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NTSB Report
October 29, 1991 · Aerospatiale AS355F1 · N101UC
Billings, MT
Overview
Report Status
Probable Cause
Event Type
Accident
Date
October 29, 1991
Injury Outcomes
No injuries (3 uninjured)
Location
Billings, MT
Aircraft
Aerospatiale AS355F1
Tail Number
N101UC
Operator
Omni Flight Helicopters
Injuries
None
Aircraft Damage
Substantial
NTSB Number
SEA92LA029
SHORTLY AFTER THE COMPANY INITIATED ABORT OF THE MEDEVAC FLIGHT, THE FLIGHT CREW OF THE AEROSPATIALE AS355 FELT A SHUDDER WHICH THEY ATTRIBUTED TO GUSTY WIND CONDITIONS. UPON LANDING AT BILLINGS INTERNATIONAL AIRPORT, MONTANA, A PORTION OF THE LEFT-REAR ENGINE COWL DOOR WAS FOUND TO BE SEPARATED, ALONG WITH DAMAGE TO THE MAIN ROTOR BLADES NECESSITATING REPLACEMENT OF THE BLADES. THE CREW HAD PREVIOUSLY NOTIFIED COMPANY PERSONNEL OF THE COWL DOOR LATCH PROBLEM AND HAD PREFLIGHTED THE COWL PRIOR TO THE ACCIDENT FLIGHT. THE MANUFACTURER WAS AWARE OF THE PROBLEM AND HAD ISSUED A RELEVANT SERVICE BULLETIN. THE SERVICE BULLETIN HAD NOT BEEN IMPLEMENTED ON THE ACCIDENT AIRCRAFT.
NTSB Probable Cause
THE UNLATCHING AND SUBSEQUENT OPENING INFLIGHT OF THE LEFT-REAR ENGINE COWL DOOR. A FACTOR CONTRIBUTING TO THE ACCIDENT WAS THE FAILURE OF COMPANY MAINTENANCE PERSONNEL TO EXECUTE THE MANUFACTURER'S SERVICE BULLETIN.
Full Narrative
SHORTLY AFTER THE COMPANY INITIATED ABORT OF THE MEDEVAC FLIGHT, THE FLIGHT CREW OF THE AEROSPATIALE AS355 FELT A SHUDDER WHICH THEY ATTRIBUTED TO GUSTY WIND CONDITIONS. UPON LANDING AT BILLINGS INTERNATIONAL AIRPORT, MONTANA, A PORTION OF THE LEFT-REAR ENGINE COWL DOOR WAS FOUND TO BE SEPARATED, ALONG WITH DAMAGE TO THE MAIN ROTOR BLADES NECESSITATING REPLACEMENT OF THE BLADES. THE CREW HAD PREVIOUSLY NOTIFIED COMPANY PERSONNEL OF THE COWL DOOR LATCH PROBLEM AND HAD PREFLIGHTED THE COWL PRIOR TO THE ACCIDENT FLIGHT. THE MANUFACTURER WAS AWARE OF THE PROBLEM AND HAD ISSUED A RELEVANT SERVICE BULLETIN. THE SERVICE BULLETIN HAD NOT BEEN IMPLEMENTED ON THE ACCIDENT AIRCRAFT.
Flight
Event TypeAccident
Event Time19:15 MST
Nearest Airport0nm N
Runway0
Flight Plan FiledCvfr
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftAerospatiale AS355F1
Tail NumberN101UC
Aircraft CategoryHeli
DamageSubstantial
OperatorOmni Flight Helicopters
Operating RulePart 91
Engines2
Engine TypeTurboshaft
Engine DetailsAllison · 250-C20 · Turboshaft · 420
Seats5
People & Injuries
Injury SummaryNo injuries (3 uninjured)
Fatal0
Serious0
Minor0
Uninjured3
Total3
Crew 1Age 46 · Second Class
Conditions
ConditionsVMC
LightDark Night
Wind220° @ 4 kt
Visibility20 sm
CeilingBroken clouds 2800 ft
Temperature / Dew Point0 C / 0 C
Altimeter0
Weather SourceWIT