Second phase follows 50 data collection missions at up to Mach 1.3 and 25,000ft

Development of advanced flight-control laws for NASA's Active Aeroelastic Wing (AAW) Boeing F/A-18A is under way after the completion of almost 50 data collection flights, which measured aerodynamic forces and structural effects throughout a flight envelope up to 25,000ft (7,620m) and Mach 1.3.

The Boeing Phantom Works-developed flight-control laws will be used for a second flight-test phase in 2004, during which NASA hopes to demonstrate that wing warping can produce faster roll rates at transonic and supersonic speeds than conventional flight controls. The joint NASA Dryden/ Boeing/US Air Force Research Laboratory AAW effort is expected to pave the way for design and flight-control technology that could lead to thinner, lighter wings, more efficient designs and greater aircraft manoeuvrability.The aircraft has been modified with additional actuators, a split leading-edge flap and thinner aft upper and lower wing skins to provide up to 5° of wing twist in the outboard section. The first phase of parameter identification flights showed the aircraft was flutter-free, although they did reveal significantly more aileron forces than expected. NASA is forming a "mini-team" to investigate the result to see if this was an unrecorded phenomenon of the early F/A-18, or a new "mystery force". NASA says aileron deflection rates in the AAW will be limited to 100% design loads, and will not affect the writing of the new flight control laws.

The new flight-control software is expected to be completed by July, and could be programmed into the Motorola 68040-based flight-control computer by September. Following installation of the computer into the aircraft around November, NASA then plans to begin a four-month software verification and validation phase. Flight tests with the fully functioning AAW configuration are expected to start in April 2004 and run until September.

Source: Flight International