What happened
On July 3, 2012, at 12:16 local time, a single-seat Grob Astir CS glider, registration OH-658, was involved in an accident during a winch launch at Rautavaara aerodrome. The flight was intended to be a training session, and weather conditions were favorable for gliding. The launch was taking place in an area west of the main paved runway, where tall grass, measuring between 60 and 70 cm, had been allowed to grow.
During the takeoff ground run, the glider's right wingtip made contact with the ground twice in rapid succession. This contact created significant drag on the right side of the aircraft. As the winch continued to pull, the glider lifted off in an unstable state, banking sharply to the right and reaching a nearly inverted position at an altitude of approximately 10 meters. The pilot was unable to release the towing cable in time. Observing the abnormal flight attitude, the winch operator aborted the launch, causing the cable to detach. Without the tension of the winch, the OH-658 struck the ground nose-first in a near-inverted attitude, bounced, and slid 14 meters on its back, coming to a stop 86 meters from the takeoff point. The pilot sustained serious injuries.
The investigation
The investigation established that there were no technical failures on the aircraft prior to the accident. Investigators examined the takeoff area and found that the tall grass was a significant factor. The investigation also looked into the pilot's training and the procedures for winch launches. It was noted that the location of the release mechanism on this aircraft type was not ideally positioned for rapid reaction during emergencies. Additionally, the investigation reviewed the regulatory discrepancies regarding aerodrome classifications between different aviation regulations.
Findings
- The direct cause of the accident was the right wing dropping during the takeoff ground run, which caused the wingtip to strike the tall grass and the ground, creating heavy drag and inducing a sharp right turn.
- A contributing factor was the decision to continue flight operations in an area with high grass.
- The pilot was unable to counteract the wing drop with aileron input or release the cable before the aircraft became unstable.
Safety action
- A safety recommendation was issued to the Finnish Aeronautical Association to update winch launch training materials, specifically regarding emergency procedures during the ground run phase, and to ensure these guides are distributed to student pilots.
- A safety recommendation was issued to the Finnish Transport Safety Agency to resolve inconsistencies between aviation regulations AGA M1-1 and OPS M1-6 regarding aerodrome classifications.