# NTSB DEN87FA147: Bell 206L-1, N4999N, Choteau, MT, June 6, 1987

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: June 5, 1987, 20:15 local (Jun 6, 1987, 02:15 UTC)
- Place: Choteau, MT
- Coordinates: 47.85918, -112.440032 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=47.8592&lon=-112.4400&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 4 fatal
- Status: Completed, report August 31, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 17111
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN87FA147
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17111/pdf
- Page: https://openairdocs.org/ntsb/DEN87FA147

## Analysis

THE EMS HELICOPTER WAS RETURNING TO GREAT FALLS, MT, ON 6/5/87 WHEN IT CRASHED. ITS OCCUPANTS HAD EARLIER PARTICIPATED IN A RESCUE SEMINAR AT MANY GLACIER, MT. THE WRECKAGE WAS NOT FOUND UNTIL 6/9/87. A VIDEO TAPE RECOVERED FROM THE WRECKAGE DISCLOSED THE HELICOPTER TO BE FOLLOWING A HERD OF BIG HORN SHEEP UP A 7000-FT MOUNTAIN SLOPE AND FLYING SLOWLY AT TREE-TOP LEVEL WHEN IT SUDDENLY YAWED TO THE RIGHT. TESTS MADE ON THE AUDIO PORTION OF THE VIDEO TAPE REVEALED MAIN/TAIL ROTOR RPM WAS AT 100% POWER UNTIL 3.5 SEC BEFORE END OF TAPE. AT THAT TIME MAIN/TAIL ROTOR RPM DROPPED TO 94%. EVIDENCE ALSO DISCLOSED HELICOPTER TO BE FLYING AT HIGH GROSS WEIGHT, HIGH DENSITY ALTITUDE, AND WITH A TAILWIND.

## Sequence of events

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

- Loss of control - in flight, maneuvering
  - in-flight planning/decision - improper, pilot in command (contributing factor)
  - weather condition - tailwind (contributing factor)
  - compensation for wind conditions - not performed, pilot in command (contributing factor)
  - diverted attention, pilot in command (contributing factor)
  - weather condition - high density altitude (contributing factor)
  - altitude - reduced, pilot in command (contributing factor)
  - airspeed - reduced, pilot in command (contributing factor)
  - collective - excessive, pilot in command (cause)
  - aircraft performance,yawing maneuvers - exceeded (cause)
  - rotor rpm - not maintained, pilot in command (cause)
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - mountainous/hilly (contributing factor)
  - terrain condition - uphill (contributing factor)

## Aircraft

- Registration: [N4999N](https://openairdocs.org/deregistered/N4999N-2013-06-12), registration cancelled 2013-06-12, S/N 45497 (OpenAirDocs)
- Reported make and model: BELL 206L-1
- Registry model: [Bell Helicopter Textron 206L-1](https://openairdocs.org/model/bell-helicopter-textron-206l-1) (registry code 1182107) (OpenAirDocs)
- Category: Helicopter
- Serial number: 45497
- Airframe hours: 1297
- Engines: ALLISON 250-C28B 435 horsepower turbo shaft
- Damage: Destroyed
- Fire: On-Ground
- Flight: Part 135
- Operator: Minuteman Aviation, doing business as [Ems]
- Registered owner: R.S. Aviation Incorporated
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, June 1, 1987
- Departed: MANY GLACIER, MT
- Destination: GREAT FALLS, MT

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 43; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; toxicology performed; flight hours: 4,548 total, 492 in this make and model, 4,236 as pilot in command, 84 in the last 90 days, 15 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 180° at 16 knots, gusting 24
- Visibility: 40 statute miles
- Lowest ceiling: 14,000 ft broken
- Temperature: 73 °F, dew point 46 °F
- Altimeter: 29.00 inHg
- Observed at: GTF, 57 nm away

## 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 19870605019129A](https://openairdocs.org/incident/19870605019129A), Jun 5, 1987: Bell 206L1, Choteau, MT, Destroyed, 4 fatal. Crashed and burned while flying low and slow up a mountainside. Indicates loss of tail rotor effectiveness downwind

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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