What happened
On August 19, 2002, a flight instructor and a student pilot were conducting training maneuvers at Burg Feuerstein. After completing several successful approaches and landings at Kulmbach, the crew returned to Burg Feuerstein for a landing practice. Following the landing, the student pilot prepared for a go-around. The engine responded immediately to full power, and the Diamond DA20-A1 entered a normal climb.
However, at an altitude of approximately 15 to 30 meters, the engine power steadily declined to idle. The flight instructor immediately declared an emergency and took control of the aircraft. Due to the extremely low altitude, there was insufficient time to plan a complex maneuver, forcing a straight-in emergency landing in a harvested grain field approximately 300 meters beyond the runway. During the final approach, the aircraft's landing gear struck a small, vegetated earthen embankment. This impact caused the aircraft to strike the ground violently, resulting in heavy damage to the airframe and the loss of a propeller blade.
The investigation
The BFU examined the aircraft, the engine, and the maintenance history. The investigation focused on the cause of the sudden power loss and the circumstances of the impact. Investigators found that the engine was operating with sufficient fuel and that the aircraft's weight and center of gravity were within limits. The investigation also looked into the maintenance of the exhaust system, noting that the internal pipes had been replaced during a major overhaul in May 2001.
Findings
- The primary cause of the engine failure was a blocked exhaust outlet caused by a collapsed internal pipe.
- Severe internal corrosion had reduced the wall thickness of the exhaust pipe from 1 mm to as little as 0.1 mm.
- The high pressure of the exhaust gases caused the weakened, hot pipe to deform and collapse, obstructing the flow of gases.
- The damage was internal and could not have been detected during standard external visual inspections or the required 200/1000-hour maintenance checks.
- The student pilot sustained serious injuries, while the flight instructor sustained minor injuries.