Engine Failure Leads to Forced Landing in Wooded Swamp (N171AS)

Incident

The pilot reported that smoke began to enter the cabin from the heater vent. He shut the vent and scanned the engine instruments, noting that there was no oil pressure. The engine started running very rough and shaking. The pilot shut down the engine to minimize vibration, established best glide angle, and conducted a forced landing in a wooded swamp. The airplane sustained substantial damage during the landing.

Examination Findings

Examination of the wreckage revealed that the lower oil separator hose was not connected to the wet vacuum pump. The number one and two connecting rod bolts were necked and fractured, and corresponding holes were punched in the crankcase. The left magneto gasket and the starter motor mounting flange exhibited evidence of oil leakage. Combustion deposits and spark plugs in the number three cylinder exhibited evidence of possible high oil consumption. The operator of the airplane reported that he had topped off the engine oil prior to the origination of the accident flight.