What happened
On 4 December 2006, an X’Air 700(1A), registration G-CBCM, was performing a flight at Sandtoft Airfield in Yorkshire as part of an annual Permit-to-Fly renewal. Following a thorough pre-flight inspection earlier that day, the pilot took off using full engine power.
During the initial climb, at an altitude of approximately 250 ft, the engine experienced a partial loss of power, dropping to roughly 20-30% of its maximum output. The pilot immediately prepared for an emergency, transmitting a PAN call and selecting a nearby field for a forced landing. However, as the aircraft reached 150 ft, the power loss intensified. Unable to reach the intended field, the pilot performed a landing in the center of a soft field. The impact caused the right main landing gear to detach and the nose gear to collapse upon contact with the soft ground, causing the aircraft to tip onto its nose and break the propeller. There were no injuries to the two occupants.
The investigation
The investigation focused on the cause of the engine's performance degradation. The pilot initially investigated potential fuel starvation by checking both the fuel filter and the carburettor float bowl, but both components were found to be clean.
Investigators examined local meteorological data from the time of the accident, which recorded a temperature of 11ºC and a dew point of 6ºC, with humidity at 71%. These atmospheric conditions were cross-referenced with the CAA General Aviation Safety Sense Leaflet 14A, which indicates such environments are highly susceptible to carburettor icing.
Findings
- The aircraft sustained damage to the nose, the propeller, the nose fairing, and the right main landing gear.
- The engine loss of power was likely caused by carburettor icing.
- The HKS 700E V3 engine used in the aircraft lacks a carburettor heat facility, a common characteristic in certain microlight engines.
- Atmospheric conditions (11ºC temperature and 6ºC dew point) were conducive to serious icing.