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NTSB Report
April 11, 1989 · Sikorsky S-58T · N4247U
Milwaukee, WI
Overview
Report Status
Probable Cause
Event Type
Accident
Date
April 11, 1989
Injury Outcomes
1 injury (1 serious injury)
Location
Milwaukee, WI
Aircraft
Sikorsky S-58T
Tail Number
N4247U
Operator
Midwest Helicopter Airways
Injuries
Serious
Aircraft Damage
Substantial
NTSB Number
CHI89FA071
THE ACCIDENT HELICOPTER DESCENDED INTO SLOPING TERRAIN AND ROLLED OVER WHILE PERFORMING EXTERNAL LOAD OPERATIONS. THE HELICOPTER HAD JUST PICKED UP A LOAD AND WAS MOVING LATERALLY WHEN IT SUSTAINED A LOSS OF ANTI-TORQUE CONTROL AND THE FUSELAGE STARTED AN UNCOMMANDED AND UNCONTROLLED ROTATION TO THE RIGHT. THE PIC WAS ABLE TO JETTISON HIS EXTERNAL LOAD INTO A CLEAR AREA AND MOVE THE HELICOPTER AWAY FROM OBSTRUCTIONS BEFORE INITIATING AN OUT OF GROUND EFFECT HOVERING AUTOROTATION.
NTSB Probable Cause
DISCONNECT OF THE TAILROTOR DRIVE SHAFT COUPLING.
Full Narrative
THE ACCIDENT HELICOPTER DESCENDED INTO SLOPING TERRAIN AND ROLLED OVER WHILE PERFORMING EXTERNAL LOAD OPERATIONS. THE HELICOPTER HAD JUST PICKED UP A LOAD AND WAS MOVING LATERALLY WHEN IT SUSTAINED A LOSS OF ANTI-TORQUE CONTROL AND THE FUSELAGE STARTED AN UNCOMMANDED AND UNCONTROLLED ROTATION TO THE RIGHT. THE PIC WAS ABLE TO JETTISON HIS EXTERNAL LOAD INTO A CLEAR AREA AND MOVE THE HELICOPTER AWAY FROM OBSTRUCTIONS BEFORE INITIATING AN OUT OF GROUND EFFECT HOVERING AUTOROTATION.
Flight
Event TypeAccident
Event Time10:31 CDT
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftSikorsky S-58T
Tail NumberN4247U
Aircraft CategoryHeli
DamageSubstantial
OperatorMidwest Helicopter Airways
Operating RulePart 133
Engines2
Engine TypeTurboshaft
Engine DetailsP&W · PT6T-6 · Turboshaft · 970
Seats3
People & Injuries
Injury Summary1 injury (1 serious injury)
Fatal0
Serious1
Minor0
Uninjured0
Total1
Crew 1Age 44 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind210° @ 10 kt, gusting 20 kt
Visibility7 sm
CeilingOvercast 25000 ft
Temperature / Dew Point43 C / 18 C
Altimeter30.00 inHg
Observation Time15:52
Weather SourceWFAC