# NTSB LAX92FA054: Aerospatiale SA 316B, N146RM, Bridgeport, CA, November 28, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: November 27, 1991, 23:21 local (Nov 28, 1991, 07:21 UTC)
- Place: Bridgeport, CA
- Coordinates: 38.270641, -119.32965 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=38.2706&lon=-119.3297&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 4 fatal
- Status: Completed, report January 27, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27392
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92FA054
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27392/pdf
- Page: https://openairdocs.org/ntsb/LAX92FA054

## Probable cause

FAILURE OF THE HELICOPTER'S TAIL ROTOR DRIVE SHAFT AND DRIVE SHAFT BEARING DUE TO UNDETERMINED REASON(S).

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, cruise
  - rotor drive system,tail rotor drive shaft bearing - failure,total (cause)
  - rotor drive system,tail rotor drive shaft - failure,total (cause)
  - reason for occurrence undetermined (cause)
- Loss of control - in flight, cruise
  - light condition - dark night
  - aircraft control - not possible, pilot in command
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - mountainous/hilly

## Analysis

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.

## Aircraft

- Registration: [N146RM](https://openairdocs.org/deregistered/N146RM-1997-10-27), registration cancelled 1997-10-27, S/N 1614 (OpenAirDocs)
- Reported make and model: AEROSPATIALE SA 316B
- Registry model: [Aerospatiale SA316B ALOUETTE III](https://openairdocs.org/model/aerospatiale-sa316b-alouette-iii) (registry code 8680515) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1614
- Airframe hours: 7525
- Engines: TURBOMECA ARTOUSTE IIIB 858 horsepower turbo shaft
- Damage: Destroyed
- Flight: Part 135
- Operator: Rocky Mountain Helicopters
- Registered owner: Rocky Mountain Helicopters
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, October 25, 1991, 53 hours before
- Departed: Q18, BRIDGEPORT, CA
- Destination: NONE, RENO, NV
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 44; airline transport; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 11,095 total, 2,163 in this make and model, 11,095 as pilot in command, 76 in the last 90 days, 28 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/dark
- Visibility: 3 statute miles
- Temperature: 12 °F

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19911127053719A](https://openairdocs.org/incident/19911127053719A), Nov 27, 1991: Aerosp SA316B, Bridgeport, CA, Destroyed, 4 fatal. En route tail rotor drive shaft broke in two places. Main rotors chopped tail in spin prior to inverted crash.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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