# NTSB DEN83LA046: Bell 47G-3B-2 (Soloy), N7039J, Great Falls, MT, January 6, 1983

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: January 6, 1983, 09:45 local (16:45 UTC)
- Place: Great Falls, MT
- Location: 47.5025° N, 111.3000° W: Placed by OpenAirDocs: center of Great Falls, MT, within about 6 miles (OpenAirDocs)
- Nearby events: https://openairdocs.org/map.md?lat=47.5025&lon=-111.3000&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 16029
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN83LA046
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/16029/pdf
- Page: https://openairdocs.org/ntsb/DEN83LA046

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering
  - maintenance - inadequate, other maintenance personnel (cause)
  - maintenance,inspection - inadequate, other maintenance personnel (cause)
  - rotorcraft flight control,swashplate assembly - disconnected (cause)
- Loss of control - in flight, maneuvering
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WHILE MANEUVERING AT LOW ALTITUDE IN SEARCH OF ANIMALS, THE PILOT EXPERIENCED A SEVERE VIBRATION THROUGH THE FLIGHT CONTROLS. THE HELICOPTER BEGAN AN UNCONTROLLED DESCENT AND ATTEMPTS TO STOP THE DESCENT BY USING THE COLLECTIVE WERE UNSUCCESSFUL. THE HELICOPTER CONTACTED THE GROUND AND WAS SUBSTANTIALLY DAMAGED. AN EXAMINATION REVEALED THAT AN AN-320-5 NUT HAD COME OFF OF A PIN ON THE ROTATING SWASHPLATE RING. THE PURPOSE OF THIS NUT WAS TO SECURE THE LINK AND SCISSORS TO THE SWASHPLATE PIN. WITH THE NUT OFF, A LOSS OF CONTINUITY OCCURRED IN THE ROTATING CONTROLS OF ONE MAIN ROTOR BLADE. A COTTER PIN WAS REQUIRED TO SECURE THE NUT. THE ABSENCE OF A COTTER PIN WOULD HAVE ALLOWED THE NUT TO EVENTUALLY WORK ITS WAY OFF. THE HELICOPTER HAD BEEN OPERATED ABOUT 26 HRS SINCE A 1200 HR INSPECTION HAD BEEN PERFORMED. DURING THAT INSPECTION, THE ABOVE MENTIONED PARTS AND COMPONENTS HAD BEEN REMOVED, INSPECTED AND REINSTALLED.

## Aircraft

- Registration: [N7039J](https://openairdocs.org/deregistered/N7039J-1989-09-14), registration cancelled 1989-09-14, S/N 6776 (OpenAirDocs)
- Reported make and model: BELL 47G-3B-2 (SOLOY) (47G-3B-2 ()
- Registry model: [Bell 47G-3B-2](https://openairdocs.org/model/bell-47g-3b-2) (registry code 1181029) (OpenAirDocs)
- Category: Helicopter
- Serial number: 6776
- Airframe hours: 3625
- Engines: ALLISON 250-C20B 317 horsepower turbo shaft
- Damage: Destroyed
- Flight: Public aircraft, Part 91
- Operator: Mark W. Duffy
- Registered owner: Central Helicopters
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, February 28, 1982, 25 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 29; commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 4,111 total, 400 in this make and model, 100 in the last 90 days, 5 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 50 statute miles
- Lowest ceiling: none
- Temperature: 39 °F, dew point -0 °F

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19830106002279A](https://openairdocs.org/incident/19830106002279A), Jan 6, 1983: Bell 47G3B2, Great Falls, MT, Destroyed. Helicopter crashed when unsaftied nut holding swivel assembly link and scissors to the swash plate came off.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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