What happened
On May 26, 1996, at approximately 12:00, a Schleicher ASW 20 L glider, registration PH-709, was performing a winch launch at Soesterberg Airbase. During the ascent, the pilot noticed a complete lack of aerodynamic pressure on the elevator. Realizing the control surface was not functioning, the pilot disconnected the winch cable at an altitude of between 50 and 70 meters.
Despite the disconnection, the aircraft entered a steep descent at an angle of approximately 20 degrees. Because the elevator was not connected to the control system, the pilot was unable to adjust the aircraft's pitch. The glider struck the ground at high speed in a level attitude, resulting in the destruction of the nose and cockpit, as well as the breakage of the tail and both wingtips. The pilot sustained serious injuries.
The investigation
The investigation focused on the assembly of the aircraft prior to flight. Earlier that morning, the pilot had assisted in assembling other club aircraft before setting up his own. While a club member assisted with the fuselage and wings, the pilot personally installed the remaining components, including the stabilizer, without further assistance.
The investigation examined the l’Hotellier quick-release mechanism used to connect the elevator to the control rod. While this mechanism has a history of issues, technical testing confirmed that the specific hardware on PH-709 was functional and that the Wedekind retaining sleeve was working correctly. Investigators also reviewed the pilot's pre-flight actions, noting that the pilot had signed off on the daily inspection but had not performed a full walk-around or a specific visual check of the elevator's movement.
Findings
- The primary cause of the accident was that the elevator connection was not secured and was not checked by the pilot.
- The pilot was under pressure to complete the launch as he was scheduled for the final cable of the day.
- The pilot failed to perform a visual check of the elevator's operation or a proper walk-around.
- The only control check performed prior to launch was moving the control stick, which was insufficient to detect the disconnected linkage.
- The pilot did not wear a parachute to avoid exceeding the maximum takeoff weight, though the low altitude of the failure would have made a parachute deployment ineffective regardless.