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ASN Wikibase Occurrence # 157632
Last updated: 23 December 2019
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Type:Silhouette image of generic UH1 model; specific model in this crash may look slightly different
Bell UH-1H Iroquois
Owner/operator:Billings Flying Service
Registration: N775AR
C/n / msn: 65-10067
Fatalities:Fatalities: 1 / Occupants: 1
Aircraft damage: Substantial
Location:Near Dove Creek, Colorado -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Dove Creek, CO
Destination airport:Dove Creek, CO
Investigating agency: NTSB
The helicopter pilot flew inbound to a seismic survey location hoisting a basket load with a long-line rope. The pilot overshot the intended drop site, and the basket load and long-line impacted the ground after the pilot likely initiated a load release. The helicopter then entered a right bank, followed by a steep left bank, and subsequently impacted the ground.

Postaccident examination of the helicopter revealed evidence consistent with a loss of hydraulic fluid from the flight control system due to a hydraulic leak of a check valve fitting near the tail rotor servo. As the pilot approached the survey location, the loss of hydraulic pressure most likely resulted in very-high collective control forces and pilot-induced oscillations. The director of maintenance stated that the pilot and a mechanic were aware of the hydraulic fluid leak and had ordered replacement parts; however, they had not yet been installed. He stated that they did not expect the leak to cause a significant issue. Thus, it is likely that they did not foresee the leak causing a significant flight hazard.
Probable Cause: Pilot-induced oscillations caused by the loss of hydraulic assist of the flight controls due to an excessive loss of hydraulic fluid during a critical phase of flight, which resulted in ground impact. Contributing to the accident was an inadequate analysis of the hydraulic fluid leak by the pilot and mechanic.


FAA register:

Revision history:

17-Jul-2013 05:21 slowkid Added
17-Jul-2013 16:02 Geno Updated [Time, Aircraft type, Registration, Cn, Source, Damage]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 08:51 ASN Update Bot Updated [Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative]

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