What happened
On August 18, 2012, a Socata TB9 Tampico, registration F-GKVI, was completing a local flight lasting one hour and forty minutes at the Meaux Esbly airfield. As the pilot entered the downwind leg for runway 16, they followed a standard procedure of activating the carburetor heat, turning on the electric fuel pump, ensuring a full-rich mixture, reducing power, and extending flaps.
During the early part of the base leg, the engine began to misfire and power decreased. The pilot attempted to switch fuel tanks, but the engine eventually stopped. Following the activation of the stall warning, the pilot performed a nose-down maneuver. Realizing the runway could not be reached, the pilot executed a forced landing in a nearby field, resulting in a heavy impact and substantial damage to the aircraft. No injuries were reported.
The investigation
The investigation focused on the engine and fuel system performance. Technical examinations of the engine and fuel circuit revealed no mechanical malfunctions that could have contributed to the power loss.
Investigators analyzed the impact of environmental conditions and pilot procedures on the engine's air-fuel mixture. They noted that high ambient temperatures (31 °C) reduce air density. When combined with the use of carburetor heat, this can lead to an excessively rich mixture, which significantly reduces engine power and causes irregular operation.
Findings
- The primary cause of the power loss was an excessive enrichment of the air-fuel mixture.
- This enrichment was triggered by the use of the carburetor heat in high-temperature conditions.
- The pilot had been trained to systematically use carburetor heat during power reduction regardless of the weather, which contributed to the event.
- The stress of the emergency may have hindered the pilot's ability to manage the forced landing, leading to the hard impact.