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Aviation History
1946
1946 - 1490.PDF
Tl6 FLIGHT AUGUST IST, 1946 JET Fl (cont nounced that the Meteor IV wing has been reduced in span to increase the rate of roll. The wing-root installation appears attractive but, on a fighter of reasonable proportions, demands jet units of very small diameter in conjunction with wing roots of deep section (as in the case of the McDonnell FD-i with two axial-flow Westinghouse units of 1,400 1b thrust) or swell- ing the wing contour to form nacelles, as proposed by Messerschmitt. By mounting the units on or in the sides of the fuselage, above and below, or side-by-side beneath, reasonable accessibility is achieved and the power plant mass centralized, but the side-by-side or superimposed internal layout must compromise maintenance, even should the rear fuselage be made detachable. A striking layout is demonstrated in — the Saro E.6/44 fighter: here two axial-flow units are mounted in parallel, partly in the hull and partly in fairings under the wing roots. There is a single intake in the bow. While the gas turbine has been making its spectacular debut aircraft designers have studied aerodynamic and structural problems to permit its safe and most effective utilization in fighters. The aerodynamic difficulties have been analysed and described by various authorities and are .largely concerned with the effects of compressibility as the speed of sound is approached. Thus the most meticulous study of airflow is demanded of the jet-fighter designer. Aerodynamic factors inevitably affect the design of the structure, particularly of the wing, while flight at speeds of the order of 600 m.p.h. imposes severe demands on strength. Wings, fuselage, fin and tailplane must be sub- jected to tests simulating the most exacting conditions to be expected in flight, while horizontal surfaces, fixed and movable, must show exceptional torsional stiffness. An ultimate strength pull-out factor for the Meteor IV is 10 at 500 m.p.h., 8.5 at 550 m.p.h. and 7 at 600 m.p.h. indicated. Armament Parallel with his study of aerodynamic, structural and power-plant problems the designer of a jet fighter must consider military requirements, notably the disposition of adequate armament. Structural distortion must be avoided and for this reason, and because the wing has become pro- gressively less amenable to armament installation, the tendency is toward the grouping of guns or rocket-projec- tile clusters in the fuselage. The gun barrels must not protrude unduly into the air stream and precautions must be taken to ensure that the pilot is not dazzled by their Hash. The armament of jet fighters is now undergoing serious consideration and, no doubt, revision. That the Meteor IV should mount the same armament as the Hurricane II C seems incongruous, though it might be argued that four 20 mm Hispanos can still deal adequately with any fighter The Ryan FR—1 Fireball (below) is an interim fighter forthe U.S. Navy, having a Wright Cyclone piston engine and a Whittle-type General Electric 1.16 turbine jet. It is saidto be very popular among pilots. CHTERS inued) or.bomber of any air force. Even so, designers may count on combinations of much greater potency, if less readily adaptable to their airframes. The low-velocity, high-capacity gun typified by the 30 mm MK 108 may be deemed superior in some instances to the high-velocity weapon of smaller bore and a similar weapon of 40 mm may ultimately find a place where large aircraft are likely to be the target. Where higher velocity and flatter trajectory are de- manded a gun on the lines of the Mauser MG 213 may provide the answer. This is available in either 20 or 30 mm calibre, muzzle velocities being about 3,000 ft/sec and 2,00c. ft/sec, while rates of fire of up to 1,200 r.p.m. are possibL The use of the rocket projectile as an air-to-air weapon has been post- poned because of the low velocity obtained, but for attacking boiflber formations nose clusters of R/Ps, with suitable fairing arrangements, may be adopted. It is of interest to compare the armament of current jet fighters. The Meteor IV carries 600 rounds for its four 20 mm Hispanos while the Me 262 is provided with 360 rounds for its 30 mm MK 108s—sufficient for 8-10 bursts of about one second's duration. The Americans, though fully aware of the merits of the 20 mm Hispano, have found it expedient to arm the Lockheed Shooting Star with six 0.5m Brownings for which a total of 1,800 rounds is provided. An experimental installation on the Me 262 was a 50 mm high-velocity gun, the barrel of which projected about five feet from the nose. Firing trials were encourag- ing. The possibilities of converting a jet fighter for bombing were discussed in Flight of July 18th. Two 1,000-lb bombs are a possible load on the Meteor IV and the Shooting Star will carry 2 x 500 lb. Bell's XP-83, a 12-ton fighter designed primarily for long-range escort, can handle 4,000 lb. These bomb loads are alternative to drop-tanks. For the present the jet fighter is noted for its essential simplicity. Controls and instruments in the cockpit are fewer than on comparable piston-engined aircraft, and absence of vibraltion facilitates instrument reading. Com- plication vrtill irfcvitably result from operational demands. Air brakes! as/on the Meteor IV and Vampire, will be Developing the Fireball theme, the U.S. Convair XP-81, above, has a T.G.100 pp jet " in the nose and an I-40 Whittle-type turbine jet with " nostril " intakes in the p, \ Q \C\ fuselage. essential unless tactics are drastically revised ; these will permit steep diving and prevent overshooting a target. Catapult seats are already being designed into new prototypes and the phenomenal rates of climb, and ceilings of over 50,000 feet, will mean that pressurized cockpits can no longer be avoided. The Americans are equipping their jet fighter pilots with anti-g suits and are providing cork-lined
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