Abstract: A break fault of pressure bellows has occurred in the propeller regulating system of a certain type of airplane. This fault led to the engine stop in the sky, influencing the airplane's flying safety. Theoretical analysis and experiments have been done for the propeller regulating system. Models of elements and pipelines structure for this system are obtained. Digital simulating calculation of hydraulic oscillation response for the system has been carried out. Measurement and frequency analysis of the hydraulic oscillation for this system have been done in the ground trial condition. The result of simulating calculation coincides well with the result of this experiment in the ground trial condition. Furthermore, the simulating calculation and analysis for the reasons of pressure bellows break fault have been done. The method of removing the fault has been offered to and used by related departments getting fine effect.

Key words: hydraulic oscillation, propeller regulating system, fault analysis