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Aviation safety reports, made easier to study

NTSB Reports is an independent research and search tool for public aviation accident and incident records. It brings NTSB aviation reports, structured fields, docket files, extracted figures, photos, videos, and update history into one searchable interface.

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NTSB Report

September 29, 1989 · Bell UH-1B · N840MC

Plains, GA

Overview

Report Status
Probable Cause
Event Type
Accident
Date
September 29, 1989
Injury Outcomes
2 injuries (2 fatalities)
Location
Plains, GA
Aircraft
Bell UH-1B
Tail Number
N840MC
Injuries
Fatal
Aircraft Damage
Destroyed
NTSB Number
ATL89DKG06

DURING A POSITIONING FLT, AN IN-FLIGHT BREAKUP OF THE HELICOPTER OCCURRED IN THE VICINITY OF WHERE IT WAS CROSSING A LINE OF TREES BETWEEN 2 CLEARED AREAS. WRECKAGE WAS FOUND SCATTERED OVER AN AREA OF APRX 300 YDS IN LENGTH, ALONG A HEADING OF 340 DEG. AT THE SE END, PIECES WERE FOUND FROM THE LEFT SPRAY BOOM & MAIN ROTOR AERODYNAMIC FAIRING. FURTHER TO THE NW, VARIOUS PARTS WERE FOUND FROM THE LEFT SIDE OF THE HELICOPTER, LEFT SPRAY BOOM & TAIL ROTOR. THE MAIN ROTOR & MAIN ROTOR HUB WERE FOUND ABOUT 120 YDS TO THE RIGHT OF THE WRECKAGE PATH. THE FUSELAGE, ENG & TRANS- MISSION WERE FOUND ABOUT 240 YDS NW OF THE 1ST PART OF THE WRECKAGE. AN EXAM OF THE WRECKAGE REVEALED THE MAIN ROTOR SYSTEM HAD SEPARATED DUE TO MAST BUMPING. THERE WAS EVIDENCE THE LEFT SPRAY BOOM HAD CONTACTED THE MAIN ROTOR BLADES DURING FLT. ALL OF THE FRACTURES OF THE SPRAY BOOM, STEEL TRUSS & ASSOC LUGS INDCD OVERLOAD FAILURE IN AFT & UPWARD DRCTN. THE SPRAY ASSEMBLY & BOOM HAD NOT BEEN INSTALLED IN ACCORDANCE WITH FAR PART 23.

NTSB Probable Cause

IMPROPER MODIFICATION OF THE HELICOPTER BY THE COMPANY/OPERATOR, AND FAILURE OF THE SPRAY BOOM, WHICH RESULTED IN MAST BUMPING, AND SUBSEQUENT FAILURE OF THE MAIN ROTOR ASSEMBLY.

Full Narrative

DURING A POSITIONING FLT, AN IN-FLIGHT BREAKUP OF THE HELICOPTER OCCURRED IN THE VICINITY OF WHERE IT WAS CROSSING A LINE OF TREES BETWEEN 2 CLEARED AREAS. WRECKAGE WAS FOUND SCATTERED OVER AN AREA OF APRX 300 YDS IN LENGTH, ALONG A HEADING OF 340 DEG. AT THE SE END, PIECES WERE FOUND FROM THE LEFT SPRAY BOOM & MAIN ROTOR AERODYNAMIC FAIRING. FURTHER TO THE NW, VARIOUS PARTS WERE FOUND FROM THE LEFT SIDE OF THE HELICOPTER, LEFT SPRAY BOOM & TAIL ROTOR. THE MAIN ROTOR & MAIN ROTOR HUB WERE FOUND ABOUT 120 YDS TO THE RIGHT OF THE WRECKAGE PATH. THE FUSELAGE, ENG & TRANS- MISSION WERE FOUND ABOUT 240 YDS NW OF THE 1ST PART OF THE WRECKAGE. AN EXAM OF THE WRECKAGE REVEALED THE MAIN ROTOR SYSTEM HAD SEPARATED DUE TO MAST BUMPING. THERE WAS EVIDENCE THE LEFT SPRAY BOOM HAD CONTACTED THE MAIN ROTOR BLADES DURING FLT. ALL OF THE FRACTURES OF THE SPRAY BOOM, STEEL TRUSS & ASSOC LUGS INDCD OVERLOAD FAILURE IN AFT & UPWARD DRCTN. THE SPRAY ASSEMBLY & BOOM HAD NOT BEEN INSTALLED IN ACCORDANCE WITH FAR PART 23.

Flight

Event TypeAccident
Event Time16:40 EDT
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo

Aircraft

AircraftBell UH-1B
Tail NumberN840MC
Aircraft CategoryHeli
DamageDestroyed
Operating RulePart 137
Engines1
Engine TypeTurboshaft
Engine DetailsLycoming · T53-11D · Turboshaft · 1100
Seats2

People & Injuries

Injury Summary2 injuries (2 fatalities)
Fatal2
Serious0
Minor0
Uninjured0
Total2
Crew 1Age 28 · Second Class

Conditions

ConditionsVMC
LightDaylight
WindCalm
Visibility7 sm
CeilingOvercast 1300 ft
Altimeter0
Weather SourceWIT

Appendix: Source Data