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 .

It was determined that the accident Catastrophe was caused Causation by a fatigue crack in the main spar of the left wing that caused Causation the outer part of the left wing , outboard of the engine nacelle , to separate Forming_relationships from the remainder of the aircraft .

Aerodynamic forces Causation acting on the wing resulted in Causation an uncommanded retraction of the outboard slats .