What happened
On 14 August 2003, a Yak-50, registration RA44461, was returning to Shoreham Airport following participation in the Eastbourne Air display. During the approach, the pilot attempted to extend the landing gear, but the starboard main leg failed to deploy. The crew entered a holding pattern at 2,000 feet to troubleshoot the issue, cycling the gear at different airspeeds and load factors and attempting to use the emergency extension system, though neither action was successful.
After visually confirming that the right main gear remained retracted, the pilot decided to retract the remaining gear and reduce the aircraft's weight by burning off fuel. The plan was to perform a gear-up landing on the grass runway. During the final approach, the pilot shut off the magnetos, fuel, and battery. The aircraft touched down level with the wings and came to a stop without fire, though the underside of the aircraft sustained damage. There were no injuries to the pilot.
The investigation
Following the incident, the aircraft was inspected by a licensed engineer. The investigation established that the right gear up-lock remained engaged because a turnbuckle linkage rod within the release mechanism had fractured. This fracture prevented the up-lock from releasing.
Technical examination revealed that the eye-end fitting at the actuator end of the linkage rod had broken. This specific component was found to be extremely stiff, which likely caused the rod to bend every time the landing gear was operated. While the investigation noted that the area is difficult to access for lubrication, the maintenance organisation suggested that factors such as over-tightening, subsequent painting, or improper lock wire routing might have contributed to the restricted movement. Detailed analysis by the AAIB confirmed the fracture was caused by a reverse bending fatigue mechanism.
Findings
- The starboard main landing gear failed to extend due to a fractured turnbuckle linkage rod in the up-lock release mechanism.
- The eye-end fitting at the actuator end of the linkage was found to be very stiff, inducing bending stresses during gear operation.
- The failure was attributed to a reverse bending fatigue mechanism caused by the stiffness in the linkage.