Variable Geometry High-Lift Airfoil for Rotorcraft

DTI has developed an integral, variable geometry airfoil for helicopter rotors that will modify the leading edge camber, or droop, through a continuous change in airfoil contour during a revolution. In Phase I, DTI designed and prototyped several versionsof LEEMA (Leading Edge ElectroMagnetic Airfoil), a variable geometry airfoil. In Phase II, DTI will build and test a full-scale LEEMA system(s) on an OH 58 blade, at full rev, in a stationary spin pit to assess its aerodynamic performance and capabilities.In Phase III, DTI will work with a commercial helicopter manufacturer to transition this technology into military and commercial rotorcraft.Army rotorcraft are being called upon to operate in much more demanding environs than in the past, particularly inareas of nap-of-the-earth (NOE), deep-penetration, and air-to-air combat. Highly maneuverable, agile, and survivable rotorcraft demand greater aerodynamic capability from the rotor system. The performance of a conventional, fixed shape rotor is primarilylimited because of compromises resulting from the conflicting design requirements of the advancing and retreating blade. LEEMA uses electromagnetic actuators distributed in the flexible and fixed structures of the airfoil to modify the leading edge camber,or droop, as the rotor changes its position between retreating and advancing. The actuator elements are specifically designed to function in the high g environment of the rotating blade. The additional leading edge camber has the potential to increase themaximum lift coefficient by up to 30%, thereby substantially increasing the available lift capability of the rotor and reducing or eliminating the dynamic stall problems inherent in current rotorcraft. LEEMA has the potential to improve maneuverability,aerodynamic efficiency, and increase cruise speed with relatively modest electrical power and weight increases. Successful development will result in widespread application throughout military and civilian rotorcraft.