SEA92LA029 · Aerospatiale AS355F1
Omni Flight Helicopters Aerospatiale AS355F1 · Accident: airframe, component or system failure en route
From St Vincent Hospital Heliport (MT25) to an unrecorded destination
Event
- NTSB case
- SEA92LA029
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Aerospatiale AS355F1
- Aircraft type
- Aerospatiale AS355
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N101UC
- Operator
- Omni Flight Helicopters
- Onboard fatalities
- Unknown
- Route
- From St Vincent Hospital Heliport (MT25), Billings, MTTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Door, inspection › Unlatched
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB 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.
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA92LA029
- Event ID
- 20001212X18400
- Case number
- SEA92LA029
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: local date, investigation status. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 1991-10-29.
- API snapshot SHA-256: ed95610ac0e40064f5388f0b9eee22e6c53702bb50eea1f6f08c004929e6e3ea; retrieved 2026-09-23T03:34:12.156Z.