What happened
On May 29, 2009, a Schempp-Hirth Ventus 2cT glider, registration D-KFGW, departed from Malden Gliding Club for a cross-country flight. The aircraft was launched using a winch system. Shortly after disconnecting from the cable at an altitude of approximately 280 meters, the pilot attempted to gain altitude using the onboard motor. However, the aircraft began to descend despite the engine being operational.
As the pilot focused on deploying the motor and managing the descent, the aircraft's airbrakes had inadvertently deployed during the launch. Unable to maintain altitude, the pilot attempted a turn to regain height but eventually decided to land on runway 31. Because the airfield is surrounded by dense forest, an off-field landing was not an option. The pilot retracted the main landing gear and shut down the engine before touchdown. The aircraft overran the runway end, coming to a stop in rough terrain, which resulted in severe damage to the fuselage underside. The pilot was uninjured.
The investigation
The investigation established that the airbrakes were not properly secured in the locked position prior to takeoff. Due to aerodynamic forces during the winch launch, the airbrakes were pulled outward. While observers on the ground noticed the deployment and attempted to warn the pilot via radio, the pilot did not hear the transmission because the onboard radio volume was set too low.
Investigators found that the pre-flight cockpit checks and the post-launch BOKS procedure (a specific safety checklist) were performed incompletely. Specifically, the pilot failed to verify that the airbrakes were locked and that the radio volume was audible. The investigation also noted that the pilot's heavy reliance on the motor's effectiveness delayed the decision to prepare for a safe landing.
Findings
- The primary cause of the accident was the incomplete execution of mandatory pre-flight and post-launch safety checks.
- The airbrakes were not in the secured position, allowing aerodynamic forces to deploy them during the launch.
- The pilot failed to notice the deployment because attention was diverted to starting the motor and managing the descent.
- The pilot did not receive radio warnings from ground personnel because the radio volume was set too low.
- A high level of experience may have led to a reliance on habit, resulting in less attention to standard procedures.
- The decision to attempt altitude gain with the motor, rather than immediately addressing the descent, delayed the landing preparations until a safe stop was no longer possible.