DURING A CROSS COUNTRY FLIGHT, THE PILOT REPORTED THAT THE ENGINE LOST POWER WHILE IN CRUISE FLIGHT. THE PILOT DECLARED AN EMERGENCY AND INITIATED A FORCED LANDING TO AN OPEN FIELD. DURING THE LANDING ROLL, THE AIRPLANE COLLIDED WITH A DITCH. DURING AN ENGINE EXAMINATION, IT WAS FOUND THAT THE CRANKSHAFT WAS BROKEN BETWEEN THE NUMBER TWO MAIN JOURNAL, EXTENDING TO THE NUMBER TWO MAIN JOURNAL CHEEK AND NUMBER TWO CONNECTING ROD JOURNAL. A METALLURGICAL EXAMINATION REVEALED AN OCCLUDED MATERIAL WHICH APPEARED TO BE OXIDES OR OTHER NON METALLIC INCLUSIONS PRODUCED DURING THE MANUFACTURE OF THE METAL PRIOR TO FORGING. THE METALLURGICAL REPORT STATED,'THESE OXIDES MOST LIKELY PROVIDED STRESS RISERS WHICH CONCENTRATED STRESSES IN THE CRANKSHAFT TO DEVELOP CRACKS UNDER CYCLIC LOADING.' THE CRACKS PROPAGATED UNTIL FAILURE OCCURRED.