What happened
On May 9, 2009, a private flight involving a modified LAK-17AT sailplane, registration D-KJGA, ended in a fatal accident near the Temploux airfield in Belgium. The aircraft had recently undergone a major modification to integrate a retractable SOLO 2350 engine and propeller.
During the flight, which began with a tow to 1,600 feet, the pilot attempted to start the newly installed engine after releasing from the tow plane. These attempts were unsuccessful, leading to a loss of altitude. As the pilot attempted to return to the airfield, the aircraft was observed with its airbrakes extended and the engine in the process of being retracted. While attempting a left turn to join the landing circuit, the sailplane stalled and entered a right-hand spin, eventually crashing alongside the E42 motorway. The pilot sustained fatal injuries upon impact.
The investigation
Investigators from AAIU(Be) examined the aircraft's recent modification history and the cockpit instrumentation. The investigation established that while the engine installation was performed under an approved major change, the aircraft's airspeed indicator had not been updated to reflect the new performance characteristics of the powered version. Specifically, the instrument still displayed the stall speed markings for the original, non-powered LAK-17A model.
Findings
- The primary cause of the accident was the sailplane being flown at a speed dangerously close to its actual stall speed, which triggered a stall during a turn at a low altitude.
- A significant contributing factor was that the airspeed indicator was still configured with the markings of the original LAK-17A, providing the pilot with inaccurate stall speed references for the modified LAK-17AT.
- The pilot's focus may have been divided by the complex and work-intensive task of attempting to start the engine and subsequently retracting it while managing the landing approach.
Safety action
- AAIU(Be) issued recommendations to the Lithuanian authorities to ensure the manufacturer revises its information bulletins to guarantee that all modified aircraft conform to the requirements of the updated Flight Manual.
- A recommendation was also made to EASA to ensure that Type Certificate holders take necessary actions to prevent similar discrepancies in airspeed markings on modified aircraft.