What happened
On January 21, 2016, while performing a pre-flight inspection at Vilnius Airport (EYVI), the crew of a Bombardier DHC-8-400 operated by PLL LOT identified a defect regarding the aircraft's landing gear assembly. Specifically, the crew discovered that the safety wire intended to secure the locking nut—which holds the pushrod bolt of the front right left main landing gear cover in a fixed position—had been broken.
Following the discovery, the issue was reported to LOT OTE. A qualified mechanic was dispatched to Vilnius to address the fault. During the process of adjusting the pushrod length, the mechanic noted that the bolt had rotated 26 full turns within the bushing thread. Due to the scope of work required to fully regulate the landing gear covers, the aircraft was ferried to Warsaw Chopin Airport (EPWA) for further maintenance.
The investigation
The investigation focused on determining why the safety wire had failed. The aircraft manufacturer was notified of the incident, and the fleet engineer filed a Global Safety Report (GSR). The investigation confirmed that the primary issue was the physical breakage of the wire securing the bolt.
Findings
- The primary cause of the incident was the breakage of the safety wire securing the locking nut for the front right left main landing gear cover pushrod bolt, the exact reason for which remained undetermined.
Safety action
Following the event, the operator recorded the incident in its Safety Management System (SMS) database for monitoring via Safety Performance Indicators (SPI). As a preventive measure, the PKBWL directed a fleet-wide inspection of the main landing gear cover pushrods for all Bombardier DHC-8-400 aircraft in the operator's fleet. Consequently, an Engineering Order (ELOT/Q40/0004/16) was issued and executed between January 29 and January 31, 2016, to perform a one-time inspection of the safety wire securing the MLG FWD ROD.