Pilot Debrief

MARTIN CHARLES A ZENITH STOL CH 750 near Paragould, AR — 2013-06-28

Final reportCEN13IA387
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Date
2013-06-28
Location
Paragould, AR, USA
Airport
PGR
Aircraft
MARTIN CHARLES A ZENITH STOL CH 750
Registration
N699TX
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Climb

Probable cause

The improper installation of the propeller flange, which resulted in an in-flight separation of the propeller assembly.

NTSB narrative

The pilot reported that, during the climb after takeoff, the engine "developed an immediate and heavy vibration." The intensity of the vibration increased, and the pilot was considering shutting the engine down when the vibration abruptly ceased. Looking out the windshield, he observed that the propeller had separated from the airplane. The pilot subsequently executed a forced landing to a field. Metallurgical examination determined that the propeller separation was initiated by a fatigue failure of two propeller flange-to-engine crankshaft flange attachment bolts. Further examination revealed that an incorrect thread lock compound was used on the propeller bolts, and the presence of a second compound suggested that the bolts were not properly cleaned before installation. In addition, washers used in the installation did not correspond with the washers specified by the manufacturer. Finally, extensive fretting damage to the propeller and crankshaft flanges in conjunction with the limited number of flight hours indicated that the attachment bolts were not torqued sufficiently at the time of installation. Available maintenance records did not include any entry noting that the propeller assembly had been removed since the initial installation.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Proper installation of the propeller could have prevented the failure.

NTSB coding

  • Part(s) separation from AC · Enroute-climb to cruise
  • Maintenance

Evidence available

  • 5 docket documents
View NTSB final reportView NTSB docket

Docket documents5

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