NTSB Identification: SEA97LA195.
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Accident occurred Sunday, August 24, 1997 in ELK CITY, ID
Probable Cause Approval Date: 04/15/1999
Aircraft: Cessna 170, registration: N3964V
Injuries: 1 Serious,2 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.

While in cruise over mountainous terrain, the pilot noticed a drop in oil pressure followed immediately by engine seizure. The pilot initiated a force landing into rugged terrain and the airplane was destroyed. Exam of the engine revealed that the no. 6 connecting rod had separated due to lack of lubrication and bearing seizure. No evidence of leaking oil was found on the underside of the airplane. The pilot stated that she checked the oil level prior to the flight and that it was adequate. The oil was last changed about one month prior to the accident. According to a maintenance log entry and the accident tachometer time, the airplane had flown about 23 hours since the oil change. The pilot stated that the airplane could not have been flown for more than about 8 hours since the inspection. The rubber seal around the no. 6 push rod tube was found detached after it was salvaged, but it could not be determined if this was a preimpact condition. The published useable oil quantity for the engine is 5.6 qts. in a 5-degree nose down attitude. Conclusive evidence for the loss of engine oil could not be determined.

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

Oil starvation of the engine due to undetermined reasons, which led to the failure and separation of a main bearing and a connecting rod. A factor contributing to the accident was the lack of suitable terrain for a successful forced landing.

Full narrative available

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