NACA-TN-3360

Abstract

An investigation has been conducted to determine the effects of several factors associated with the propeller installation on the ability of a wing with plain flaps to deflect a propeller slipstream downward as a means for achieving vertical take-off. The factors considered were propeller blade angle, mode of propeller rotation, propeller location, and ratio of wing chord to propeller diameter. The investigation was made at zero forward speed on models of semispan wings. <br>Lowering the thrust axis appreciably below the wing-chord plane reduced the diving moment of the flaps but had little effect on the turning angle of the slipstream or on the ratio of resultant force to thrust when the thrust axis was lowered only 20 percent of the propeller radius. The best turning effectiveness was obtained when the propeller made of rotation was such that the outboard propeller rotated against the tip vortex and the inboard propeller rotated in the opposite direction. On the basis of tests with flat plates of various chords, the best turning angle was obtained with a ratio of wing chord to propeller diameter equal to 1.00, which was the largest ratio investigated; however, increasing the ratio of wing chord to propeller diameter from 0.75 to 1.00 led to only a small improvement in turning effectiveness but caused a large increase in the diving moment.