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Aviation History
1955
1955 - 1721.PDF
840 FUGHT * MORE THOUGHTS ON THE P.I (continued from page 837) the supersonic drag of the F.I as a complete aircraft would bevery much lower. Together with its ability to bury its engines in the optimum shape of fuselage, this could well explain theapparent ability of the English Electric fighter to climb super- sonically on two turbojets of moderate thrust without reheat. It is, of course, possible to improve the performance of pre-area rule aircraft by adding to or subtracting from the cross- section of the fuselage at various stations, and this has in factbeen done on some American designs. These belated attempts to make use of aerodynamic theory, much of which has been avail-able for many years, cannot achieve the optimum result possible in a design which is area ruled from the start. Bulges andnipped-in waists are thought of as the hallmark of the area rule; but such an outlook is completely incorrect. The best super-sonic aircraft have no such distinguishing features and any design which has is merely betraying the fact that it was in-correctly planned at the outset. Thus, if the original design in our illustration (p. 837) had suffi-cient volume for its purpose, then an area-ruled development will have too much. Excessive volume can cause nearly as muchsupersonic drag as can a poor shape. For example, if the volume is 20 per cent more than it need be, G. N. Ward's formula sug-gests that the wave drag will be 44 per cent more than that of an aircraft having the same length and shape of area curve.Moreover, bulges can result in a weight penalty—particularly when they represent a modification of an existing design—whichbecomes severe for interceptions at 50,000ft or above. Alterna- tively, the loads set up in fuselage frames may be significant evenwhen a double-curvature skin is assumed from the outset. It is also apparent that area ruling as a modification cannot be carriedto extremes in correcting a basically poor shape. Taking an extreme (absurd) example, if a cylindrical aerialmast were mounted on a supersonic fighter, the simple concep- tion of the area rule would suggest that its drag could be reducedto zero by cutting out a cylindrical hole in the fuselage plating anywhere in line with the aerial. In practice, however, thiswould actually result in a drag roughly equal to that of the aerial plus that of the hole. This result could be changed appreciablyonly if the aerial mast were made extremely slender, and the hole likewise, the latter being adjacent to the mast. This con-ception of smooth, slender shapes is an assumption in the mathe- matical analysis upon which the area rule is based. (Flight,November 18th, 1955.) No information has been released either in this country or theU.S.A. on the nature of the area rule for higher supersonic speeds, although the expert in fluid mechanics could deviseappropriate rules from the wealth of aerodynamic theory that has already been published. But it does not need an expert torealise that a bulge designed for transonic Mach numbers will be wrongly shaped for higher Mach numbers and beyond agiven Mach limit can actually increase the drag. At these speeds, the various components of the aircraft become less interdependentso that a good shape will be required for each individual com- ponent. Nevertheless, it is possible to design a fighter such that,although area rule is followed to reduce transonic interference drag, the overall shape is also suitable for high supersonic Machnumbers with considerably inclined shocks. Undoubtedly the best American example is the Chance Vought F8U Crusader, anaircraft of the P.I generation and not dissimilar from the British fighter in its shape of fuselage. A notable feature of this designis its high-mounted wing, which is particularly beneficial in reducing interference drag and in altering the flow of the stream-lines across the aircraft as little as possible. In contrast, the Lockheed F-104 design does not have a highwing, neither was it—in its conception at any rate—an area rule aircraft. On the other hand, the principles of its design aredefinitely weighted in favour of the supersonic regime, and the wing is of such small frontal area and volume as to be of lessthan usual significance in plotting the axial distribution of area. Two other contemporary supersonic shapes of exceptionalinterest are those of the Fairey F.D.2 and the SAAB 35, both of which are remarkable approaches to the problem of obtaining thehighest possible performance from a single afterburning turbojet —a Rolls-Royce Avon in each case. The British aircraft has atrue delta wing, of extremely low thickness/chord ratio, carried right up to the fuselage and meeting the latter at the mid position.The Swedish aircraft employs the double-delta configuration which, although less "clean-limbed", provides increased stow-age space without penalizing the distribution of area. None of the aircraft mentioned showed any obvious evidence ofmeeting area-rule requirements for minimum transonic drag. In the P.I, for example, nothing is apparent which should com-promise the achievement of considerably increased Mach numbers when more powerful engines, with afterburners, becomeavailable. The importance of this trend towards more economical supersonic flight is apparent not only for the bomber but alsofor the fighter, which must maintain a supersonic cruising speed in order to intercept fast bombers well away from its base. The P.I appears to introduce a new era of aerodynamicshapes that will make the achievement of supersonic flight much easier and cheaper whilst retaining good characteristics through-out the transonic range-—and also, incidentally, down to ex- tremely low indicated airspeeds. It will be interesting to seewhat changes are made to the aerodynamic shape of the P.I as the emphasis eventually turns to the upper end of the Machscale. One may certainly expect revision of the main intake to avoid the occurrence of a single normal shock (we suggested this whenwe first referred to the aircraft over a year ago). Apart from this there may, in fact, be few superficial changes, for fightersmust retain the ability to intercept subsonic aircraft for many years to come. THE AERONAUTICAL BOOKSHELF "I Burned My Fingers" by William Simpson. Putnam, 42 Great Russell Street, London, W.C.I. Price 18s.O N the afternoon of May 10th, 1940, a Fairey Battle of theAdvanced Air Striking Force was hit by light flak while attacking a German column advancing into Luxembourg. Unableto reach his base, the pilot landed in a small field in the Belgian Ardennes, where the Battle burst into flames. The pilot wastrapped in his seat, but the observer and the radio operator/gunner managed to drag him clear and roll him in the grass, "smoulder-ing like a dying torch," his face, hands and legs savagely burned. That pilot, S/L. William Simpson, O.B.E., D.F.C., now tellsthe story of his long struggle to recover from his injuries, regain a normal place in society and to assist others similarly afflicted.As indicated, perhaps, by the tide—7 Burned my Fingers—this is a candid book which comes straight to the subject. Sensibly,the author neither dramatizes nor sugar-coats such topics as the physical and mental effects of disfigurement and plastic surgery.Any other approach might have defeated the object of the book, either by giving too rosy an impression of the very real but notunsurmountable problems faced by the "Guinea Pigs," or by hardening the reader's natural reluctance to associate himself withtheir suffering. I Burned my Fingers is a success story. Its author's woundshave healed, and though the scars remain he enjoys good health; his life is "full to overflowing, free and independent." His workas a member of the National Advisory Council on the Employment of the Disabled for the past ten years has won him an O.B.E.We on Flight know Bill Simpson well as chief Press and informa- tion officer of B.E.A., a job which, he says, "has kept me going most hours of the day and often some hours of the night." Hisappointment has enabled him to practise his belief that the dis- abled person "ought deliberately to make himself conspicuous inhis disablement—not only for his own sake, but to help others." Simpson stresses that die scarred and disabled want not senti-mental pity but encouragement and understanding: "We are more conscious of our remaining abilities than our obvious or hiddendisabilities. We do not want anyone to feel sorry for us. We just want to be treated as equals and allowed and where necessaryhelped to live normal lives." Bill Simpson himself is today widely known and respected within and beyond aviation circles. Hisvery readable book will increase that recognition and respect. "A Picture History of Flight," by John W. R. Taylor. HultonPress Ltd., Shoe Lane, London, E.C.4. Illustrated. Price 25s. NOBODY was better qualified to undertake this work dianJohn W. R. Taylor, still-youthful doyen of aeronautical archivists (though the dry-as-dust implication of die term is un-fortunate, for Mr. Taylor's writing is always clear and bright). The book is a glossy quarto comprising some 190 pages whereinappear 648—no less—pictures, garnered from varied sources in many countries and each concisely and informatively captioned.The pages of commentary and introduction are a valuable con- tribution in themselves, and a few hours' browsing through diebook (for it is the kind that invites infinite browsing) will equip a person with as much air-history as he is likely to need andafford him die utmost pleasure in its acquisition. A book, thi?, for the shelf by die fire; a must for the schoollibrary, or any other library; and one to watch out for in the mess.
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