American Airlines Flight 289

American Airlines flight 289 encountered moderate to severe convective turbulence while in cruise flight at flight level (FL) 360 [36,000 feet], enroute from the Leonardo da Vinci (LIRF) Airport, Rome, Italy to the Dallas Fort Worth International Airport (DFW), Dallas-Fort Worth, Texas. As a result of the turbulence, one flight attendant (FA) sustained a serious injury, and another FA and one passenger sustained a minor injury. The aircraft continued to DFW and landed without further incident. The accident occurred while air traffic control (ATC) services were being provided by Kansas City Air Route Traffic Control Center (ZKC). The involved position was R92 (Rivers Sector).

The event flight was operated by three flight crewmembers that consisted of a captain, a first officer (FO), and a relief FO. At the time of the turbulence encounter, the FO was the pilot flying (PF), and the relief FO was the pilot monitoring. There were also eight flight attendants (FAs) on the flight. During the event, four FAs (number 2, 3, 6, and 8) were located in the aft galley, two FAs (number 1, and 5) were located in the business galley, and two FAs (number 4, and 7) were located in the forward galley.

The flight crewmembers reported that the flight had intermittently encountered cirrus clouds with light chop while at FL360. Due to the turbulence, they decided to keep the fasten seatbelt sign illuminated.

About 2256 Coordinated Universal Time (UTC), the flight was near navigational point LOAMY in southwest Missouri and flying through some cirrus clouds. When the flight emerged from the cirrus clouds, the flight crewmembers saw a narrow, towering, cumulus cloud that appeared to be building in front of them. They informed ATC and, immediately turned toward the right to avoid the cloud. They indicated that the airplane caught the upwind edge of the cloud and the flight experienced turbulence for a duration of about 15 seconds.

Although the flight crew had checked in with the R92 controller and was on the R92 controller's frequency for almost ten minutes before they requested to deviate around the cumulus cloud, the R92 controller did not issue the depicted weather that the flight crew had requested to deviate around (see figure 1). The controller also did not request pilot reports (PIREPS) from any flight crews in the sector.

Figure 1. WSR-88D composite radar image at 2257Z with aircraft position and flight track overlay.

The onboard aircraft weather radar system is the primary source for weather avoidance while enroute. The flight crewmembers stated that their aircraft weather radar was on and was not showing any precipitation returns. They also stated that there was no WIFI connectivity, it was placarded “inop”, and therefore inhibited their ability to use the weather applications installed on their electronic flight bag.

After the event, the PF called the galley to check on the FAs and to let them know they were clear of the turbulence. After the PF hung up, the purser called back to inform them of an FA injury. Medical personnel onboard assisted the injured FA. The captain, who was on a crew break in the cabin, called to inform them of the situation in the cabin. After he checked on the injuries he returned to the flight deck. The flight crew declared an emergency and expedited the flight to DFW.

The aft FAs reported that, before the turbulence event, they were preparing to complete the final cabin service of the flight. The fully loaded beverage carts had been positioned in the aft galley and the beverage inserts were on top of the carts. Coffee had just been poured into the coffee thermos containers sitting in the inserts in preparation for service. The number 2 FA was about to load the hot entrees when, suddenly and without warning, the aircraft encountered two “really bad” turbulence events. During the second encounter, the number 3 and number 8 FAs flew up in the air and were slammed to the floor. The number 8 FA sustained a serious injury, and the number 3 FA sustained a minor injury due to hot coffee being spilled on her.

After landing, emergency personnel met the aircraft at the gate and attended to the injured. The number 8 FA was diagnosed with a fractured ankle and the number 3 FA had a burn on her arm. Additionally, one passenger reported a sore ankle.

A post-accident review of meteorology data showed that a convective Significant Meteorological Information (SIGMET) was in effect immediately east of the area and did not extend over the flight track. A review of the satellite and radar imagery showed an area of convective clouds developing over the region at the time of the turbulence event. The Kansas City WSR-88D depicted echoes with maximum reflectivity near 55 dBZ or extreme intensity under the flight track, with echoes of 15 dBZ extending through FL360. While airborne weather radar does not typically detect echoes less than 20 dBZ or light intensity echoes, proper down tilt of the beam would have detected significant echoes developing below the flight path as the they approached the area and air traffic control radar should have observed the echoes and issued advisories. Based on the aircraft location and the echoes over the position, this event was a convectively induced turbulence (CIT) event within the clouds.

Eddy dissipation rate (EDR) is a universal measure of turbulence rate. Recorded data from the airplane revealed that at about 2256 UTC, the EDR indicated values of 0.340 with a peak at 0.9877. The peak value equates to strong turbulence.

Verbatim NTSB analysis and probable cause from the NTSB dataset