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ASN Wikibase Occurrence # 176785
Last updated: 30 January 2020
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Date:31-MAY-2015
Time:11:26
Type:Silhouette image of generic UH1 model; specific model in this crash may look slightly different
Bell-Garlick UH-1H Iroquois
Owner/operator:Private
Registration: N462CC
C/n / msn: 6509666
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:Minam Lodge Airport (7OR0), Cove, OR -   United States of America
Phase: Landing
Nature:Unknown
Departure airport:Cove, OR
Destination airport:Cove, OR (7OR0)
Investigating agency: NTSB
Narrative:
The commercial pilot reported that, while maneuvering the helicopter at low altitude during logging operations, he felt a vibration and heard a howling sound coming from the transmission area. He immediately initiated a precautionary landing; however, as the helicopter settled to the ground, the main rotor rpm dropped, and the pilot attempted to cushion the landing with aggressive collective input. The helicopter subsequently landed hard.
Postaccident examination revealed multiple fractures of the Kaflex engine-to-transmission drive shaft coupling assembly. According to the flight manual, a failure of the engine-to-transmission drive shaft would lead to a complete loss of power to the main rotor. The coupling assembly failure was initiated by the failure of an attachment bolt due to a fatigue crack on the flange section that attached the coupling assembly to the transmission shaft flange. No evidence of any material anomalies were found in the fractured bolt, and the fatigue crack was likely caused by the severe stress imposed by logging operations. The manufacturer did not specify a replacement interval for the bolt. The investigation could not determine when the fatigue crack developed and propagated; therefore, it could not be determined whether the crack would have been identified during an annual inspection.

Probable Cause: The failure of the engine-to-transmission drive shaft coupling assembly due to a fatigue fracture of one of its attachment bolts, which resulted in a loss of power to the main rotor.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20150604X72128&key=1
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=N462CC

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration: 3 years 1 month
Download report: Final report


Revision history:

Date/timeContributorUpdates
09-Jun-2015 18:11 Geno Added
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
08-Jul-2018 13:14 ASN Update Bot Updated [Time, Cn, Operator, Nature, Departure airport, Destination airport, Source, Narrative]
08-Jul-2018 13:42 harro Updated [Aircraft type, Nature, Source, Narrative]

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