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ASN Wikibase Occurrence # 169256
Last updated: 19 February 2020
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Type:Silhouette image of generic UH1 model; specific model in this crash may look slightly different
Bell UH-1B
Owner/operator:Northern Pioneer Helicopters Llc
Registration: N70NW
C/n / msn: 60-3568
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Location:Tok Junction Airport, AK -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Departure airport:Tok, AK (PFTO)
Destination airport:Tok, AK (PFTO)
Investigating agency: NTSB
The pilot had just completed a water drop with a long-line and water bucket when he noticed a degradation of the helicopter’s directional control. He returned to the airport, released the bucket, and attempted a “stuck-pedal” run-on landing. During the attempted landing, the helicopter began to drift left toward trees. Unable to maintain directional control, the pilot initiated a go-around, and the main rotor blades then struck the treetops. After realigning with the runway, he executed a “slow-speed” run-on landing to a gravel area adjacent to the runway. During touchdown, the helicopter bounced multiple times, and it then came to rest upright. The helicopter sustained substantial damage to the fuselage, vertical fin, and tail rotor blades.
A postaccident examination of the tail rotor assembly revealed that the tail rotor crosshead bearing’s split inner ring’s inboard shoulder was spalled and completely worn away, which allowed the outboard set of bearing balls to run over the pitch change rod’s seating flange for the split inner ring’s inboard shoulder. The pitch change rod was then free to migrate outboard, and it machined a hole through the end of the crosshead. The movement of the pitch change rod decreased the effectiveness of the left antitorque pedal and increased the effectiveness of the right antitorque pedal.
Probable Cause: The failure of the tail rotor crosshead bearing, which resulted in a loss of tail rotor control.



Revision history:

28-Aug-2014 06:16 Aerossurance Added
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 08:59 ASN Update Bot Updated [Cn, Operator, Total occupants, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative]

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