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NTSB Report
May 9, 1985 · Bell 47G · N951B
Calwood, MO
Overview
Report Status
Preliminary report
Event Type
Accident
Date
May 9, 1985
Injury Outcomes
2 injuries (2 fatalities)
Location
Calwood, MO
Aircraft
Bell 47G
Tail Number
N951B
Injuries
Fatal
Aircraft Damage
Destroyed
NTSB Number
MKC85FA100
N951B CRASHED IN A WOODED AREA DURING A POWERLINE PATROL FLT WHICH INCLUDED PHOTOGRAPHY OF THE POWERLINE. ACCORDING TO WITNESSES, THE HELICOPTER WAS FLYING PARALLEL TO THE POWERLINE IN A WESTERLY DIRECTION WHEN THE ACCIDENT OCCURRED. EXAM OF THE WRECKAGE REVEALED THE TAIL ROTOR GEAR BOX AND HUB, ALONG WITH ON TAIL ROTOR BLADE HAD SEPARATED IN FLT AND WAS LOCATED APRX 50 YARDS FROM THE MAIN WRECKAGE. THE OTHER TAIL ROTOR BLADE WAS LOCATED APRX 160 YARDS AWAY FROM THE MAIN WRECKAGE. METALLURGICAL EXAM OF THE BROKEN YOKE REVEALED A FATIGUE FRACTURE WHICH PROGRESSED FROM MULTIPLE ORIGINS AT THE ROOT OF THE INTERNAL THREADS OF THE SPLINE. THE EXAM ALSO SHOWED THAT THE INTERNAL THREADS WERE NITRIDE TREATED. THIS WAS NOT A BELL HELICOPTER PART. THE PMA, UNDER WHICH THIS PART WAS MANUFACTURED, PROHIBITS NITRIDE TREATMENT OF THE SPINDLE BORE & THREADS.
Full Narrative
N951B CRASHED IN A WOODED AREA DURING A POWERLINE PATROL FLT WHICH INCLUDED PHOTOGRAPHY OF THE POWERLINE. ACCORDING TO WITNESSES, THE HELICOPTER WAS FLYING PARALLEL TO THE POWERLINE IN A WESTERLY DIRECTION WHEN THE ACCIDENT OCCURRED. EXAM OF THE WRECKAGE REVEALED THE TAIL ROTOR GEAR BOX AND HUB, ALONG WITH ON TAIL ROTOR BLADE HAD SEPARATED IN FLT AND WAS LOCATED APRX 50 YARDS FROM THE MAIN WRECKAGE. THE OTHER TAIL ROTOR BLADE WAS LOCATED APRX 160 YARDS AWAY FROM THE MAIN WRECKAGE. METALLURGICAL EXAM OF THE BROKEN YOKE REVEALED A FATIGUE FRACTURE WHICH PROGRESSED FROM MULTIPLE ORIGINS AT THE ROOT OF THE INTERNAL THREADS OF THE SPLINE. THE EXAM ALSO SHOWED THAT THE INTERNAL THREADS WERE NITRIDE TREATED. THIS WAS NOT A BELL HELICOPTER PART. THE PMA, UNDER WHICH THIS PART WAS MANUFACTURED, PROHIBITS NITRIDE TREATMENT OF THE SPINDLE BORE & THREADS.
Flight
Event TypeAccident
Event Time13:30 CDT
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireGrd
Aircraft ExplosionNo
Aircraft
AircraftBell 47G
Tail NumberN951B
Aircraft CategoryHeli
DamageDestroyed
Operating RulePart 91
Engines1
Engine TypeReciprocating
Engine DetailsFranklin · 6V-335-A · Reciprocating · 200
Seats3
People & Injuries
Injury Summary2 injuries (2 fatalities)
Fatal2
Serious0
Minor0
Uninjured0
Total2
Crew 1Age 24 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind230° @ 13 kt
Visibility20 sm
CeilingNone
Temperature / Dew Point50
Altimeter30.00 inHg
Observation Time18:50
Weather SourceWFAC