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Aviation History
1943
1943 - 0945.PDF
AIRCRAFT ENGINEER FIRST AERONAUTICAL WEEKLY IN THE WORLD •• FOUNDED WO9 Editor C. M. POULSEN Managing Editor G. GEOFFREY SMITH, M.B.E. Chief Photographer JOHN YOXALL Editorial, Advertising and Publishing Offices: DORSET HOUSE, STAMFORD STREET, LONDON, S.E.I Telegrams : Truditur, Sedist, London. COVENTRY : 8-10. CORPORATION ST. Telegrams : Autocar, Coventry. Telephone: Coventry 52 10. BIRMINGHAM, 2 : GUILDHALL BUILDINGS, NAVIGATION ST. Telegrams: Autopress, Birmingham. Telephone: Midland 297 1 (5 lines). Telephone: Waterloo 3333 (35 lines). MANCHESTER, 1 : GLASGOW, C.2 : 260, DEANSGATE. 26B, RENFIELD ST. - Telegrams : lliffe, Manchester. Telegrams : Iliffe, Glasgow. Telephone : Blackfriars 4412. Telephone: Central 4857. No. 1790. Vol. XUII. Registered at the G.P.O. as a Newspaper. April 15th, 1943. Thursdays, One Shilling^ Outlook Aii Elusive IdealS UGGESTIONS for post-war air transport designs nearly always include tailless types. It is very natural that this should be so. Superficially the tailless is undoubtedly "clean," and as the authors of an article in this issue point out, the rear portion of a fuselage cannot in any case be used for housing heavy loads, owing to the need for keeping the centre of gravity of the aircraft in its proper place. The idea of tailless aircraft is, of course, almost as old as flying itself. Professor Hugo Junkers visualised it in about 1909, and, indeed, took out patents on what he termed a Nurfiiigel (all-wing) design. But in those days we did not know a great deal about stability, the most delicate aspect of tailless design. There were excep- tions, of course. For example, Col. J. W. Dunne, who in more recent years has occupied himself with the even more complicated subject of relativity, realised the advantages and disadvantages of the tailless type. He foresaw that to get longitudinal stability it was necessary to sweep back the wings sharply so as to get the wing- tip control surfaces (they were elevators and ailerons combined) well aft of the centre of gravity, thus giving them a reasonable "lever arm" to work upon. That was in 1910-11-12. Later, in fact during the years between the wars. Cap- tain Geoffrey Hill revived the tailless ideal with his Pterodactyls'. In them the sweep-back was rather less pronounced than in the Dunne, but still fairly consider- able. Shoitly before the outbreak of the present war Handiey Page was experimenting with a tailless design, of which a flying scale model was built but not, so far as we know, ever flown.- Still more recently Jack North- rop has built a flying scale model in California. It underwent many modifications, notably to its wing tips, and the sweep-back in this type was relatively slight. The point to note here is that the natural process of "evolution of the tailless appears to have been towards nearly straight wings, with the elevator control surfaces working on a very short lever arm. In one of the designs in this issue this lever arm has become very short in- deed (the technicians talk of control surface "volume, ' which is meant to convey the product of area and lexer arm), and one wonders how the designers expect fo obtain not only control but stability. Both must be achieved, for an aircraft of this size which was control- lable but unstable would be a dangerous proposition, and one that was stable but uncontrollable would be little better. Stability and Control Qt)ITE earl / in the history of flying it was dis-covered that a wing section could be made in-herently stable by reflexing (that is to say, up- turning) its trailing edge. That was in the days before the discovery" of the split trailing-edge flap, and it was found that the maximum lift coefficient was rather dis- appointingly low. Split or slotted flaps can be made to restore the lift, but probably not in conjunction with a trailing-edge reflexed sufficiently to give the desired longitudinal stability. Directional stability is another difficulty. Col. Dunne used large fins and rudders at the wing tips. His example was largely followed by Hill. Northrop tried other means ; he tilted the wing tips down at a sharp angle. Insufficient information has been published to enable one to know whether the tilted Northrop tips worked in the way they were intended to work. Those of the six-engined design by Pollitt and Laver in this issue appear totally inadequate, especially in view of the
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