Failure of hydraulic pressure seals in a flight control actuator

Examination of an actuator revealed leakage had occurred past nitrile “O” rings which were backed up by teflon anti extrusion seals. Analysis showed progressive damage to the nitrile seals had occurred because of anomalies in the backup rings. Testing was performed to determine which of two theories best explained how the backup rings became degraded, so as to enable informed risk mitigation in the fielded fleet.