What happened
On 23 November 2003, a Pegasus Flash, registration G-MNKS, was conducting a private flight near Ince Blundel. While cruising at approximately 2,000 feet, the aircraft's Rotax 447 engine experienced a sudden drop in revolutions, falling from 5,200 RPM to 3,800 RPM. Although the engine remained operational, it could no longer accelerate, leaving the pilot with insufficient power to maintain level flight or return to the home airfield.
Seeking a safe area, the pilot identified a large, unobstructed field near Halsall, Lancashire, for an emergency landing. The field surface was extremely wet following recent heavy rainfall. Upon touchdown, the nosewheel sank into the soft ground, causing the aircraft to pitch inverted. The pilot sustained serious injuries and was rendered unconscious by the impact, though nearby witnesses successfully alerted emergency services.
The investigation
The AAIB examined the engine, which had undergone a complete rebuild only a month prior following a previous seizure. Testing conducted by the manufacturer's UK agent showed the engine could reach maximum power and operate within normal limits, with no debris found in the fuel filter. While the fuel flow was found to be well within requirements, investigators noted that the installed paper-type filter was no longer recommended by the manufacturer.
Further inspection of the carburettor revealed wear on certain components, though no direct failure was identified. Investigators also examined the ignition system, noting that the 'screw-on' top spark plugs used were susceptible to vibration-induced wear, which can lead to electrical tracking and engine misfires.
Findings
- The engine experienced a sudden loss of power that prevented the pilot from maintaining altitude.
- The aircraft's nosewheel dug into the saturated ground during the forced landing, causing the inversion.
- The specific cause for the loss of engine power could not be definitively identified through the engine examination.
- While the symptoms of the power loss suggested the engine might have been running on a single cylinder, the investigation could not confirm a mechanical failure of the components tested.