Accident Overview
The airplane was substantially damaged during a forced landing after a complete loss of engine power during initial climb following takeoff. The aircraft came to rest on the median of a four-lane highway approximately 4 miles north of the departure airport.
Pilot Report
The pilot reported that about 10 minutes after takeoff, while at approximately 3,000 feet mean sea level, he heard a loud bang followed by extreme vibrations. He executed a forced landing on the highway. During the landing flare, a car turned in front of the airplane. The pilot avoided the car, but the left wing struck trees. The airplane then came to rest on the highway median.
Post-Accident Inspection
A post-accident inspection of the engine revealed that the crankshaft had failed aft of the number 2 main bearing journal. Metallurgical examination of the fracture surface showed crack arrest markings (beach marks) indicative of fatigue cracking. Fatigue initiation occurred at the surface of the main bearing journal slightly forward of the aft radius. The adjacent journal surface was roughened and discolored, with multiple longitudinally oriented parallel cracks (ladder cracks). Magnified examination determined that the fatigue fracture originated at one of the ladder cracks and propagated aft through approximately 75 percent of the crank cheek before the crankshaft failed. Other journals exhibited circumferential scratches and light wear, but none showed the level of surface damage observed on the fractured main journal.
According to the maintenance logbook, the engine had accumulated 3,109.8 total hours and 876.8 hours since overhaul.