The Aspect-Ratio Equivalence of Conventional Aircraft with Configurations Featuring Outboard Horizontal Stabilizers

A description is included of the outboard horizontal-stabilizer (OHS) concept in which horizontal stabilizer surfaces are supported downwind, and outboard, of aircraft wing tips by means of booms. The essential purpose of such a configuration is to place each horizontal-stabilizer surface in the wing upwash. It is thus possible, as has been verified by wind-tunnel tests, to employ the horizontal stabilizers not only for meeting the requirements of providing pitch stability but also, as shown analytically, for generating additional lift efficiently to augment that due to the wing. A comparison is presented of the performances of comparable OHS and conventional light aircraft configurations showing that for equal cruise drags the conventional configurations employ mainplane aspect ratios two to three times those of the OHS units. It was also found that for equal aspect ratios, and other operational parameters, the OHS aircraft offered approximately 20% less drag, and 15% smaller planform areas, than otherwise comparable conventional units.