What happened
On February 24, 2004, an EADS SOCATA TB 20 GT, registration F-GTYH, was performing a flight from Auch to Muret. After completing two training circuits at Auch, the pilot proceeded to Muret for a direct arrival on runway 12. During a subsequent circuit at Muret, the pilot noticed that all three green landing gear indicators remained illuminated while flying in a downwind pattern. Believing he had failed to retract the gear after takeoff, the pilot did not check the physical position of the gear lever but proceeded with the landing approach.
Upon touchdown, the aircraft bounced and then descended. During the subsequent pitch-up maneuver, the aircraft sank unexpectedly, causing the landing gear to collapse. The aircraft slid approximately 150 meters along the runway. An eyewitness observed the aircraft on final approach with the gear extended, noting a low pitch attitude during the flare, a bounce, and a subsequent sequence where the gear retracted.
The investigation
The investigation focused on the landing gear mechanism and the electrical signaling system. While the gear lever was found in the "up" position on the ground, the inspection of the landing gear revealed a broken electrical wiring harness at the upper terminals of the ground/flight position sensor connector.
This fault was identified as intermittent. The severed wire was being held in contact by the cable clamps that secure the wiring along the landing gear strut. Under normal operating conditions, the sensor is designed to open the circuit when the aircraft is on the ground, preventing the gear from being retracted inadvertently.
Findings
- The primary cause of the gear collapse was the failure of the landing gear to remain extended due to an intermittent electrical connection.
- A maintenance error involving the improper positioning of cable clamps during a previous maintenance operation had caused the wiring harness to become overly rigid.
- The broken wire in the sensor harness allowed the system to intermittently signal a "flight" status even while the aircraft was on the ground.
- The pilot failed to perform the post-takeoff checklist, which would have identified that the gear lever was already in the retracted position.
- The aircraft sustained damage to the propeller and flaps.