What happened
On 10 November 2001, a Luton LA4A Minor, registration G-ATCJ, was conducting a flight test to facilitate its annual Permit to Fly renewal. The flight originated from a farm strip at Top Farm, Cambridgeshire, and included performance checks such as climbing, cruising at 2,500 feet, and descending to the never exceed speed (VNE).
During the flight, the pilot attempted a practice forced landing into a microlight landing strip. While at approximately 1,800 feet, the pilot applied carburettor heat and closed the throttle, at which point the engine ceased operation. Due to the presence of water at the northern end of the intended landing strip, the pilot diverted toward an alternative field. However, a high hedge obstructed the approach to this second field, necessitating a right-hand turn toward an adjacent area. The aircraft was at too low an altitude to complete the maneuver safely, leading to a heavy impact on the right wheel. The wheel collapsed upon contact with the ground, causing the aircraft to nose-over. The landing area was noted to be heavily rutted with mud and winter wheat. There were no injuries to the pilot.
The investigation
The investigation examined the engine failure and the environmental conditions at the time of the accident. The pilot identified carburettor icing as the cause of the engine loss. Meteorological data from the time of the incident showed an air temperature of 8°C with a dewpoint of 4°C and a surface humidity of 76%. While a full vertical temperature profile was unavailable, the presence of cloud between 1,800 and 2,500 feet indicated that humidity levels would have increased from the surface up to the cloudbase.
Findings
- The engine failure was attributed to the effects of carburettor icing.
- When assessed against standard aviation icing charts, the prevailing temperature and humidity levels indicated that moderate to serious carburettor icing was a significant risk.
- The aircraft sustained damage to the wing fabric, propeller, and cowling, and the collapse of the right landing gear.