What was found
CRANKSHAFT FAILURE DURING TAKEOFF WITH NO REPORTED ENGINE ROUGHNESS OR LOSS OF POWER. CRANKSHAFT FOUND TO BE BROKEN AT COUNTERWEIGHT ATTACHMENT FLANGE RESULTING IN METAL FRAGMENTS CIRCULATING THROUGHOUT ENGINE RESULTING IN SEVERE DAMAGE TO ENGINE CASE AND ALL INTERNAL COMPONENTS. FAILURE FOUND TO BE CAUSED BY MECHANIC CONFUSION OF LYCOMING OVERHAUL MANUAL P/N 60294-7 REGARDING THE REQUIREMENTS OF COUNTERWEIGHT REPLACEMENT AND INSPECTION.