The Efficiency of Airscrews on Wings of Large Chord

摘要

Information was required on the effect on propulsive efficiency of varying the distance between the plane of the airscrew and the leading edge of the wing, when the airscrew diameter was half the wing chord and the wing thickness was sufficient to enclose the engine nacelle. A rectangular wing, 18-4 per cent, thick, of 12-ft. span and 2-67-ft. chord was used for the tests. A small 1-h.p. electric motor, built into the wing, drove a three-blader tractor airscrew of 1 -35-ft. diameter, the distance of whose plane of rotation ahead of the leading edge could be altered between the limits 24 per cent and 6 per cent of the wing chord. The thrust axis was approximately central with respect to the wing thickness and inclined at — 3 deg to the wing chord. Measurements of thrust were made at 0 deg wing incidence.nIt was found that for P/D ratios of 1.5 and 1.85, the propulsive efficiency with the airscrew 15 per cent of the wing chord ahead of the leading edge was practically the same as with the airscrew in the 24 per cent position, and only slightly less when the distance was reduced to 6 per cent.