Summary of the Accident
On July 24, 2011, at approximately 15:27 Japan Standard Time, a privately owned SOCATA TB21, registered JA4123, was taxiing on the apron at Tajima Airfield in preparation for a flight to Nagoya Airport. During taxiing, the left-hand main landing gear (L/H MLG) retracted, causing the left wing to contact the ground surface and sustain damage. The aircraft came to a stop with its nose directed west-northwest, approximately 51 meters northwest of Spot 11. Scratch marks from the wing tip and flap hinge, each about four meters long, were left on the apron.
Flight History
Earlier that day, the aircraft had departed from Nagoya Airport with the owner piloting and the captain on the right seat. Upon arrival at Tajima Airfield at about 13:30, the owner encountered a problem extending the landing gear: the circuit breaker for the landing gear system (Gear CB) had popped up. After several unsuccessful reset attempts, the landing gear was lowered using the emergency landing gear knob. The three green down-lock indicator lights illuminated, and a normal landing was made.
Before departure from Tajima, the captain and owner performed an exterior preflight check. During the interior check, the owner found that the Gear CB was popped up. When the landing gear test switch was pressed, the three green lights illuminated, leading the owner to conclude the landing gear was down locked. The captain relied on this judgment. The engine was started and warmed up, and the owner reset the emergency landing gear knob to normal, which triggered an aural warning that ceased when the throttle was advanced. Taxiing then began. After checking brakes, the aircraft turned left; as it proceeded, the Aircraft gradually leaned left, and the left wing contacted the ground.
Aircraft and Personnel Information
The aircraft, a SOCATA TB21 (serial number 1055, manufactured April 23, 1990), had a valid certificate of airworthiness. At the time of the accident, its weight and center of gravity were within allowable limits. The captain, age 55, held a private pilot certificate with a single-engine land rating and a valid second-class medical certificate. His total flight time was 832 hours 44 minutes, with 10 hours on type. The owner, age 67, also held a private pilot certificate with a single-engine land rating, but his medical certificate had expired. His total flight time was 1,036 hours 11 minutes, with 179 hours 25 minutes on type. There were no injuries.
Damage and Site Conditions
The aircraft sustained substantial damage to the left wing, including cracks in the plastic wing tip cover, scratch marks on the lower surfaces of the wing tip and aileron, a scratched outer flap hinge, and deformation in the flap fitting structure. The footsteps on the left side of the fuselage were fractured. The apron surface showed scratch marks from the wing tip and flap hinge. Weather conditions were benign: wind from 360° to 010° at 8 knots, visibility 20 km, few clouds at 2,500 ft, temperature 26°C, dew point 20°C, and altimeter setting 29.81 inHg.
Investigation Findings
A functional test of the landing gear system revealed that when the main switch was turned on after resetting the popped Gear CB and returning the emergency landing gear knob, with the landing gear lever in the down position, all landing gears immediately moved to the up position and the motor buzzed. The three green lights went out and a red light illuminated as the gears moved from the down-lock position. This indicated that the landing gear was not in a down-locked configuration prior to taxiing.