During a spray run, the pilot heard a loud bang, followed by a power loss and smoke in the cabin. He elected to land the aircraft in a paddock ahead. The mainwheels struck a log during the landing role and the aircraft nosed over. Inspection revealed that the top of the number three cylinder head had separated at the second barrel attachment thread. This failure caused a drastic loss of power and allowed combustion products into the engine cowling and cabin. Specialist examination indicated that the cylinder head separated due to metal fatigue cracking. The age of the cylinder could not be established.
