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Aviation History
1992
1992 - 0927.PDF
The F-15B's display was enlarged to present attack profiles The F-15 STOL/MTD was an early vehicle for testing thrust vectoring was fitted to a 125kN (28,0001b)-thrust Fl 10-100 and controlled by a vectoring engine controller — a reprogrammed digital engine controller from the more-powerful Fl 10-129, installed in addition to the -100's analogue controller. In the tests, thrust was vectored up to an angle of 20° in all directions (through 360°) and at rates in excess of 45°/s. The engine's ability to carry the sideforce generated limits thrust-vectoring, but Mishler says the AVEN-equipped engine was tested to "1.8 times the design sideforce" with no failures. Mishler describes the ground runs as "...a preliminary flight rating test — the nozzle can be put on the aircraft and flown". P&W's axisymmetric nozzle is also ready to fly, says programme manager Roger Bursey. "It is a flight-weight design in a flight-qualified configuration," he says. The nozzle has been ground-tested on a 129kN- thrust F100-229 using a controller for the STOL/MTD F-15 and modified to control the pitch/yaw nozzle. Bursey says tests have shown the ability of the "beefed-up" engine structure to carry the 2t sideforce generated by the vectoring. P&W plans to ground-test the nozzle on its 160kN-thrust IPE-94, a growth version of the F100, and Bursey believes the device, which "...could fly today", will fly "within about a year". NASA's highly integrated digital engine control (HiDEC) F-15 programme repre sents another near-term opportunity to flight-test axisymmetric thrust vectoring, and Bursey confirms P&W is negotiating to fit pitch/yaw nozzles to the FlOO-powered aircraft. NASA reports, meanwhile, that the conventionally powered HiDEC F-15 is well on its way to meeting its final targets of flying safely without any working aerody namic control surfaces and landing using engine power alone for control. STEP FORWARD A major step toward this goal was achieved recently when the HiDEC team at NASA's Ames-Dryden flight research centre in stalled in the testbed the core computer elements of a vehicle management system (VMS), developed jointly with MDC and Smiths Industries, to integrate and control flight-critical systems. "The VMS augments the existing onboard computers and provides much-needed proc essing capability," says NASA. "We're plan ning to use the computer for the performance-seeking control [PSC] project, which is the real-time optimisation of the engine and its fuel system, digital flight controls and engine intake, to give us greater engine control, lower turbine entry temperatures, reduced specific fuel con sumption [sfc] and higher thrust." A pre liminary subsonic PSC phase was completed in October 1991, and NASA hopes to demonstrate bigger improvements in sfc in supersonic testing, beginning around April. The VMS will help directly with HiDEC's demonstration of a self-repairing flight con trol system, which will enable the aircraft to continue flying safely even if control surfaces are damaged or disabled. To this end a propulsion-controlled aircraft pro gramme will be included in advanced PSC testing planned for 1993. "With this concept we will land the aircraft with engines only," says NASA. "We have demonstrated approaches and descents down to 200ft with the pilots using throt tles only." Initial trials indicate engine-only roll control is limited, while pitch control is achieved using simultaneous power changes on the two engines. Some of NASA's HiDEC goals would appear to overlap those planned for PACIR. In the current funding famine, this could lead to changes in the USA's next major fighter-technology demonstration effort. D ..with the vectoring angle limited only by the side-loads which the engine can take FLIGHT INTERNATIONAL 8 - 14 April, 1992 27
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