ASN Wikibase Occurrence # 355801
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| Date: | Tuesday 3 June 1997 |
| Time: | 06:30 LT |
| Type: |  Bell-Garlick UH-1H |
| Owner/operator: | Northwest Helicopter, Inc. |
| Registration: | N85NW |
| MSN: | 66-0792 |
| Total airframe hrs: | 8782 hours |
| Engine model: | Lycoming T53-L-13B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Addy, WA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Unknown |
| Departure airport: | , WA |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While returning to pick up another log, the pilot heard a high-speed shredding sound' accompanied by high-frequency vibrations. As the noise and vibration increased, the pilot turned downhill and looked for a location where he could make an emergency landing. He then heard a second loud noise, and the rotor RPM immediately began to decay. He stretched his glide over the 130 foot high trees and managed to maneuver the helicopter so that it 'fell into' a switchback on an old dirt logging road. A post accident examination of the K-FLEX drive shaft, which runs between the engine and the transmission, revealed that one of its flex band legs had experienced an inflight fatigue fracture. A review of the records revealed that the shaft had accumulated 459 hours while being used by the United States Army, and had accumulated an additional 432 hours during civilian logging operations.
Probable Cause: The inflight failure of the K-FLEX engine-to-gear box drive shaft and no suitable site in which to make a forced/emergency landing. A factor was the mountainous/hilly terrain.
Accident investigation:
 |
|
Sources:
NTSB SEA97LA126
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 12-Mar-2024 15:46 | ASN Update Bot | Added |
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