Vibration Measurements of an OH-58D Helicopter Planetary Gear Under Operating Conditions

Planetary gear vibration is a major source of noise in helicopter drivetrains. Designers could lower noise levels and prevent fatigue-induced failures if they understood the dynamic nature of these systems better. Mathematical models to analyze potential designs and troubleshoot existing problems remain unverified by experiments. This experimental study completely characterizes the dynamic behavior of a production planetary gear under representative operating conditions, focusing on the independent motion of planetary components by mounting accelerometers directly to individual gear bodies. Data is processed to obtain rotational and translational acceleration. The results add several findings to the limited experimental research on planetary gear dynamics. Different gear bodies exhibit significantly different frequency response characteristics. Higher harmonics of mesh frequency may excite natural frequencies as much as the fundamental harmonic. Different natural frequencies are seen in rotational and translational degrees of freedom, agreeing with analytical results published in the literature.