An Experimental Study of the Sensitivity of Helicopter Rotor Blade Tracking to Root Pitch Adjustment in Hover
NATIONAL AERONAUTICS AND SPACE ADMIN LANGLEY RESEARCH CENTER HAMPTON VA
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The sensitivity of blade tracking in hover to variations in root pitch was examined for two rotor configurations. Tests were conducted using a four-bladed articulated rotor mounted on the NASA-Army aeroelastic rotor experimental system ARES. Two rotor configurations were tested one consisting of a blade set with flexible fiberglass spars and one with stiffer by a factor of five in flapwise and torsional stiffnesses aluminum spars. Both blade sets were identical in planform and airfoil distribution and were untwisted. The two configurations were ballasted to the same Lock number so that a direct comparison of the tracking sensitivity to a gross change in blade stiffness could be made. Experimental results show no large differences between the two sets of blades in the sensitivity of the blade tracking to root pitch adjustments. However, a measureable reduction in in-track coning of the fiberglass spar blades with respect to the aluminum blades is noted at higher rotor thrust conditions.