Ground resonance is a potentially dangerous instability associated with rotary wing aircraft on flexible supports (landing gear).
Question:
Ground resonance is a potentially dangerous instability associated with rotary wing aircraft on flexible supports (landing gear). When the aircraft's rotor blades are disturbed to the point that the mass center of the rotor blade system is no longer in the center of the rotor, an inertial force is generated and passed via the rotor to the fuselage. The fuselage will begin to oscillate because of its ability to displace relative to the ground. One of two outcomes is possible depending on the system features. The vibration will be damped out if ground resonance does not exist. However, if the aircraft's stiffness and damping properties are such that ground resonance can occur, and if the rotor speed is within a critical band of frequencies, the displacement of the fuselage can cause the mass center of the rotor blades to move away from the rotor center. The oscillation of the fuselage increases as the inertial force increases. As a result, an unstable scenario exists in which the fuselage and blades interact, increasing the total amount of aircraft vibration.
Intermediate Accounting
ISBN: 978-0176509736
10th Canadian Edition, Volume 1
Authors: Donald Kieso, Jerry Weygandt, Terry Warfield, Nicola Young,