What happened
On 25 January 2002, a Gulfstream AA-5A, registration G-ODAM, was conducting a training flight at Biggin Hill Airport. The flight, consisting of an instructor and a student, was intended to perform a series of circuits. During the pre-takeoff engine run-up, the crew noted that the carburettor heat lever was stiff, though it still produced a functional RPM drop when exercised.
After taxiing from the run-up area to the runway threshold, the student pilot initiated a short-field takeoff using full power. The climb proceeded normally until the aircraft reached approximately 300 feet, at which point the engine began to sputter and RPM decreased. The instructor took control and leveled the aircraft at 450 feet. Suspecting ice in the carburettor, the instructor applied full carburettor heat. This action resulted in an immediate and total loss of engine power. Despite attempts to rectify the issue by adjusting the throttle, carburettor heat, and fuel tanks, the engine failed to recover. The instructor subsequently selected a field for an emergency landing.
During the landing sequence, the aircraft's nosewheel struck a low wire fence. This impact sheared the nosewheel strut and caused the aircraft to veer sharply to the left. The aircraft sustained a bent propeller, a shock-loaded engine, and minor dents to the wing and underside panels. There were no injuries to the two crew members, who vacated the aircraft immediately after it came to rest.
The investigation
Investigators examined the engine and the carburettor induction system. An inspection by the operator's engineer found no mechanical anomalies or hardware faults in the engine, magnetos, or the carburettor heat mechanism. The fuel system was also found to be functional, with no evidence of water or sediment in the tanks. The engine was unable to be run for testing because the propeller impact had shock-loaded the unit.
Findings
- The atmospheric conditions at the time involved a temperature of 5°C and a dewpoint of 3°C with light rain, creating a high risk of induction icing.
- Carburettor icing is considered the likely cause of the power failure.
- The crew did not reapply carburettor heat after the initial engine checks and during the taxi to the runway.
- While applying carburettor heat typically causes a momentary power drop due to a richer mixture, it does not usually result in a total engine failure, yet the timing of the application coincided with the loss of power.