Bell UH-1B N70NW

Summary

On 8 August 2013 at about 22:30 local time, a Bell UH-1B registered N70NW, operated by Northern Pioneer Helicopters LLC, was involved in an accident near Tok, Alaska, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

8 August 2013 at 22:30

Classification

Accident

Location

Tok, Alaska, United States

Nearest airport

Tok Junction (PFTO)

Coordinates

61.2599, -149.6002

Aircraft

Bell UH-1B

Registration

N70NW

Category

Helicopter

Engines

1

Operator

Northern Pioneer Helicopters LLC

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

External Load

Phase of flight

Not recorded

Route

Tok → Tok

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC13TA076

Nobody was injured.

The failure of the tail rotor crosshead bearing, which resulted in a loss of tail rotor control.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

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.

Quoted verbatim from the NTSB record.