What happened
On October 7, 2023, at approximately 14:10 JST, a privately owned Christen Industries A-1, registration JA408SS, was performing a glider tow operation at Hida Airpark in Takayama City, Gifu Prefecture. After releasing a glider, the pilot returned to the airfield for landing.
Upon approach, the pilot observed the windsock and estimated wind conditions of approximately 5 m/s from the north or north-northwest. The pilot elected to land on Runway 10 to avoid potential crosswinds from the side. The landing was initially stable, with the pilot maintaining a 30-degree flap setting and a speed of roughly 60 MPH.
During the landing roll, the pilot held the elevators in the full up position and allowed the aircraft to coast without applying brakes. As the aircraft decelerated, it began to veer toward the left. Despite the pilot applying full right rudder to correct the deviation, the aircraft's directional control failed as the speed dropped. The aircraft veered sharply to the left, causing the right wing tip to strike the runway surface. This movement triggered a roll to the right, and as the aircraft slowed further, the aft fuselage lifted, resulting in a nose over where the propeller and spinner made contact with the runway. There were no injuries to the pilot, though the aircraft sustained damage to the wing tip, propeller blades, and spinner.
The investigation
The JTSB investigation examined the aircraft's structural integrity, the runway surface, and meteorological data. Investigators noted that while the pilot's visual assessment of the windsock suggested manageable conditions, an anemometer near the administration office recorded a north wind of 8 m/s (approximately 16 kt). This exceeded the aircraft's demonstrated crosswind limitation of 15 MPH (about 6.7 m/s).
The investigation also reviewed the aircraft's tailwheel configuration, noting that such aircraft are inherently susceptible to the weathervane effect, where the wind pushes the tail, causing the aircraft to pivot around the main gear. The investigators found no mechanical failures in the braking or flight control systems, and the runway surface was found to be in good condition.
Findings
- The aircraft was operating in wind conditions that likely exceeded its certified crosswind limits.
- As the aircraft decelerated, the aerodynamic effectiveness of the control surfaces decreased, reducing the pilot's ability to counteract the weathervane effect.
- The loss of airspeed reduced the downward force on the tail caused by the up-elevator position, making directional control via the rudder and tailwheel steering increasingly difficult.
- The combination of a leftward yaw, centrifugal force from the turn, and a crosswind from the left caused the aircraft to roll onto its right wing tip.
- The final nose over was caused by the wind lifting the left side of the horizontal stabilizer, leading to a forward tip of the aft fuselage.