What happened
On 21 May 2017, a Piper PA-24-250 Comanche, registration G-BYTI, was conducting a flight at Retford Gamston Airfield in Nottinghamshire. This flight was intended as a functional test following recent maintenance, specifically the refitting of the main landing gear and the installation of a new squat switch. The pilot planned to complete a single circuit with the landing gear in the extended position before landing and coming to a stop.
During the flight, the pilot observed that the landing gear indicators remained in the down and locked position. However, once the aircraft had touched down and the pilot applied the brakes, the undercarriage collapsed. The incident resulted in damage to the propeller, the left flap, and the lower fuselage, though there were no injuries to the pilot.
The investigation
Investigators examined the aircraft's landing gear retraction mechanism and found no evidence of structural damage to the mechanism itself. Analysis of the ball screw and transmission configuration revealed that the electric motor had actually retracted the landing gear. Additionally, the circuit breaker for the electric motor was found in the tripped position.
Regarding the safety systems, the investigation looked into the newly installed squat switch, which is designed to prevent gear retraction while the left main landing gear leg is compressed. The investigation established that the pilot had not moved the landing gear selector lever at any point during the flight.