LOCKHEED MARTINIS studying flight controls for advanced tailless fighters under two USAir Force contracts. Under the RESTORE reconfigurable-controls programme, the company is developing control algorithms for a stealthy, yet agile, tailless-fighter designed under the earlier Improved Control Effectiveness (ICE) programme.

The ICE effort is aimed at developing new control effectors to allow removal of the vertical tail while retaining high agility, high angle-of-attack capability and supersonic performance. Under Phase 1 of the programme, the company studied variations to two baseline designs - an Air Force aircraft with a 67í-sweep delta planform, and a Navy aircraft with foreplanes for carrier suitability.

Under Phase 2 of the ICE programme, now essentially complete, Lockheed Martin windtunnel-tested the most promising control effectors to emerge from Phase 1. These were an all-moving wingtip and a "spoiler-slot-deflector" - a combination of a forward-hinged upper-surface spoiler and an aft-hinged lower-surface deflector, which open to create a slot in the wing. Lockheed Martin says both devices have been used on previous aircraft for lateral control, but on the ICE configuration they are used for directional control.

The most promising configuration to emerge from Phase 2 is now being used as the basis of the RESTORE programme, which is developing algorithms for the real-time allocation, prioritisation and reconfiguration of multiple, highly coupled control effectors on a tailless fighter. McDonnell Douglas is also working on the RESTORE programme, which will culminate in piloted simulations.

Lockheed Martin is drawing on its experience with the earlier Self-Designing Controller programme, under which it developed a control system that could estimate aircraft parameters, such as aerodynamic derivatives, in real time, rather than having them programmed in, based on flight-test results. This resulted in the successful flight-test of adaptive algorithms in the USAF's Lockheed Martin VISTA/ F-16 in-flight simulator aircraft.

On the fourth flight, the F-16 was landed under fully adaptive flight control and on the fifth and last test flight, the system adapted to the induced failure of a horizontal stabiliser, and the aircraft was landed safely, the company says.

Source: Flight International