Aerodynamic Performance of an Aircraft Equipped with Horizontal Tail-Mounted Propellers

This paper presents an experimental and numerical study of the aerodynamic interaction between horizontal tail-mounted propellers and the airframe. A representative aircraft model was installed in a low-speed wind-tunnel and measurements were taken with an external balance to determine the effect of propeller installation on integral forces and moments. Total pressure measurements were performed downstream of the model for qualitative analysis of the propeller–airframe interaction. The experimental data were complemented by full blade CFD analyses, which correlate excellently to the experimental data. Balance measurements indicate that the propeller installation results in an offset and a change in the slope of the pitching moment curve over the complete range of angles of attack. The extent to which the propellers contribute to the longitudinal control and stability was shown to be dependent on the angle of attack of the aircraft and the rotation direction of the propellers. The flowfield and computed propeller loads show that an inboard-up rotating propeller results in a neutral contribution to longitudinal stability towards higher angles of attack, while an outboard-up rotation enhances the stability for all positive angles of attack. The non-uniform inflow to the propeller induced by the airframe leads to a lateral shift of the thrust which influences the trim condition.