ASN Wikibase Occurrence # 353503
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| Date: | Tuesday 8 December 1998 |
| Time: | 13:45 LT |
| Type: |  Hughes 369D |
| Owner/operator: | Eagle Air Helicopter |
| Registration: | N1096L |
| MSN: | 800789 |
| Total airframe hrs: | 5582 hours |
| Engine model: | Allison 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Taholah, WA -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Unknown |
| Departure airport: | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
While conducting external load operations the helicopter sustained substantial damaged after a loss of engine power, autorotation, and forced landing. A witness reported hearing a loud bang, followed by the engine spooling down. The witness also reported seeing smoke coming from the engine as the helicopter descended through the trees, landing hard on a tree stump under the pilot's seat area. Postaccident inspection of the turbine engine revealed excessive blending in the web of the first stage turbine wheel. Within the blending, a notch exhibited a radius sharper than allowed by blend limits, which the manufacturer' metallurgists believed to have been created by a hand-held grinder. It could not be determined whether the manufacturer of the turbine wheel or an overhaul facility made the subject grinding marks.
Probable Cause: Turbine wheel failure as the result of a low-cycle fatigue crack that initiated in a beyond-limits grinding gouge. Factors include improper maintenance by unknown parties and tree stumps that prohibited a successful emergency landing.
Accident investigation:
 |
|
Sources:
NTSB SEA99FA018
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Mar-2024 07:30 | ASN Update Bot | Added |
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