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Aviation History
1950
1950 - 0168.PDF
FLIGHT. 26 January 1950 jg H t e r s . the normal Thunderjet. However efficient an intake may be in respect of energy recovery and thrust increase, the designer must ensure that these advantages are not can- celled out by increased aerodynamic drag. In most instances the jet exit is in the extreme rear of the fuselage or nacelle, but exceptions are to be seen in the new Hawker fighters, having a bifurcated jet pipe and twin exits partially countersunk into the fuselage behind the wing roots, and the Swedish SAAB-29, from which the jet stream is ejected through a short tailpipe forward of the empennage. Though, as affecting a simple turbojet, a long tailpipe is undesirable, it may prove an asset if an after- burner is to be incorporated, though this somewhat bulky fitment, in torn, may mar the original fuselage lines. This has, in fact, occurred in the " Reheat Vampire," Shooting Star night fighter (F-94) and Chance Vought Pirate. That a long tailpipe and spoiled fuselage lines are not insepar- able from " reheat" is proved by the XF-88, with specially developed short afterburners and F-86D. Republic's F-91 intercepter is the only fighter known to be flying with both turbojet and rocket power. The prototype has four solid-fuel rocket -motors, disposed in fairings above and below the turbojet nozzle in the ex- treme tail, but a Curtiss-Wright XELCW-i liquid rocket is intended. Obviously it is desirable to enclose the bulk, if not the whole, of a rocket unit in the fuselage; so the latest Hawker, ajfframes, with their sweeping lower-fuselage lines, appear especially suitable for the installation of an auxiliary rocket unit in the lower rear body. , For take-off the most heavily loaded American fighters are occasionally given rocket assistance. The Shooting Star, for instance, has provision for two JATO units, each of 1,000 lb thrust. No British land-based fighter requires such aid. A twin-jet fighter affords a greater safety margin than a single-jet type, especially at night or in bad weather, and, if the jets are mounted near the centre-line, allows economical cruising on a single unit. In laying out a twin- jet fighter a designer has the choice of attaching the power units to the wing outboard of the fuselage; of burying them in the wing roots; countersinking them partially into the fuselage sides; placing them above and/or below the fuse- lage; or—in the case of an internal installation—disposing them side by side, superimposed or staggered. Classic examples of outboard wing installations are the Gloster Meteor and the Me2O2A. Both are of wartime design, but De Havilland Sea Hornet fighters aboard H.M.S. Implacabtt. McDonnell F2H-I Banshee naval fighter (t their basic layout, which is obviously beneficial to main- tenance, is by no means obsolete and is, in fact, reproduced in the all-weather Curtiss F-87 and the English Electric Canberra, a light bomber with potentialities as a fighter. Wing-root mounting (which introduces the difficulty of transferring spar loads) is illustrated by the McDonnell naval fighters and Vought Cutlass, while the twin jet- units of the Avro Canada CF-100, Northrop Scorpion and Douglas Skyknight are built in to the sides of the fuselage. The hull of the S.R./Ai flying boat is distended to allow the twin Metrovick Beryls (mounted side by side, and fed by a bow intake) to discharge aft of the wing. Representative of an underslung installation is the Soviet Mig-9. The power plants of the following fighters are wholly internal: Lockheed XF-90 (side-by-side units, out- lets at rear of fuselage); McDonnell XF-88 (side-by-side units, outlets in lower fuselage); French S.E.2410 fighter/ attack aircraft (staggered units, outlets in tail). On the score of accessibility, it will be observed that the Vampire, by virtue of its short nacelle, completely detachable cowlings, and the single-sided impeller of its turbojet, is advantageously placed, as is the Meteor, with its outboard nacelles. In the Sabre, Shooting Star and Thunderjet the rear fuselage is detachable as a unit, allow- ing access to the turbojet and permitting rapid replace- ment. The twin axial-flow units in the wing roots of McDonnell naval fighters can be withdrawn rearwards. With intakes located some distance aft along the fuse- lage (which arrangement, by leaving the nose section free for the cockpit and service equipment, is gaining in popu- larity), it becomes necessary to dispose of the boundary layer at the intakes. This can be accomplished either by suction slots, as on the Supermarine and Hawker fighters; by providing shoulders, exemplified by the Venom and Avro CF-100; or by arranging the intake scoop(s) to stand proud of the fuselage (first Espadon prototype, now being redesigned). Where it is proposed to cruise on one of two turbojets, or to provide for failure, as on the McDonnell Phantom, the intakes are provided with controllable shutters, to permit closure of a duct to an inoperative unit. Fuel tankage on a typical jet fighter is mainly in the fuselage, the wings in general being too thin, but auxiliary jettisonable tanks of substantial capacity can be carried beneath the fuselage (if ground clearance allows), at the wing tips, or—where sharp sweep or other considerations render tip-mounting impossible due to consideration of e.g. displacement—beneath the wing, as r on the Sabre. The tip tanks in the Lockheed XF-90 hold 180 gallons each, and a 250-gallon ventral tank has been developed for the Supermarine Attacker. With a multiplicity of tanks it is necessary to provide an automatic transfer system to jretain the e.g. within limits as fuel is consumed. Bag-type ^fWks are now commonly employed. There is no indication that the " Deichselschlepp" towed-tank arrangement, as studied jointly by Messer- schmitt and Arado late in the war, and intended for the Me 262 and Ar 234, has found any favour with British or American authorities, but the feasibility of refuelling jet fighters in the air was demonstrated by Flight Refuelling, Ltd., during August last year, when a Meteor 3, its tanks replenished ten times from a converted Avro Lancaster, remained airborne for twelve hours. In all jet fighters, other than the Soviet Yak~i5, the
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