What happened
On 5 August 2003, a Socata TB10 Tobago, registration G-BNIJ, was preparing for a flight from Sandtoft Airfield to Skegness following a previous leg from Kemble. After completing standard engine start procedures and power checks, the pilot commenced a takeoff from Runway 05. The aircraft achieved a normal takeoff roll and began a climb at 80 knots.
At an altitude of approximately 100 feet and a speed of 86 knots, the engine experienced a 90% reduction in power. The aircraft was passing over a trading estate near the upwind end of the airfield when the loss of thrust occurred. The passenger, also a pilot, verified that the throttle, mixture, and propeller levers were all in the forward position and that the carburettor heat was fully engaged. The pilot attempted to restore power by checking the magneto switch and switching fuel tanks, but the aircraft approached a stall condition.
The pilot subsequently performed a forced landing in a field roughly 800 metres beyond the upwind end of the runway. During the landing, the aircraft struck a wire fence and sustained substantial damage to the engine, propeller, wings, nose, and landing gear. There were no injuries to the two occupants.
The investigation
The investigation examined the engine controls and fuel system following the impact. An engineer who recovered the aircraft noted that the right fuel tank had split upon impact and was empty. While the carburettor had been torn from the engine, the fuel feed pipe remained connected and intact.
Testing of the fuel system revealed that operating the electric fuel pump failed to produce fuel pressure. When the fuel selector was switched to the left tank, which was intact and contained fuel, the pump failed to establish a consistent fuel flow, despite the presence of fuel in the tank and the apparent integrity of the lines between the tank, pump, and carburettor. The carburettor contained a partial amount of fuel, which was identified as 100LL.
Findings
- The engine suffered a sudden and massive loss of power during the initial climb phase.
- Environmental conditions (25°C and 43% humidity) were considered unlikely to have caused significant carburettor icing.
- A fuel vapour lock was considered a possibility, though the pilot noted the ambient temperature was not particularly high.
- The investigation could not definitively determine the cause of the power reduction, as the fuel system failed to establish flow during post-accident testing despite the availability of fuel in the left tank.