What was found
AIRCRAFT DESTROYED AS A RESULT OF FORCED LANDING INDUCED BY A SEPARATION OF THE ENGINE CRANKSHAFT. SUBSEQUENT INVESTIGATION DISCLOSED A FATIGUE FAILURE ADJACENT TO THE CENTER MAIN BEARING JOURNAL. THIS ENGINE HAD EXPERIENCED 2 PREVIOUS PROPELLER STRIKES WHICH DID NOT REQUIRE CRANKSHAFT INSPECTION UNDER LYC AD 91-14-22. SUBMITTER SUGGESTED REVISING LYCOMING AD 91-14-22 TO REQUIRE CRANKSHAFT INSPECTION IAW LYC SL L163C, FOLLOWING ANY PROPELLER STRIKE RESULTING IN PROP REWORK OR REPLACEMENT.