What happened
On July 11, 2011, a Vixen II ultralight aircraft, registration OK-QUD16, crashed near the Medlánky airfield (LKCM) in the Czech Republic. The pilot had been performing several test flights that day after reporting engine irregularities, specifically describing the engine as "stuttering."
During the final flight, the pilot took off from runway 34. Shortly after takeoff, while climbing, witnesses observed a significant drop in engine power. The aircraft transitioned into a level flight and then entered a sharp left turn. During this maneuver, the aircraft's airspeed dropped to near-stall levels. The aircraft subsequently entered a spin, pitching steeply toward the ground, and impacted a beet field approximately 220 meters from the runway threshold. The impact was followed by a fire that completely destroyed the aircraft. The pilot sustained fatal injuries.
The investigation
The ÚZPLN investigation examined the aircraft's technical history, the pilot's experience, and the engine's performance. Investigators noted that the aircraft did not have a valid technical certificate at the time of the accident, as the pilot had proceeded with the flight despite warnings from a technical inspector.
Regarding the engine, while the pilot reported irregularities, investigators found no evidence of a mechanical failure. However, fuel samples taken from canisters used to refuel the aircraft contained mechanical impurities, likely debris from the containers themselves. The investigation also noted that the aircraft's elevator control lacked the required physical stops to limit the range of aerodynamic surface deflection.
Findings
- The pilot elected to continue flying despite known engine irregularities and the lack of a valid technical certificate.
- An engine power loss prompted the pilot to attempt a 180-degree return maneuver at a very low altitude.
- The pilot failed to maintain sufficient airspeed during the turn, leading to a stall and the subsequent spin.
- The presence of mechanical impurities in the fuel supply may have contributed to the reported engine fluctuations.
- The aircraft was flying at a speed near its stall limit during the critical phase of the maneuver.