What happened
On June 25, 2023, at approximately 12:30 UTC, a towing operation at Lienz-Nikolsdorf airfield in Austria resulted in a fatal accident. A Robin DR400/180R was performing a glider tow, pulling a Schempp-Hirth Duo Discus.
Shortly after takeoff, the glider pilot climbed more rapidly than anticipated, causing the glider to rise above the level of the tug. During this phase of flight, at an altitude of approximately 10 meters, the cockpit canopy of the glider suddenly opened from left to right. The sudden aerodynamic forces caused the canopy to remain partially open. As the glider continued to climb, it pulled upward on the 30-meter tow rope, forcing the tail of the Robin DR-400/180R upward. This sudden pitch change caused the tug to enter a steep dive toward the ground.
The tow rope eventually broke at the glider's coupling at an altitude between 50 and 70 meters. Due to the extreme pitch angle and low altitude, the pilot of the tug was unable to recover the aircraft. The Robin DR400/180R struck the ground and was destroyed by a post-impact fire, resulting in one fatality. The glider, which remained intact, was able to land safely at the airfield.
The investigation
The SUB investigation reconstructed the flight sequence using eyewitness accounts, statements from the glider pilots, and data from the local police and authorities. The investigation examined the flight conditions, the mechanical state of both aircraft, and the maintenance history of the equipment. Investigators specifically looked into the cockpit configuration of the glider, noting that while the large side windows were closed, the small ventilation windows were open. The investigation also reviewed the maintenance of the tow rope and the implementation of manufacturer technical notes regarding canopy security.