# NTSB DEN90LA168: Gulfstream G-II, N405MM, Cheyenne, WY, July 28, 1990

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Limited investigation · Final report
- Date: July 27, 1990, 18:00 local (Jul 28, 1990, 00:00 UTC)
- Place: Cheyenne, WY
- Coordinates: 41.409721, -104.099082 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=41.4097&lon=-104.0991&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 1 serious, 7 minor, 2 uninjured
- Status: Completed, report November 23, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 17977
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN90LA168
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/17977/pdf
- Page: https://openairdocs.org/ntsb/DEN90LA168

## Probable cause

AN UNFORESEEN ENCOUNTER WITH CLEAR AIR TURBULENCE.

## Sequence of events

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

- In flight encounter with weather, climb - to cruise
  - weather condition - turbulence,clear air (cause)
  - compensation for wind conditions - not possible, pilot in command

## Analysis

THE AIRPLANE WAS APPROXIMATELY 100 NM NORTHEAST OF DENVER, DEVIATING AROUND THUNDERSTROM ACTIVITY, WHEN CLEAR AIR TURBULENCE (CAT) WAS ENCOUNTERED. THE CAPTAIN STATED AFTER THE ACCIDENT THE FLIGHT ATTENDANT HAD LEFT HIS SEAT TO PERFORM CABIN DUTIES AND WAS SQUATTING DOWN IN THE GALLEY WHEN THE AIRPLANE WAS BUFFETED BY THE TURBULENCE. TH FLIGHT ATTENDANT INJURED HIS ANKLE WHILE IN THIS POSITION. THE AIRPLANE RETURNED TO ENGLEWOOD, CO., AND THE FLIGHT ATTENDANT WAS TRANSPORTED TO THE HOSPITAL. ACCORDING TO THE DENVER ARTCC, THERE WERE NO REPORTS OF TURBULENCE BY OTHER AIRCRAFT PRIOR TO THE ENCOUNTER.

## Aircraft

- Registration: N405MM (not matched to a registry record)
- Reported make and model: Gulfstream G-II
- Category: Airplane
- Serial number: 220
- Engines: Rolls-Royce SPEY MK 511-8 11400 horsepower turbo fan
- Damage: No damage
- Flight: Executive/Corporate, Part 91
- Operator: Martin Marietta Corporation
- Registered owner: Martin Marietta Corp.
- Airworthiness certificate: Standard, Normal
- Departed: APA, ENGLEWOOD, CO
- Destination: IAD, CENTERVILLE, VA
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: unknown, unknown

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 12 knots, gusting 16
- Visibility: 50 statute miles
- Lowest ceiling: 16,000 ft broken
- Temperature: 81 °F, dew point 45 °F
- Altimeter: 30.00 inHg
- Observed at: DEN, 75 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 19900727029429A](https://openairdocs.org/incident/19900727029429A), Jul 27, 1990: Gulstm G1159, Cheyenne, WY. Seat belt sign on for turbulence broke into clear. Cabin attendant left seat as cat turbulence ensued. Was injured.

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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