Tuesday, October 17, 2017

Hughes 269C, N7432F, Snohomish Flying Service Inc: Accident occurred August 11, 2014 in Darrington, Snohomish County, Washington

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf 

NTSB Identification: WPR14LA340
14 CFR Part 91: General Aviation
Accident occurred Monday, August 11, 2014 in Darrington, WA
Probable Cause Approval Date: 10/23/2017
Aircraft: HUGHES 269C, registration: N7432F
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The commercial pilot was conducting a local, personal flight in the rented helicopter. The pilot reported that, while descending the helicopter from 5,000 ft and approaching 4,000 ft, he increased the collective and noticed that the engine was slowing down; he was unable to recover the engine rpm to a normal range. The helicopter continued to descend until the pilot entered an autorotation. The helicopter then impacted a tree and came to rest in a small stream. The pilot stated that he did not believe that the engine ever quit but that it did not produce enough power to continue flight.

Postaccident examination of the helicopter revealed that the throttle mount bracket was hanging by the throttle cable linkage and was not secured to the servo mount studs, which would have led to the loss of throttle movement for acceleration. The operator stated that the engine had been installed in the helicopter 10 flight hours before the accident. It is likely that maintenance personnel did not properly secure the throttle mount bracket during the engine installation, which led to the loss of throttle movement and inability to control engine power.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
Maintenance personnel’s failure to secure the throttle mount bracket during a recent engine installation, which resulted in the loss of throttle movement and an inability to control engine power.

Federal Aviation Administration / Flight Standards District Office; Renton, Washington

Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Snohomish Flying Service Inc: http://registry.faa.gov/N7432F

NTSB Identification: WPR14LA340
14 CFR Part 91: General Aviation
Accident occurred Monday, August 11, 2014 in Darrington, WA
Aircraft: HUGHES 269C, registration: N7432F
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On August 11, 2014, about 1130 Pacific daylight time (PDT), a Hughes 269C Helicopter, N7432F, impacted terrain following a partial loss of engine power near Darrington, Washington. The airline transport pilot was not injured; the helicopter sustained substantial damage. Snohomish Flying Service (SFS) was operating the helicopter under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The local personal flight departed Snohomish, Washington, about 0815. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot reported that during a flight in the rented helicopter he was descending out of 5,000 ft. As he approached 4,000 ft, he increased collective and noticed that the engine was slowing down; he was unable to recover the engine rpm to a normal range. The helicopter continued to descend until the pilot entered an autorotation. The helicopter impacted a tree about 30 ft high and then came to rest in a small stream.

The pilot stated he did not believe the engine ever quit, but the engine would not produce enough power to continue flight.

The helicopter was recovered on August 12, 2014, by SFS and examined by Federal Aviation Administration inspectors with assistance from SFS personnel. They found that the throttle mount bracket was hanging by the throttle cable linkage and was not secured to the servo mount studs as it should have been. This would prevent the loss of throttle movement for acceleration.

The operator stated that the engine had just been installed into the helicopter 10 flight hours prior to the accident.

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