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Aviation History
1982
1982 - 0309.PDF
llli* Fighters: tomorrow's terminology by GRAHAM WARWICK EVERY few years, technology comes along which overturns the art of aircraft design. Nowhere is this more evident than in fighter design. After all, more research resources are pour ing into combat aircraft design than into any other branch of aeronautics. During the 1980s, this technology will be defined, refined, tested, and finally built into aircraft which will enter service in the 1990s. Several critical advances have been identified as the keys to tomorrow's fighters. Here is Flight's guide to the ever-changing alchemy of aircraft design. Active controls THE basic elements of an active con trol system are: pickoffs to measure pilot inputs, motion sensors to detect aircraft response, high-speed com puters, and control-surface actuators. Communication between these com ponents is by electrical impulse, as in fly-by-wire, or by fibreoptic path, as in fly-by-light. The computer compares aircraft re sponse with pilot demand, and deflects the control surfaces to remove any error. Undemanded motion is coun tered automatically. Aircraft response to disturbances, commanded or un- commanded, is determined by soft ware in the digital, programmable flight-control computers. Active-control benefits include: arti ficial stability—unstable, divergent motion is opposed, allowing natural stability to be reduced (see Relaxed static stability); and carefree man oeuvring—a u t o m a t i c protection against exceeding aerodynamic and structural limits, and spin prevention by washing out pilot inputs as limits are approached. Other benefits include: gust allevia tion—improving low-level ride quality by sensing gusts and moving control surfaces to reduce aircraft response; manoeuvre-load control—transferring lift inboard to reduce wing bending; and flutter suppression. These in crease airframe life by reducing wear and tear on the structure. Complete reliance on an active con trol system—without backup mech anical linkages—requires high integ rity. The ability to withstand two similar failures without degradation, a reliability of one catastrophic failure in 107 flying hours, requires multi plexing—multiple redundant control lanes. Most current systems are quad- ruplex—four of everything—but digital data transmission and more in tensive self-monitoring will allow lighter triplex-redundant systems. Be cause the control laws are stored as software, aircraft behaviour can be modified, based on flight-test or opera tional experience, by reprogramming the computers. Heading and below Grumman concept of a 1990s fighter able to cruise supersonically at high altitude, releasing stanrf-o/f air-to-ground weapons at long range to avoid both surface-to-air and look-down I shoot-down defences. The 5l,500lb design is 77-8ft long fUGHT International, 6 February 1982 291
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