What happened
A component failure involving a gearbox retainer ring occurred during operations. The aircraft's maintenance program included various preventive measures designed to identify potential issues before they resulted in mechanical failure.
The investigation
The investigation focused on the maintenance history and the condition of the gearbox prior to the event. The operator utilized several inspection protocols, including SOAP analysis, inspections of the magnetic drain plug, and propeller dynamic balance checks. Records indicated that the gearbox had undergone an overhaul approximately 2,429 hours before the failure, at which time a new retainer ring was installed.
During the period between the overhaul and the failure, none of the routine inspections—specifically the SOAP analysis or the magnetic drain plug checks—identified any anomalies or signs of wear. The investigation confirmed that the failure of the retainer ring occurred while the component was still within its required service life and inspection intervals.
Findings
- The retainer ring failed without any prior warning or detectable indicators.
- All scheduled maintenance, including the overhaul and subsequent inspections, had been performed according to the required intervals.
- Previous inspections, such as the magnetic drain plug and SOAP analysis, did not reveal any precursor to the component's failure.