What happened
On June 3, 2004, a Mooney M20J, registration F-GHEL, departed from Limoges aerodrome for Saint-Girons. Shortly after takeoff, at an altitude of approximately 150 feet, the pilot retracted the landing gear. During this process, a sharp noise was heard beneath the passenger seat, followed by the tripping of the circuit breaker for the landing gear actuator motor.
Recognizing an anomaly in the retraction sequence, the pilot extended the gear. Although the cockpit's mechanical indicator and the landing gear down-lock light suggested the gear was locked in the extended position, the pilot coordinated with air traffic control to perform visual inspections. After three flypasts, the controller confirmed that the right landing gear was extended but not locked. The pilot subsequently executed a precautionary landing on the unpended runway 04 at Limoges. During the landing roll, the right wing gradually collapsed as the pilot attempted to maintain control using the nose and left main gear. The pilot shut down the engine before the aircraft came to a complete stop to mitigate damage.
The investigation
Investigators examined the aircraft's landing gear assembly and found that the end of the actuator rod tube had become detached from its ball joint. The two pins intended to secure this assembly had pulled out of their holes in the tube due to deformation of the tube itself.
Technical analysis of the cockpit indicators revealed that the landing gear down-lock light was triggered by a sensor on the left gear leg; because the left gear had deployed and locked correctly, the light indicated a successful deployment for the entire system. However, the right gear's sensor, which is responsible for stopping the actuator motor, failed to function because the mechanical disconnection of the rod prevented the sensor from completing its circuit. The circuit breaker functioned as intended to protect the motor.
Findings
- The investigation established that the deformation of the holes in the actuator rod tube caused the assembly to disengage.
- A functional play in the mechanism had been noted during the previous 100-hour maintenance inspection.
- Existing manufacturer maintenance procedures were insufficient to detect the specific deformation occurring within the tube's holes.