Pilot Debrief

PIPER PA 25-235 near Westphalia, KS — 2017-09-28

Final reportCEN17LA372
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Date
2017-09-28
Location
Westphalia, KS, USA
Aircraft
PIPER PA 25-235
Registration
N7336Z
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

A total loss of engine power due to a fatigue failure of the crankshaft that resulted from main bearing shift and lack of lubrication.

NTSB narrative

The commercial pilot reported that he departed in the airplane with full fuel and chemical for the aerial application flight. After spraying a field for about 20 minutes, the engine experienced a total loss of power. The pilot jettisoned the chemical load and initiated a forced landing to a field. About 5 ft above the field, as the pilot tried to bleed off airspeed, the airplane stalled and impacted terrain. Disassembly and examination of the engine revealed that the crankshaft was fractured, and the main bearings displayed thermal damage and smearing. Material examination of the crankshaft showed features consistent with a subsurface crack initiation and fatigue crack propagation. The fatigue striations, particularly near the initiation site, were consistent with high-cycle fatigue. The forward main bearings exhibited spalling, displacement, and cracking consistent with bearing wear fatigue. All the bearing damage was typical of similar bearings that had been operated at elevated temperatures using inadequate lubrication. The main bearing damage was likely the result of main bearing shift and a blockage of the lubrication paths. The blockage resulted in a lack of lubrication, main bearing failure, and a fatigue failure of the crankshaft. The reason for the main bearing shift could not be determined based on the available information.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted the flight after engine issues were first noticed.

NTSB coding

Evidence available

  • 4 docket documents
View NTSB final reportView NTSB docket

Docket documents4

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