What happened
On January 14, 2012, a private Beechcraft P35 Bonanza, registration F-BASF, was performing a takeoff roll on the unpaved runway 32 at the Pont-sur-Yonne aerodrome. The flight was intended to proceed to Meaux-Esbly. During the acceleration phase, the aircraft encountered a bump on the runway, causing it to briefly lift off the ground before reaching rotation speed. As the aircraft descended back to the surface, the landing gear had already begun the retraction process. The gear subsequently retracted completely, causing the aircraft to come to a halt on the runway. The aircraft sustained heavy damage.
The investigation
Investigators examined the landing gear control, which was found in the "UP" position. This specific control mechanism is equipped with a locking system designed to require the pilot to pull the lever before it can be moved to the up position. However, the investigation established that the locking mechanism on F-BASF was worn to the point that the lever could be moved without being pulled.
While mechanical locks and electrical switches are designed to prevent accidental retraction while the landing gear struts are compressed, these protections were bypassed when the aircraft hit the bump. The impact caused the struts to extend, momentarily releasing the mechanical and electrical safeguards. This allowed the retraction sequence to initiate while the aircraft was still in the takeoff roll.
Furthermore, the investigation revealed that the aircraft had undergone a 100-hour inspection approximately 15 hours prior to the accident, yet the faulty locking mechanism went undetected. The pilot, who had operated the aircraft since 1995, had become accustomed to the faulty lever and routinely operated it without pulling the safety lock, perceiving the lack of resistance as normal behavior.
Findings
- The primary cause of the accident was an undetected failure of the landing gear control locking system, which allowed for an involuntary movement of the lever.
- The pilot's long-term familiarity with the faulty mechanism led to a habit of bypassing the safety procedure.
- The pilot failed to verify that the landing gear lever was in the correct position prior to takeoff.