What happened
On April 26, 2010, a CZAW Sportcruiser, registration F-PELA, departed from the private airfield at Voves-Viabon for a flight toward Rouen. Approximately thirty minutes into the flight, the pilot switched the fuel selector to the left tank. Immediately following this action, the pilot observed a rapid decrease in engine power accompanied by engine surges. In an attempt to rectify the issue, the pilot activated the electric fuel pump and switched to the right fuel tank, but the engine continued to malfunction. Due to the low altitude of approximately 500 feet caused by cloud cover, the pilot performed a forced landing in a field. There were no injuries and the aircraft sustained no damage.
The investigation
The investigation focused on the fuel system and the refueling process at the Voves-Viabon airfield. Because the airfield lacks a dedicated refueling station, fuel is transported using canisters. It was discovered that the aircraft's left tank, carburetor, fuel filter, and fuel strainer all contained green engine coolant. This liquid, which is denser than aviation fuel, was not present in the right tank.
Investigators determined that the contamination occurred during refueling the previous day. One of the opaque canisters used for transporting fuel had previously contained engine coolant. Although the pilot had performed fuel sumping procedures for both tanks prior to departure, the contaminant was not detected during the pre-flight checks. The pilot had started the engine using the right tank and did not switch to the left tank until the in-flight incident occurred.