What happened
On December 19, 2013, during a scheduled technical inspection at the BW Wanicki hangar base at Pobiednik Wielki Airport (EPKP), technicians identified a discrepancy regarding the tail rotor shaft of an EC 13 and B helicopter. Specifically, the colored security seals (seals) that should have been present at the junction between the clutch and the front part of the tail rotor shaft were missing.
The investigation
An investigation conducted by the operator's internal committee examined the maintenance logs and the physical state of the aircraft. The inquiry established that the missing seals were a direct result of unauthorized maintenance work being performed on the front shaft. According to the aircraft maintenance manual (AMM), specific procedures regarding the balancing and servicing of these components are restricted to the manufacturer. The investigation confirmed that a maintenance organization had performed work on the shaft without the necessary authorization.
Findings
- The primary cause of the incident was unauthorized technical maintenance performed by a maintenance organization.
- The absence of colored security seals indicated that the front shaft had been tampered with or serviced outside of the permitted manufacturer-level protocols.
- To rectify the issue, the affected shaft was sent to the manufacturer for proper servicing. The manufacturer subsequently provided a serviceable replacement shaft, which was installed, allowing the helicopter to return to flight operations.