NTSB Identification: MIA91LA113.
The docket is stored on NTSB microfiche number 43703.
Accident occurred Tuesday, March 12, 1991 in VERO BEACH, FL
Probable Cause Approval Date: 01/25/1993
Aircraft: BELL UH-1B, registration: N9687R
Injuries: 1 Minor.

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

SHORTLY AFTER TAKEOFF AT 40 FT AGL, THE PLT STATED THAT HE OBSERVED THE HIGH/LOW ROTOR/ENG WARNING LIGHT WAS ILLUMINATED & THE HELICOPTER ENTERED AN UNCOMMANDED RT YAW. HE ENTERED AN AUTOROTATION & WHILE DESCENDING, THE MAIN ROTOR BLADES CONTACTED TREES. HE PULLED COLLECTIVE PITCH BEFORE IMPACT WITH TERRAIN. EXAM OF THE HELICOPTER REVEALED THAT THE UPPER RT TAILBOOM ATTACH BOLT WAS STRIPPED WHICH ALLOWED THE TAILBOOM TO SHIFT RESULTING IN THE SEPARATION OF THE NOS. 1 & 2 TAIL ROTOR DRIVE SHAFT SECTIONS AT THE COUPLING. EXAM OF THE STRIPPED BOLT BY A QUALIFIED INDIVIDUAL REVEALED THAT IT FAILED DUE TO BEING OVERTORQUED. THE COMPANY MECHANIC STATED THAT THE TAILBOOM ATTACH BOLTS ARE CHECKED FOR PROPER TORQUE EVERY 100 HRS & WAS LAST ACCOMPLISHED ABOUT 55 HRS EARLIER.

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

IMPROPER MAINTENANCE ADJUSTMENT BY COMPANY MAINTENANCE PERSONNEL RESULTING IN OVERTORQUE OF A TAILBOOM ATTACH BOLT WHICH ALLOWED THE TAILBOOM TO SHIFT. THIS DISENGAGED THE TAIL ROTOR DRIVE SHAFT AT A COUPLING RESULTING IN THE LOSS OF TAIL ROTOR DRIVE.

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