What happened
On May 7, 2016, a single-seat LS 4-b glider departed from the Klippeneck glider airfield via winch launch. The pilot intended to perform a standard circuit. During the climb, at an altitude of approximately 150 meters, the winch cable snapped.
Following the cable break, the pilot maintained forward momentum and initiated a shortened right-hand circuit. During the downwind leg, the aircraft descended rapidly toward tree height at a high airspeed of approximately 130 km/m. The pilot reported that the aircraft struck trees during the downwind phase and again while maneuvering into the final approach. The glider ultimately came to rest in the branches of a 10-meter-tall spruce tree near a local campsite. The pilot sustained serious injuries, and the aircraft was heavily damaged.
The investigation
The BFU investigation examined the flight data from a GPS device, which confirmed the cable break at 150 meters and recorded the high-speed descent during the circuit. The investigation also reviewed the pilot's training records, the aircraft's maintenance history, and the club's operational procedures. The aircraft, which was registered in Germany, had undergone its last airworthiness inspection in September 2015 and had flown only 26 hours since that date. Investigators also looked into the pilot's recent flight experience and the club's established emergency protocols for winch launch failures.
Findings
The investigation established that the primary cause of the accident was that the pilot misjudged the obstacle clearance required for his landing pattern, leading to a loss of control over the flight path and subsequent collision with trees.
Several contributing factors were identified:
- The pilot's overall flight experience was below average.
- There was a lack of recent practice at the start of the flying season.
- The pilot had not flown the LS 4-b model for over eighteen months, affecting his proficiency with the aircraft's handling.
- A lack of mental preparation regarding launch interruptions.
- The pilot had not performed a cable-break drill with an instructor at the beginning of the season.
- The pilot was unaware of the club's standardized emergency procedures for such events.