# NTSB ANC90FA117: Bell 206L-1, N300AH, Farewell, AK, July 14, 1990

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: July 14, 1990, 09:00 local (17:00 UTC)
- Place: Farewell, AK
- Coordinates: 55.920726, -159.490539 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=55.9207&lon=-159.4905&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 5 serious
- Status: Completed, report May 10, 1993
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5302
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC90FA117
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5302/pdf
- Page: https://openairdocs.org/ntsb/ANC90FA117

## Probable cause

AN INTERNAL ENGINE FAILURE DUE TO A THERMAL FATIGUE FAILURE OF THE 1ST STAGE TURBINE WHEEL AS A RESULT OF OVERTEMPERATURE. THE HIGH ROUGH/UNEVEN TERRAIN PREVENTED A SUCCESSFUL AUTOROTATION.

## Sequence of events

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

- Loss of engine power(total) - mech failure/malf, approach - vfr pattern - final approach
  - turbine assembly,turbine wheel - overtemperature (cause)
  - turbine assembly,turbine wheel - failure,total (cause)
- Hard landing, landing - flare/touchdown
  - weather condition - high density altitude (contributing factor)
  - terrain condition - high terrain (contributing factor)
  - terrain condition - rough/uneven (contributing factor)

## Analysis

WHILE APPROACHING A REMOTE MOUNTAINTOP SITE TO LAND, AT ABOUT 100 FT AGL AND 40 MPH, THE ENGINE LOST ALL POWER AS A RESULT OF A CONTAINED ENGINE FAILURE, AND THE HELICOPTER MADE A HARD LANDING. ENGINE TEARDOWN REVEALED THAT THE 1ST STAGE TURBINE WHEEL HAD FAILED DUE TO THERMAL FATIGUE WHICH ORIGINATED ON THE TRAILING EDGE O.D. RIM SURFACE. IN ADDITION, BOTH THE 1ST AND 2ND STAGE TURBINE WHEEL AIRFOILS EXHIBITED EVIDENCE OF OVERTEMPERATURE OPERATION. THE FUEL CONTROL WAS PROPERLY SET. THERE WAS NO EVIDENCE OF AN INTERNAL ENGINE OIL FIRE. FAST ENGINE SHUTDOWNS CAN ALSO RESULT IN OVERTEMPERATURES IF SUFFICIENT COOL DOWN TIME AT IDLE POWER IS NOT ALLOWED BEFORE THE ENGINE IS SHUTDOWN. THE TURBINE OUTLET TEMPERATURE GAUGE DID NOT INCORPORATE THE 'OVERTEMPERATURE LIGHT' FEATURE.

## Aircraft

- Registration: [N300AH](https://openairdocs.org/deregistered/N300AH-1991-03-28), registration cancelled 1991-03-28, S/N 45519 (OpenAirDocs)
- Reported make and model: BELL 206L-1
- Registry model: [Bell Helicopter Textron 206L-1](https://openairdocs.org/model/bell-helicopter-textron-206l-1) (registry code 1182107) (OpenAirDocs)
- Category: Helicopter
- Serial number: 45519
- Airframe hours: 6380
- Engines: ALLISON 250-C28B 500 horsepower turbo shaft
- Damage: Substantial damage
- Fire: On-Ground
- Flight: Part 135
- Operator: Alaska Helicopters, Inc.
- Last inspection: 100 hour, July 7, 1990, 12 hours before
- Departed: SVW, SPARREVOHN AFS, AK
- Flight plan: Company VFR
- Airport: NONE

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; commercial, flight instructor; medical: class 2, valid medical--w/ waivers/lim; flight hours: 4,641 total, 330 in this make and model, 4,487 as pilot in command, 36 in the last 90 days, 12 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 40 statute miles
- Lowest ceiling: 6,500 ft overcast
- Temperature: 52 °F, dew point 48 °F
- Altimeter: 30.00 inHg
- Observed at: MCG, 55 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 19900714025549A](https://openairdocs.org/incident/19900714025549A), Jul 14, 1990: Bell 206L1, Farewell, AK, Substantial damage. First stage turbine wheel fractured due to overtemp. Made hard vertical landing on rocky mountain top.

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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