ASN Wikibase Occurrence # 165876
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| Date: | Tuesday 29 April 2014 |
| Time: | 10:28 |
| Type: |  Hughes OH-6 Cayuse |
| Owner/operator: | U.S. Department of Agriculture APHIS |
| Registration: | N37929 |
| MSN: | 0518 |
| Year of manufacture: | 1967 |
| Total airframe hrs: | 19761 hours |
| Engine model: | Rolls Royce 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Near Lake Powell, Garfield County, UT -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Hanksville Intermediate Airport, UT (HVE/KHVE) |
| Sandy Ranch, UT | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During a hover about 50 ft above ground level over steeply sloped terrain, the helicopter suddenly made an uncommanded left yaw, and the rotor rpm started to drop. The pilot lowered the collective and performed an autorotation to a rock ledge. After touching down on the ledge, the helicopter tipped over and tumbled downslope about 60 ft, and the tailboom was severed from the helicopter.
The rotor blade damage observed during the postaccident wreckage examination was consistent with low-rotor energy at the time of ground impact. Postaccident examination of the engine, rotor drive system, and fuel control unit revealed no anomalies that would have precluded normal operation. The engine’s damaged external components were replaced, and a test run was conducted. The engine started and produced full power. The helicopter’s operating manual stated that an uncommanded left yaw and a drop in rotor rpm could be indications of a loss of engine power. Given the uncommanded left yaw and drop in rotor rpm during the flight, it is likely that the engine lost power; however, the reason for the loss of engine power could not be determined.
Probable Cause: A loss of engine power while the helicopter was hovering for reasons that could not be determined because postaccident examination of the engine and rotor drive system revealed no evidence of a mechanical malfunction or failure that would have precluded normal operation.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N37929
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 30-Apr-2014 06:59 | gerard57 | Added |
| 01-May-2014 04:52 | Geno | Updated [Aircraft type, Registration, Cn, Operator, Location, Nature, Source, Narrative] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 29-Nov-2017 14:03 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
| 12-Nov-2022 02:14 | Ron Averes | Updated [Operator, Departure airport, Source] |
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