What happened
On April 22, 2021, at approximately 18:13 local time, a Zephyr 2000 ultralight aircraft departed from Kulmbach airfield for a planned sightseeing flight. The aircraft was carrying the pilot and one passenger. After a takeoff roll of approximately 190 meters on runway 27, the aircraft entered a climb. However, only about 13 seconds after liftoff, the aircraft rolled around its longitudinal axis and struck the asphalt approximately 30 meters before the end of the runway. The impact resulted in two fatalities and the total destruction of the aircraft.
The investigation
The BFU investigation examined the aircraft's technical condition, the pilot's recent experience, and the environmental conditions at the time of the accident. Investigators analyzed surveillance footage from the airfield, which captured the takeoff and the subsequent loss of control. The investigation also included a detailed examination of the engine and the variable-pitch propeller. While the engine was found to be functioning under load at the time of impact, the propeller lever was set to the cruise position rather than the takeoff position, which reduced the maximum available power for the climb.
Findings
Several critical factors contributed to the uncontrolled flight attitude during the initial climb:
- Severe Overloading: The aircraft was carrying a payload of at least 260 kg, exceeding the maximum allowable payload of 110 kg by at least 150 kg. This weight imbalance likely resulted in an aft center of gravity outside of permissible limits.
- Inadequate Pilot Currency: The pilot had only performed one landing in this aircraft type within the previous 90 days, failing to meet the regulatory requirements for carrying passengers.
- Reduced Engine Performance: The variable-pitch propeller was set to the cruise setting, preventing the engine from reaching the maximum RPM required for optimal takeoff performance.
- Adverse Weather: The aircraft encountered a strong crosswind of 10 knots with gusts up to 16 knots, which exceeded the aircraft's maximum allowable crosswind component of 22 km/h and negatively impacted maneuverability.