MICHAEL PHELAN / LONDON
NASA's Dryden Flight Research Center is performing the final ground vibration and structural mode interaction tests on its Active Aeroelastic Wing (AAW) Boeing F/A-18A. Tests are expected to be completed this month, leading to a first flight in October.
The project aims to demonstrate improved roll control through aerodynamically induced wing twist on the supersonic demonstrator (Flight International, 2-8 April). The technology could enable improved manoeuvrability of future high performance aircraft, and lead to thinner, higher aspect ratio wings, reducing aerodynamic drag.
In the structural mode interaction tests, the flight controls are fully operational to check for flutter-inducing resonance to vibration inputs. During the tests the aircraft is isolated on three large airbags.
AAW is a joint programme of the US Air Force Research Laboratory (AFRL), Boeing's Phantom Works and NASA Dryden. The US Navy F/A-18A has been modified with additional actuators, a split leading edge flap actuation system and thinner wing skins that allow the outer wing panels to twist up to five degrees. Traditional wing control surfaces - ailerons and leading- and trailing-edge flaps - provide the aerodynamic force needed to warp the wing. Project engineers hope to obtain almost equivalent roll performance to production F/A-18s at transonic and supersonic speeds without using the horizontal stabilators and with smaller control surface deflections.
The two-phase AAW flight tests will begin with 30 to 40 parameter identification flights. Boeing's Phantom Works will use the data to refine wing effectiveness models and design the AAW flight control laws for the second phase next year.
Source: Flight International