Pilot Debrief

PIPER J3C-65 near Belfair, WA — 2023-06-04

Final reportWPR23LA215
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Date
2023-06-04
Location
Belfair, WA, USA
Airport
PWT
Aircraft
PIPER J3C-65
Registration
N77583
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Approach

Probable cause

The total loss of engine power due to the fatigue failure of the crankshaft accessory drive gear.

NTSB narrative

The flight instructor reported that during an instructional flight, while approaching the airport to land, there was a loud noise followed by a total loss of engine power. The flight instructor took control of the airplane and initiated a forced landing to an open area. During the landing roll, the airplane impacted rough and rising terrain. The left wing was partially separated, and landing gear was collapsed. Postaccident examination of the engine found the crankshaft accessory drive gear had failed. Metallurgical examination of the crankshaft and gear remnants revealed the fracture surfaces of two of the gear teeth had signatures of fatigue. Mechanical damage to the terminus of the observed fatigue cracks prevented determination of the initiating event that resulted in the eventual failure of the gear. The failed gear prevented both magnetos from operating, which resulted in a total loss of engine power due to a lack of ignition.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Performing engine checks before approach could have identified issues.

NTSB coding

Evidence available

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

Docket documents4

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