# NTSB DEN90FA172: Aerospatiale SA316B, N83776, Meeteetse, WY, August 20, 1990

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: August 19, 1990, 18:00 local (Aug 20, 1990, 00:00 UTC)
- Place: Meeteetse, WY
- Coordinates: 44.150619, -108.869316 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.1506&lon=-108.8693&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 3 serious, 4 minor
- Status: Completed, report December 14, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 17844
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN90FA172
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17844/pdf
- Page: https://openairdocs.org/ntsb/DEN90FA172

## Probable cause

A MAIN ROTOR HEAD BLADE DAMPENER FAILURE. A FACTOR IN THE ACCIDENT WAS THE SUBSEQUENT FAILURE OF A BLADE RESTRAINING CABLE.

## Sequence of events

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

- Loss of control - in flight, cruise
  - rotor system,main rotor hub lead-lag stop/damper - failure,total (cause)
  - cyclic - uncontrolled, pilot in command
  - rotor system,main rotor hub stop(static/dynamic) - failure,total (contributing factor)
- Forced landing, descent - uncontrolled
  - terrain condition - open field
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

APPROXIMATELY 2 MINUTES INTO THE FLIGHT, THE PILOT EXPERIENCED A SLIGHT 1 TO 1 VIBRATION THROUGH THE CYCLIC. THIS TYPE VIBRATION IS ASSOCIATED WITH MAIN ROTOR DAMPERS AND THE PILOT 'STIRRED' THE CYCLIC IN AN EFFORT TO PURGE AIR OUT OF THE BLADE DAMPERS. THIS ELIMINATED THE PROBLEM, HOWEVER, IT RECURRED AND COULD NOT BE ELIMINATED. THE VIBRATION INCREASED TO THE POINT OF LOSS OF CONTROL. AN EMERGENCY LANDING WAS ATTEMPTED WITH TOUCHDOWN OCCURRING AT ABOUT 60 KNOTS. THE HELICOPTER CAME TO REST INVERTED AND WAS LARGELY CONSUMED BY POST-IMPACT FIRE. METALLURGICAL ANALYSIS ON A FAILED BLADE RESTRAINING CABLE REVEALED A CATASTROPHIC FAILURE IN A LOW CYCLE FATIGUE MODE CONSISTENT WITH A SECONDARY CAUSE, AND DUE TO SHORT TERM VIBRATIONS. IN ADDITION TO FATIGUE, THERE WAS EVIDENCE OF PLASTIC DEFORMATION DUE TO VIBRATORY LOADS FROM THE DAMPER SYSTEMS. FIRE DAMAGE PREVENTED ADDITIONAL FAILURE ANALYSIS.

## Aircraft

- Registration: [N83776](https://openairdocs.org/deregistered/N83776-1997-12-06), registration cancelled 1997-12-06, S/N 1827 (OpenAirDocs)
- Reported make and model: AEROSPATIALE SA316B
- Registry model: [Aerospatiale SA316B ALOUETTE III](https://openairdocs.org/model/aerospatiale-sa316b-alouette-iii) (registry code 8680515) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1827
- Engines: TURBOMECA 316B 600 horsepower turbo shaft
- Damage: Destroyed
- Fire: On-Ground
- Flight: Part 135
- Operator: Rocky Mountain Helicopter
- Registered owner: Unknown
- Destination: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; commercial, airline transport, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 1, valid medical--w/ waivers/lim; flight hours: 6,635 total, 500 in this make and model, 5,000 as pilot in command, 50 in the last 30 days, 5 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 240° at 10 knots
- Visibility: 7 statute miles
- Lowest ceiling: 6,000 ft overcast
- Temperature: -0 °F, dew point -0 °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 19900819034069A](https://openairdocs.org/incident/19900819034069A), Aug 19, 1990: Aerosp SA316B, Meeteetse, WY, Destroyed. Vibration and cylic began slamming around. Made hard out of control landing. Suspect main rotor dampner failure.

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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