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Flexible--and better--wings. (Test & Measurement).

In a project to demonstrate that twisting or warping wings can enhance aircraft performance, engineers and technicians at NASA's Dryden Flight Research Center, Edwards, Calif., are finishing the last major ground tests before starting the first research flights. The Active Aeroeleastic Wing (AAW) F/A-18A is a joint program of the US Air Force Research Laboratory, Boeing's Phantom Works, and NASA Dryden. Tests began in late August and were completed in September.

For testing, the F-18 rests on three large airbags, while electro-mechanical shakers induce vibrations into the wings at varying amplitudes and frequencies. Instrumentation measures structure reaction as these vibrations propagate through the aircraft to determine potentially adverse effects.

In these ground vibration tests, the F18's hydraulics were powered up, but the control surfaces were inactive. The structural mode interaction tests take the process one step further, with the flight controls operating and the interaction of the flight control surfaces with the aircraft structure observed. This test assures that vibrations caused by the actions of the flight controls are damped or suppressed, rather than reinforcing each other to cause large, uncontrolled vibrations of "flutter" that could lead to catastrophic failure of the aircraft structure.

The testbed F/A has been modified with additional actuators, a split leading edge flap actuation system, and thinner wing skins that will allow the outer wing panels to twist up to five degrees. The traditional wing control surfaces--trailing edge ailerons and the leading and trailing edge flaps--are used to provide the aerodynamic force needed to twist or "warp" the wing. Engineers hope to obtain almost equivalent roll performance on production F/A-18s at transonic and supersonic speeds without using the horizontal stabilators and with smaller control surface deflections.

NASA Dryden Right Research Center 661-276-3449 www.dfrc.nasa.gov

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Title Annotation:Active Aeroeleastic Wing program
Publication:R & D
Article Type:Brief Article
Geographic Code:1USA
Date:Oct 1, 2002
Words:294
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