United States Army CH-47 Chinook Rotor Head Liner Slippage on Pitch Varying Housings - An Investigative Report

摘要

This paper presents the investigative engineering used to document, test, evaluate, and correct a liner slipping problem on the CH-47 pitch varying housing. Liners began slipping shortly after installation of the rotor head on the aircraft, with some liners slipping within the first two hours of flight. The liners are installed in the pitch varying housing blade attachment lugs and are used to secure the vertical hinge pin bearings and the lubrication oil tanks to the housing. They are held in place by a 0.005"-0.0085" press fit and a rolled spring pin. When the liner slips, the oil seal is compromised, and the lubrication fluid is cast all over the aircraft. Many theories were presented as to the mechanism leading to the liner slippage. They included over-torque of the oil tank, improper mixing of the Proseal, improper interference fit, and improper bearing removal tooling. A test plan was developed to prove or discount each theory, and the results are presented in this paper.