What happened
On May 29, 2011, a Schleicher ASK 21 glider departed from the Iserlohn-Rheinermark airfield for a short instructional flight. The aircraft was performing a winch launch with two occupants: a highly experienced pilot and a 17-year-old passenger.
Shortly after takeoff, the glider struggled to gain altitude, reaching a maximum height of approximately 40 meters above the center of the runway. During the climb, the towline became disconnected from the aircraft's release mechanism. Following a brief period of straight flight, the glider entered a 90-degree left turn and drifted away from the airfield at a very low altitude.
To avoid colliding with rows of trees and bushes, the pilot executed a controlled descent toward the ground. As the aircraft approached a building, the pilot intentionally maneuvered the left wing toward the ground to initiate a side-slip maneuver. The aircraft struck the ground, resulting in heavy damage to the glider and one serious injury to the pilot, who suffered a broken lumbar vertebra. The passenger sustained minor injuries.
The investigation
The BFU examined the wreckage and the flight path recorded by the aircraft's IGC logger. The investigation focused on the mechanical state of the release mechanism and the structural integrity of the glider. The aircraft came to rest in a grain field approximately 312 meters south of the airfield reference point.
Physical examination of the Schleicher ASK 21 revealed significant structural damage, including fractures in the fiber structure of both wings and a broken vertical stabilizer support. The underside of the left wing showed delamination near the aileron. However, the investigation found no technical defects in the aircraft's systems or the release mechanism.