What happened
On May 5, 2024, at approximately 14:04 JST, a privately owned Grob G109B motor glider, registration JA2416, was performing a familiarization flight when it experienced a serious incident during landing at the Fukushima Sky Park. The flight originated from Hanam/maki Airport, and the pilot was navigating toward the Fukushima City Temporary Operation Site.
During the final approach to Runway 14, the aircraft encountered variable winds. To compensate for potential altitude loss due to wind fluctuations, the pilot initially increased engine power and retracted the airbrakes. However, upon touchdown, the aircraft experienced a series of significant bounces. The pilot attempted to maintain level flight to prevent the aircraft from floating, but the glider subsequently touched down multiple times, eventually deviating from the runway centerline.
During the landing roll, a sudden gust of wind caused the right wing to lift and the aircraft to yaw heavily to the left. In an attempt to regain directional control and stop the aircraft, the pilot applied the brakes forcefully. This sudden braking caused the main landing gear tires to lock, triggering a nose-over maneuver where the aft fuselage lifted and the aircraft tilted forward. Consequently, the propeller blades, spinner, and the lower section of the engine cowl struck the runway surface.
The investigation
The JTSB investigation examined the aircraft's flight history, meteorological conditions, and the mechanical state of the Grob G109B. Investigators analyzed the sequence of the multiple touchdowns and the physical evidence left on the runway, which included scratch marks from the landing gear and the propeller. The investigation also reviewed the pilot's actions regarding the use of airbrakes and the decision-making process during the bouncing sequence.
Findings
- The initial unstable touchdown and subsequent significant bouncing were likely caused by the pilot's failure to correct the aircraft's attitude amidst variable winds and an insufficient flare maneuver.
- The pilot's decision to continue the landing rather than executing a go-after a significant bounce contributed to the unstable landing sequence.
- The aircraft's high sink rate during the second touchdown was likely due to the airbrakes being fully deployed.
- The primary cause of the nose-over was the application of excessive braking force at an insufficiently reduced speed, which locked the main landing gear and caused the aircraft to pitch forward.
- The pilot's heavy braking was likely a reactive attempt to stop the aircraft after losing directional control due to wind-induced yaw.