What happened
On March 22, 1997, at approximately 17:00, a fatal hang gliding accident occurred at Oripää Airport during a training session organized by Turun seudun Riippuliitäjät r.y. The aircraft involved was a Sinisiipi SV 1 (registration not provided, manufactured in 198/80).
The training session, which included ground handling and low-altitude flight practice, transitioned from manual rope towing to a fixed-line towing method. During the student's first attempt at a fixed-line launch, the glider ascended rapidly to a height of 2–3 meters but began drifting significantly to the right of the tow line. As the glider reached an altitude of approximately 5–7 meters and drifted roughly 20 meters off-course, the 5 mm polypropylene tow rope snapped. The glider then entered a sharp right-hand turn, eventually striking the ground at high speed. The pilot sustained fatal injuries from the impact.
The investigation
The OTKES investigation examined the aircraft, the towing equipment, and the training procedures. Investigators inspected the site, the tow vehicle, and the Sinisiipi SV 1 at the Oripää hangar. The investigation also included interviews with the tow driver, the instructor acting as the release person, and several witnesses.
Technical analysis of the tow rope revealed that the rope had broken under a load of approximately 1400–1500 N during subsequent testing. The investigation also reviewed the student's training progress, noting that the student had received their student permit only recently and was performing their first fixed-line launch.
Findings
- The primary cause of the accident was the glider entering a lock-out state, a condition where a continuous, increasing turn away from the tow line becomes unrecoverable by the pilot unless tow tension is drastically reduced.
- The fixed-line towing method used was inappropriate for a student at this stage of training.
- The tow rope was too short for fixed-line operations, which reduced the time available for the crew to correct deviations.
- The tow driver did not use a tension meter to monitor pulling force, instead relying on visual assessment of the vehicle's speed.
- The instructor's position in the vehicle may have hindered the rapid release of the tow line during the emergency.
- The glider itself was too large for the student's skill level and experience.