RedactedNarrative: ACCORDING TO OPERATOR, WHILE UNDERWAY AT IDLE SPEED, THE ENGINE BEGAN TO SPUTTER.  OPERATOR OPENED THE HATCH AND REMOVED THE AIR FILTER.  OPERATOR EXPLAINED THAT THE ENGINE THEN BEGAN TO RUN ADEQUATELY.  OPERATOR THEN SAID THAT THERE WAS A LOUD BOOM AND FLAMES BEGAN SHOOTING OUT OF THE TOP OF THE ENGINE.  THE FIRE DAMAGED THE ENGINE COWELL AND ENGINE.