What happened
On March 13, 2016, an EC135 P2+ helicopter was undergoing a scheduled 1000-hour flight hour (FH) hangar maintenance inspection at the SOT Warsaw-Babice airfield. The maintenance task was being performed in accordance with specific work orders.
During the inspection of the fenestron blade pitch control elements, specifically while cleaning the pitch link assembly for verification, technicians discovered a crack in the metal pitch control strap. This component serves as the connection between the tail rotor blade and the rotating fenestron hub body. The crack was observed in the longitudinal plane.
The investigation
The investigation focused on the condition of the tail rotor assembly during the maintenance procedure. The aircraft had reached a total of 1727 flight hours at the time the defect was identified. The inspection was being conducted following the Aircraft Maintenance Manual (AMM) protocols for pitch control element verification.
Findings
- The inspection revealed a longitudinal crack in the metal pitch control strap.
- The set of pitch control straps was deemed unfit for continued use and was marked for replacement with new components.
- The fatigue wear of the strap was identified as the probable cause of the crack.