Pilot Debrief

AIR TRACTOR INC AT 301 near Weiser, ID — 2016-08-02

Final reportWPR16LA159
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Date
2016-08-02
Location
Weiser, ID, USA
Aircraft
AIR TRACTOR INC AT 301
Registration
N23923
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Approach

Probable cause

A partial loss of engine power due to an internal catastrophic failure of the master rod crankpin bearing.

NTSB narrative

The airline transport pilot reported that, during an aerial application flight, he observed rising engine cylinder head temperatures and a partial loss of engine power. Unable to maintain altitude, he jettisoned the load of liquid fertilizer and made a forced landing to an alfalfa field. During the landing, the airplane collided with a wheel line sprinkler system. A postaccident examination of the radial engine revealed damage to the No. 1 cylinder lower piston skirt and the oil scraper ring. The inside of the piston exhibited multiple indentations consistent with continued battering. The remaining eight cylinders and pistons were removed and exhibited similar signatures. Multiple metallic fragments that resembled bearing material were found in the crankcase, and the magnetic chip detector displayed metallic debris. The master rod and link rod assembly were removed from the crankshaft, and the front side of the master rod exhibited two perpendicular dents. The master rod crankpin bearing revealed substantial wear and gouging-type damage, consistent with its failure initiating the engine failure. The master rod crankpin bearing was thinned, or gouged out, consistent with the metallic shavings found in the crankcase and oil galley. No maintenance records were provided, and the engine's service and maintenance history could not be determined.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted the flight after observing high cylinder head temperatures.

NTSB coding

Evidence available

  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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