What happened
On 2 December 2019, a Quik GT4SB, registration G-CFKJ, was conducting a private local flight from Caernarfon Airport. Approximately 15 minutes after departing from Runway 25, the engine began to sputter. Despite the pilot attempting to reduce power to a cruise setting, the engine failed completely and could not be restarted.
At an altitude of roughly 1,200 ft, the pilot identified a suitable field for an into-wind forced landing. However, during the final stages of the approach, the aircraft struck and severed 11,000-volt overhead power cables. The impact caused extensive damage to the aircraft's electrical systems, as well as damage to the windshield, pod, and wheel spat. There were no injuries to the pilot or the passenger.
The investigation
The investigation focused on the cause of the engine failure and the failure to detect the cables. Investigators examined the aircraft at a maintenance facility, where the engine was tested and found to be functioning correctly after the ignition system was replaced.
Regarding the visibility during the approach, the pilot reported that condensation on the windshield and helmet visor, combined with the low angle of the winter sun, obscured the view. The passenger's view was also restricted by the pilot. The investigation also looked into the thermal management of the engine, noting that the Rotax 912 engine relies on hot coolant to prevent ice formation in the carburettor.
Findings
- The engine failure was likely caused by carburettor icing.
- High humidity levels and a temperature of 3°C provided conditions conducive to ice formation.
- While the aircraft featured a system to prevent icing by using engine coolant, only 25% of the radiator was covered, which may have prevented the coolant from reaching the necessary temperature to keep the carburettor warm.
- The power cables were not detected due to a combination of low sun position and condensation on the aircraft's windshield and the pilot's visor.