# NTSB DCA23LA421: Boeing 777-222, N209UA, Over the (Atlantic Ocean), August 18, 2023

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 4 · Limited · Final report
- Date: August 18, 2023, 19:11 local (14:11 UTC)
- Place: Over the (Atlantic Ocean)
- Coordinates: 40, -60
- Nearby events: https://openairdocs.org/map.md?lat=40.0000&lon=-60.0000&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, 8 minor, 247 uninjured
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 4 - Basic report with no Prelim publish
- NTSB office: Major Investigations Division
- Parties: FAA AVP100, United
- NTSB case key (mKey): 192927
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DCA23LA421
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192927/pdf
- Page: https://openairdocs.org/ntsb/DCA23LA421

## Probable cause

An inadvertent encounter with clear air turbulence during cruise flight.

## Findings

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

- [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Effect on personnel; cases with it: [Boeing 777-222, 2 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md?model=1385219), [All aircraft, 78 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md)
- [Turbulence: clear air turbulence](https://openairdocs.org/ntsb-findings/03032015): Environmental issues › Conditions/weather/phenomena · Awareness of condition; cases with it: [Boeing 777-222, 2 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md?model=1385219), [All aircraft, 78 cases](https://openairdocs.org/ntsb-findings/03032015/cases.md)
- [Knowledge: knowledge of meteorologic cond](https://openairdocs.org/ntsb-findings/02032020): Personnel issues › Experience/knowledge · Cabin crew; cases with it: [Boeing 777-222, 2 cases](https://openairdocs.org/ntsb-findings/02032020/cases.md?model=1385219), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/02032020/cases.md)
- [Knowledge: knowledge of meteorologic cond](https://openairdocs.org/ntsb-findings/02032020): Personnel issues › Experience/knowledge · Flight crew; cases with it: [Boeing 777-222, 2 cases](https://openairdocs.org/ntsb-findings/02032020/cases.md?model=1385219), [All aircraft, 30 cases](https://openairdocs.org/ntsb-findings/02032020/cases.md)
- [Impairment/incapacitation: illness/injury](https://openairdocs.org/ntsb-findings/02012010): Personnel issues › Physical · Cabin crew; cases with it: [Boeing 777-222, 1 case](https://openairdocs.org/ntsb-findings/02012010/cases.md?model=1385219), [All aircraft, 34 cases](https://openairdocs.org/ntsb-findings/02012010/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

United Airlines flight 918 encountered clear air turbulence during cruise flight, while en route to the London Heathrow International Airport (LHR), London, United Kingdom resulting in one flight attendant (FA) sustaining a serious injury. The flight originated at Dulles International Airport (IAD), Dulles, Virginia. The flight crew reported that their preflight weather briefing revealed no significant areas of weather or turbulence over their planned route to LHR. During their preflight checks an open status message “PASS ADDRESS SYSTEM” displayed on their engine indication and crew alerting system (EICAS) display and maintenance was called. A technician responded who reinitialized the entire passenger address (PA) system and cleared the status message. The flight crew reported that prior to the JOBOC intersection, there was minimal light turbulence, and the seatbelt sign had been on and off sporadically as required. They also indicated that no turbulence was identified in their immediate vicinity from their inflight weather resources. About 80 nm east of JOBOC, the flight encountered very light turbulence and the first officer (FO), who was the pilot flying, made the PA announcement: “Flight Attendants take your seats.” In a postaccident statement, the captain reported that while in the forward lavatory, the flight encountered very light turbulence and he heard through the lavatory wall, the FO make the PA announcement: “Flight Attendants take your seats.” However, because he did not hear the PA announcement over the lavatory speaker he didn’t know if the rest of the crew or passengers heard this announcement. The in-flight service manager (ISM), who was in the cockpit at the time also heard the FO make the announcement “Flight Attendants take your jumpseats.” As the captain attempted to take his seat (left seat) the flight encountered a moderate turbulence spike that made his knees buckle and threw him back down into the 1st observer’s seat. He indicated that he was able to flash the seatbelt sign on and off three times rapidly. The flight crew then executed all the steps of the TURBULENCE IMMEDIATE ACTION GUIDE. The turbulence ended as abruptly as it had begun. The captain then made a PA announcement “Flight attendants check in.” The ISM advised the captain that all the flight attendants had been knocked to the floor and one was seriously injured. The flight crew contacted dispatch and advised of the clear air turbulence encounter. The dispatcher had no reports of turbulence from any other United flights in the area. According to the cabin crew, they did not hear the PA announcement “Flight Attendants take your seats” and therefore they were completing their normal duties when, without warning, the airplane encountered turbulence. One FA, who was delivering meals at the time of the turbulence encounter, was thrown down, impacted the floor, and was injured. According to the ISM, shortly after the encounter, the captain came on the PA and said“Flight Attendants, Check In.” The cabin crew heard that announcement and the ISM reported to the flight crew that one FA was on the floor and was unable to get up. Upon being notified of the injured FA, the flight crew declared a medical emergency and requested paramedics meet the aircraft at the gate in LHR. The injured FA was moved to an unoccupied passenger seat, given ice, and was assisted by an onboard medical doctor for the rest of the flight. After landing the FA was transported to a local hospital where she was diagnosed with a fractured left fibula. A postaccident functional check of the passenger address system revealed no malfunctions or anomalies with the system.

## Aircraft

- Registration: [N209UA](https://openairdocs.org/aircraft/N209UA), registered now, S/N 30215, built 1999 (OpenAirDocs)
- Reported make and model: BOEING 777-222
- 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
- Year built: 1999
- Airframe hours: 92517
- Engines: P&W PW4000 SER 60000 lbs thrust turbo fan; P&W PW4000 SER 60000 lbs thrust turbo fan
- Damage: No damage
- Flight: Part 121
- Operator: United Airlines Inc
- Registered owner: United Airlines Inc
- Airworthiness certificate: Standard, Transport; Standard, Normal
- Last inspection: Continuous airworthiness, September 22, 2023
- Departed: KIAD, Dulles, VA
- Destination: LHR, London, OF
- Flight plan: IFR
- Equipment: Angle of attack indicator, Auto-pilot, Data recorder, Electronic flight bag or handheld device, Electronic multifunction display, Electronic primary flight display, Onboard weather, Satellite tracking device, Stall warning system, ADS-B

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 64; injuries: none; flight engineer, airline transport, commercial; airplane ratings: multi-engine land, single-engine land; medical: class 1, waiver time limited special; seat: left; restraint: 5-point; flight hours: 21,000 total, 3,441 in this make and model, 18,307 as pilot in command, 214 in the last 90 days, 73 in the last 30 days, 0 in the last 24 hours
- Co-pilot; age 48; injuries: none; commercial, airline transport; airplane ratings: multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; seat: right; restraint: 5-point; flight hours: 15,000 total, 1,575 in this make and model, 10,000 as pilot in command, 245 in the last 90 days, 88 in the last 30 days, 0 in the last 24 hours
- Flight instructor; injuries: none; seat: rear; restraint: 5-point; flight hours: 0 total, 0 in this make and model
- Cabin crew; injuries: none; restraint: 4-point
- Cabin crew; injuries: serious; restraint: 4-point
- Cabin crew; injuries: none; restraint: 4-point
- Cabin crew; injuries: none; restraint: 4-point

## Weather

- Conditions: Visual (VMC), Night
- Wind: 65 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Observed at: CYQX

## 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 DCA10FA012](https://openairdocs.org/ntsb/DCA10FA012), Nov 19, 2009: Boeing 777-200 (N209UA), New Market, VA, no damage. 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.

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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