19981112034869A

On November 12, 1998, at 1300 hours mountain standard time, a Piper PA-28-150, N991PK, experienced a loss of engine power, made a forced landing, and struck a sign on the landing rollout on interstate 8 near Gila Bend, Arizona. The aircraft sustained substantial damage and the private pilot was not injured. Visual meteorological conditions existed for the personal flight that departed montgomery field, san diego, California, at 1000 pacific standard time. The flight was scheduled to terminate at the sky harbor airport, phoenix, Arizona. In an interview with the safety board, the pilot reported that no mechanical anomalies existed prior to the loss of engine power. He stated that all instruments were in the "green" and that the engine was running smoothly. The engine then began to sputter and was still running, but it was not developing any power. The pilot contacted albuquerque center and declared an emergency. He stated that the landing was normal, but on the landing rollout he struck a road sign that he had not seen. The aircraft turned 45 degrees and came to rest after sliding on gravel (.4)the pilot said that no engine discrepancies were noted during either the preflight or the initial cruise portion of the flight, and that all engine instrument readings were normal. Between 500 and 1,100 mean sea level, the engine suffered a significant loss of power accompanied by sputtering, vibration, and the RPM fluctuating. He declared an emergency, performed the emergency checklist with no changes, and made a forced landing on a road. During the landing rollout the airplane struck a road sign that he had not seen. Postaccident inspection of the engine revealed the gear at the back of the crankshaft was detached and moving freely between the corresponding gears. The crankshaft gear attaching bolt and threads were undamaged and the bolt appeared to have backed out of the crankshaft and was resting in the crankshaft gear bore. The bolt locking plate remained at the head of the bolt, and exhibited fretting signatures. Fretting signatures were also located around the mating surfaces of the gear and crankshaft bore. The crankshaft gear dowel pin had failed, with fatigue striations visible to the naked eye. An engine overhaul was completed 1 month after an airworthiness dirctive (AD) was published requiring inspection of the crankshaft gear and the bolt to prevent the bolt from backing out and liberating the crankshaft gear. No evidence of compliance with this AD was found in the engine maintenance records.