What happened
On 10 December 2006, a Pitts S-1S, registration G-BOXH, was conducting a familiarisation flight in the vicinity of Goodwood. The flight, which included basic aerobatic manoeuvres such as loops, rolls, and spins, was interrupted when the engine began misfiring. After an initial attempt to resolve the issue using carburettor heat, the engine power fluctuated significantly. While the engine briefly recovered, it failed again at approximately 1,000ft.
Following the loss of power, the pilot performed a forced landing into a ploughed field. Although the aircraft was positioned at the appropriate attitude and speed for the landing, the impact caused the aircraft to nose over and come to rest in an inverted position. There were no injuries to the pilot, though the cockpit side was pressed so close to the ground that she was initially trapped. Nearby helicopter crews from a Robinson R2/R44 flight were able to assist by lifting the tail of the aircraft, allowing the pilot to crawl to safety.
The investigation
The investigation focused on the cause of the engine failure and the subsequent aircraft movement. The aircraft sustained severe damage to the engine, propeller, landing gear, fin, rudder, and the lower right wing. Investigators examined the atmospheric conditions, noting that the temperature and dew point in the Goodwood area were +9.5ºC and +5ºC, respectively. These conditions are known to be highly conducive to the formation of serious carburettor icing.
Findings
- The engine failure was likely caused by carburettor icing.
- Atmospheric conditions at the time were suitable for ice accumulation in the carburettor.
- The pilot was unable to confirm the exact position of the carburettor heat control (HOT or COLD) at the moment the engine ceased functioning.
- The aircraft overturned during the forced landing, resulting in the inverted position of the wreckage.