ASN Wikibase Occurrence # 134807
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| Date: | Monday 25 October 2004 |
| Time: | 14:25 |
| Type: |  Hughes OH-6A |
| Owner/operator: | Tucson Sector Air Operations |
| Registration: | N6188L |
| MSN: | 891257 |
| Year of manufacture: | 1969 |
| Total airframe hrs: | 9463 hours |
| Engine model: | Allison 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Tucson, AZ -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Unknown |
| Departure airport: | Ajo, AZ |
| Tucson, AZ (TUS) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The engine spooled down during a law enforcement surveillance flight, and the pilot made a hard forced landing in uneven terrain. The crew was performing surveillance at low altitude above an uneven wash, and the pilot was in slow sideward flight. He pulled the collective to gain altitude and airspeed to make another pass. Then he heard and felt the engine spool down. He said that it quit producing power completely, and he attempted to autorotate to the ground. He said that he had insufficient airspeed and altitude to complete a successful autorotation. The helicopter hit the ground hard in a near level attitude. It bounced backwards, and rotated 45 degrees to the right. Metallurgical examination revealed that the governor tee to fuel control PC line fractured as a result of fatigue. The tubes were bent with contours differing from the original manufactured shape, indicative of handling/assembly damage. Disassembly and inspection of the starter/generator revealed conditions indicative of wear and misassembly, including the wrong bearings being installed, which would cause the unit to operate in an out-of-balance condition and induce vibrations.
Probable Cause: The loss of engine power due to a fatigue fracture of the PC line from the governor to fuel control, resulting from fretting damage induced by excessive vibration, which was due to the failure of maintenance personnel to install the proper bearings in the starter/generator. A contributing factor was the loss of power at low altitude and airspeed (height/velocity limitation) which diminished the possibility of a successful autorotation.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20041116X01830&key=1
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Dec-2016 19:26 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 07-Dec-2017 18:29 | ASN Update Bot | Updated [Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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