ASN Wikibase Occurrence # 353957
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| Date: | Monday 10 August 1998 |
| Time: | 11:05 LT |
| Type: |  Hughes 369D |
| Owner/operator: | Eagle Air Helicopters, Inc. |
| Registration: | N1096L |
| MSN: | 800789D |
| Total airframe hrs: | 5499 hours |
| Engine model: | Allison 250C20B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Oso, WA -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Arlington, WA (AWO |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
At about 250 feet above the ground, the pilot-in-command heard a bang and saw the tail rotor gear box fly past the rotorcraft on the left side. The rotorcraft then 'nosed over and started turning to the right at a fast rate of speed.' The pilot-in-command then entered an autorotation and the rotorcraft impacted the ground. The tail rotor gearbox, tail rotor output shaft, fork assembly, swash-plate with pitch links, tail-boom aft fitting, and tail rotor driveshaft flex-coupling were recovered. Those items were inspected and tested at Boeing Helicopters, Mesa. The fracture mode for all of the components evaluated was ductile overload. The output shaft exhibited severe bending displacement of approximately 0.925 inches relative to a theoretical line along the centerline, characteristic of a brief, unbalanced load. The conical bearing surfaces of the tail rotor fork assembly were examined and determined to be void of heavy or unusual wear patterns. The tail rotor blades were not found during the course of the investigation.
Probable Cause: The separation of the 90 degree gearbox and tail rotor assembly for undetermined reasons followed by the inability of the pilot-in-command to maintain control of the rotorcraft.
Accident investigation:
 |
|
Sources:
NTSB SEA98LA160
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Mar-2024 17:23 | ASN Update Bot | Added |
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