What happened
On January 12, 1985, at approximately 16:15, a Fournier RF-3, registration CS-ALI, was conducting training flights at the Aeródromo Municipal de Cascais under favorable weather conditions, characterized by clear skies and no wind. The pilot successfully completed the first landing of the flight without incident. However, during the second landing attempt, the landing gear unexpectedly retracted immediately after the aircraft made contact with the runway.
The sudden retraction of the gear caused the aircraft to strike the ground with significant force, resulting in damage to the propeller, the landing gear doors, and the lower portion of the wing and fuselage. The pilot, who was the sole occupant of the aircraft, escaped the accident without any injuries.
The investigation
The GPIAAF investigation examined the mechanical operation of the aircraft's landing gear system. The investigation established that the aircraft and its engine were properly maintained and certified according to manufacturer instructions and regulatory requirements. The pilot was also found to be properly certified and qualified for the flight operations.
Technical analysis focused on the landing gear mechanism, which utilizes a relatively rudimentary system involving a roller and a spring-loaded latch that engages with a slotted sector to lock the gear in place. The investigation also reviewed the pilot's account, noting that while the gear had appeared to be unlocked during the initial climb-out following the first landing, the pilot had verified the "down" position twice before the second landing approach.
Findings
- The landing gear retracted during the landing roll, leading to structural damage.
- The mechanical failure was attributed to either the incorrect engagement of the roller or the failure of the locking lever to secure the mechanism.
- An alternative possibility was considered where the purely mechanical locking lever may have inadvertently dislodged from its position due to the impact of the touchdown, despite being correctly positioned.
- The aircraft sustained damage to the propeller tips, the landing gear fork, and the underside of the fuselage and wing.