What happened
On 16 May 2000, a BAE ATP, registration G-MANJ, was operating a scheduled public transport flight from Manchester to Belfast. Shortly after takeoff, the crew identified that the left main landing gear had failed to indicate as locked in the up position. After climbing to 5,000 feet, the crew declared a 'PAN PAN' and decided to return to the area to manage the situation, eventually selecting Liverpool Airport as their landing destination.
During the period of holding, the crew attempted various emergency checklists to rectify the gear position. This included an attempt to force the gear down by accelerating the aircraft to 175 kt. Despite these efforts, the left main landing gear remained in an unsafe state.
The aircraft landed at Liverpool Airport at 2003 hrs. While the touchdown was initially gentle, the left wing settled onto the runway surface as the airspeed decreased. The contact caused significant damage to the left propeller, engine nacelle, wingtip, flap, and tailplane. A brief flash fire was observed in the left landing gear bay due to hydraulic fluid release. The crew successfully evacuated all 44 passengers and 4 crew members with no injuries.
The investigation
The AAIB examined the aircraft and found that the left main landing gear doors were partially closed, causing the tyres to make contact with the inside of the doors. This interference prevented the gear from extending properly.
Detailed inspection of the door actuating rods revealed that the eye-end fitting had unscrewed from the rod. This occurred because the locking method was insufficient to prevent the fitting from rotating. As the eye-end moved, the threaded bearing at the other end eventually bottomed against a rivet, effectively locking the rod in a position that prevented the necessary rotation for the 'A' frame to move. This mechanical restriction caused the hook fitting to contact the forward face of the 'A' frame roller rather than engaging it, which prematurely closed the doors during the retraction cycle.
Findings
- The failure of the left main landing gear to extend was caused by interference between the tyres and the forward landing gear doors.
- This interference was triggered because the door actuating rod was unable to accommodate the required motion during the retraction cycle.
- The mechanism was restricted because the eye-end fitting had unscrewed from the rod, a condition made possible by an ineffective locking method.
- The loss of thread engagement at the eye-end was likely due to the locking nut being loosened during the installation or adjustment of the rod.