What happened
On March 8, 2010, a Z-37 A agricultural aircraft was performing fertilizer spreading operations near Bönitz, Germany. The pilot had been conducting several sorties from an improvised grass airfield since early morning, though operations had been intermittently interrupted by snow showers.
At approximately 10:58 AM, the pilot departed for a field located southeast of the airfield. The mission involved spreading solid fertilizer along the edge of a field, parallel to a 110-kV high-voltage power line. Following a turn, the aircraft proceeded toward the field on a heading of approximately 190 degrees. During the flight, the pilot noted that horizontal visibility was roughly 2.5 km, but conditions were rapidly deteriorating due to increasing snowfall.
Upon deciding to abort the mission and turn right to return to the airfield, the pilot identified the power lines. In an attempt to reduce altitude to fly beneath the cables, the aircraft's left wing struck the lower wires of the high-voltage line at approximately 11:10 AM. The impact tore the leading edge from the wing and damaged the power lines. The aircraft subsequently struck the ground roughly 75 meters away, impacting first with the propeller and engine. The aircraft was destroyed, though the pilot escaped without injury.
The investigation
The BFU investigation examined the flight path, the aircraft's condition, and the meteorological environment. Investigators analyzed the impact site, noting that the lower cables had a clearance height of approximately 15 meters. The investigation also reviewed the pilot's credentials, noting extensive experience in agricultural aviation, and evaluated the weather reports provided by the Leipzig aviation advisory center, which had indicated fluctuating visibility and cloud ceilings due to a low-pressure system.
Findings
- The primary cause of the accident was the collision with the lower cables of the high-voltage power line while the pilot attempted to descend under the wires.
- Rapidly deteriorating visibility caused by increasing snowfall significantly contributed to the difficulty in maintaining safe clearance.
- The aircraft's left wing struck the cables, leading to the structural failure of the wing's leading edge and the subsequent crash.
- The impact also caused damage to the high-voltage infrastructure and the ground area.