Bell 206B II accident near Chickaloon, Alaska, August 15, 1998
On August 15, 1998, a Bell 206B II (helicopter), registered N70711, was substantially damaged in an accident near Chickaloon, Alaska. It was a public-use flight under general aviation rules (Part 91). No one was hurt; 2 people were on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A fracture of the main rotor drag pin assembly.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 15, 1998
- Place
- Chickaloon, Alaska · map
- Type
- Accident
- Injuries
- No one was hurt; 2 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Bell 206B II · all 206B IIs on the register
- Registration
- N70711 · no longer on the register · serial 1331
- Damage
- Substantial damage
- Flight
- Public-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The commercial helicopter pilot said that he had completed a normal, westerly approach, and subsequent landing atop a 4,000 feet msl mountain. The pilot stated that as he reduced the throttle to the flight idle position, in preparation for engine shut down, a severe airframe vibration occurred. A postaccident inspection revealed that the helicopter's main rotor transmission had been torn from the lower isolation mount assembly, and the helicopter's transmission deck sustained substantial damage. The main rotor drag pin assembly, main rotor driveshaft, forward coupling assembly, and associated fasteners, were sent to the NTSB Materials Laboratory for inspection. The inspection discovered no evidence of a progressive fracture mechanism, and all fracture faces displayed features typical of overstress separation. The main rotor transmission isolation mount was retained by the NTSB, and sent to the manufacture for evaluation, and testing. An FAA airframe certification engineer attended the evaluation process, and reported that the isolation mount operated slightly below acceptable stiffness limits. He added that since the isolation mount sustained damage during the accident, an accurate stiffness value was unattainable.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: commercial pilot
- Ratings: multi-engine land; single-engine land; single-engine sea; instructor: airplane single-engine; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 3,000 hours in all; 30 in the last 90 days; 10 in the last 30 days; 2,700 as pilot in command; 300 on instruments
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: rgt
The aircraft
- Airframe total time: 14,159 hours
- Last inspection: 100-hour inspection, June 10, 1998; 107 hours since
- Maximum gross weight: 3,200 lb
- Seats: 5
- Landing gear: fixed
- Engine: Allison 250-C20 (turboshaft); 0 hours total
The flight
- Departed from: UUO Willow AK at 9:45 am
- Destination: AK
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 270° at 10 knots, gusting 15
- Visibility: 20 statute miles
- Sky: scat at 7,000 ft
- Temperature: 50°F (10°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.