The investigating Board believed Know the most likely cause of the accident to be a malfunctioning over-speeding outboard propeller caused by metal particles obstructing oil feed line regulator valves .

The malfunctions of the propeller pitch might have provoked Causation a flight disturbance and as a consequence the propeller may have sheared off .

The malfunctions of the propeller pitch might have provoked Causation a flight disturbance and as a consequence the propeller may have sheared off .

The crew were unable Confronting_problem to extinguish the fire Use_firearm or feather the propeller so made an emergency descent with the intention Aiming of landing Motion at Winton , a small town along the route .