Pilot Debrief

BELL UH-1H near Dove Creek, CO — 2013-07-16

Final reportCEN13FA415
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Date
2013-07-16
Location
Dove Creek, CO, USA
Aircraft
BELL UH-1H
Registration
N775AR
Category
Helicopter
Highest injury
Fatal
Fatalities
1
Phase of flight
Maneuvering

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.

Contributing factors

Contributing to the accident was an inadequate analysis of the hydraulic fluid leak by the pilot and mechanic.

NTSB narrative

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.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have aborted the drop after overshooting the intended site.

NTSB coding

Evidence available

  • Photos
  • 17 docket documents
View NTSB final reportView NTSB docket

Docket documents17

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