AN EXPERIMENTAL INVESTIGATION OF GROUND EFFECT ON A FOUR-PROPELLER TILT- WING V/STOL MODEL
Final technical rept.
PRINCETON UNIV NJ DEPT OF AEROSPACE AND MECHANICAL SCIENCES
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Tests were conducted on a one-tenth scale model of a tilt-wing VSTOL at specified points simulating flight conditions at various heights above the ground. The model was moved at selected velocities through still air and lift, drag, and pitching moment were measured at various heights above the ground. Investigations included combinations of 30, 40, and 60 deg wing incidence angle with 30, 40, and 60 deg flap deflection, and thrust coefficients ranging from 0. 80 to 0.95. Model ground clearances of 3.5 to 36 inches were investigated both at constant altitude and with the altitude continuously varying during the run. The data are presented as plots of lift, drag, and pitching moment coefficients. Also included are data from wind tunnel tests on similar models. A brief analysis is made of ground effect phenomena and an understanding of the general data trends is obtained. The magnitude and direction of the force change in ground effect are predictable. However, the pitching moment change is strongly influenced by factors such as the flow field beneath the fuselage, the change in downwash at the horizontal tail, the other effects.