# NTSB DCA10FA012: Boeing 777-200, N209UA, New Market, VA, November 19, 2009

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: November 18, 2009, 19:30 local (Nov 19, 2009, 00:30 UTC)
- Place: New Market, VA
- Coordinates: 38.655555, -78.708053 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=38.6556&lon=-78.7081&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 minor, 198 uninjured
- Status: Completed, report December 27, 2011
- Report: Approved by Office Director
- NTSB office: Major Investigations Division
- Parties: FAA FSDO
- NTSB case key (mKey): 75093
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA10FA012
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/75093/pdf
- Page: https://openairdocs.org/ntsb/DCA10FA012

## Probable cause

The flight crew’s inadvertent encounter with a small area of cumulous clouds at night that resulted in moderate to severe convectively induced turbulence.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Turbulence: convective turbulence](https://openairdocs.org/ntsb-findings/03032020): Environmental issues › Conditions/weather/phenomena · Effect on personnel (probable cause); cases with it: [Boeing 777-222, 2 cases](https://openairdocs.org/ntsb-findings/03032020/cases.md?model=1385219), [All aircraft, 145 cases](https://openairdocs.org/ntsb-findings/03032020/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Enroute-cruise: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event); cases with it: [Boeing 777-222, 6 cases](https://openairdocs.org/ntsb-events/360/sequence.md?model=1385219), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md)

## Analysis

Prior to and after the turbulence encounter the captain reported smooth air while level at FL310. There were no reported sigmets, airmets, or pilot reports issued, nor were there “watch boxes” that warned of adverse weather. The onboard weather radar was functioning when suddenly the airplane went through a cloud at Mach 0.84 and encountered moderate turbulence for about 10 to 15 seconds. He said that there was an overspeed warning alarm and he immediately took over manual control of the airplane maintaining control, and activated the seat belt warning sign which had previously been off, since the flight had been smooth. The first officer statement was consistent with the captain’s and in addition he reported seeing “considerable St. Elmo’s Fire” throughout the duration of the turbulence. The aircraft’s flight data recorder indicated that while the aircraft was level at FL310, the vertical acceleration changed from 1.25 g’s to -0.5 g’s in less than one second and then abruptly reached 2.0 g’s within a few seconds before reducing to minor oscillations that were between 1.25 g’s and 0.75 g’s which lasted for about 15 seconds. According to the FDR data, the turbulence lasted about 20 seconds. The NTSB conducted a meteorological study to assess weather conditions in the area where the flight encountered turbulence, and the National Weather Service’s Radar Summary for 1918 EST depicted an extensive area of rain showers over the region with a few radar echo tops between 31,000 feet and 48,000 feet. In addition, the regional radar composite imagery showed that between 1910 and 1940 EST there was a small area of reflectivity between 5 and 25 decibels in the area of the turbulence encounter.

## Factual narrative

HISTORY OF FLIGHT On November 18, 2009, about 1930 Eastern Standard Time (EST), N209UA, a Boeing 777-200, registered to and operated by United Airlines Inc., as a Title 14 CFR Part 121 domestic passenger flight, encountered turbulence in the vicinity of New Market, West Virginia. The flight was en route from Chicago, Illinois, to Dulles International Airport, Sterling, Virginia. The airline transport-rated captain, first officer, 7 flight attendants, and 189 passengers were not injured. One flight attendant received minor injuries and a passenger received a serious injury. The flight originated from O'Hare International Airport, Chicago, Illinois, about 1819 Central Standard Time. According to the captain, who was the pilot flying at the time of the accident, there were no reports of turbulence or significant weather from other aircraft in the vicinity or from air traffic control, nor had United Flight Dispatch informed him of any airman meteorological information (airmets), or significant meteorological information (sigmets). He added that there were also no “watch boxes” that warned of possible adverse weather. The radar was on and tilted down one degree at the 40 mile range, when suddenly the airplane skimmed the top or went through a cloud at mach 0.84, while in cruise flight at FL310. He further stated that the turbulence was moderate and that it lasted about 10 to 15 seconds. According to the captain, at the same time the turbulence occurred, there was an overspeed warning and the autopilot tripped off. He said he immediately took manual control of the situation and turned on the seat belt sign in the cabin, which had previously been off because conditions had been smooth. He said that at no time was the airplane out of control, and that after the turbulence, conditions immediately became smooth. He said he later learned that there was an injury in the passenger cabin and that he informed Washington Air Route traffic Control Center. The flight proceeded and otherwise landed uneventfully at Dulles International Airport. The first officer stated that the weather radar was operating while in cruise flight at FL310 and that no radar returns were observed along their route, adding that the flight was “in the clear, well above any cloud tops.” He further stated that while seated he experienced a sudden jolt of moderate turbulence, followed by the overspeed warning alarm during which the autopilot tripped off. He said at the time that the airplane was in instrument meteorological conditions and there was considerable “St. Elmo’s Fire”, which lasted 10 to 20 seconds. He said he then called back to the cabin and asked if everyone was “all right”, and that the lead flight attendant told him that he would check the condition of everyone and will let the flight deck know if there were injuries. He then communicated with FAA Air Route Traffic Control to let them know about the turbulence. The first officer said that a few minutes later while in thedescent to land they were informed that a passenger and flight attendant had been hurt, and he sent a “quick note” to the dispatcher requesting paramedics when the flight arrive at the gate. One flight attendant, who had been standing in the rear galley when the turbulence occurred noted seeing a passenger “rise up and down then fall to the floor” while walking by the lavatory. Another flight attendant stated that she had fallen to her knees during the turbulence encounter, and received minor injuries, adding that the turbulence was of a short duration but had been very extreme. After the turbulence ceased, a flight attendant attended to the fallen passenger who was found to have received a serious injury. The lead flight attendant then informed the flight deck that one passenger had been injured and was in need of emergency medical care. FLIGHT RECORDERS The airplane’s flight data recorder was recovered and sent to the NTSB’s Recorder Laboratory in Washington, DC for readout. The recorder was found to contain 53 hours of data. The data indicated that while the aircraft was level at 31,000 feet, vertical acceleration changed from about 1.25 g’s to about -0.5 g’s in less than one second, and then abruptly became 2.0 g’s within a few seconds, before reducing to minor oscillations varying 1.25 g’s and 0.75 g’s which lasted for about 15 seconds. The duration of the turbulence encounter was about 20 seconds from the first disturbance until the last. In addition, the recorder data showed that the autopilot had been engaged prior to encountering turbulence and that it was disconnected when the force on the aircraft first reached about -0.5 g’s. METEOROLOGICAL INFORMATION As part of the investigation, the NTSB conducted a meteorological study to assess weather conditions in the area where the flight encountered turbulence. It was noted that the National Weather Service’s Radar Summary for 1918 EST, depicted an extensive area of rain showers over the region with a few radar echo tops between 31,000 feet and 48,000 feet. In addition the regional radar composite imagery showed that between 1910 and 1940 EST there was a small area of reflectivity between 5 and 25 decibels in the area of the turbulence encounter.

## Aircraft

- Registration: [N209UA](https://openairdocs.org/aircraft/N209UA), registered now, S/N 30215, built 1999 (OpenAirDocs)
- Reported make and model: BOEING 777-200
- Registry model: [Boeing 777-222](https://openairdocs.org/model/boeing-777-222) (registry code 1385219) (OpenAirDocs)
- Registry engine: [Pratt & Whitney PW4000 series](https://openairdocs.org/engine/pratt-whitney-pw4000-series) (registry code 52119, turbo-fan) (OpenAirDocs)
- Category: Airplane
- Serial number: 30215
- Airframe hours: 41788
- Engines: Pratt Whitney PW 4090 90000 lbs thrust turbo fan; Pratt Whitney PW 4090 90000 lbs thrust turbo fan
- Damage: No damage
- Flight: Part 121
- Operator: United Airlines Inc.,
- Registered owner: United Airlines Inc.,
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, November 9, 2008
- Departed: ORD, Chicago, IL
- Destination: IAD, Sterling, VA
- Flight plan: IFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 60; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; last flight review August 8, 2009; seat: left; flight hours: 2,252 in this make and model
- Co-pilot; age 44; injuries: none; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; last flight review October 9, 2009; seat: right; flight hours: 1,763 in this make and model

## Weather

- Conditions: Instrument (IMC), Night

## 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 20091118054099A](https://openairdocs.org/incident/20091118054099A), Nov 18, 2009: Boeing 777-222, New Market, WV, No damage. While in cruise flight at FL 310, united flt. 976 encountered clear air turbulence (cat). Because ATC reported no turbulence ahead, the air was clear and…

## Other investigations on N209UA (1)

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 DCA23LA421](https://openairdocs.org/ntsb/DCA23LA421), Aug 18, 2023: Boeing 777-222 (N209UA), Over the (Atlantic Ocean), no damage. Probable cause: An inadvertent encounter with clear air turbulence during cruise flight.

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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