Pilot Debrief

Cessna 170 near Baker City, OR — 2020-02-27

Final reportWPR20LA097
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Date
2020-02-27
Location
Baker City, OR, USA
Airport
BKE
Aircraft
Cessna 170
Registration
N5478C
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Cruise

Probable cause

The failure of the No. 2 connecting rod bearing as a result of oil starvation due to a contaminated oil filter screen.

NTSB narrative

The pilot reported that during a local flight, the engine started to knock and vibrate, and the oil pressure indication was low. He initiated a precautionary landing to an open field, and during the landing rollout, the airplane impacted a small ditch, which resulted in substantial damage to the left wing. A postaccident examination of the engine revealed that the No. 2 connecting rod was separated from the crankshaft. The No. 2 connecting rod journal exhibited thermal distress and mechanical damage. The remaining connecting rod journals and the crankshaft main bearings also exhibited thermal discoloration consistent with oil starvation. When the engine was rotated, no oil flow was observed through the crank journals and lifters. The oil filter screen was covered in dark thick oil and metallic debris and was collapsed. It is likely that the contaminated oil filter screen collapsed under pressure from the oil pump, which prevented the normal flow of oil through the engine; this resulted in the oil starvation of the No. 2 connecting rod bearing and subsequent separation of the connecting rod from the crankshaft.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have conducted a preflight engine inspection to identify issues.

NTSB coding

Evidence available

  • Photos
  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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