Bell 206L-1 N300AH

Summary

On 14 July 1990 at about 17:00 local time, a Bell 206L-1 registered N300AH, operated by Alaska Helicopters, Inc., was involved in an accident near Farewell, Alaska, United States. 5 people were on board and 5 were seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

14 July 1990 at 17:00

Classification

Accident

Location

Farewell, Alaska, United States

Coordinates

55.9207, -159.4905

Aircraft

Bell 206L-1

Registration

N300AH

Category

Helicopter

Engines

1

Operator

Alaska Helicopters, Inc.

Operating rule

Part 135: Air Taxi & Commuter

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Sparrevohn Afs → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC90FA117

5 people were seriously injured.

AN INTERNAL ENGINE FAILURE DUE TO A THERMAL FATIGUE FAILURE OF THE 1ST STAGE TURBINE WHEEL AS A RESULT OF OVERTEMPERATURE. THE HIGH ROUGH/UNEVEN TERRAIN PREVENTED A SUCCESSFUL AUTOROTATION.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

WHILE APPROACHING A REMOTE MOUNTAINTOP SITE TO LAND, AT ABOUT 100 FT AGL AND 40 MPH, THE ENGINE LOST ALL POWER AS A RESULT OF A CONTAINED ENGINE FAILURE, AND THE HELICOPTER MADE A HARD LANDING. ENGINE TEARDOWN REVEALED THAT THE 1ST STAGE TURBINE WHEEL HAD FAILED DUE TO THERMAL FATIGUE WHICH ORIGINATED ON THE TRAILING EDGE O.D. RIM SURFACE. IN ADDITION, BOTH THE 1ST AND 2ND STAGE TURBINE WHEEL AIRFOILS EXHIBITED EVIDENCE OF OVERTEMPERATURE OPERATION. THE FUEL CONTROL WAS PROPERLY SET. THERE WAS NO EVIDENCE OF AN INTERNAL ENGINE OIL FIRE. FAST ENGINE SHUTDOWNS CAN ALSO RESULT IN OVERTEMPERATURES IF SUFFICIENT COOL DOWN TIME AT IDLE POWER IS NOT ALLOWED BEFORE THE ENGINE IS SHUTDOWN. THE TURBINE OUTLET TEMPERATURE GAUGE DID NOT INCORPORATE THE 'OVERTEMPERATURE LIGHT' FEATURE.

Quoted verbatim from the NTSB record.