Computational simulations and wind-tunnel tests have demonstrated the feasibility of using inflatable boots on the leading edges of airplane wings, both as devices to increase lift and as pneumatic deicing actuators. Assuming success in further research and development, the first applications would likely occur as retrofits to single- and twin-engine airplanes in general aviation (GA). Later, corporate and commuter turboprop airplanes would be included. The eventual incorporation of these boots into new GA airplane designs would be even more desirable because the boots could be integrated with overall wing structures to provide laminar flow in cruise.
The model used in the wind-tunnel tests and as the basis for the computational simulations was a standard airfoil (type 63-212 of the National Advisory Committee for Aeronautics) with a faired circular-arc boot installed on the leading edge (see Figure 1). A boot of this type comprises front and rear cells. The front cell is shaped so that when it is inflated, its exposed leading-edge surface is nominally a portion of a circular cylinder. The rear cell serves as a fairing; it is vented to the atmosphere instead of inflated, and it is formed by attachment between a tangent line on the front cell and a line on the bottom surface of the airfoil.
Faired circular-arc boots for the wind-tunnel model were made of a standard deicing-boot material, and two different designs called "inlaid" and "overlaid" were tested. In the tests, inflation of both boots resulted in significant increases in the maximum coefficient of lift and the angle of the stall break (see Figure 2). Results of preliminary calculations based on the data from these tests suggest that it should be possible to achieve substantial increases in gross weight and reductions in stall speeds by use of faired circular-arc boots.
The use of inflatable leading-edge boots on GA airplanes would enable operation under known icing conditions and would thereby reduce the incidence of weather-related flight delays. High-lift features could be incorporated into deicing systems with very small increases in weight. Inflation of the boots for high lift would greatly extend angles of attack for maximum lift and would broaden the peaks of lift-vs.-angle-of-attack functions, thereby helping to prevent stall accidents.
This work was done by Kenneth G. Wernicke and Rodney K. Wernicke of Sky Technology Vehicle Design & Development Co. and Norbert A. Weisend, Jr., Consultant, for Glenn Research Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Mechanics category.
Inquiries concerning rights for the commercial use of this invention should be addressed to
NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
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Refer to LEW-16660.