What happened
On September 23, 2016, at approximately 15:30 UTC, an amateur-built D8 Straton ultralight aircraft, known as Moby Dick, was involved in a fatal accident on a private airfield near Dolní Němčí, Czech Republic. The pilot was performing ground taxi trials on his property to troubleshoot issues following a recent engine installation.
During the final taxi attempt, the aircraft suddenly veered sharply to the right and unexpectedly lifted off the ground. The pilot, flying at a very low altitude, entered a continuous right-hand turn. As the aircraft followed this circular trajectory, the bank angle increased abruptly, leading to a loss of control. The aircraft struck the ground with its nose and left wing, resulting in the total destruction of the aircraft and the death of the pilot.
The investigation
An investigation by the ÚZPLN established that the aircraft was a homebuilt construction by the owner. Investigators examined the wreckage and recovered various construction documents, including assembly instructions and weight and balance calculations.
Technical analysis of the wreckage revealed significant discrepancies in the aircraft's configuration. The empty weight of the aircraft was found to be approximately 292 kg, which exceeded the manufacturer's specified empty weight range of 180–195 kg by more than 100 kg. Furthermore, the center of gravity was located 130 mm behind the allowable rear limit. Investigators also noted unauthorized modifications, such as an altered exhaust silencer length and improper propeller pitch settings.
Findings
- The primary cause of the accident was the crash of an unairworthy ultralight aircraft while flying at low speed and low altitude during a turn.
- The takeoff was likely unplanned, and the pilot failed to immediately abort the flight by landing ahead of the aircraft.
- The aircraft's weight and balance were significantly outside of safe operating limits, which negatively impacted its handling and flight characteristics.
- The pilot lacked the necessary pilot license and medical certification.
- The aircraft was not in a condition for safe flight, lacking a valid technical certificate and required insurance.
- The pilot was not wearing a safety harness at the time of the impact.