What happened
On May 2, 2015, a glider tow operation commenced at Elz airfield using a Diamond Aircraft Industries GmbH HK 36 TTC “Super Dimona” acting as the tug and a Rolladen Schneider LS 6 b glider. The takeoff began from the grass area at the northwest edge of runway 07.
As the aircraft accelerated down the asphalt runway, the HK 36 TTC lifted off approximately three seconds before the glider. At a speed of roughly 100 km/h, the glider pilot, perceiving a potential issue with the elevator, released the tow cable immediately after the glider's liftoff. Following touchdown, the glider drifted approximately 10 degrees to the left. To prevent the aircraft from overrunning the end of the airfield, the pilot initiated a sharp right-hand braking turn, known as a "Ringelpiez," by dropping the right wing. During this maneuver, the aircraft was traveling at approximately 90 km/h. The right wingtip struck the ground, causing the aircraft to tilt at a 45-degree angle. The fuselage subsequently struck the ground, resulting in significant structural damage.
The investigation
The BFU investigation utilized cockpit video from the LS 6 b, webcam footage, and physical inspections of the aircraft. The investigation examined the flight sequence, the mechanical state of the aircraft, and the communication between the pilots. The investigation confirmed that the glider was carrying 90 kg of water ballast, a fact that had not been communicated to the tug pilot prior to departure. The inspection of the LS 6 b revealed a compressed cockpit, a shattered canopy, and a broken fuselage tube forward of the tail boom. The trim wheel was found to be blocked, and the brake flap linkage was bent.
Findings
- The pilot of the LS 6 b initiated an emergency braking maneuver to avoid overrunning the airfield.
- The glider pilot released the tow cable shortly after takeoff due to a perceived elevator malfunction.
- The pilot of the glider failed to inform the tug pilot that the aircraft was carrying 90 kg of water ballast.
- The glider sustained heavy damage to the fuselage and cockpit during the ground impact.