably exploded by a contributor to our American con- temporary, Western Flying. He suggests that 20,000ft. will be the most advantageous height for some time to come and quotes as an instance of how little operating speed may be raised by increasing height figures for the new Boeing 307-S four-engined transport under construc- tion for Pan-American Airways, which, according to esti- mates, will be capable of 269 m.p.h. at 25,000ft., using 75 per cent, power. It has been calculated that at 30,000ft., with the engines at full throttle, a gain of only 1.67 m.p.h. would be obtained, and, to quote the author, "to get any more than that 1.67 m.p.h. would require engine gadgets much too costly for any sustained flight operation, at least for some years to come." Discoursing on the benefit to be derived from the '' thin air " at great altitudes, the writer explains that at 20,000ft. more than half this benefit is obtained, but, he proceeds, " to get just 25 per cent, more of that stratosphere benefit planes would have to go clear up to 40,000ft." To put it more simply, by climbing 20,000ft. higher (which would be much harder) would do only half as much good as the first 20,000. The precise advantages conferred by operation around the 20,000ft. level will soon be demonstrated by "Pan- Ams.' " first pair of 307-Ss, which, like many another useful development in commercial flying, are largely the out- come of research conducted by that company's brilliant technical staff. Nor is Pan-American alone in its contention that 20,000ft. is the present optimum height for continuous commercial operation, for Transcontinental and Western Air, which is pursuing a programme of intensive high- altitude flying, is said to concur. Getting the Load AcrossI T has now become possible to reveal the fact that the eight flying boats ordered by Imperial Airways from Short Brothers will be specially strengthened in order that their maximum permissible gross weight may be in- creased from the 45,000 lb. of the two long-range boats Caledonia and Cambria to some 52,000-53,000 lb. The two older boats have but little pay load over and above the fuel for the westward Atlantic flight. If they are to carry a reasonable pay load, their gross weight will have to be increased. It is thought, from the take-off tests made at 45,000 lb., that the boats will be able to get off under their own power at 50,000 lb. gross weight at least and probably more. As the addition contemplated is 8,000 lb., there should be a sufficient margin for structural strengthening, still leaving some 5,000 lb. for pay load Whatever success may ultimately be achieved by the Short-Mayo composite aircraft, the existing upper compo- nent, Mercury, is designed for a pay load of 1,000 lb. only and if the eight Short boats can get off under their owii power with a pay load of 5,000 lb. or so, an experimental Atlantic mail service may be a possibility towards the end of the coming summer. Refuelling in the air is another form of '' assisted take- off " which comes into the picture in this connection. Sir Alan Cobham has been working on the problems for many months, and recently a successful refuelling flight was made (see Flight of January 27, 1938). The system is similar to that developed at Farnborough, and, provided thick weather does not prevent contact being made, the technical problems appear to be fairly well solved. At any rate, Imperial Airways may be congratulated on looking ahead and, getting ready to take advantage of any development likely to be made in the near future. Easier ApproachT HE technique of the flapped approach must of necessity develop parallel with increasing perform- ance, and various attempts are being made abroad to facilitate the landing characteristics of heavily loaded high-speed monoplanes. One of the most practical of these seems to have been made in the new Junkers Ju.90 four-engined transport, which may be regarded as Ger- many's "Ensign." Not only is this huge machine pro- vided with the latest version of the familiar Junkers "double-wing" arrangement, but it is fitted, in addition, with an auxiliary split flap. This combination, according to Junkers technicians, offers the following advantages: On the approach the '' double-wing '' flaps are lowered to the fullest extent, the machine then being set at a good gliding angle. On crossing the boundary the pilot also opens the split flap, the increased braking action of which makes the glide even steeper. The system has proved particularly effective for blind landing, the split flap then not being opened until the machine passes over the main beacon or receives the ZZ signal. In America the Seversky concern is using a three-piece flap, the centre part being of the split type whereas the outboard units are really sections of the trailing edge. Though the outer panels may be operated independently of the centre panel, combined operation is available for landing, the outboard sections being lowered automatic- ally before the central portion at what is described by the manufacturers as "the most efficient interval." Take-oft and climb are benefited by judicious use of the outer sec- tions, the central portion, of course, being intended solely as a landing " discelerator." It does seem, judging from results obtained with the Junkers and Seversky flap systems, that a welcome im- provement can be obtained in the landing characteristics of a typical monoplane by the increased application 01 proven technique. Where the Seaplane ScoresA FEW weeks ago comment was made in Flight on the incident when an Imperial Airways flying boat returning to Southampton found fog over the land- ing place off Hythe, and accordingly alighted on the water outside the murky area and taxied up Southampton Water. A landplane in similar circumstances would not have been able to get its passengers to their destination. Now another instance of the advantage of the seaplane comes to hand. When Signor Mario Stoppani was forced to put his machine on the water 120 miles off the coast 01 DIARY OF FORTHCOMING EVENTS—PAGE 146
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