What happened
On September 23, 2008, a privately owned Piper PA-46-310P, registration JA4140, was performing a leisure flight from Kitakyushu Airport to Yamaguchi-Ube Airport. The flight was operated by a single pilot under visual flight rules. Upon approaching Runway 07 at Yamaguchi-Ube Airport, the pilot was managing a landing with an expected westerly tailwind.
After a stable touchdown near the runway aiming point, the aircraft's nose suddenly dropped, causing the propeller blades to strike the runway surface. This impact caused the engine to stop. Shortly after, the aircraft began to veer to the right, eventually running off the side of the runway and coming to rest on its belly in a grassy area. The pilot was uninjured, and while the aircraft sustained minor damage, there was no fire.
The investigation
Investigators from the JTSB examined the aircraft's landing gear system, including the actuators and downlock mechanisms. The investigation focused on why the landing gear failed to remain locked after touchdown. Examination of the site revealed propeller strike marks along the runway centerline and tire scuff marks indicating the aircraft had tilted significantly during its rollout.
Technical analysis of the landing gear showed that all three gears were found in the stowed position after the incident. However, the mechanical components, including the struts and actuators, were found to be in normal working order, with no evidence of mechanical failure or hydraulic system malfunction. The investigation also reviewed the pilot's actions and the cockpit configuration, noting that the gear selector lever was found in the UP position following the incident.
Findings
- The landing gear downlocks for all three gears disengaged after the aircraft touched down.
- The disengagement was likely caused by the gear selector lever being temporarily moved to the UP position immediately after landing.
- The pilot may have mistakenly operated the gear selector lever instead of the flaps selector lever, a common error as the pilot noted a habit of retracting flaps immediately after touchdown.
- The nose gear collapsed due to the loss of the downlock, and the propeller strike acted as a cushion that prevented the nose from hitting the ground more violently.
- Although the pilot did not recall hearing the audible landing gear warning alarm, investigators concluded the alarm and warning lights were functioning normally and likely sounded during the period of downlock disengagement.