Bell UH-1B N99676

Summary

On 11 June 1985 at about 20:00 local time, a Bell UH-1B registered N99676 was involved in an accident near Juneau, Alaska, United States. One person was on board and one died. The aircraft was destroyed. No probable cause statement is available for this record.

Date

11 June 1985 at 20:00

Classification

Accident

Location

Juneau, Alaska, United States

Coordinates

Not recorded

Aircraft

Bell UH-1B

Registration

N99676

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Juneau → Unknown

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA85FA134

1 person died.

The NTSB has not published a probable cause for this record. No probable cause statement is present in the source data.

Nothing about the cause is stated here that is not in the source record.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.