Propeller Empennage Interaction Effects on the Vertical Tail Design of Multiengine Aircraft

Abstract

A potential-flow model for conceptual design and vertical tail sizing purposes, currently under development, has been applied and tested in an investigation of the influence of the propeller slipstream on the empennage flowfield. Additionally, the model is intended to increase the understanding of the phenomena arising in propeller-empennage interaction. For verification purposes and complementation to limited wind-tunnel results in open literature, dedicated measurements were performed and supplemented by a Reynolds-averaged Navier-Stokes analysis. From wind-tunnel measurements, in one-engine-inoperative condition, it is found that the empennage experiences a propeller-induced crossflowfield, which is found to be the main contributor to the additional yawing moment experienced by the measured multiengine propeller aircraft. The most probable cause for deviation in yawing moments in measurements and the potential-flow model is incorrect modeling of the flowfield behind the wing. This was verified by a comparison of the measured and computed flowfield behind the wing and in front of the vertical tail. Efforts to create a potential model to aid in conceptual vertical tail sizing should, therefore, focus on achieving realistic wing-wake behavior. In this respect, the effect of the propeller on the wing-lift distribution, as well as the wing-wake aircraft interaction, should be treated with care.