What happened
On September 15, 1965, a Beech Bonanza F-35, registration HB-EII, was performing a private flight from Basel to Samedan. The aircraft, carrying the pilot and his daughter, arrived at Samedan Airport at approximately 11:56 h.
According to the pilot's account, the aircraft touched down roughly halfway down runway 21, resulting in a long landing. After rolling for approximately 400 meters, the pilot retracted the landing flaps and proceeded to perform a post-landing checklist. During this sequence, the pilot manually manipulated the landing gear control button. Approximately four to five seconds later, while applying the wheel brakes, the landing gear collapsed. The aircraft slid for about 40 to 50 meters along the runway before coming to a complete stop.
The investigation
An investigation was launched immediately following the incident. The technical examination of the aircraft, which was sent to Transair in Colombier for repairs, revealed that the aircraft was in good condition and well-maintained. Investigators found that the landing gear mechanism, gear doors, and locking components were fully functional. The safety switch, designed to prevent accidental gear retraction under load, was found to be in proper working order and was actually set to trigger 1 mm earlier than the manufacturer's specifications.
Findings
- The investigation established that the pilot failed to verify the landing gear position indicators (the green light and gauge) prior to touchdown.
- The primary cause of the accident was a pilot error involving the manual manipulation of the landing gear control button while the aircraft was on the ground.
- While the pilot suggested that the safety locks failed, no evidence of mechanical failure or malfunction in the locking mechanism or the safety switch was found.
- The collapse likely occurred because the pilot's manipulation of the gear button happened so quickly after touchdown, or the aircraft's ground speed was such, that the safety mechanism had not yet been triggered by the weight of the aircraft.