What happened
According to the pilot, the engine was running smoothly during flight but appeared to lack sufficient power. Instrument readings indicated that manifold pressure and engine revolutions per minute were within normal parameters. Approximately 60 feet above ground level, all power was lost. The aircraft subsequently crashed onto rolling terrain.
The investigation
An examination of the accident scene and the aircraft revealed that it was operating near its maximum weight limit. The pilot had not jettisoned his load prior to the incident. A teardown of the engine disclosed that the number one exhaust valve rocker shaft cover was missing. The corresponding shaft had dislodged, allowing the rocker arm to become loose. Additionally, the top rings on the number one and number four cylinders were found to be broken. Evidence suggested these components had been damaged for an extended period. Oil was also discovered on the air side of the fuel control manifold. The engine had accumulated only 43 flight hours since its major overhaul.
Findings
The aircraft was overweight due to the failure to jettison the load. Internal engine damage included a missing exhaust valve rocker shaft cover and broken cylinder rings that had persisted for some time. These mechanical failures contributed to the loss of power.