What happened
On 21 February 2005, a BAe 146-200, registration EI-CWA, was performing a ferry flight from Dublin Airport to Paris CDG following maintenance. Shortly after takeoff, the crew observed red "gear unlocked" and "gear in transit" warning lights, indicating the landing gear had failed to reach the up-locked position.
Following the indications, the crew performed the abnormal checklist and attempted to cycle the gear to resolve the issue. After consulting with maintenance, a gear swing was performed, but the warning persisted. The crew subsequently requested a quick return to Dublin. During the approach, the warning lights cleared, and the aircraft landed safely on runway 28 without any unusual vibrations or noises. Upon arrival at the stand, an inspection revealed that a left-hand undercarriage door hinge had broken.
The investigation
Investigators examined the aircraft's maintenance history and the mechanical operation of the landing gear doors. The main gear doors are designed to close and lock via a mechanism linked to the gear retraction. The investigation found that the aircraft had experienced a similar unsafe gear indication on a flight the previous day, which maintenance had been unable to replicate in the hangar.
Further examination of the hardware revealed severe corrosion on the bearing housing of the hinge. The investigation also noted that the aircraft manufacturer had previously issued an "All Operator Message" regarding similar hinge failures caused by undetected corrosion. While the operator had been in the process of implementing recommended maintenance to address this, EI-CWA was still scheduled for the modification.
Findings
- The failure of the left-hand undercarriage door forward hinge was caused by severe corrosion.
- The structural failure of the hinge allowed aerodynamic forces to pull the door laterally, preventing the door roller from properly engaging the up-lock.
- The corrosion was located between the bracket and the bearing housing, making it difficult to detect during standard inspections.
- The landing gear warning lights were a direct result of the door's inability to reach the up-locked position due to the broken hinge.