Overview of the DARPA Smart Wing project

The recently completed DARPA/AFRL/NASA Smart Wing program, performed by a team led by Northrop Grumman Corporation (NGC), addressed the development and demonstration of smart materials based concepts to improve the aerodynamic and aeroelastic performance of military aircraft. This paper presents an overview of the program. The program was divided into two phases. Under Phase I (January 1995 to February 1999), the NGC-led team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. An important limitation of the Phase I effort, the low bandwidth achievable in Shape Memory Alloy (SMA)-based actuation, was addressed in Phase 2 (January 1997 to November 2001). Under Phase 2, a 30-percent scale full span wind tunnel model of an NGC Uninhabited Combat Air Vehicle (UCAV) design was developed. For the Phase 2 first wind tunnel test, completed in March 2000, SMA-actuated, hingeless, smoothly contoured, flexible leading and trailing edge control surfaces were incorporated on one wing of the model and conventional trailing edge control surfaces actuated using electric motors on the other. This test provided baseline steady-state data at Mach numbers ranging from 0.3 to 0.8. The test also demonstrated the benefits of the smart leading edge control surface to compensate for loss of aileron effectiveness with increasing dynamic pressure. The second test, performed in May 2001, demonstrated a hingeless, smoothly contoured, structurally compliant, trailing edge control surface actuated using piezoelectric motors. Spanwise and chordwise shape control was demonstrated for the smart trailing edge control surface at deflection rates of up to 80degrees/s. Performance improvements in terms of increased rolling and pitching moments and lower control surface deflections were quantified. The work performed under this program has demonstrated the feasibility of developing smart control surface designs to provide optimal aerodynamic performance at a wide range of flight conditions.