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Aviation History
1946
1946 - 1489.PDF
AUGUST IST, 1946 FLIGHT body forms. In some designs horizontal tail surfaces will be eliminated ; in others they will be set at a sharp dihedral and displace the fin. Alternatively, a monstrous growth of the fin may, in effect, become a boom carrying the horizontal surfaces sufficiently far aft of the e.g. and clear of the jet stream, A tricycle undercarriage will generally be chosen, but stowage will promote acute difficulties. One of the most interesting, if perplexing, design prob- lems will be the location of the power plant and air intakes. Many solutions which appear ideal on paper will prove inadmissible because they restrict breathing, promote undue duct losses or compromise maintenance. I The configuration of the axial-flow turbine-jet readily permits external attachment to an airframe. This attribute was effectively exploited on the German Ju 287 prototype bomber, on which various jet combinations were possible, an<f on some Blohm and Voss asymmetric designs, but the classic illustration is the Heinkel Volksjaeger on which the BMW 003 unit is mounted on top of the fuselage. No fighter having an external jet unit below the fuse- lage has materialized, designers having preferred to develop, this concept into a buried, lower-fuselage installation. The latter layout was, in fact, favoured by the principal German designers for their new single-jet fighter projects. A long intake duct, undercarriage stowage difficulty and the neces- sity for making wheels-up landings more or less on the jet unit itself were disadvantages. Accessibility Undesirable duct length or curvature and exasperating inaccessibility must be contended with in the true buried installation, exemplified in the Lockheed P-80 Shooting Star, Republic XP 84, Ryan Fireball and Messerschmitt Pino, though on the sqore of maintenance the possibility has been successfully demonstrated both in the Shooting Star and the Ryan Fireball of disconnecting the rear fuse- lage as a unit. On the Republic fighter zip-fasteners are applied to the intake duct to afford access to the front of the turbine jet. In certain installations boundary layer suction may be necessary to reduce entry losses. Simplicity and accessibility are offered by mounting the power plant in a nacelle and supporting the tail surfaces on booms, but at high Mach numbers this may induce severe down-loads on the tail. Though doubtless aware of this theoretical restriction the de Havilland Company pro- ceeded with the twin-boom Vampire (just as the D.H. jet team adhered to the single-sided compressor), while in Germany Focke-Wulf abandoned the Vampire arrange- The deep wing roots of the McDonnell FD-i (Phantom)deck-landing fighter of the U.S. Navy, house two axial-flow Westinghouse turbine jets. The gross weight of this neatfighter is under 10,000 lb. A Heinkel single-jet proposal with the intake between twonacelles, one housing the nose wheel and armament, the other accommodating the pilot. ment which they had considered in the early design stages of the Ta 183. A similar scheme has been studied by the Swedes for a jet fighter of their own design. Whatever its future, the Vampire design has served its purpose well: it has made possible rapid production of a sound single-jet fighter with adequate performance and first-class handling qualities. Future D.H. fighters will doubtless reflect experience the company is now acquiring with the D.H. 108 research aircraft. With the twin-boom arrangement a straight-through duct with nose entry is a possible alternative to the wing root intakes used on the Vampire ; as on any fuselage or nacelle installation, scoops on the fuselage sides might be adopted. Similar nacelle and intake arrangements could be retained for a tailless or semi-tailless design, the latter having only vertical surfaces and being exemplified by the D.H. 108 and certain Messerschmitt and Heinkel designs. Annular Intakes The annular intake round the fuselage, with pilot and/01 armament in the nose portion, as in the Miles M 52 super- sonic project (now shelved), is an interesting possibility. The Russians are believed to have designed a fighter along these lines, in which the nose cone houses the guns. Equally striking but less promising is the mounting oi a turbine-jet unit in the nose of the fuselage with the efflux at the sides and beneath, as on certain radial piston-engine installations. This scheme was at one time proposed for a jet version of the Fw 190, using a radial-flow Focke- Wulf unit. In planning a twin-jet fighter the designer has the choice of installing the units on the wing (Gloster Meteor and Me 262A), or in the wing roots (McDonnell FD 1 and Me 262 HG III). He may bury them partially in the fuse- lages sides (Bell XP-83) or place one above and one below the fuselage (Gotha P.60). A side-by-side layout above or below the fuselage is a further possibility (Arado Night Fighter Project 1) or the units may be disposed side-by side or superimposed inside the fuselage (Focke-Wuli Night Fighter III and Bv P.215). The Meteor, with its long and bulky wing-mounted nacelles, holds the world's speed record, lending weight to its designer's contention that this arrangement belies the first impression of being less favourable for high-speed development than a single-jet design. Although the low- speed drag of the twin may be as much as 50 per cent higher, the critical factor is percentage increase in drag, and experience is beginning to show that wing nacelles do not greatly influence the rise in drag due to compressibility. They are three-dimensional bodies, and Mr. Carter believes that if precautions are preserved to harmonize the asso- ciated air-flow characteristics of wing and nacelle, super- sonic flight may be accomplished. Against this promise must be set the increased inertia in roll and yaw of a fighter with wing-mounted units. It has lately been an-
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