What happened
On 15 October 1998, a Piper PA-24-250, registration G-BUTL, was conducting a private flight from Bembridge to Blackbushe. As the pilot entered the circuit at Blackbushe, an attempt to deploy the landing gear via the electric transmission system failed. This failure caused the electric motor circuit breaker for the gear to trip.
In an effort to resolve the issue, the pilot disconnected the motor from the transmission screw to utilize the manual extension system. However, the gear remained partially extended. After consulting with a maintenance engineer via radio, the pilot decided to divert to Lasham Airfield. During the diversion, the pilot repeatedly attempted to use the manual telescopic lever, noting that the mechanism became increasingly stiff with each attempt.
Upon arriving at Lasham, the pilot performed a fly-past to allow emergency services to observe the partially deployed gear. A subsequent approach to Runway 09 resulted in a successful emergency landing. There were no injuries to the pilot, though the aircraft sustained moderate damage to the propeller, undercarriage, and the underside of the fuselage.
The investigation
Following the incident, the aircraft was moved to a hangar for a detailed inspection. While the transmission motor was found to be functional, investigators discovered that the right main landing gear outboard sliding sleeve guide had detached from its swaged housing.
Testing of the push-pull control cables revealed that the right main gear cable was extremely stiff, requiring significant force to operate, whereas the left cable moved easily. Further examination of the cables at the AAIB laboratory showed kinks at both ends of the right-hand cable. These kinks were located at points where the cable's travel coincided with the swaged joint. The investigation also noted that the swaged joint had been subjected to a single lateral load exceeding its design limits, a condition that may have occurred during maintenance.
Findings
- The primary cause of the gear failure was the detachment of the right main landing gear sliding sleeve guide from its swaged housing.
- This detachment led to the kinking of the inner push-pull cable, which created excessive friction and prevented full gear extension.
- The lateral load that damaged the swaged joint likely occurred during maintenance, though the exact timing could not be determined.
- The maintenance engineer had lubricated accessible components but did not specifically inspect the freedom of the cables, as there was no specific requirement in the Maintenance Manual to do so.