What happened
On March 20, 2018, at approximately 11:00 local time, an SZD 9Bis Bocian 1E glider, registration SP-2589, departed from the airfield in Żernica Wyżna, Poland, using a winch launch system. The flight was operated by Aeroklub Bieszczadzki and included an instructor pilot and one passenger.
After being released from the winch cable at an altitude of approximately 350 meters, the pilot performed several basic aerobatic maneuvers before transitioning to low-altitude flight. During a turn intended to return to the airfield, the glider encountered a wind rotor, which caused a significant loss of airspeed. As the pilot continued the turn at low altitude, the left wing of the glider struck a tree. This impact caused the aircraft to enter a vertical dive, resulting in a high-impact collision with the ground. The aircraft was destroyed in the accident.
The investigation
The PKBWL investigation focused on the sequence of events following the winch launch and the aerodynamic conditions during the low-altitude maneuvers. The investigation established that the aircraft encountered turbulent air (rotor) during a turn, leading to a loss of airspeed and the subsequent collision with an obstacle.
Findings
- The primary cause of the accident was the loss of airspeed caused by encountering a wind rotor during a low-altitude turn.
- The pilot's decision to perform maneuvers at a low altitude left insufficient margin for error when the aircraft's performance was degraded by turbulence.
- The impact with a tree during the turn initiated the vertical descent and subsequent ground impact.
- The accident resulted in serious injuries to the passenger and minor injuries to the pilot.