What happened
On May 6, 2004, an ASK-21 glider, registration PH-687, was performing a local flight near Terlet. Following an initial check flight, the pilot and an instructor decided to conduct a second flight to build the pilot's confidence, despite existing crosswinds. The plan was to fly the aircraft via a paved path toward the hangar's flyover strip.
During the flight, the aircraft lost significant altitude during a turn, which the instructor attributed to downwash. As the glider continued toward the flyover strip, the instructor noticed a further decrease in airspeed and advised the pilot to land on the paved path. The pilot did not follow this instruction and continued the approach. Due to the prevailing crosswind, the aircraft drifted toward a nearby heath slope. The airspeed dropped to a critical level, causing both wings to stall sequentially. The right wing struck the slope, causing the aircraft to spin 90 degrees and slide sideways. The impact resulted in the fuselage breaking in two behind the cockpit. There were no injuries to the two occupants.
The investigation
The investigation focused on the decision-making process and the roles of the occupants. While the pilot was the designated person in command, the instructor was acting as an observer. The investigation examined why the instructor's recommendation to land on the pavement was ignored and why the instructor did not intervene to take control of the aircraft when the situation became critical.
Findings
- The pilot's lack of experience and currency contributed to an unsafe flight profile.
- The pilot failed to follow the instructor's specific instruction to land on the paved path.
- The instructor failed to take immediate control of the aircraft when the pilot's non-compliance led to a dangerous flight state.
- Ambiguity regarding the instructor's role and the authority structure during the flight prevented timely intervention.
- The combination of a crosswind and low airspeed led to a wing stall and subsequent impact with the terrain.