What happened
On 6 June 2001, a Cessna 310R, registration G-BGTT, was taxiing at Bournemouth International Airport for a scheduled cargo flight to Guernsey. During the backtrack, the pilot experienced a sensation of tyre deflation. Following a visual inspection by ground personnel that yielded no issues, the pilot proceeded with takeoff.
Shortly after takeoff, the pilot attempted to retract the landing gear. The red "in transit" light failed to extinguish, and subsequent attempts to cycle the gear resulted in the nose and port main gears locking, but the starboard main gear remained unsecured. The pilot entered a holding pattern for approximately one hour, during which time air traffic control observed that the starboard main wheel was oriented 90 degrees to the longitudinal axis of the aircraft.
To mitigate risk, the pilot opted for an emergency landing on Runway 26. The approach was configured with the gear down, but flaps and lights were retracted to minimize potential damage. During the landing roll, the pilot shut down the starboard engine before touchdown, followed by the port engine. Upon contact with the runway, the starboard main landing gear collapsed, causing the starboard wingtip to strike the ground. The pilot steered the aircraft onto the grass, where it came to a halt. The single crew member escaped the aircraft without injury.
The investigation
Investigators examined the wreckage and found that the upper and lower torque links of the starboard landing gear had disconnected at the central hinge. This disconnection allowed the wheel to rotate laterally. When the gear was retracted, the misaligned wheel struck the internal structure of the landing gear bay, creating excessive loads that fractured the gear actuating bellcrank. This fracture prevented the gear from being locked in the down position.
Technical analysis revealed that a bolt connecting the torque links had pulled through the upper link. While the bolt and nut remained intact, the washer that should have been positioned under the bolt head was missing. Instead, an undersized washer was found under the nut. This absence allowed the bolt head to migrate through the link, displacing the bushing and causing the links to separate.
Findings
- The primary cause of the gear failure was the absence of a washer under the head of the bolt on the starboard torque link hinge.
- An incorrect, smaller diameter washer had been installed under the nut, which failed to provide necessary support.
- Maintenance records indicated the torque links had been previously disconnected for component replacement, at which time the washer may have been misplaced.
- The Cessna 310R Illustrated Parts Catalogue (IPC) and Maintenance Manual lacked clear instructions or diagrams specifying the exact placement of these washers, creating a risk of assembly errors.
Safety action
- The manufacturer was advised to issue an All Operators Letter to Cessna 310 owners to inspect torque link assemblies for correct washer installation.
- It was recommended that the manufacturer amend the IPC and Maintenance Manual to clearly define the required locations for part number 5045018-1 washers.