Accident Bell 47G N951B,
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ASN Wikibase Occurrence # 42628
 
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Date:Thursday 9 May 1985
Time:13:30
Type:Silhouette image of generic B47G model; specific model in this crash may look slightly different    
Bell 47G
Owner/operator:Dick Hill Helicopters
Registration: N951B
MSN: 695
Total airframe hrs:9280 hours
Engine model:FRANKLIN 6V-335-A
Fatalities:Fatalities: 2 / Occupants: 2
Aircraft damage: Destroyed
Category:Accident
Location:Calwood, MO -   United States of America
Phase: En route
Nature:Survey
Departure airport:Columbia, MO (COU)
Destination airport:
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
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. CAUSE:

Sources:

NTSB: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001214X36540

Revision history:

Date/timeContributorUpdates
24-Oct-2008 10:30 ASN archive Added
21-Dec-2016 19:24 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]

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