DCA24LA097

The airplane’s encounter with an unanticipated localized region of moderate-to-severe turbulence while in instrument meteorological conditions (IMC) associated with strong upper-level wind shear and convective cells. Contributing to the severity of the outcome was the failure of air traffic control to disseminate a recently reported moderate turbulence pilot weather report, which reduced the flight crew’s situational awareness and opportunity to prepare the cabin for the encounter.

United Airlines flight 1890 (UAL1890) encountered turbulence during descent into Newark Liberty International Airport (EWR) which resulted in three flight attendants receiving serious injuries. The encounter occurred within a localized region of moderatetosevere turbulence near flight level (FL) 215 (21,500 feet). The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from Los Angeles International Airport (LAX), Los Angeles, California to EWR.  The flight was in instrument meteorological conditions (IMC) and descending along an air traffic control (ATC) assigned route, toward the Hancock (HNK) VOR. The turbulence encounter resulted in significant cabin vertical accelerations, with quick access recorder (QAR) data showing fluctuations between -0.55 g and +1.82 g over a period of several seconds.  Although the flight crew conducted standard preflight turbulence assessments using Weather Services International (WSI) and SkyPath tools, these products depicted only light to moderate turbulence along the planned route. The dispatcher similarly reported only one moderate turbulence report, from a regional jet on descent into EWR, with no updated concerns during the subsequent hours of the flight. Throughout cruise and initial descent, the flight crew continued monitoring WSI and SkyPath, and neither indicated significant turbulence activity along their descent path. The captain ensured that the onboard radar was active for descent; however, no returns indicating convective or turbulent weather were noted by the flight crew.  ATC did not provide any real-time weather advisories during the period the airplane was under Boston Center’s control, despite receiving a moderate turbulence report from ACA548 (an uninvolved airplane) about three minutes prior to the encounter. ACA548 was operating ahead of UAL1890, on the same route and reported moderate turbulence to the Boston Air Route Traffic Control Center (ZBW ARTCC), R24C controller. The controller did not acknowledge or disseminate this report to other aircraft, including UAL1890, as required by Federal Aviation Administration (FAA) procedures for Pilot Weather Reports (PIREPs) solicitation and dissemination. The controller stated during their interview they did not hear the PIREP. UAL1890 subsequently encountered turbulence in approximately the same area. A turbulence PIREP was transmitted to the flight at 1541 eastern standard time (EST), although it could not be conclusively determined if the crew saw or read the message. Meteorological analysis revealed that there was a cold front in the vicinity of the accident site along with a relatively strong jet stream of 150 knots near 30,000 ft. The cold front and associated upper level trough provided the support for the formation of a band of rain showers and embedded thunderstorms in western and central New York that was moving eastward with time. The tops of the convection ranged from 21,000 to 23,000 ft in the vicinity of the accident site based on the Geostationary Operational Environmental Satellite number 16 (GOES-16) imagery and pilot statements. Lightning was noted in the convective line encountered by the accident flight in the GOES-16 lightning flash imagery about 20 to 30 minutes prior to the encounter. Figure 1 presents the GOES-16 visible image at 1546 EST at 3X magnification with the accident site highlighted with a red square. There was cloud cover indicated above the accident site with the cloud cover moving from west to east. Figure 2 presents the GOES-16 infrared image at 1546 EST (closest image to the accident time) at 8X magnification with the accident site highlighted with a red square. Cloud cover was indicated above the accident site with lower brightness temperatures (green colors; higher cloud tops) located above and to the northeast through south of the accident site. Figure 1. GOES-16 visible image at 1546 EST at 3X magnification.    Figure 2. GOES-16 infrared image at 1546 EST at 8X magnification.   In addition, the High-Resolution Rapid Refresh (HRRR) model soundings showed a large change of wind speed between 17,000 ft (around a 45-knot wind) and 21,000 ft (around 110-knot wind) and this caused wind shear and turbulence at the tops of the rain shower/thunderstorm activity. The sounding analysis also indicated moderate or greater clear-air turbulence (CAT) between 18,000 and 21,000 ft near the time and location of the encounter. The turbulence at the tops of the cloud cover is visible on the GOES-16 imagery as evidence by the transverse banding. UAL1890 checked in with the R24A controller at 1535:10, while level at FL270, but did not receive an immediate response because the controller was occupied with other coordination tasks. As the airplane continued descending under successive clearances, ATC did not pass along the moderate turbulence PIREP issued by ACA548 at 1540:38. This omission reduced the crew’s situational awareness regarding developing turbulence in the same airspace. When UAL1890 encountered turbulence descending through FL210, the airplane was already committed to the assigned crossing restriction near the HNK VOR. The crew reported the encounter as “severely moderate turbulence,” and ATC also did not respond to that advisory. Shortly thereafter, when handed to the R05 controller, the facility advised of only “light to moderate turbulence,” further indicating that ATC personnel had not fully integrated or disseminated the earlier PIREP information.   QAR data show that autopilot and autothrottle remained engaged throughout the encounter, and the airplane remained within design structural limits. As shown in figure 3, the turbulence generated rapid vertical accelerations and short-duration negative-g forces sufficient to lift unsecured crewmembers from the cabin floor. At the time of the event, the captain had recently re-illuminated the seatbelt sign and instructed the flight attendants to prepare the cabin for landing, a phase during which some flight attendants were completing final safety tasks and not seated. As a result, three crew members were injured.  Figure 3. Time history plot presenting accelerations and attitude control parameters from 1535:00 EST to 1607:00 EST, including activity observed near 1543 EST.  A peak EDR value of 0.431 was noted as the accident aircraft was in IMC at 1543 EST while descending through both the convective updrafts in the rain shower and thunderstorms and the wind shear layer in the jet stream. This value corresponds to moderate to severe turbulence for a “heavy” class of aircraft. The evidence indicates the flight crew performed standard preflight and in-flight turbulence risk mitigation, used available tools, and operated the airplane within procedures. The turbulence encountered was not forecast to be significant at the precise altitude, time, and location of the airplane by the operator’s weather provider. Further, the most relevant real-time warning—the moderate turbulence PIREP issued minutes prior—was not disseminated to the flight crew by ATC in accordance with FAA requirements. The location of the three seriously injured flight attendants (FAs) were two positioned in the aft galley area and one located in the mid-cabin aisle near door 3. FA 2 was lifted into the ceiling and forcefully thrown to the cabin floor, resulting in a spinal fracture. FA 3 was thrown to the ceiling, lost consciousness, struck a beverage cart, and landed heavily on the left leg, sustaining a shattered femur, crushed spinal vertebrae, and a head injury with bleeding. FA 9 was thrown upward and then into galley structures, lost consciousness, and sustained facial lacerations and a diagnosed intracranial bleed.

The airplane was a Boeing 777-222ER, manufacturing Serial Number 26942. The airplane was manufactured in 1997, delivered to United Airlines in July of 1997 and it held a transport category airworthiness certificate. The airplane was configured with 4 flight crew seats, 14 flight attendant seats, and 276 passenger seats. Figure 4: Accident Airplane, N788UA (Courtesy of planespotters.net) At the time of the event, the airplane had two deferrals from the minimum equipment list (MEL). Those deferrals were for the broadband antenna and the autoland system. On February 10, 2024, about 15:43 EST, UAL1890, a Boeing 777-222ER, N788UA, encountered moderate to severe turbulence while descending to FL190 inbound to EWR. Of the 280 passengers and crewmembers on board, three flight attendants sustained serious injuries. The flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight from LAX to EWR. Both flight crewmembers reported being well-rested before the flight and stated that they conducted a thorough preflight briefing, which included a review of forecasted turbulence near the EWR terminal area. The first officer (FO) used the WSI and SkyPath electronic flight bag (EFB) applications to assess turbulence reports, noting light to moderate activity near the usual WILLIAMSPORT3 arrival. Based on this, the crew anticipated and accepted a northerly routing via the FLOSI4 arrival for turbulence avoidance.  According to Automatic Dependent Surveillance–Broadcast (ADS-B) data, flight UAL1890 departed LAX at approximately 0831 Pacific Standard Time (PST). The FO was the pilot flying (PF) and the captain was the pilot monitoring (PM). The flight crew stated that the departure from LAX was uneventful, and the airplane leveled off at a cruise altitude of FL350.  About 1334 EST, the flight crew sent a message via Aircraft Crew Alerting and Reporting System (ACARS) to their dispatcher, stating that they were having a “smooth ride past hour or so, how’s descent into EWR.” About one minute later, the dispatcher replied, “so far only complaint is a moderate by a regional jet.” The flight subsequently climbed to its cruise altitude of FL370. There was no additional communication between the flight and the dispatcher until after the encounter with turbulence. The seatbelt sign was cycled ON and OFF in accordance with standard turbulence mitigation procedures, including passenger address (PA) announcements. The WSI and Skypath applications were continuously monitored, and no significant turbulence was indicated along the route or during the approach phase.    The FO stated that he was responsible for briefing the approach/arrival into EWR and in preparation for the brief, checked for potential turbulence using the WSI and SkyPath application to see if there were any reports of turbulence. Neither application revealed any significant indications of turbulence along their route. After the brief, the captain turned the onboard weather radar ON for the eventual descent into EWR.  As the airplane began its descent into EWR, ATC issued step-down clearances. About 1437, the flight began a descent to FL350 where it remained for about 20 minutes. The flight then turned towards an easterly direction and began a descent to FL330. About 1510, the flight began to descend to FL310.   At 1532:30, the crew of ACA548 (an uninvolved airplane) checked in with the R24A controller and was provided with a pilot weather report (PIREP) indicating moderate to heavy precipitation near the Hancock VOR (HNK), with light to moderate chop, in the descent from FL220 to FL190. At 1535:10, the flight crew of UAL1890 checked in with the R24A controller and indicated that they were level at FL270. The R24A controller did not respond. In a postaccident interview, the R24A controller stated they did not respond at the time because they were completing other coordination. According to the flight crew, while passing through FL270, the captain announced via the PA that the flight attendants prepare the cabin for landing, followed by turning the seatbelt sign ON.  At 1536:00, the R24A controller instructed the flight to descend to FL240.  At 1538:14, the R24A controller conducted a position relief briefing with the R24C controller.   At 1540:38, the R24C controller instructed the crew of ACA548 to contact the Stewart sector (R05) controller. The crew of ACA548 acknowledged the frequency change and advised the R24C controller they had encountered moderate turbulence. The controller did not acknowledge or disseminate this PIREP to other aircraft, including UAL1890, as required by FAA procedures for Pilot Weather Report (PIREPs) solicitation and dissemination. In a postaccident interview, the controller stated they did not hear the PIREP. At 1540:52, the R24C controller instructed UAL1890 to cross five miles past the HNK VOR at FL190. The crew acknowledged the instructions. The FO stated that he observed an overcast layer of clouds ahead and below that the flight would penetrate during descent. The flight crew stated there was no indication of potential turbulence as nothing showed on the airplane's weather radar or the SkyPath app. Additionally, there were no reports of turbulence provided by ATC or dispatch directly to the flight crew.   At 1541, a turbulence pilot report (PIREP) was sent to the flight via ACARS stating “YOUR FLIGHT IS IN CLOSE PROXIMITY TO A MOD TURB PIREP EVENT REPORTED BY A B789 AT 2022 (1522 local) Z FL220 LOCATION HNK RMK TB MOD CHOP 220-190 YOU CLOSEST POINT TO EVENT AT 2041Z”.  It could not be conclusively determined if the crew saw or read the message.   At 1542:18, the crew of UAL1890 asked the R24C controller to confirm they were instructed to cross five miles past the HNK VOR and the controller responded in the affirmative.    At 1543:06, the R24C controller instructed the crew of UAL1890 to contact the R05 controller. The crew acknowledged the frequency change and advised the R24C controller they had encountered “severely moderate turbulence.” The controller did not respond.    At 1544:07, the crew of UAL1890 checked in with the R05 controller and reported descending to FL190. The R05 controller acknowledged and advised the crew of precipitation and light to moderate turbulence along their route of flight. The crew responded and stated that they had encountered moderate turbulence when they were at FL210.  The flight crew reported that while descending through about FL210 in IMC, the airplane encountered moderate turbulence lasting a few seconds that caused unsecured items on the flightdeck to be thrown about. A visual break in the clouds was observed, and the crew initiated a right turn using heading select mode to exit the turbulent layer.  Following the event, the captain immediately called the cabin crew and was informed of multiple injuries with one flight attendant sustaining a head laceration. The flight crew declared a medical emergency and requested paramedics meet the airplane at the gate.  The remainder of the approach, landing, and taxi were uneventful. Upon arrival at the gate, passengers were instructed to remain seated to allow emergency medical services (EMS) personnel to board. Port Authority Police and EMS responded and attended to the injured flight attendants. Three aft-galley flight attendants (FA 2, FA3, FA 9) were transported to the hospital by ambulance. The captain and FO assisted in managing the cabin and supporting the crew and passengers during deplaning. Additional crewmembers later sought medical evaluation for head, neck, back, and extremity pain. Post-flight, two FAs were diagnosed with fracture injuries and a third was diagnosed with a sub-cranial bleed. ZBW ARTCC was a level 12 enroute ATC facility located in Nashua, New Hampshire, and was part of the FAA’s eastern service area. The r