NTSB Identification: CHI97LA085.
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Accident occurred Tuesday, March 11, 1997 in MARQUETTE, MI
Probable Cause Approval Date: 02/02/1998
Aircraft: Cessna 172, registration: N171AS
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot reported that smoke started to enter the cabin from the heater vent. He shut the vent and scanned the engine instruments. He noted there was 'no oil pressure.' The engine 'started running very rough and shaking.' He 'shut the engine down 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 of the wreckage revealed 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. 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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

multiple oil leaks in the engine lubrication system. Factors were the disconnected wet vacuum pump line and the oil exhaustion.

Full narrative available

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