Mechanical Impedance Approach to Engine Vibration Transmission Into an Aircraft Fuselage

The paper demonstrates a mechanical impedance approach to an aircraft vibration problem. The desire is to reduce cabin noise resulting from fuselage vibration generated by engine rotor unbalance disturbances. A simplified analytical model is used in combination with experimental impedance data to investigate the effectiveness of several schemes applied to the engine/airframe interface. Airframe vibration absorbers are found to be the most effective. Qualitative correlation is achieved with the results of the installation of absorbers on the Douglas DC-9 aircraft. A more comprehensive analytical model is generated to account for three-dimensional effects; data acquistion for this model is discussed.