What happened
On November 27, 2021, at approximately 14:24 JST, a privately owned Cristen Industries A-1, registration JA408 and 83, was involved in a serious incident at the Menuma Gliding Field in Kumagaya City, Saitama Prefecture. The aircraft, which had been operating as a tow plane, completed a flight after detaching a glider in mid-air and returned to the unpaved landing strip.
Upon touchdown, the pilot utilized 30-degree flaps and maintained idle engine power. After the main wheels touched down at approximately 50 mph, the tailwheel subsequently made contact as the aircraft decelerated. During the landing roll, the pilot steered toward a parking position to prepare for subsequent operations. While rolling toward the parking area without applying brakes, the aircraft's right wing suddenly lifted, causing the airframe to lean heavily to the left. The pilot, maintaining neutral aileron input and believing the wind was a steady headwind, did not immediately realize the left wingtip had struck the ground. The pilot only became aware of the contact after being notified by a witness once the aircraft had reached the parking position.
The investigation
The investigation focused on the meteorological conditions and the aerodynamic stability of the aircraft during the landing roll. Investigators examined the wind conditions at the gliding field, noting that while a northwesterly wind of approximately 6 m/sec was prevailing, the day was characterized by gusty conditions. The investigation also reviewed the aircraft's flight manual regarding crosswind limitations and the specific training procedures of the gliding field, which mandate the suspension of flights if crosswind components exceed 4 m/sec or headwinds exceed 10 m/sec.
Findings
- The aircraft sustained minor damage, specifically the partial peeling of paint on the left wingtip, though no significant structural rub marks were identified.
- Meteorological data indicated that while the prevailing wind was within safe limits, the wind direction was fluctuating between northwest and north, with gusts reaching approximately 10 m/sec.
- At the moment the tailwheel touched down, the aircraft was in an upward attitude with flaps extended, which increased the angle of attack of the main wing and made the airframe susceptible to instability.
- A gusty wind from the right likely shook the aircraft during the landing roll, causing the right wing to float and resulting in the left wingtip making contact with the ground.