What happened
On May 31, 2009, a Glaser-Dirks DG-50 500M motor glider, registration PH-983, was performing a self-start from the Veendam glider airfield. The aircraft, which utilizes a retractable engine and propeller for independent takeoffs, was operated by a pilot and one passenger. During the takeoff roll, which proceeded in an easterly direction, a person known as a wing walker was assisting to maintain wing levelness.
As the aircraft reached a speed of approximately 75 km/h, it encountered a small depression in the grass runway. This impact caused the wings to dip, leading the left wingtip to strike the ground. The resulting loss of control triggered a ground loop that continued for approximately 300 meters. While there were no injuries to the two occupants, the aircraft sustained heavy damage, including a broken tail boom and a detached horizontal stabilizer.
The investigation
The investigation focused on the runway conditions and the takeoff procedure. The pilot, an experienced aviator with over 15,500 hours in powered aircraft, provided a statement regarding the sequence of events. Investigators examined the takeoff area, noting that self-starts require a significantly longer and smoother runway than winch-assisted starts.
It was established that the takeoff roll transitioned from an area used for winch starts to a section of the runway where the grass was notably taller. The investigation also reviewed the technical state of the Glaser-Dirks DG-500M, finding no evidence of mechanical failure or technical malfunction prior to the incident.
Findings
- The primary cause of the accident was an unevenness in the grass runway.
- The pilot underestimated the impact that the increased grass height in the latter part of the takeoff roll would have on the aircraft's stability.
- The decision to perform a self-start was complicated by the varying terrain and grass height along the required takeoff distance.