Abstract:
The Aviation Development Directorate of the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) conducted a drag test of a non-rotating 2/5 scale Lockheed AH-56 Cheyenne main rotor hub in the U.S. Army 7- by 10-foot Wind Tunnel located at NASA Ames Research Center in Moffett Field, CA. The purpose of the test was to quantify the drag reduction on the Cheyenne's unique "door-hinge" style hub when the mechanical control gyro is removed, with the implicit assumption that the control and stabilization functions of the gyro could be replaced by a modern flight control system located somewhere within the aircraft’s outer mold line. The model was tested in a number of non-rotating configurations, orientations, and tunnel conditions. Baseline results compared favorably with historical drag measurements, and showed approximately a 50% reduction in hub drag with the gyro removed, with an additional 10% reduction due to rudimentary streamlining of the bluff outer hub arm.