Model tests on the effects of slipstream on the flow at various tailplane positions on a four-engined aircraft. Part 1 tests with contra-rotating propellers. Part 2 tests with single rotating propellers

Abstract

Systematic wind-tunnel tests have been made to investigate the effects of slipstream on the flow near the tailplane of a typical civil transport with four contra-rotating propellers. Tailplane height has been varied for each of several wing-body arrangements ; only one tailplane and one propeller position have been used. This report presents the main results in the form of changes in mean downwash angle, and velocity at the tailplane, as functions of tailplane position, lift coefficient, and propeller thrust. It is shown that the regions of increased downwash and velocity each extend for a range of tailplane height of about one propeller diameter whilst the region of increased downwash is displaced upwards a quarter of a diameter relative to the region of increased velocity. A comparison of this work with flight results (R. & M. 2701), in which the propellers were single rotating, show an apparent difference in the spread of the slipstream between single rotating and contra-rotating propellers.