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Building on the research performed during the DARPA / AFRL Smart Wing Phase 1 program to improve vehicle aerodynamic efficiency using control surfaces actuated by smart materials, the goal of the Phase 2, Test 1 effort was to increase the size of the model and the control surfaces and conduct wind tunnel tests at higher dynamic pressure and Mach number. This paper describes 1) model design for required safety and increased aileron effectiveness at high dynamic pressure; 2) model instrumentation; 3) SMA actuator control system design and implementation and 4) wind tunnel test results. Pictured below (Figure 1) is the model installed in the NASA Langley's Transonic Dynamic Tunnel (TDT).

The DARPA/AFRL/NASA Smart Wing program, conducted by a team led by Northrop Grumman Corporation (NGC) under the DARPA Smart Materials and Structures initiative, addresses the development of smart technologies and demonstration of relevant concepts to improve the aerodynamic performance of military aircraft. This paper presents an overview of the smart wing program. The program is divided into two distinct phases. Under Phase 1, (Jan 1995 - Feb 1999) the NGC 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. A smart wing 16% scale wind tunnel model, representative of an advanced military aircraft wing, was fabricated and tested in the NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) wind tunnel during two series of tests, conducted in May 1996 and June 1998, respectively. The smart wing model incorporated contoured, hingeless flap and aileron designs actuated using built-in SMA tendons. Control surface deflections of up to 10 degrees were obtained. Variable spanwise twist of the model was achieved using SMA torque tubes that employed novel connection mechanisms to effect a high degree of torque transfer to the structure. Up to 5 degrees of twist at the tip was demonstrated. Under steady-state conditions, performance improvements of 8-12% in comparison to a conventional design incorporating hinged control surfaces, over a broad range of wind tunnel and model test conditions, were established. The paper summarizes the Phase 1 effort. Detailed discussions of the wind tunnel testing, model design and fabrication, and torque tube development, are presented in References 6-8. An important limitation of the Phase 1 effort, i.e., the limited band-width provided by the SMA based actuation mechanisms, is being addressed in Phase 2 by developing and validating hybrid concepts. Phase 2 research and development is focused on application of smart technologies to uninhabited air vehicles (UAVs) that (from a scaling standpoint), offer a higher near-term technology transition potential than their tactical aircraft counterparts. Phase 2 efforts are also discussed, albeit briefly, in the paper.

The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A -18 E/F for the on-going DARPA/WL Smart Materials and Structures - Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (C m ), increased rolling moment (C l ) and improved pressure distribution These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16ft Transonic Dynamic Tunnel (TDT). Among the benefits demonstrated are 8-12% increase in rolling moment due to wing twist, a 10-15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.