Pilot Debrief

STINSON 108 1 near Lodi, CA — 2013-12-27

Final reportWPR14LA079
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Date
2013-12-27
Location
Lodi, CA, USA
Airport
O20
Aircraft
STINSON 108 1
Registration
N8848K
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Initial climb

Probable cause

The fatigue failure of the crankshaft, which resulted in a total loss of engine power and subsequent forced landing.

NTSB narrative

The pilot reported that, shortly after takeoff, the engine began to sputter and that it eventually lost all power. The pilot was unable to return to the airport and initiated a forced landing to an open field. During the landing, the airplane struck a berm, nosed over, and then came to rest inverted. A postaccident examination of the engine revealed that the crankshaft and camshaft had broken adjacent to the accessory section. A metallurgical examination of the crankshaft fracture surfaces revealed a thumbnail-shaped pattern consistent with fatigue that had initiated at the crankshaft surface near the edge of the No. 2 connecting rod journal. It is possible that the fatigue initiated due to the No. 2 connecting rod bearing shifting during operation. The camshaft fracture features were consistent with overstress. Maintenance records indicated that the last annual inspection was completed about 9 months before the accident and that, at that time, the engine had accumulated about 250 hours since major overhaul.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted takeoff after engine started to sputter.

NTSB coding

Evidence available

  • 6 docket documents
View NTSB final reportView NTSB docket

Docket documents6

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