What happened
On March 16, 2011, a pilot was operating an Avions Pierre Robin DR 315 on a VFR flight from Leck to Hamburg-Fuhlsbüttel. During the flight, the pilot reduced the cruising altitude from 1,000 ft to 800 ft due to a lowering cloud base. Approximately 30 minutes into the flight, the engine experienced a significant loss of power.
After initially contacting Hohn military airfield to declare an intention to divert, the pilot decided to perform an immediate emergency landing due to the low altitude and the continuing decline in engine performance. While attempting to land on a narrow, paved farm track, the aircraft struck vegetation. The impact caused the aircraft to capsize, coming to rest upside down next to the path. The pilot, who was the sole occupant, escaped the wreckage without injury, though the aircraft was destroyed.
The investigation
The BFU investigation examined the aircraft, the meteorological conditions, and the pilot's actions. The investigation found that the aircraft, which had approximately 2,811 total flight hours, showed no signs of mechanical failure. Meteorological data indicated high humidity and a low dew point spread, creating conditions highly conducive to carburetor icing. The investigation also noted that the pilot's attention had been diverted by a malfunctioning fuel gauge indicating "low fuel," leading to a mental fixation on the fuel level.
Findings
- Carburetor icing was the primary cause of the engine power loss.
- The pilot's use of the carburetor heat was improper; after an initial attempt to use the heat, the pilot returned it to the "cold" position based on incorrect advice previously received from a mechanic.
- The flight was conducted under marginal VFR conditions with a low altitude of less than 1,000 ft.
- The pilot's situational awareness was compromised by a preoccupation with a faulty fuel gauge.
- The surrounding terrain, consisting of marshy ground, offered very few suitable alternatives for an emergency landing.