What happened
On August 4, 2002, a Rockwell Commander 690C was taxiing for takeoff at Dortmund airport when the right main landing gear suddenly retracted. This unexpected movement caused the right wing to make contact with the ground. The impact resulted in damage to the propeller, the engine, and the underside of the fuselage. There were no injuries to the pilot, and no third-party damage was reported. Following the incident, the aircraft was recovered by lifting the right wing and manually extending the gear, which was then secured with wooden strips to prevent further retraction.
The investigation
The BFU examined the aircraft's maintenance history and the mechanical condition of the landing gear system. Records showed that the aircraft had undergone an annual inspection and a 100/200-hour check on May 24, 2002, at which time the landing gear was functioning correctly and no leaks were detected. Additionally, the landing gear system had been overhauled in November 2001.
During the subsequent repair of the aircraft, technicians discovered slight play in several ball joints and bellcranks within the mechanical linkage connecting the landing gear lever to the control valve. While the maintenance facility suggested that the issue could be mitigated by pulling the gear lever firmly into the "Down" position, the BFU rejected this as a viable safety solution.
Findings
- The investigation established that the mechanical linkage between the landing gear lever and the control valve was incorrectly adjusted.
- This improper setting likely allowed the control valve to shift out of the "Down" position, permitting hydraulic fluid to enter the upstream system and trigger the gear retraction.
- Although the maintenance facility had performed an overhaul and recent inspections, the specific misalignment of the linkage was the primary cause of the malfunction.