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Aviation History
1958
1958 - 0229.PDF
FLIGHT, 21 February 1958 239 Fighter Design Philosophy A Designer's Appraisal By R. F. CREASEY, B.Sc. ALMOST the only statement that can be made with assurance on the subject of missiles displacing fighters is that nothing drastic is going to happen overnight; even intercepter fighters will be with us for many years to come. In this article the deputy chief engineer of the English Electric Company's aircraft division examines target-defence against manned bombers and discusses some of die variables affecting the design of a fighter. THOUGH it once appeared that the long history of thefighter would come to an end soon after defensive guidedweapons had been developed, further reflection suggests that the fighter will have an important part to play so long as thereare bombers or reconnaissance aircraft to intercept. For this purpose the manned aircraft must be properly combined withthe guided weapon. It is difficult to imagine defensive guided missiles undertakinga semi-offensive tactical role comparable with that of the fighter in all situations up to and including Korea, Suez and Oman. Offen-sive missiles can threaten only well-established targets, and then mainly by resort to warheads that would also destroy civilization.The ability of the manned aircraft to fly in and intercept, or to reconnoitre and strike at small targets, underlines its value insituations that have actually occurred, as well as in any ultimate conflict. The design of fighters must change radically, however,and a change is already apparent in such aircraft as the English Electric P.1B with its Ferranti fire-control system and radar. THE WEAPON SYSTEM. An illustration of a modernfighter is given by Fig. 1. That the fighter is now considered as a complete weapon system is a change in tradition as much as intechnical detail. It was usual at one time for the fighter designer to concern himself only with airframe design. It is true that healways expected the engine designer to ensure that maximum performance was being extracted, but his primary concern withequipment and armament was to ensure that it could be installed inside the airframe. This was in an era when the superiority ofa fighter was measured largely in terms of miles per hour or ceiling. Performance in this sense is still important, although itnow has much more complex definitions in terms of the ability to climb, accelerate and turn into positions to launch smallmissiles. Rocket-propelled Missiles are the main reason for a change inphilosophy. Small airborne missiles have much more speed and manoeuvrability than the fighter, and this enables them to com-plete the last part of an interception with greater economy. Although this is true only up to the limits of guidance andreliability, it can be made sufficient for the last few miles of an interception against almost anything a bomber can do. A rocket-propelled weapon can climb so steeply that it can be launched ten or twenty thousand feet below the bomber at the expense ofa small increase in the size of missile. This does, however, allow a very large reduction in die size of the fighter and thereby inthe overall cost. This cost is still the lowest for many tasks since the most expensive component (i.e., the fighter) is not expendableand can destroy a number of targets in successive sorties. Airborne Radar is another reason for a change in design philo-sophy. This is due to the fact that high-altitude combat involves distances to accelerate or turn which are often too great formanoeuvring up to the final interception point with human eyes alone. Ground-based radar has neither the accuracy nor capacityfor this purpose, particularly in the presence of enemy jamming. Fig. 1. Elements of a fighter weapon system. DUPLICATED TURBOJETS WITH REHEAT. AND ROCKET BOOST POWERFUL CONTROLS INSTRUMENT AND FIRE- CONTROL DISPLAYS AIRbORNE RADAR OF WIDE COVERAGE GUIDED - WEAPON AND CONVENTIONAL ARMAMENTS Airborne radar is now a well-developed method for augmentingthe pilot's vision and may itself be augmented by infra-red techniques. But unless the equipment is designed in parallel witha high-performance aircraft one is liable to end up either with equipment which itself is outclassed by the enemy or with noequipment ready at all. This does not prohibit the use of the same equipment in aircraft with less rigorous requirements, or itsdevelopment for use in later aircraft. All-weather Fighters used to be much larger than daylightfighters of equal performance, due to the extra equipment required to operate at night or in bad weather. But the major item ofequipment is now required in daylight, if we accept radar as a necessary adjunct at high altitude. Since an enemy is likely to usemodern navigational aids in order to attack by night or in bad weather, it seems useless to spend much of our future effort orexchequer on the day fighter. Accurate navigation and blind- approach aids are other items required for all-weather operation.Development of these has now reached the stage where they can be made small and semi-automatic for the use of the pilot. These are not the only ways in which the advances in elec-tronics and servo systems required for the guided-missile industry can be utilized to improve the fighter itself. There is no reasonwhy a large part of the all-weather fighter force should not be single-seaters, with an autopilot to fly the aircraft whilst the pilotis concentrating on his radar screen. Man himself seems essential for the latter task and any setbackin electronic warfare could well restore the case for a second crew-member. A balanced solution might rely on electronicsand other automatic aids up to the point where each man can carry out his functions with sufficient time to cope with emer-gencies brought on by malfunctioning of some part of his equip- ment. The reliability of much of this equipment seems to beapproaching the stage where it can be developed to work 90 per cent of the time, but the remaining 10 per cent must not beallowed to abort the interception. Ground-launched Guided Missiles already have more thansufficient range to replace the heavy anti-aircraft gun. These can provide protection to key targets as a supplement to the broadercover offered by the fighter. Weapons like the English Electric Thunderbird are inevitably much larger than airborne missilesbut much smaller than a fighter. Their development provides some hope for the interception of high-performance missiles.If these are launched from a bomber, however, it would be more satisfactory to shoot down the bomber itself before it came inclose enough to release its powered missiles. This still appears to be the task of the fighter. Guided weaponswith an interception range of some hundreds of miles seem to rely on so many components to complete their interceptionthat the various percentages of unreliability soon add up to make the interception more a matter of chance than anythingelse. Furthermore, the size of the weapon eventually grows to the point where it becomes too expensive to be thrown awayon every test flight or to be destroyed completely after each inter- ception. It will then pay economically, as well as in reliability, tomake it large enough to carry a crew to ensure its recovery after each flight and to carry a number of smaller but more manoeuvrablemissiles to destroy a variety of targets. The presence of the crew to interpret the airborne radar also provides accurate guidanceat much greater distances from the ground radar. The presence of a crew throughout the flight-test developmentand operational periods reduces the time taken to develop or adapt the system to meet technical advances which the enemymight make. This is most important now that it takes so many years to develop any new system. In guided-missile jargon this long-range intercepter might bedescribed as a two-stage weapon. The man in the first stage is provided with approximate mid-course guidance from groundradar and airborne navigation, but with accurate terminal guidance from airborne radar. The smaller second-stage weaponscan have guidance provided either from the first stage (beam- riding) or partly from the first stage (semi-active radar) or be com-pletely self-contained (fully-active radar or passive homing with infra-red). Simplest of all, the weapons need have no guidance
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