Quad Tilt Rotor Download and Power Measurements in Ground Effect

Abstract

This paper explores the performance characteristics of a Quad Tilt Rotor (QTR) in hover and low speed forward flight, in ground eect (IGE) and out of ground eect (OGE), by employing a somewhat unique experimental testing method, i.e., using an instrumented moving test apparatus. Airframe download and rotor performance data were acquired by testing a 0.031-scale QTR aircraft model in hover and low speed forward flight, in and out of ground eect. Rotor downwash velocity profiles were measured and compared with full-scale V-22 rotor measurements. The range of rotor wake skew angles (non-dimensionalized forward speeds) being tested, was extended by reducing the thrust level of the vehicle, which increases the rotor wake skew angle for a given forward velocity. The upload on the vehicle, observed at low heights above the ground, did not disappear with an increase in forward speed. The small-scale fixed-pitch variable-rpm rotor power measurements were corrected using an analytical procedure to obtain the equivalent power of a variable-pitch fixed-rpm rotor and to remove the profile power contributions.