What happened
On 27 February 2001, a Beech C2 and registration G-BBTX was participating in a flight at Blackbushe Airport for the purpose of a pilot rating re-validation. The flight, a dual instruction session, involved a pilot and an instructor performing practice forced landings (PFL) from an altitude of 2,000 feet.
After successfully completing an initial engine-out landing, the crew began a second descent with the engine at idle power. During this phase, the carburettor heat was applied several times to warm the engine. However, during the final approach of the second attempt, the engine failed to respond to the pilot's application of power. As the airspeed decreased, the aircraft entered a stall and struck the paved undershoot area, short of the runway threshold. The impact caused damage to the propeller, the nose, and the left main landing gear, as well as the underside of the fuselage. Both occupants vacated the aircraft without injury.
The investigation
Investigators examined the aircraft and its Lycoming O-360-A4J engine. While the aircraft had recently undergone engine work following a previous propeller strike, no mechanical defects were found in the fuel system, ignition, or engine components during on-site inspections or subsequent test cell running. The engine responded smoothly to throttle inputs during testing.
Prior to the accident, some members of the aircraft's flying group had reported intermittent rough running during engine checks. However, the pilot on the day of the accident was unaware of these reported issues. The investigation also noted that the carburettor heat flap box had recently been replaced, and the engine was being operated at low power settings during the descent.
Findings
- The engine failed to respond to throttle inputs, a symptom consistent with carburettor icing.
- Weather conditions at the time were such that severe carburettor icing was expected at all power settings.
- The use of low power settings during the practice landings increased the aircraft's susceptibility to ice formation.
- The aircraft was not equipped with a carburettor icing detection system.
- Communication of engine serviceability issues within the flying group was unreliable due to the lack of a formal technical log requirement.