# NTSB ANC92GA155: Bell 206B, N83139, Fairbanks, AK, August 25, 1992

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Final report
- Date: August 25, 1992, 09:43 local (17:43 UTC)
- Place: Fairbanks, AK
- Coordinates: 64.669815, -147.039627 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=64.6698&lon=-147.0396&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report August 26, 1993
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5654
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC92GA155
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5654/pdf
- Page: https://openairdocs.org/ntsb/ANC92GA155

## Probable cause

POOR MAINTENANCE AND INSPECTION PROCEDURES BY THE CONTRACT MAINTENANCE PERSONNEL, AS WELL AS IMPROPER MAINTENANCE AND INSTALLATION OF THE FUEL LINE BY THE CONTRACT MAINTENANCE PERSONNEL. FACTORS RELATING TO THE ACCIDENT WERE THE TURBOSHAFT ENGINE VIBRATIONS AND THE CRACKED FUEL LINE(S).

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise
  - turboshaft engine,free(power) turbine - vibration (contributing factor)
  - maintenance,inspection - poor, other maintenance personnel (cause)
  - fuel system,line - cracked (contributing factor)
  - maintenance,installation - improper, other maintenance personnel (cause)
- Fire, landing - flare/touchdown
  - fuel system,line - fire

## Analysis

THE STATE OF ALASKA HELICOPTER EXPERIENCED A FUEL LEAK AND AN UNEVENTFUL PRECAUTIONARY LANDING. THE LEAKING FUEL LINE WAS REPLACED IN FIELD MAINTENANCE WITHOUT MANUFACTURER'S REQUIRED SECURING CLAMPS. A SECOND FUEL LEAK, PRECAUTIONARY LANDING AND FUEL LINE REPLACEMENT WAS EFFECTED, AGAIN WITHOUT CLAMPS. A THIRD FUEL LEAK AT THE SAME REPLACEMENT LINE WAS FOLLOWED BY A FIRE FOLLOWING A PRECUATIONARY LANDING. THE NTSB SUPERVISED MANUFACTURER'S ENGINE EXAMINATION REVEALED VIBRATION IN ROTATING COMPONENTS OF 15 TIMES THE ALLOWED LIMITS, AS WELL AS A FATIGUE CRACK IN THE HOT SECTION. THESE VIBRATIONS AND CRACKS WERE NOT DISCOVERED DURING ENGINE MAINTENANCE AND INSPECTIONS BY COMPANY CONTRACT MAINTENANCE PERSONNEL. THE METALLURGICAL EXAMINATION OF THE FUEL LINES IN EACH EVENT REVEALED FATIGUE PROPAGATION AND THE LACK OF CLAMP MARKS ON THE FUEL LINES FROM EVENTS 2 AND 3.

## Aircraft

- Registration: N83139 (not matched to a registry record)
- Reported make and model: BELL 206B
- Category: Helicopter
- Serial number: 1018
- Airframe hours: 11658
- Engines: ALLISON 250-C20 317 horsepower turbo shaft
- Damage: Substantial damage
- Fire: Both
- Flight: Public aircraft, Public use
- Operator: Alaska Public Safety, doing business as Alaska State Troopers
- Registered owner: State Of Alaska
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, June 30, 1992, 39 hours before
- Departed: FAI
- Destination: TKJ, TOK, AK
- Flight plan: Company VFR
- Airport: FAI, Fairbanks

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 54; airline transport; airplane ratings: single-engine land; instrument ratings: airplane, helicopter; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 8,700 total, 4,500 in this make and model, 8,000 as pilot in command, 100 in the last 90 days, 40 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 360° at 8 knots
- Lowest ceiling: none
- Temperature: 52 °F, dew point 39 °F
- Altimeter: 29.00 inHg
- Observed at: FAI, 1 nm away

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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