NTSB Identification: ATL88LA030.
The docket is stored on NTSB microfiche number 35585.
Accident occurred Saturday, November 07, 1987 in NEWNAN, GA
Probable Cause Approval Date: 02/14/1989
Aircraft: HILLER UH-12B, registration: N922TE
Injuries: 2 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 TAIL ROTOR 90 DEGREE GEARBOX MOUNTING FLANGE FRACTURED DURING APCH TO LAND, WHILE THE HELICOPTER WAS AT ABOUT 75 FT AGL. THE GEARBOX SUBSEQUENTLY SEPARATED FROM THE HELICOPTER. THE PLT INITIATED AN AUTOROTATION. THE HELICOPTER ROLLED OVER ON LDG. METALLURGICAL ANALYSIS INDICATED THAT THE FLANGE FAILED AS A RESULT OF EXTENSIVE PREEXISTENT FATIGUE CRACKING, AND THAT THE CRACKING WAS THE RESULT OF EXCESSIVE VIBRATION.

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

ROTOR DRIVE SYSTEM,TAIL ROTOR GEARBOX(90 DEG)..VIBRATION

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

ROTOR DRIVE SYSTEM,TAIL ROTOR GEARBOX(90 DEG)..FATIGUE

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

ROTOR DRIVE SYSTEM,TAIL ROTOR GEARBOX(90 DEG)..SEPARATION


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