Rocky Mountain Helicopters Aerospatiale SA 316B accident
Aerospatiale SA 316B · Accident: airframe, component or system failure en route
From Q18 · Bridgeport, CA to Reno, NV (no airport)
Event
- NTSB case
- LAX92FA054
- 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
- 4 · 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
- Charter & commuter
- 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 SA 316B
- Aircraft type
- Aerospatiale SA-316
- 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
- N146RM
- Operator
- Rocky Mountain Helicopters
- Onboard fatalities
- Unknown
- Route
- From Q18 · Bridgeport, CATo Reno, NV (no airport)
- 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 135: Air Taxi & Commuter
- 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
- Destroyed
Cause areas
- Reason for occurrence undetermined
- Rotor drive system, tail rotor drive shaft bearing › Failure, total
- Rotor drive system, tail rotor drive shaft › Failure, total
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE AEROMEDICAL EVACUATION (EMS-MEDEVAC) FLT WAS MADE AT NGT OVR MTN TRRN. THE PLT INTERRUPTED HIS NORMAL PSN RPRT & BROADCAST 'MAYDAY' 3 TIMES, GIVING HIS PSN TO A COMPANY DISPATCHER. HE DID NOT STATE THE NATURE OF THE EMERGENCY. NO FURTHER COMM WAS RECORDED. WITNESSES IN A SOUTHBOUND AUTO SAW THE HELICOPTER FLYING TOWARD THEM FROM THE SOUTH. THEY STATED THE HELICOPTER'S FUSELAGE STARTED ROTATING COUNTER-CLOCKWISE. IT THEN VEERED TO THE WEST, WENT OUT OF SIGHT, AND CRASHED. ALL MAJ COMPONENTS, EXCEPT ABOUT 33 INCHES OF THE TAIL ROTOR DRIVE SHAFT & ITS #5 BRG, WERE LOCATED. THE TAIL BOOM WAS FOUND IN 3 SECTIONS. ROTATIONAL & LONGITUDINAL SCORING DAMAGE WAS NOTED ON THE TAIL BOOM IN THE VCNTY OF THE #3 & #5 BRG SUPPORTS. A LAB RPRT STATED THAT THE ROTATIONAL DMG OCCURRED BEFORE THE GROSS DEFORMATION OF THE TAIL BOOM & SUBSEQUENT IN-FLT BREAKUP OF THE HELICOPTER.
Probable cause
FAILURE OF THE HELICOPTER'S TAIL ROTOR DRIVE SHAFT AND DRIVE SHAFT BEARING DUE TO UNDETERMINED REASON(S).
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX92FA054
- Event ID
- 20001212X18461
- Case number
- LAX92FA054
- 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 1991-11-28.
- API snapshot SHA-256: 22f3d436125a98adcb322aeee2e039bf9d94ccc283dca9862addfc474b760ee1; retrieved 2026-09-18T14:01:24.925Z.