What happened
On April 9, 2012, a Tecnam P2002, registration F-GYJF, was conducting a local flight near Epinal, France. After an initial training circuit with an instructor, the pilot continued the flight alone. While flying at approximately 2,500 ft, the pilot identified a break in the cloud layer and decided to climb to 6,000 ft to fly in visual conditions.
After roughly 20 minutes, the pilot initiated a descent back to 2,500 ft through the cloud break, utilizing a low engine power setting and a tight turning radius. Approximately four minutes into the descent, the pilot attempted to increase power to 2,000 rpm and engaged the carburetor heat. However, the engine RPM dropped sharply from 2,000 to 700 rpm. Despite attempts to use the electric fuel pump, switching fuel tanks, and re-applying carburetor heat, the engine failed. The pilot performed a forced landing in a field, but during the landing roll, the aircraft struck a fence post, causing damage to the airframe.
The investigation
The investigation focused on the engine's performance and the environmental conditions. Post-accident examination of the Rotax 912 S engine revealed that it functioned normally after restarting. While no mechanical malfunction was found, investigators noted black deposits and soot on the spark plugs and exhaust pipes, which were consistent with carburetor icing in both carburetors.
Meteorological data confirmed that the conditions—characterized by high humidity (80%) and temperatures around 8°C—presented a severe risk of carburetor icing. The investigation also noted that the aircraft was using SP98 unleaded gasoline, which can increase icing susceptibility compared to Avgas 100LL.
Findings
- The primary cause of the engine failure was carburetor icing.
- The pilot's decision to perform a prolonged descent at low engine power contributed to the event. The pilot was unaware that during such a descent, the exhaust gas temperature is insufficient to allow the carburetor heat system to operate effectively.
- The pilot's maneuver, involving a steep 45-degree turn with reduced power and flaps extended, was an attempt to avoid instrument meteorological conditions (IMC) but inadvertently facilitated the icing process.