# NTSB SEA85FA134: Bell UH-1B, N99676, Juneau, AK, June 11, 1985

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: June 11, 1985, 12:00 local (20:00 UTC)
- Place: Juneau, AK
- Location: 58.3019° N, 134.4197° W: Placed by OpenAirDocs: center of Juneau, AK, within about 29 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=58.3019&lon=-134.4197&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 40048
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA85FA134
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/40048/pdf
- Page: https://openairdocs.org/ntsb/SEA85FA134

## 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
  - compressor assembly - undertorqued (cause)
  - maintenance,overhaul - improper, other maintenance personnel (cause)
  - compressor assembly,rotor disc - unlocked (cause)
  - compressor assembly,impeller - disconnected (cause)
- Forced landing, landing
- In flight collision with terrain/water, landing
  - object - tree(s) (cause)
  - terrain condition - none suitable (contributing factor)

## Analysis

WHILE ENGAGED IN A LOG SLINGING OPERATION OVER MOUNTAINOUS, DENSELY FORESTED TERRAIN THE ROTOR CRAFT SUFFERED A TOTAL POWER LOSS FORCING THE PILOT TO EXECUTE AN AUTOROTATIVE LANDING INTO HIGH CONIFER TREES. DISASSEMBLY OF THE ENGINE REVEALED EVIDENCE THAT THE SPACER BETWEEN THE NO. 5 COMPRESSOR AND THE IMPELLER HAD NOT BEEN POSITION SEATED DURING THE LAST OVERHAUL AND THAT DURING THE ACCIDENT FLIGHT THE SPACER SLIPPED INTO ITS PROPER POSITION THUS RELEASING THE COMPRESSIVE TORQUE LOAD UNDER WHICH THE ASSEMBLY HAD BEEN SUFJECTED DURING BUILDIP. THE COMPRESSOR ASSEMBLY SUBSEQUENTLY BECAME UNCOUPLED FORCING THE IMPELLER FORWARD INTO ITS MAGNESIUM HOUSING. THIS ACTION RESULTED IN AN OVERTEMPERATURE CONDITION AND BREAKUP WITHIN THE TURBINE ASSEMBLY BROUGHT ON BY THE COMBUSTION OF MAGNESIUM PARTICLES.

## Aircraft

- Registration: [N99676](https://openairdocs.org/deregistered/N99676-1991-04-23), registration cancelled 1991-04-23, S/N 638513 (OpenAirDocs)
- Reported make and model: BELL UH-1B
- Registry model: [Bell UH-1B](https://openairdocs.org/model/bell-uh-1b) (registry code 1181410) (OpenAirDocs)
- Category: Helicopter
- Serial number: 63-8513
- Airframe hours: 5043
- Engines: LYCOMING T53-L-11 1250 horsepower turbo shaft
- Damage: Destroyed
- Flight: Other work use, Part 133
- Registered owner: Temsco Helicopters, Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, April 17, 1985, 62 hours before
- Departed: JNU, JUNEAU, AK
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; commercial; medical: class 2, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 3,914 total, 2,100 in this make and model, 3,485 as pilot in command, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 60° at 14 knots
- Visibility: 14 statute miles
- Lowest ceiling: 3,000 ft overcast
- Temperature: 52 °F, dew point 46 °F
- Altimeter: 29.00 inHg
- Observed at: FNR, 13 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 19850611023879A](https://openairdocs.org/incident/19850611023879A), Jun 11, 1985: Bell UH1B, Juneau, AK, Destroyed. During overhaul, metal shavings prevented proper assembly of compressor rotor. Engine failed. Aircraft hit 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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