What happened
On July 29, 2021, an MH-46 Eclipse ultralight aircraft, registration OM-M919, was performing a test flight at Frýdlant nad Ostravicí Airport (LKFR) to certify its airworthiness. Shortly after takeoff from runway 26, at an altitude of approximately 30 meters, the pilot experienced a significant loss of engine power.
Facing a tailwind and unable to maintain sufficient climb performance, the pilot attempted to maneuver the aircraft toward a nearby cornfield to perform an emergency landing. However, the aircraft struck the treetops while attempting to clear a wooded area, subsequently crashing into the forest. The impact triggered a fire that destroyed the aircraft. The pilot sustained serious injuries during the accident.
The investigation
The ÚZPLN investigation examined the engine, the aircraft's configuration, and the circumstances surrounding the flight. Investigators noted that the aircraft had undergone modifications to its fuel system venting following a similar power loss event during a test flight in 2020.
Technical analysis of the Jabiru 3300 A engine revealed that the engine had not been warmed to the manufacturer's required temperature prior to takeoff; the cylinder head temperature was only 70°C, whereas a minimum of 100°C is prescribed. Additionally, the investigation reviewed the pilot's pre-flight procedures, noting that several tasks were performed with the assistance of another person, which may have led to incorrect flap settings.
Findings
- The primary cause of the accident was engine power loss caused by fuel flooding (an excessively rich mixture), occurring in combination with low cylinder head operating temperatures.
- A significant contributing factor was the presence of a tailwind during takeoff, which hindered the aircraft's ability to climb.
- The aircraft was operating with an disproportionately high fuel load, which increased the total weight and negatively impacted the flight profile.
- The investigation also identified the potential for incorrect flap configuration due to the collaborative nature of the pre-flight checks.