Optimum Flap Angles for Roll Control on Wings with Multiple Trailing-Edge Flaps

Abstract

This research effort explores the use of multiple trailing-edge flaps for efficiently generating rolling moment on aircraft. Using the concept of basic and additional lift distributions, the induced drag of the wing is expressed in terms of the flap angles. The theory of relative extrema is then used to determine the optimum flaps angles for minimum induced drag with a constraint on the rolling moment. By setting the mean of the flap angle for operation of the wing within the low-drag range, profile drag is also minimized. The general methodology can also be used on tailless aircraft and to study the effect of failure modes such as a stuck flap. The results show that multiple flaps can be used to generate rolling moments with lower drag than when ailerons are used. They also provide redundancy that helps efficiently handle control failures such as stuck flaps. The current research serves as a starting point for further investigation into the use of multiple flaps for efficient aircraft control.