What happened
On May 23, 2010, a Robin DR400-180, registration F-GGXZ, departed from Brest-Bretagne for a private flight to the Ouessant aerodrome. While flying the downwind leg for runway 06 at an altitude of 1,500 ft, the pilot performed several configuration changes, including activating the electric pump, engaging the carburetor heat, and extending one notch of flaps. During this phase, the pilot noticed engine roughness for several seconds. In response, the pilot advanced the throttle, but the engine power subsequently dropped significantly.
Realizing that a landing on the runway was no longer possible, the pilot executed an emergency landing in a field located approximately 850 meters south of the runway. During the landing roll, the nose gear collapsed, and the engine cowling and one propeller blade sustained damage. There were no fatalities among the two occupants.
The investigation
The investigation focused on the engine, the propeller, and the fuel system. The pilot, holding a PPL(A) with 380 total flight hours, reported that no anomalies were noted during pre-flight checks. During the engine roughness, the pilot attempted to switch the fuel selector from the main tank to the right tank, but after no improvement, returned the selector to the main tank position.
Technical examinations of the engine and fuel system revealed no mechanical failures or blockages. A subsequent test flight using the remaining fuel in the tanks was completed without issue. Meteorological data indicated that the ambient temperature and dew point (approximately 11°C) were conducive to carburetor icing, particularly as power was reduced during the downwind leg.
Findings
- The investigation could not definitively identify the specific cause of the engine power loss, as no technical failure was found in the engine or fuel circuit.
- Atmospheric conditions were favorable for carburetor icing.
- The possibility of a pilot error involving the fuel selector—specifically an incorrect positioning between the 'off' and 'main' positions—could not be ruled out.