SEA83FA093

Factual narrative

THE ACFT WAS TAKING OFF FOR A 1 HOUR ENGINE RUN-IN FOLLOWING A TOP OVERHAUL. AFTER LIFTOFF THE ENGINE BEGAN A GRADUAL POWER LOSS AND ROUGH RUNNING. THE PILOT WAS TRYING TURNING BACK TO THE RUNWAY TO LAND WHEN TOTAL POWER LOSS OCCURRED. THE ACFT HAD TURNED 45 DEGREES WHEN THE NOSE FELL THROUGH, THE WINGS ROTATED 180 DEGREES TO THE LEFT AND THE ACFT IMPACTED NOSE FIRST ON THE RUNWAY. THE MECHANIC WHO PERFORMED THE REMOVAL AND REINSTALLATION OF THE CYLINDERS FOR THE TOP OVERHAUL WAS OCCUPYING THE LEFT SEAT. THE MAINTENANCE SUPERVISOR WAS THE PILOT-IN-COMMAND IN THE RIGHT SEAT. THE LOCKING NUT ON THE #1 CYLINDER EXHAUST VALVE ADJUSTING SCREW WAS FOUND LOOSE AND THE ADJUSTING SCREW HAD BACKED OUT OF THE ROCKER ARM BY PUSHROD ACTION DURING TAKEOFF, NEGATING ROCKER ARM ACTION AND EXHAUST VALVE OPENING. THE LOCKING NUTS FOR ALL OF THE OTHER VALVE ADJUSTING SCREWS WERE FOUND PROPERLY TORQUED. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12