NTSB Identification: CEN13IA387
14 CFR Part 91: General Aviation
Incident occurred Friday, June 28, 2013 in Paragould, AR
Probable Cause Approval Date: 08/07/2014
Aircraft: MARTIN CHARLES A ZENITH STOL CH 750, registration: N699TX
Injuries: 1 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

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.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

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

Full narrative available

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