What happened
On June 11, 2011, at approximately 08:05 local time, a motor hang glider (MZK) with an MW 155 wing was involved in a fatal accident northwest of Syrovic, Czech Republic. The pilot was performing a takeoff from a private, prepared grass strip.
According to witness testimony, immediately after the aircraft became airborne, it initially tilted to the left, which the pilot corrected. However, at an altitude of approximately 30 meters, the aircraft entered a sharp right-hand turn with an increasing angle of descent. The aircraft subsequently struck the ground in a steep, right-banked attitude. The impact resulted in the total destruction of the aircraft and fatal injuries to the pilot.
The investigation
The ÚZPLN investigation examined the wreckage and reviewed photographic evidence of the aircraft's assembly. The investigation established that the aircraft was not registered with the Lightweight Aircraft Association (LAA) and did not possess a valid technical certificate. The owner had personally assembled the wing in Syrovice following its purchase on May 1, 2011.
Technical examination of the wreckage revealed that the spreader bar tensioner was not properly secured within the metal fitting at the rear end of the keel tube. Specifically, the tensioner was not held in place by the pin as required during flight. Further inspection showed that the tensioner had fractured at a point where the cross-section was narrowed by a hook-shaped cutout used during assembly.
Findings
- The primary cause of the accident was the incorrect securing of the spreader bar tensioner.
- During the takeoff roll and initial climb, the structural load caused the spreader bar tensioner to break at its weakened point.
- The failure of the tensioner led to the release of the tensioned spreader bar, which fundamentally altered the shape and aerodynamic properties of the wing.
- This structural failure resulted in an immediate loss of control and the subsequent high-angle descent into the ground.
- The pilot was found to be in good health, with no evidence of alcohol or prohibited drugs influencing the flight.