When the aircraft was at about 50 feet above ground level after take off, the engine lost power, recovered to full power, then lost power again. The pilot commenced an approach for a landing, straight ahead. During the approach the engine again recovered power, the pilot closed the throttle and landed the aircraft in a tree strewn paddock. The left wheel struck a dead tree lying in the paddock and the aircraft groundlooped before coming to rest. The loss of engine power resulted from a design defect within the aircraft fuel system. Wear in the internal valves of the engine driven fuel pump caused valve seats to move off centre and stick open. This allowed fuel under pressure to be recycled back to the inlet of the electric fuel pump and resulted in a loss of fuel pressure to the carburettor. The loss of fuel pressure may have also resulted in fuel vapour locks forming downstream of the electric fuel pump which had been selected on prior to take-off.
