What happened
On May 20, 2002, at approximately 18:45, a Kitfox A (ultralight, registration HB-YFS) was performing a flight near Carcassonne, France. While descending through 1,500 feet to join the traffic pattern at Carcassonne aerodrome, the aircraft's Rotax 582 engine suddenly ceased operation due to a seizure. The pilot was forced to execute an emergency landing in a wheat field located approximately five kilometers northeast of the airfield. The aircraft struck a pylon during the maneuver. There were no fatalities or injuries reported.
The investigation
Investigators examined the aircraft and found that approximately 40 liters of fuel remained in the tank and fuel lines. However, the two-stroke oil reservoir was found to be completely empty at the time of the accident. The engine was observed to rotate freely when cold.
Technical analysis of the throttle system revealed that the throttle controls three separate cables: two for the carburetors and one for the oil pump. This system maintains a 2% oil-to-fuel ratio by drawing from a 100-liter fuel tank and a 2-liter oil reservoir. The pilot noted that since the last oil refill, the aircraft had flown for five hours and fifteen minutes, which should have consumed approximately 1.6 liters of oil based on standard consumption rates.
Findings
- The primary cause of the engine seizure was an excessive oil consumption resulting from a mechanical failure.
- The oil pump control cable was prone to sticking in a fully open position, which leads to higher oil consumption.
- The pilot failed to perform a visual check of the oil level prior to the flight.
- The pilot had previously experienced intermittent issues with the oil pump cable sticking several years prior.