NTSB Identification: ATL90LA042.
The docket is stored on NTSB microfiche number 41968.
Accident occurred Wednesday, December 20, 1989 in CREOLA, AL
Probable Cause Approval Date: 10/07/1992
Aircraft: BELL TH-1, registration: N106SR
Injuries: 1 Uninjured.

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

THE ENGINE FAILED WHILE THE PILOT WAS HOVERING AT 110 FT DURING AN EXTERNAL LOAD OPERATION. THE PILOT RELEASED THE LOAD AND AUTOROTATED INTO A SWAMPY AREA. ENGINE TEARDOWN SHOWED EVIDENCE OF SEIZURE AND HEAVY WEAR AT THE #21 BEARING ASSEMBLY ROLLER/SHAFT INTERFACE. METALLURGICAL EXAM REVEALED A BREAKDOWN OF THE TUNGSTEN CARBIDE AND COBALT COATING REPAIR. THE DETONATION GUN (DGUN) REPAIR BUILDUP ON THE BEARING/SEAL JOURNAL, SEO T53-LO-R0035, WAS USED IN 1969, AND CANCELED IN 1970. THE PROCEDURE WAS NOT APPROVED OR PRACTICED BY LYCOMING, AND THE MANUFACTURER RECOMMENDED THAT PARTS REPAIRED IAW THE SEO NOT BE INSTALLED IN ENGINES. THE PILOT WAS OPERATING WITHIN THE 'AVOID OPERATION' AREA OF THE AIRSPEED VELOCITY CHART.

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

THE LOSS OF ENGINE POWER DUE TO A #21 BEARING FAILURE. THE BEARING FAILED AS A RESULT OF INADEQUATE MAINTENANCE. A FACTOR IN THE ACCIDENT WAS THE PILOT OPERATING THE HELICOPTER WITHIN THE AVOID OPERATING ENVELOPE.

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