What happened
On April 25, 2021, a Schempp-Hirth Ventus cM glider, registration OK-3636, was engaged in a cross-country flight from Břeclav toward České Budějovice. Approximately 50 minutes into the flight, near Znojmo, the pilot was unable to locate thermal lift. At an altitude of roughly 400–500 meters AGL, the pilot attempted to restart the engine to continue the flight.
The pilot made three unsuccessful attempts to start the engine. Due to the low altitude, there was insufficient time to retract the engine or extend the landing gear. The pilot initiated a series of left-hand turns to find a landing site, descending to approximately 200 meters AGL. During the final turn, which was performed into the wind, the aircraft lost lift and began a wing-over maneuver.
While attempting to level the wings, the right wing struck a concrete fence post belonging to a nearby vineyard. The impact broke the post and caused the glider to strike the ground, followed by a short skid. The pilot sustained serious injuries but remained conscious and was able to call for help via mobile phone.
The investigation
An investigation by the ÚZPLN examined the flight data from the .igc file, witness statements, and the wreckage. The investigation focused on the pilot's decision-making process, the engine restart procedure, and the aircraft's technical state.
Investigators found that the pilot had performed a proper pre-flight check and used fresh batteries. However, the investigation noted that the pilot did not follow the full engine restart procedure required for a "cold" engine. Because the engine had been running earlier that day, the pilot believed the standard ground-start procedure (including fuel enrichment via the primer bulb) was unnecessary. Furthermore, the investigation examined the pilot's flight path, noting that the turns performed at low altitude led to a loss of situational awareness regarding the vineyard obstacles.
Findings
- The pilot did not direct the aircraft toward a suitable emergency landing field before attempting the engine restart, which increased the workload and stress.
- The pilot failed to account for the engine temperature, treating the engine as "warm" when it actually required the full cold-start procedure.
- The unsuccessful engine restart and the subsequent high-stress maneuvers led to a loss of situational awareness.
- The aircraft's speed dropped significantly due to the aerodynamic drag of the extended, non-functioning engine and a strong headwind component.
- The pilot's fatigue may have been a contributing factor, as he had completed two long-duration flights (over 5 hours each) in the preceding days.