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October 14, 1982 · Boeing Vertol 107 · N6676D
Cascade, ID
Overview
Report Status
Preliminary report
Event Type
Accident
Date
October 14, 1982
Injury Outcomes
2 injuries (2 fatalities)
Location
Cascade, ID
Aircraft
Boeing Vertol 107
Tail Number
N6676D
Operator
Columbia Helicopters
Injuries
Fatal
Aircraft Damage
Destroyed
NTSB Number
SEA83FA009
DURING A LOG SLINGING OPERATION A LOUD BANG WAS HEARD & THE ACFT WAS OBSERVED TO RAPIDLY DESCEND VERTICALLY TO THE GROUND WITH NUMEROUS SMALL FRAGMENTS FALLING IN THE SAME VICINITY. THE #5 SYNCHRONIZATION SHAFT WAS FOUND TO BE FRACTURED AT THE FORWARD END ABOUT 9 INCHES AFT OF THE CONNECTION ASSY TO THE #4 SHAFT. THIS RESULTED IN AN OUT OF SYNCHRONIZATION CONDITION BETWEEN THE FORWARD & AFT ROTOR BLADES AS WELL AS A LOSS OF POWER TO THE FORWARD ROTOR. A FATIGUE FRACTURE ORIGINATED IN THE AFT MOST RING OF RIVET HOLES. THE FATIGUE CRACKS PROPOGATED FROM MULTIPLE ORIGINS WITHIN THOSE RIVET HOLES WHERE A "STEP" WAS FOUND AT THE BASE OF THE HOLE & CLOSEST TO THE INSIDE DIAMETER OF THE SHAFT.ALL RIVET HOLES IN THE FORWARD END OF THE SHAFT HAD TOPOGRAPHIC FEATURES SIMILAR TO THOSE PRODUCED IN A STEEL PLATE BY DELIBERATELY DRILLING HOLES WITHOUT COMPLETE PENETRATIONS.
Full Narrative
DURING A LOG SLINGING OPERATION A LOUD BANG WAS HEARD & THE ACFT WAS OBSERVED TO RAPIDLY DESCEND VERTICALLY TO THE GROUND WITH NUMEROUS SMALL FRAGMENTS FALLING IN THE SAME VICINITY. THE #5 SYNCHRONIZATION SHAFT WAS FOUND TO BE FRACTURED AT THE FORWARD END ABOUT 9 INCHES AFT OF THE CONNECTION ASSY TO THE #4 SHAFT. THIS RESULTED IN AN OUT OF SYNCHRONIZATION CONDITION BETWEEN THE FORWARD & AFT ROTOR BLADES AS WELL AS A LOSS OF POWER TO THE FORWARD ROTOR. A FATIGUE FRACTURE ORIGINATED IN THE AFT MOST RING OF RIVET HOLES. THE FATIGUE CRACKS PROPOGATED FROM MULTIPLE ORIGINS WITHIN THOSE RIVET HOLES WHERE A "STEP" WAS FOUND AT THE BASE OF THE HOLE & CLOSEST TO THE INSIDE DIAMETER OF THE SHAFT.ALL RIVET HOLES IN THE FORWARD END OF THE SHAFT HAD TOPOGRAPHIC FEATURES SIMILAR TO THOSE PRODUCED IN A STEEL PLATE BY DELIBERATELY DRILLING HOLES WITHOUT COMPLETE PENETRATIONS.
Flight
Event TypeAccident
Event Time14:18 MDT
Nearest Airport0nm N
Runway0
Runway Length0
Runway Width0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftBoeing Vertol 107
Tail NumberN6676D
Aircraft CategoryHeli
DamageDestroyed
OperatorColumbia Helicopters
Operating RulePart 133
Engines2
Engine TypeTurboshaft
Engine DetailsGe · CT-58-140 · Turboshaft · 1500
Seats3
People & Injuries
Injury Summary2 injuries (2 fatalities)
Fatal2
Serious0
Minor0
Uninjured0
Total2
Crew 1Age 36 · Second Class
Conditions
ConditionsVMC
LightDaylight
WindCalm
Visibility30 sm
CeilingNone
Temperature / Dew Point16 C / 0 C
Altimeter30.00 inHg