# NTSB SEA91LA028: Aerospatiale SA316B, N316BS, Vernal, UT, December 3, 1990

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: December 3, 1990, 14:45 local (21:45 UTC)
- Place: Vernal, UT
- Coordinates: 40.550571, -109.569252 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.5506&lon=-109.5693&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 3 minor
- Status: Completed, report December 30, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 41369
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA91LA028
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/41369/pdf
- Page: https://openairdocs.org/ntsb/SEA91LA028

## Probable cause

A MALFUNCTION/FAILURE OF THE HELICOPTER'S MAIN ROTOR LEAD-LAG DAMPER.

## Sequence of events

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

- Airframe/component/system failure/malfunction, descent
  - rotor system,main rotor hub lead-lag stop/damper - failure,total (cause)
- Loss of control - in flight, landing
- In flight collision with terrain/water, landing

## Analysis

THE ACFT DEVELOPED VIBRATIONS IN FLT WITH SEVERE FEEDBACK THROUGH THE CONTROL SYSTEM TO THE CYCLIC STICK. THE PILOT INITIATED AN EMERGENCY LANDING AND LOST CONTROL JUST BEFORE TOUCHDOWN. THE ACFT IMPACTED THE GROUND WHILE SPINNING AND ROLLED OVER. EVIDENCE INDICATED A MALFUNCTION/FAILURE OF A MAIN ROTOR DAMPER.

## Aircraft

- Registration: [N316BS](https://openairdocs.org/deregistered/N316BS-1991-04-22), registration cancelled 1991-04-22, S/N 5399 (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: 5399
- Engines: TURBOMECA ARTOUSTE III 858 horsepower turbo shaft
- Damage: Destroyed
- Flight: Part 135
- Operator: Avman Aviation Helicopter Svc
- Airworthiness certificate: Standard, Normal

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; commercial; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 7,363 total, 2,055 in this make and model, 7,363 as pilot in command, 147 in the last 90 days, 35 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 40 statute miles
- Lowest ceiling: none
- Temperature: 34 °F, dew point 28 °F
- Altimeter: 30.00 inHg
- Observed at: VEL, 19 nm away

## 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 19901203052389A](https://openairdocs.org/incident/19901203052389A), Dec 3, 1990: Aerosp SA316B, Vernal, UT, Destroyed. Vibration in cyclic. Elected to land in clearing. Lost rotor RPM. Spun prior impact. Suspect rotor blade dampers.

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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.