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AN INVESTIGATION OF THE EFFECT OF DOWNWASH FROM A VTOL AIRCRAFT AND A HELICOPTER IN THE GROUND ENVIRONMENT
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON D C
Dynamic-pressure measurement, in ground effect, have been obtained about a single-rotor helicopter and a dual-propeller VTOL aircraft. The results indicate that the slipstream dynamic pressure along the ground, some distance from the center of rotation, is not a function of disk loading but merely a function of the gross weight or thrust of the aircraft. Furthermore, for a given gross weight the thickness of this outward flowing sheet of air is less for a small-diameter propeller higher disk loading propeller. The variation of the dynamic-pressure flow field for single and dual propellers or rotors is significantly different in the plane of symmetry between the two rotors than in a direction normal to this plane. The interaction of the two flows produces a region of upflow in this plane where the fuselage is located, and the decay of the maximum dynamic pressure with distance ahead of the fuselage is slower. Author