What happened
On October 4, 2009, a pilot planned a private flight from Erding to Zell am See, but diverted to the nearby Straßham airfield due to unsuitable weather. The flight, involving a B&F Technik FK 9 Mark 3 Utility, arrived at the airfield around 15:15 local time. During the landing on runway 21, the aircraft touched down approximately 50 meters behind the threshold. The impact caused the aircraft to bounce, prompting the pilot to immediately initiate a go-around.
Following the touchdown, the aircraft began to drift to the left with an increasing bank angle. After the aircraft had drifted approximately 90 degrees from its original heading, the pilot attempted to pull back on the elevator. This input led to an abrupt stall, causing the aircraft to drop sharply over its left wing. The aircraft struck the ground nearly vertically, resulting in one fatality and one serious injury.
The investigation
The BFU examined the aircraft's technical condition, the pilot's credentials, and the environmental factors at the time of the accident. The investigation included a review of radar data, witness video footage, and the aircraft's flight logs. Investigators also measured the airfield to verify its compliance with official permits. The investigation confirmed that the aircraft was mechanically sound and that the engine and flight controls were functioning correctly prior to the impact. No evidence of substance or alcohol impairment was found in the pilot.
Findings
Several critical factors contributed to the accident:
- Overloading and Center of Gravity: The aircraft was significantly overloaded, with a total takeoff mass of approximately 547 kg, exceeding the maximum allowable mass of 472.5 kg by over 70 kg. Furthermore, the pilot's weight of approximately 120 kg exceeded the 100 kg per-seat limit, placing the center of gravity outside the permitted range. This made the aircraft's flight characteristics, including stall speed and handling, unpredictable.
- Pilot Input: During the go-around, the pilot likely misjudged the actual airspeed due to the ground speed effects of the wind, leading to an excessive elevator input that triggered the stall.
- Environmental Conditions: The pilot was operating in turbulent, gusty winds of 10 to 15 knots. The combination of these conditions and the aircraft's unstable weight distribution pushed the aircraft to the limits of controllability.
- Lack of Experience: The pilot had relatively limited experience flying this specific aircraft type and was performing his first landing on a grass runway with such a short available distance.