THE AUTO-TRIM ROTOR STABILITY SYSTEM

This paper describes how the combination of a carefully tailored flapping flexure with a small amount of forward blade sweep can result in a composite/bearingless rotor that has the inherent capability to eliminate rotor moments caused by gusts, speed and angle of attack changes, and gyroscopic rotor moments due to vehicle angular velocity. This feature allows the rotor itself to be used as a very large attitude gyro, thus eliminating the need for electronic SAS systems. Forward blade sweep creates a negative spring effect that cancels out the positive torsional spring rate of the flexure, thus tuning the feathering frequency to near 1P and minumizing cyclic control forces. This eliminates the need for power boost. Included are the author's experiences with wind tunnel model, rotor whirl, and flight testing of this type of rotor.