# NTSB MKC89FA004: Hughes 500C, N506WW, Branson, MO, October 8, 1988

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: October 8, 1988, 11:50 local (16:50 UTC)
- Place: Branson, MO
- Coordinates: 36.639663, -93.23999 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=36.6397&lon=-93.2400&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 4 serious, 2 minor
- Status: Completed, report May 7, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 34663
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MKC89FA004
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/34663/pdf
- Page: https://openairdocs.org/ntsb/MKC89FA004

## Sequence of events

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

- Abrupt maneuver, approach
  - planned approach - improper, pilot in command (cause)
  - airspeed - inadequate, pilot in command (contributing factor)
  - maneuver - excessive, pilot in command (contributing factor)
  - proper descent rate - exceeded, pilot in command (contributing factor)
- Airframe/component/system failure/malfunction, approach - vfr pattern - base leg/base to final
  - rotor drive system,freewheeling sprag unit - slipped (contributing factor)
  - rotor rpm - not maintained, pilot in command (cause)
  - remedial action - delayed, pilot in command (contributing factor)
  - diverted attention, pilot in command
- Hard landing, landing - flare/touchdown
  - rotor rpm - inadequate (contributing factor)
  - emergency procedure - not possible (cause)
- Roll over, landing - roll
  - landing gear,main gear strut - overload

## Analysis

THE FLIGHT WAS CONDUCTED FOR SIGHTSEEING WITH 5 PASSENGERS ONBOARD.  THE PILOT TURNED ON FINAL APPROACH WITH 35 KNOTS OF AIRSPEED AND ENCOUNTERED A HIGH RATE OF DESCENT.  THE PILOT REPORTED THAT HE NOTED A SPLIT TACH AND INITIATED AN AUTOROTATION, BUT WAS OUTSIDE THE ENVELOPE FOR A SAFE RECOVERY.  THE SKIDS COLLAPSED IN THE RESULTING HARD LANDING, AND THE HELICOPTER ROLLED OVER.  METAL FLECKS WERE FOUND IN THE FREEWHEELING SPRAG ASSEMBLY, WHICH HELD VERY LITTLE OIL, BUT NO EVIDENCE OF SLIPPAGE WAS FOUND.

## Aircraft

- Registration: [N506WW](https://openairdocs.org/deregistered/N506WW-1992-03-25), registration cancelled 1992-03-25, S/N 150699S (OpenAirDocs)
- Reported make and model: HUGHES 500C
- Registry model: [Hughes 369HS](https://openairdocs.org/model/hughes-369hs) (registry code 4470728) (OpenAirDocs)
- Category: Helicopter
- Serial number: 150699S
- Airframe hours: 3745
- Engines: ALLISON 250-C20 278 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Business, Part 91
- Operator: Tablerock Helicopters Inc.
- Registered owner: A And S Associates
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, September 17, 1988, 1 hours before
- Airport: MO38, Table Rock Heliport

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 27; commercial; airplane ratings: single-engine land; instrument ratings: helicopter; medical: class 1, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 2,064 total, 450 in this make and model, 1,591 as pilot in command, 270 in the last 90 days, 60 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 180° at 9 knots
- Visibility: 7 statute miles
- Lowest ceiling: 3,900 ft overcast
- Temperature: 55 °F, dew point 48 °F
- Altimeter: 30.00 inHg
- Observed at: SGF, 46 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 19881008047559A](https://openairdocs.org/incident/19881008047559A), Oct 8, 1988: Hughes 369HS, Branson, MO, Substantial damage. Reported rotor decay caused hard landing and rollover. No oil in drive clutch but clutch was working on impact.

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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