Overview
On January 9, 2013, during scheduled maintenance of a Boeing 737-500 at Warsaw Chopin Airport (EPWA), a fragment of an HPC Compressor Shaft Retaining Ring was discovered in the Flame Arrestor while disassembling the Low Pressure Turbine (LPT) Major Module from the engine.
Findings
After the LPT module was removed, circumferential scuffing was observed on the front and rear sections of the LPT Shaft. This damage was likely caused by the separated fragment of the retaining ring. The damaged parts were sent to the overhaul facility and the engine manufacturer for repair and further investigation.
Investigation Outcome
On May 11, 2016, the maintenance organization sent an email inquiry to the engine manufacturer regarding the status of the investigation. The manufacturer responded that the case (reference SR-SER/2013-…) was closed on their side, stating that it was a long-term investigation. Consequently, the Polish State Commission on Aircraft Accident Investigation (PKBWL) closed its investigation into the incident at that stage, noting that the manufacturer would continue technical examination.
Cause
The cause of the incident was damage to the HPC Compressor Shaft Retaining Ring from an undetermined source. No preventive actions or safety recommendations were issued by the investigating entity.