# NTSB DEN84LA288: Bell 206B, N1086Y, Vernal, UT, September 12, 1984

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: September 12, 1984, 16:30 local (22:30 UTC)
- Place: Vernal, UT
- Coordinates: 40.550109, -109.569396 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.5501&lon=-109.5694&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 1 uninjured
- Status: Completed
- Report: Approved by Office Director
- NTSB case key (mKey): 16484
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN84LA288
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/16484/pdf
- Page: https://openairdocs.org/ntsb/DEN84LA288

## Sequence of events

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

- Loss of control - in flight, cruise
  - aircraft handling - improper, pilot in command (cause)
  - lack of total instrument time, pilot in command (contributing factor)
  - directional control - not maintained, pilot in command (cause)
  - spiral - uncontrolled, pilot in command (cause)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

PLT STATED THAT WHILE ON A HEADING OF 050 DEGS (WIND FROM 270 DEGS AT 5 KTS) THE ACFT BEGAN TO SHUDDER AND VEERED TO THE RIGHT. PLT ATTEMPTED REMEDIAL ACTION BUT ACFT CONTINUED DESCENDING IN A RIGHT SPIRAL TO GROUND CONTACT. EXAMINATION OF THE HELICOPTER DID NOT DISCLOSE ANY MECHANINCAL FAILURE/MALFUNCTION. BELL HELICOPTER TEXTRON, INC., PUBLISHED INFORMATION LETTER 206-84-41 DATED JULY 6, 1984 IN WHICH IT DESCRIBES UNANTICIPATED RIGHT YAW AS, '... THE OCCURRENCE OF AN UNCOMMANDED RIGHT YAW RATE WHICH DOES NOT SUBSIDE OF ITS OWN ACCORD AND WHICH, IF NOT CORRECTED CAN RESULT IN LOSS OF AIRCRAFT CONTROL.' THE PLT WAS IN THE POST SOLO PHASE OF HIS HELICOPTER TRAINING. ONE PASSENGER WAS ON BOARD WHEN THE ACCIDENT OCCURRED.

## Aircraft

- Registration: N1086Y (not matched to a registry record)
- Reported make and model: BELL 206B
- Category: Helicopter
- Serial number: 2988
- Airframe hours: 2587
- Engines: ALLISON 250-C20B 317 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Business, Part 91
- Operator: Telestar Inc
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, September 8, 1984, 8 hours before
- Departed: VERNAL, UT

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 1,634 total, 57 in this make and model, 1,493 as pilot in command, 88 in the last 90 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 5 knots
- Visibility: 40 statute miles
- Lowest ceiling: none
- Temperature: 39 °F
- Observed at: VEL

## 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 19840912048179A](https://openairdocs.org/incident/19840912048179A), Sep 12, 1984: Bell 206B, Vernal, UT, Substantial damage. Student helicopter pilot allowed high yaw rate to develop due to weathervaning. Unchecked spiraled to ground.

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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