On the day of the crash the pilot had intended flying from Trim Airfield to Weston Airport. In the initial climb out the engine suddenly stopped producing power. The pilot applied carburettor heat which restored engine power for a few seconds before it again cut out. The pilot elected to make a forced landing in a field of barley adjacent to the airfield where substantial damage was caused to the aircraft. Both the pilot and passenger were taken to hospital but did not sustain any injuries. There was no fire at the scene.
Substantial damage was caused to the aircraft during impact. The nose wheel had detached as had the port main wheel which was found under the port wing. The port flaps were damaged as were firewalls. One propeller blade was badly bent rearward whilst the second had a slight bend.
There were no propeller slash marks on the ground which indicated that the blade had been stationary at impact.
The investigation found that the engine could be restarted which indicated that there had been fuel in the carburettor at the time of the incident. However a Met Eireann aftercast for Trim Airfield indicated that the temperature of 16 degrees combined with a dew point of 12 degrees created a 'serious risk of carburettor icing at any power'. The pilot had reported that there had been no standing water on the runway at the time of the crash but that there had been dew on the runway.
Carburettor icing is caused by the refrigeration effect of fuel vaporization causing moisture in the inlet air to freeze. The temperature drop can be as high as 20 to 30 degrees. The ice gradually builds up in the carburettor venturi, reducing the 'breathing' ability of the engine. The engine consequently runs richer and richer until the point is reached where combustion is no longer possible due to oxygen starvation. During the taxi to the runway holding point the prop wash would have kicked moisture off the dew laden grass and increased the relative humidity around the engine. Although the pilot did apply carburettor heat during taxi the report finds that the 10 seconds that it was applied for was probably not sufficient to clear whatever ice was present. The report states that application of carburettor heat after the onset of icing can make matters worse by displacing air with water vapour. It is better to prevent icing from occurring in the first place by the application of heat.
In conclusion, the report finds that the crash was probably caused by carburettor icing upsetting the air / fuel ratio which in turn caused the engine to stop.
The report does not sustain any safety recommendations, although it does recommend that the pilots of all piston engine aircraft study useful information on the safety hazards associated with carburettor icing which can be found at : hazards
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