Pilot Debrief

STINSON 108 near Ninilchik, AK — 2023-07-13

Final reportANC23LA051
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Date
2023-07-13
Location
Ninilchik, AK, USA
Airport
NIN
Aircraft
STINSON 108
Registration
N97719
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

A partial loss of engine power due to failure of the No. 1 cylinder intake valve head.

NTSB narrative

The pilot reported that while en route he noticed a loss of engine power and the oil pressure decreasing. He performed a forced landing to a road. During the landing rollout the right wingtip struck a sign, which resulted in substantial damage. Postaccident examination of the engine revealed the No. 1 cylinder was fractured from the engine and remained partially attached by exhaust tubes and the intake manifold. The intake valve stem was fractured about an inch from the interior base of the valve. The piston and intake valve were destroyed by the internal forces in the engine and the fragments were not located.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have returned to NIN airport after noticing engine issues.

NTSB coding

Evidence available

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

Docket documents5

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