Pilot Debrief

PIPER PA-25-235 near Bainbridge, GA — 2009-08-27

Final reportERA09LA490
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Date
2009-08-27
Location
Bainbridge, GA, USA
Aircraft
PIPER PA-25-235
Registration
N7339Z
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Maneuvering

Probable cause

A total loss of engine power due to the loss of camshaft timing as a result of the displacement of the idler gear assembly.

NTSB narrative

The airplane was performing a training aerial application over a farm field when the engine lost power and the pilot performed a forced landing to a field, where the airplane impacted a tree. A subsequent examination of the engine revealed that within the accessory section, the idler gear assembly, which normally transferred power from the crankshaft to the left magneto and the camshaft, had been displaced. The short shaft had also been displaced. The mounting plate retaining screws appeared to be sheared. The crankcase surface area around the screw hole exhibited rotational scoring, and the idler gear, located in the oil sump, had no missing or damaged gear teeth. Metal particles were found in the bottom of the crankcase and oil sump. The engine operating time was below the recommended time between overhaul. The failure sequence could not be determined, and although the left magneto had been replaced approximately 12 flight hours prior, the replacement of the magneto could not be correlated to the displacement of the idler gear assembly.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have checked engine thoroughly before departure after magneto replacement.

NTSB coding

Evidence available

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

Docket documents7

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