SYMPOSIA PAPER Published: 01 January 2001

Failure Mechanism of a Hydraulic Log Piston and Slipper Assembly


A failure investigation was conducted on hydraulic log piston and slipper socket interfaces from aircraft Integrated Drive Generators (IDGs) to determine the reason for the occurrence of several in-service failures. Typically, one piston out of nine broke through the slipper socket. Once this occurred, secondary damage led to the removal of the unit from the aircraft. The effort to determine root cause proved difficult because despite the widespread usage of the components in numerous aircraft applications, only a few operators were experiencing failures. The scope of the effort was expanded from analysis of failed units to those exhibiting poor wear performance in order to define in detail the wear mechanism leading to failure. Expansion of the effort revealed that a complex wear process consisting of several stages and classic wear mechanisms was occurring, due primarily to the rapid deterioration of the lubrication film.

Author Information

Sikes, JT
Hamilton Sundstrand, United Technologies, Rockford, IL
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Developed by Committee: D02
Pages: 370–381
DOI: 10.1520/STP38288S
ISBN-EB: 978-0-8031-5567-1
ISBN-13: 978-0-8031-2883-5