What happened
On December 20, 2015, a Piper PA-18-150, registration JA4048, was performing a routine glider towing operation at the Fujikawa gliding field in Shizuoka Prefecture. During the second flight of the day, the pilot completed the glider release near Mt. Kanamaru and transitioned into the landing phase.
As the aircraft approached the runway, the pilot noted a higher-than-normal approach angle and airspeed, likely due to a tailwind component. During the final stages of the approach, the pilot utilized a wing-low technique to align the aircraft with the runway centerline. However, the aircraft began to yaw to the right. Upon touchdown, which occurred beyond the runway's halfway marking, the pilot attempted to pull the control column back to ground the tailwheel quickly. This maneuver, combined with the existing right rudder input, caused the aircraft to veer toward the right edge of the runway.
As the aircraft exited the paved surface and approached a patch of bushes, the pilot applied heavy braking to decelerate. Due to the uneven terrain near the vegetation, the aircraft rolled forward and overturned, resulting in significant airframe damage.
The investigation
The Japan Transport Safety Board (JTSB) examined the flight path, the aircraft's mechanical condition, and the pilot's maneuvers. The investigation focused on the sequence of events from the moment the aircraft deviated from the centerline to the moment of the rollover. Investigators analyzed the aircraft's tailwheel configuration and the impact of the braking application on the uneven ground. The investigation also reviewed the standard operating procedures used by the Shizuoka Prefecture Aeronautical Association for towing flights.
Findings
- The primary cause of the runway excursion was the deflection of the aircraft to the right following rudder inputs and the inherent tendency of the tailwheel-type landing gear to swing the nose during direction changes.
- The subsequent rollover was caused by the pilot applying full braking while the aircraft was traversing uneven ground near the bush area.
- The pilot's decision to pull the control column back to ground the tailwheel contributed to the loss of directional control.
- The existing towing procedure, which requires dropping the towrope and landing in quick succession, necessitates a steep approach angle and reduces the effective usable runway length, making stable landings more difficult.