Incident Details
On Wednesday, May 15, 2024, at approximately 13:45 JST, a privately owned SOCATA TB21, registration JA4022, was involved in a serious incident during landing on Runway 18 at Fukui Airport. The aircraft's lower fuselage and propeller contacted the runway surface after all landing gears returned to the retracted position upon touchdown. The pilot, who was the only person on board, did not sustain any injuries. The incident was classified as dragging during landing of any part other than the landing gears under Japanese regulations.
Aircraft and Pilot Information
The aircraft, serial number 780, was manufactured on October 9, 1987, and held airworthiness certificate No. DAI-2023-146 valid until June 12, 2024. The pilot was an 80-year-old private pilot with a total flight time of 1,154 hours and 24 minutes, including 17 hours and 5 minutes on type. The pilot held a valid Class 2 aviation medical certificate and a pilot competency assessment valid until March 31, 2026. The pilot had flown 20 minutes in the 30 days prior to the incident.
Sequence of Events
According to the pilot's account and eyewitness statements, the pilot was conducting touch-and-go training. After takeoff, the aircraft entered the west downwind leg at about 800 ft. The pilot lowered flaps to take-off position (10°) abeam the runway center, but decided to delay landing gear and flap extension to reduce time in the traffic pattern. Starting the base turn with landing gears retracted, the aircraft became unstable on final approach due to low altitude and wind. The pilot focused on correcting approach angle and speed. When operating the throttle prior to landing, the pilot heard the landing gear warning, immediately lowered the landing gear lever, and set flaps to landing position (40°). At 13:45, the aircraft touched down with the main wheels first, then the nose wheel, after which all landing gears retracted, causing the lower fuselage to contact the ground. The aircraft skidded to a stop near the aiming point marking.
An eyewitness mowing grass beside Runway 18 reported that the landing gears were retracted when the aircraft passed the runway threshold; they began to extend after passing the eyewitness, but were not fully extended before touchdown.
Damage
The aircraft sustained minor damage: scratch marks on the main wheels, trailing edge of flaps, and lower fuselage. Both propeller blades were damaged.
Investigation Findings
The Japan Transport Safety Board (JTSB) conducted an investigation. Maintenance records showed no pre-existing anomalies with the landing gear; however, post-incident testing revealed that the landing gear extended correctly via emergency extension but not via normal lever operation, and the landing gear warning system had lost function. The JTSB concluded that the failure of the normal extension and warning system likely resulted from the belly landing impact. The landing gear downlock mechanism was found normal.
The investigation determined that the pilot had intentionally delayed landing gear extension as part of training habit and did not use a checklist during solo flight. The JTSB concluded it is probable that the pilot forgot to extend the landing gear due to corrective maneuvers on final approach, which also prevented the landing gear warning from sounding until the throttle was retarded near the threshold. The landing gear began to extend after the runway threshold but was not downlocked before touchdown, causing the unlocked gears to retract under the aircraft's weight.
The report noted that using a checklist could help prevent such oversights, as humans are prone to forgetting tasks when interrupted.