What happened
On August 17, 2024, a Grob G102 ASTIR CS, registration OY-XSD, was conducting a local training flight from Ejstruphede (EKVE). The flight was a significant milestone for the student pilot, marking their first flight in a single-seat glider. During the landing phase on runway 31, the aircraft experienced an unstable approach characterized by periodic "porpoising" as the pilot struggled to manage the unexpected effectiveness of the air brakes.
As the glider touched down, it briefly bounced off the runway twice. A left crosswind pushed the aircraft toward a cluster of trees located to the left of the runway. The pilot was unable to apply sufficient rudder input to correct the drift and avoid a parked glider. In the ensuing confusion, the pilot could not immediately locate the wheel brake lever, which was mounted on the control stick. Consequently, the OY-XSD drifted into the parked aircraft at an estimated speed of 15-20 km/h.
The investigation
The investigation examined the flight dynamics during the final approach and the cockpit ergonomics of the aircraft. It was noted that the student pilot's previous training had been conducted in gliders where the wheel brake lever was integrated into the air brake handle, whereas in this aircraft, the lever was located separately on the control stick. The investigation also reviewed the environmental conditions, noting a wind from 260° at 10 knots.
Findings
- The primary cause of the collision was the student pilot's inability to maintain directional control due to mental workload issues during a challenging landing.
- The student pilot experienced mental overload during the final approach because of the unexpected aerodynamic behavior caused by the air brakes.
- The pilot's previous experience with different brake configurations contributed to a delay in locating the wheel brake lever.
- The aircraft sustained light damage to its nose, while the parked glider suffered significant damage to its fuselage and canopy near the wing attachment point.