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ASN Wikibase Occurrence # 76837
Last updated: 17 August 2021
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Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell 206B-3 Jet Ranger III
Owner/operator:Rocky Mountain Helicopters (RMH) Aerologging
Registration: N21424
MSN: 3466
Fatalities:Fatalities: 0 / Occupants: 4
Other fatalities:0
Aircraft damage: Substantial
Location:Annette Bay, near Ketchikan, Alaska -   United States of America
Phase: Approach
Nature:External load operation
Departure airport:
Destination airport:Annette Bay, near Ketchikan, Alaska
Investigating agency: NTSB
On June 17, 1993, at 18:00 ADT (Alaska Daylight Time) a skid equipped Bell 206B-3 helicopter, N21424, registered to Rocky Mountain Helicopters (RMH), and operated by RMH Aerologging, was substantially damaged when it experienced a tail rotor drive shaft failure and subsequent loss of tail rotor control while on short final to a field site at Annette Bay located near Ketchikan, Alaska.

The business flight, operating under 14 CFR Part 91, departed a different field site and was transporting loggers employed by RMH Aerologging. A company flight plan was in effect and visual meteorological conditions prevailed. The helicopter was substantially damaged and the Pilot-in-Command and the three passengers were not injured.

According to the Pilot-in-Command, the helicopter started rapidly rotating about 50 feet above the landing zone, an open spot on a mountain logging road. He successfully stabilized the aircraft over the road and accomplished a hovering autorotation with a complete tail rotor failure. Although the aircraft landed with little vertical speed, the rapid rotation separated the right landing gear mounts and the aircraft settled slightly to the left without main rotor contact with the ground. There were no injuries.

The subsequent investigation found that the adapter on the tail rotor drive shaft number 4 had de-bonded and would rotate on the shaft, but the mode for the de-bonding could not be determined due to rotational damage. Other shaft adapters showed de-bonding caused by plastic blasting. The inspection procedure calls for inspections on the shaft using magnetic particle or fluorescent penetrant methods and does not call for plastic medium blasting. The helicopter had been involved in a previous tail rotor strike, in November 1992, and the drive shaft was inspected.

The NTSB determined the probable cause to be: The failure of the tail rotor drive shaft coupling and the inadequate inspection of the tail rotor drive system by company maintenance personnel after the first tail rotor strike.

US registration N21424 cancelled by the FAA on 27-02-1995 as "Exported to Australia"; believed repaired/rebuilt and became VH-HRZ, later VH-WCG.


1. NTSB Identification: ANC93LA095 at
2. FAA:

Revision history:

30-Nov--0001 00:00 ASN Archive
28-Aug-2016 15:51 Dr.John Smith Updated [Date, Time, Aircraft type, Registration, Cn, Operator, Total fatalities, Total occupants, Other fatalities, Location, Country, Phase, Nature, Destination airport, Source, Damage, Narrative]
28-Aug-2016 15:55 Dr.John Smith Updated [Source]
21-Dec-2016 19:25 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
13-Jul-2018 12:28 Anon. Updated [Narrative, Photo, ]
13-Jul-2018 12:29 tkairshows Updated [Narrative, Photo, ]

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