DCA23LA462

JetBlue Airlines flight 1256 encountered convective turbulence while in cruise at 34,000 ft over the Caribbean Sea approximately 200 nautical miles (nm) south of Negril, Jamaica. As a result of the turbulence, three flight attendants received minor injuries, two passengers received minor injuries, and four passengers received serious injuries. The aircraft continued to Fort Lauderdale International Airport (FLL), Florida without further incident. According to the Captain, the takeoff climb, and initial cruise at 34,000 ft progressed normally, and the flight conditions were dark, clear with no convective activity observed. The flight crew stated they had the aircraft radar on, had Wi-Fi connectivity, and were continually updating radar images on their Jeppeson FliteDeck (JeppFD) and Weather Services International (WSI) iPad applications. The first officer stated there was significant precipitation and storms to the north of their location in the area near Cuba. As the flight proceeded north, the crew noted an additional area of weather between Jamaica and Cuba that required weather deviations. The first officer stated that he and the captain changed weather ranges on their radar displays multiple times to maintain their situational awareness of the precipitation. At 0335:47 local time, flight data recorder (FDR) data indicated the weather radar was engaged in “weather and turbulence mode” on both the captains and first officer navigational display, with the captain’s range set at 160 nm and the first officer’s set at 320 nm. According to the Airbus Flight Crew Operations Manual (FCOM), when engaged in “weather and turbulence mode”, the navigation display will indicate turbulence and precipitation areas. Autopilot number 2 and the auto thrust were engaged, with Mach target of 0.8 selected, and the seatbelt sign was illuminated. At 0336:20 the airplane encountered turbulence. The flight crew stated they entered severe turbulence and extreme precipitation without warning, with no returns on their weather radar. The FDR data indicated that the airplane varied in pitch angle between -1.8° and +6.3°, the roll angle varied from -8.4° left wing down to 8.8° right wing down, and the vertical acceleration varied between -0.69G and +1.68G. During the encounter, the airplane climbed from 33,980 ft to 34,790 ft, and the Mach varied between 0.732 and 0.820. During this time, the computed longitudinal wind recorded on the FDR varied between 13 knots headwind and 39 knots tailwind, and the computed crosswind varied from 31 knots right crosswind and 24 knots left crosswind. At 0337:08, with the airplane at 34,776 ft altitude, the autopilot was disengaged and a nose down input was applied on the captain’s controller. By 0337:40, the airplane had exited the turbulence, the autopilot was reengaged, and the airplane began to descend back to its assigned attitude of 34,000 ft. The flight crew stated that before the encounter there were no returns on the airplaneweather radar, they did not see the cloud ahead, there was no visible lightning, and the weather was not depicted on any weather applications on their iPads. The flight crew stated the only radar returns that were displayed were north of their location near Cuba. Once clear of the weather the crew proceeded to FLL. FDR data showed the flight landed at 0518:27. Once on the ground, the flight crew entered “weather radar inoperative and severe turbulence encounter” in the maintenance logbook. A post accident review of meteorology data showed that there were no Significant Meteorological Information (SIGMET) advisories issued by a Meteorological Watch Office that were active for the accident location at the accident time. A review of the Earth Networks Total Lightning Network (ENTLN) lightning database revealed no flash total lightning activity in the 10 minutes preceding and 4 minutes following the turbulence encounter within 20 miles of the accident location. A Global Data Assimilation System (GDAS) model sounding for near the accident site at 0500 was retrieved from the National Oceanic and Atmospheric Administration’s (NOAA) Air Resources Laboratory and analyzed by the Rawinsonde Observation (RAOB) program. The model showed wind near 35,000 ft was from the south at about 15 knots. RAOB did not identify any moderate or greater clear air turbulence in the atmosphere. Geostationary Operational Environmental Satellite (GOES)-16 infrared (10.3µm) data were obtained from an archive at the Space Science Engineering Center at the University of Wisconsin-Madison. Images from these data at 0340 are presented in Figures 1 and 2. Figure 1 presents a regional view of cloud coverage. The accident location is coincident with a cloud pattern consistent with convective activity. Figure 2 presents a closer view of the accident location. An approximately 2-minute portion of the accident aircraft’s flight path (south-to-north) across the cloud pattern consistent with convective activity reveals that the accident aircraft flew across the coldest portion of the cloud, which was at a brightness temperature of -55°C. According to the GDAS sounding, this temperature corresponded to a cloud top height of about 42,000 ft. Figure 1. GOES-16 infrared imagery from 0340. Image is not corrected for parallax error. The accident location is denoted by the red dot inside the red circle. Figure 2. GOES-16 infrared imagery from 0340. Image is not corrected for parallax error. An approximately 2-minute portion of the accident aircraft’s flight path (south-to-north) is depicted by the light blue line. After being logged as inoperative by the flight crew, the weather radar unit was initially electrically tested on the airplane with no electrical shorts detected. The weather radar was then removed from the event airplane and sent to the manufacturer for testing. The manufacturer testing found that the unit passed all test requirements.