What happened
On March 22, 1973, a pilot was conducting training maneuvers consisting of several circuit patterns at Geneva-Cointrin Airport. After completing an initial five-minute flight, the pilot landed on the grass runway 23 with the flaps extended to approximately 15 degrees. Following the landing, the pilot reset the trim, closed the carburetor heat, and applied full power to initiate a second takeoff.
As the Beech Bon to Bonanza A 35, registration HB-EGE, reached takeoff speed, the nose pitched downward because the nose gear had collapsed. The main landing gear subsequently retracted, causing the aircraft to slide on its belly. The aircraft traveled approximately 250 meters past the runway threshold and came to a stop after pivoting 135 degrees to the left.
The investigation
The investigation examined the mechanical state of the aircraft and the pilot's actions. The aircraft was airworthy and had undergone maintenance between March 19 and March 21, 1973, which included the replacement of a right "up lock" cable and landing gear testing. At the time of the accident, the aircraft weight was well within limits, though the center of gravity was at the forward limit.
Investigators inspected the wreckage and found that the nose and right landing gear legs were retracted, while the left leg was partially extended. The landing gear control mechanism, located on the dashboard, was found to be deformed and broken. While tests indicated that the electrical motor and the control switch were functional, the landing gear warning lights remained unlit during testing. The pilot stated that the landing gear lever was not moved following the first landing.
Findings
- The investigation could not find evidence of mechanical or electrical defects prior to the accident.
- The fact that all three landing gear legs were found in a retracted or partially retracted state made a simple breakage of the linkage unlikely.
- The investigation focused on two possibilities: an accidental movement of the landing gear lever or an accidental unlocking of the gear mechanism.
- The unintended retraction of the landing gear was the primary cause, though the specific trigger for the retraction could not be definitively established.