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Aviation History
1955
1955 - 1629.PDF
748 FLIGHT, November 1955 Cenrair F-W2A. LEAD-COLLISION ATTACK America's Development of Automatic Interception THE weapons system which includes the "lead-collisionattack" equipment has hitherto been talked of almost withbated breath and hailed by the publicity-conscious U.S.A.F. as a deadly defence against the bomber. It is without any doubta remarkable achievement in electronics and armament, but full automaticity and sure-fire accuracy are not yet achieved. Thedetails of the working of present equipment has remained a closely guarded secret, and not many are even now privileged to know theexact working of the system or, more important, its capability defined as a kill-rate. But even as the radar and ballistic rocketfighter is becoming fully established in U.S.A.F. squadron service the more advanced combination of radar and guided missile withremote G.C.I.-controlled aircraft manoeuvring is in course of preparation. The lead-collision system originated in a 1949 proposal for afighter which could attack a bomber accurately from somewhere abeam, thus successfully avoiding tail armament which was be-coming more and more powerful and increasingly accurate. The fighter could no longer afford to creep up to the tail of a bomberwith a marginal dosing speed and expose itself to the radar- Fighter making pursuit-curve type attack is exposed to bombers toll turret fire throughout this interval fr«n bomber's tail turret f/' Conventional pursuit- curve type attach (using guns) Radar scope during lead collision course attack. (After target lock-on) Lead collision course (using rockets) directed automatic fire of two or even four 20 mm cannon. Sucharmament has now become almost standard in American bombers, and the beam attack is the Americans' own answer to it. Theaccompanying diagram shows that a fighter following the tradi- tional aiming-off pursuit curve would be exposed to the tail turretfor a comparatively long part of its attack. Furthermore, the use of the standard U.S.A.F. 0.5in machine gun requires long steadybursts to have appreciable effect on the strongly constructed jet-bomber airframes of today. The Hughes Aircraft Company therefore began the develop-ment of their fire-control system, and other agencies provided a new weapon in the form of the Mighty Mouse folding-finrocket. This could be discharged from tubes in external pods or retractable packs. Though the ballistic accuracy of theseweapons was not great, they could be easily fired in salvos which gave a shot-gun type spread and therefore reduced the accuracylimitations of the fire-control system. Just one hit was sufficient to destroy a bomber, and the area covered by a full salvo of 24Mighty Mice was stated to be equivalent to that of an American football field—an area through which it nevertheless proved sur-prisingly easy for a bomber to pass unscathed. Proximity fuses were not needed since the rocket's effect was small unless itobtained a direct hit. The Mighty Mouse was therefore not an expensive weapon. Another advantage was that the fighter nolonger required a great speed margin over the bomber. Based on the Mighty Mouse rocket salvo, the Hughes fire-control system works in the following way. The pilot is vectored towards his target by G.C.I, in much the same way as for a sternchasing attack, but he is not placed astern of his quarry. The attack can be made theoretically from any quarter at the sameheight, but aircraft characteristics make a head-on approach rather dangerous and it is the object to avoid stern-chasing. The idealis 90 deg abeam. The pilot has in front of him, in the centre of his normal blind-flying panel, a radar scope. His aerial is scanninga vertical fan beam backwards and forwards laterally, and the trace of this appears as a fast-moving vertical line on the scope. Super-imposed on this presentation is a line resembling in aspect and function the horizon bar of the normal artificial horizon, so thatthe pilot can fly blind watching the scope alone and occasionally referring to the A.S.I, or other instruments. At a certain point the target echo will appear as a blip on thescreen. Its range and bearing will be indicated by its position on the scope, vertically for range and sideways for bearing relative tothe interceptor's centreline. The pilot then locks his aerial to follow the blip only by manoeuvring the aerial's search trace bymanipulating a handle until the line is stationary across the blip. He then presses a switch on the grip which causes the blip to glowlarger. The set is then locked on. The old and the new attacks, as represented in an "Aviation Week" diagram. At left, the "lead-pursuit" curve requires a high closing speed and long tiring time and brings the tighter into the bomber's cone of fire a little before reaching position 3. "Lead-collision" tactics on the right show that the fighter does not need a great speed margin over the bomber. At position 5 both aircraft are very close to each other and the fighter is breaking away behind. The scope pictures show the presentation for the corresponding numbered positions along the intercepter's track during an ideal automatic lead-collision course.
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