# NTSB ANC90LA170: Bell 206B, N385EH, Kokhanok, AK, September 9, 1990

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: September 9, 1990, 14:00 local (22:00 UTC)
- Place: Kokhanok, AK
- Coordinates: 59.849311, -154.559753 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=59.8493&lon=-154.5598&mi=10
- Phase of flight: [Other](https://openairdocs.org/ntsb-phases/800) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious
- Status: Completed, report December 8, 1992
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5449
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC90LA170
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5449/pdf
- Page: https://openairdocs.org/ntsb/ANC90LA170

## Probable cause

THE FAILURE OF THE COMPRESSOR END OF THE AIR COMPRESSOR SCROLL TO TEE TUBE ASSEMBLY CAUSING THE ENGINE TO SPOOL DOWN. THE FORCED LANDING IN ENEVEN, UNPREPARED, AND LIGHTLY FORESTED TERRAIN WERE FACTORS.

## Sequence of events

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

- Loss of engine power(partial) - nonmechanical, other
  - fuel system,pc line - failure,total (cause)
- Forced landing, descent - emergency
  - terrain condition - rough/uneven (contributing factor)
  - terrain condition - high vegetation (contributing factor)

## Analysis

THE PILOT EXPERIENCED A SPOOL DOWN ON THE TURBINE ENGINE. EXAMINATION OF THE ENGINE REVEALED THAT THE AIR COMPRESSOR SCROLL TO TEE TUBE ASSEMBLY COMPRESSOR END FITTING HAD BROKEN. METALLURGICAL EXAMINATION OF THE PART SHOWED THAT THERE WERE NO MATERIAL IRREGULARITIES, THAT THE TUBE BEND DEVELOPMENT AND LINEAR MEASUREMENTS VARIED FROM THE ENGINEERING DRAWINGS, AND THAT THE TUBE ASSEMBLY FAILED IN A FATIGUE MODE. THE ORIGIN WAS ON THE TUBE O.D. APPROXIMATELY 0.020 INCH BELOW THE 'B' END FLARE RADIUS.

## Aircraft

- Registration: [N385EH](https://openairdocs.org/deregistered/N385EH-1990-11-29), registration cancelled 1990-11-29, S/N 1674 (OpenAirDocs)
- Reported make and model: Bell 206B
- Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs)
- Category: Helicopter
- Serial number: 1674
- Airframe hours: 6837
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Other work use, Part 133
- Operator: Era Aviation Inc., doing business as Era Helicopters
- Registered owner: Era Aviation Inc.
- Airworthiness certificate: Standard, Utility
- Last inspection: AAIP, August 27, 1990, 865 hours before
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 44; commercial; instrument ratings: helicopter; medical: class 1, valid medical--w/ waivers/lim; seat: right; flight hours: 3,570 total, 1,775 in this make and model, 3,100 as pilot in command, 144 in the last 90 days, 85 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 15 knots, gusting 20
- Visibility: 15 statute miles
- Lowest ceiling: 3,000 ft broken
- Temperature: 50 °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 19900909038379A](https://openairdocs.org/incident/19900909038379A), Sep 9, 1990: Bell 206B, Kaknohak, AK, Substantial damage. Lost power. Dropped sling load. Autorotated. Hard landing. Air compressor scroll tee tube assembly worn and cracked

## Other investigations on N385EH (1)

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.

- [NTSB ANC85FA065](https://openairdocs.org/ntsb/ANC85FA065), Apr 19, 1985: Bell BH-206-B (N385EH), Valdez, AK, substantial damage

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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