# NTSB ANC91LA059: Bell UH-1B, N87729, Smith Cove, AK, May 22, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: May 22, 1991, 09:45 local (17:45 UTC)
- Place: Smith Cove, AK
- Coordinates: 55.610195, -131.580734 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=55.6102&lon=-131.5807&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB office: Alaska Regional Office
- NTSB case key (mKey): 5544
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC91LA059
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/5544/pdf
- Page: https://openairdocs.org/ntsb/ANC91LA059

## Probable cause

A COMPLETE LOSE OF ENGINE POWER DUE TO A TOTAL DISINTEGRATION OF THE TURBINE WHEEL.

## 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, maneuvering
  - turbine assembly,turbine wheel - failure,total (cause)
  - turbine assembly,turbine wheel - disintegrated
- Forced landing, descent - emergency
- In flight collision with object, descent - emergency
  - terrain condition - none suitable (contributing factor)
  - object - tree(s)

## Analysis

THE PILOT STATED THAT HE WAS MANEUVERING JUST ABOVE THE TREE LEVEL WHEN THE ENGINE QUIT.  EXAMINATION OF THE ENGINE REVEALED THAT THE TURBINE WHEEL DISINTEGRATED IN FLIGHT CAUSING A TOTAL LOSS OF POWER.

## Aircraft

- Registration: N87729 (not matched to a registry record)
- Reported make and model: BELL UH-1B
- Category: Helicopter
- Serial number: 622034
- Airframe hours: 5337
- Engines: LYCOMING T55-L11D 1100 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Other work use, Part 133
- Operator: Northwest Helicopter, Inc.
- Registered owner: Northwest Helicopter, Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: 100 hour, May 21, 1991, 2 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 50; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 4,950 total, 600 in this make and model, 5,145 as pilot in command, 100 in the last 90 days, 100 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 30 statute miles
- Lowest ceiling: none
- Temperature: 52 °F, dew point 39 °F
- Altimeter: 30.00 inHg

## 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 19910522016829A](https://openairdocs.org/incident/19910522016829A), May 22, 1991: Bell UH1B, Smith Cove, AK, Substantial damage. Turbine engine failure during external load operations. Dropped into trees.

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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