The pilot in command was continuing a mustering endorsement which had been commenced the previous day. After flying for about 85 minutes the pilots stopped for a break of some 30 minutes. About 75 minutes after flying had recommenced a person on the ground heard a thump, and the wreckage of the aircraft was discovered shortly afterwards. It had struck the ground in a steep nose down attitude while spinning or turning to the left, about 270 metres to the south of the 30 strip. Investigation revealed that, at some stage prior to the final impact with the ground, the undersurface of the left wing had contacted the ground, causing left aileron failure followed by a loss of controllability. Medical evidence indicated that the pilot may have suffered a partial or complete loss of consciousness due to a pre-existing heart condition. However, it could not be determined whether this was a factor in the accident.