# NTSB DEN89LA059: Bell 206B III, N16733, Park City, UT, January 8, 1989

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: January 8, 1989, 14:27 local (21:27 UTC)
- Place: Park City, UT
- Coordinates: 40.640933, -111.490097 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.6409&lon=-111.4901&mi=10
- Phase of flight: [Standing](https://openairdocs.org/ntsb-phases/150) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report January 11, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 17662
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN89LA059
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17662/pdf
- Page: https://openairdocs.org/ntsb/DEN89LA059

## Probable cause

THE SELECTION OF AN UNSUITABLE LANDING SITE BY THE PILOT, RESULTING IN TAIL ROTOR CONTACT WITH THE TERRAIN AND SHEARING OF THE TAIL ROTOR DRIVESHAFT.

## Sequence of events

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

- On ground/water encounter with terrain/water, standing - idling rotors
  - terrain condition - snow covered (contributing factor)
  - terrain condition - uphill (contributing factor)
  - unsuitable terrain or takeoff/landing/taxi area - selected, pilot in command (cause)
  - clearance - not maintained, pilot in command (cause)
- Loss of control - in flight, hover
  - rotor drive system,tail rotor drive shaft - sheared
  - directional control - not possible
- On ground/water encounter with terrain/water, landing - flare/touchdown
  - autorotation - performed

## Analysis

THE COMMERCIAL PLT FLEW A RESCUE TEAM TO A MOUNTAIN AVALANCHE AREA. THE TEAM DEPLANED AND DURING THE UNLOADING PROCEDURE THE HELICOPTER SETTLED BACKWARDS INTO LOOSE SNOW. THE PLT ADDED COLLECTIVE PITCH AND ATTEMPTED TO HOVER. AS THE HELICOPTER LEFT THE GROUND, AN UNCOMMANDED RIGHT SPIN BEGAN. THE PLT PERFORMED A HOVERING AUTOROTATION 30 FEET AWAY FROM THE GROUND PERSONNEL. AT TOUCHDOWN THE TAIL BOOM ENTERED DEEP SNOW AND THE ACFT CAME TO REST NOSE HIGH. THE PLT DISCOVERED THE TAIL ROTOR SHAFT HAD BROKEN FORWARD OF THE TAIL ROTOR GEAR BOX. A POST ACCIDENT INVESTIGATION SHOWED EVIDENCE THAT THE TAIL ROTOR BLADES ENTERED LOOSE SNOW AND WERE SUBJECTED TO RAPID DECELERATION. THE SHAFT HAD SHEARED UNDER APPLIED TORQUE.

## Aircraft

- Registration: [N16733](https://openairdocs.org/deregistered/N16733-2013-06-18), registration cancelled 2013-06-18, S/N 2138, built 1977 (OpenAirDocs)
- Reported make and model: BELL 206B III
- Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs)
- Registry engine: [Allison 250 SER 400HP](https://openairdocs.org/engine/allison-250-ser-400hp) (registry code 03013, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 2138
- Airframe hours: 3439
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Other work use, Part 91
- Operator: Avman Inc, doing business as Helicopter Svcs
- Registered owner: Avman, Inc
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, December 2, 1988, 31 hours before
- Departed: NONE
- Destination: NONE
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 43; flight instructor, commercial, private; airplane ratings: single-engine land; medical: class 2, valid medical--w/ waivers/lim; seat: right; flight hours: 7,404 total, 2,663 in this make and model, 7,280 as pilot in command, 107 in the last 90 days, 33 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 10 knots, gusting 15
- Visibility: 50 statute miles
- Lowest ceiling: none
- Temperature: 19 °F
- Altimeter: 30.00 inHg

## 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 19890108001319A](https://openairdocs.org/incident/19890108001319A), Jan 8, 1989: Bell 206B, Park City, UT, Substantial damage. Landed on upslope snow. Slid backwards on skids,tail rotor hit snow,picked up settled into snow, broke drive shaft.

## Other investigations on N16733 (2)

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.

- [NTSB DEN89FA101](https://openairdocs.org/ntsb/DEN89FA101), Apr 5, 1989: Bell 206B-III (N16733), Park City, UT, substantial damage. Probable cause: AN ENCOUNTER WITH STRONG DOWN-SLOPE WINDS AND GUSTS DURING A CRITIACAL PHASE OF FLIGHT WHICH CAUSED POWER REQUIRED TO EXCEED POWER AVAILABLE. CONTRIBUTING FACTORS TO THE ACCIDENT WAS THE DOWNHILL…
- [NTSB LAX78FUM34](https://openairdocs.org/ntsb/LAX78FUM34), Aug 18, 1978: Bell 206B (N16733), Holtville, CA, substantial damage

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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