NTSB Factual Report

On February 25, 2003, about 1616 eastern standard time, a Boeing 777-223, N790AN, operated by American Airlines Inc. (Flt AA1614), as a Title 14 CFR Part 121 scheduled domestic flight, encountered turbulence while on descent to Miami International Airport, Miami, Florida. Visual meteorological conditions prevailed. An instrument flight rules flight plan was filed. The airplane was not damaged. The two airline transport-rated pilots, six flight attendants, and 123 passengers reported no injuries. Two flight attendants reported serious injuries. The flight had departed from the Dallas-Fort Worth International Airport, Arlington, Texas en route to Miami, Florida, at 1356 eastern standard time.

According to the captain, while descending into Miami, they began deviating well south of a few small cumulous developments. The first officer was flying the airplane at the time of the event. They had begun reducing speed to turbulence penetration prior to encountering a few pockets of light chop at about FL240. The captain gave a public address system announcement to the flight attendants and passengers leaving FL180, asking that the cabin be prepared for landing early, due to possible chop during our approach. Air Traffic Control was advised of the speed reductions, and subsequently caused traffic behind them to also have to slow. As they approached the tops of a very thin cloud layer at about 11,000 feet, descending to 10,000 feet, at a speed of about 260 knots, they encountered a very brief pocket of moderate chop. Several minutes after the event, the number one flight attendant, advised the captain that two of the flight attendants in the aft part of the airplane had been injured during the turbulence event. She requested that medical assistance meet the airplane.

According to interviews with the cabin crew, the seatbelt sign was on, they were in the process of securing the cabin for landing, and the purser had made the announcement for passengers to prepare for landing right after the captain's pre-landing announcement. During the turbulence encounter, most of the flight attendants reported being lifted off their feet, and thrown to the floor. Three of the flight attendants commented that they were able to steady themselves with hand holds which kept them from falling. Following the turbulence encounter, two flight attendants noted a passenger exiting a lavatory uninjured. A few passengers had left their seats following the turbulence encounter to assist the injured flight attendants. After arriving at the gate, paramedics boarded the airplane, then the passengers were deplaned, and two flight attendants were transported to the hospital by ambulance.

Meteorological information obtained by an NTSB Meteorologist showed a convective SIGMET was valid for Florida and coastal waters at the time of the turbulence encounter. The convective SIGMET was issued in response to a developing area of thunderstorms moving from 260 degrees at 10 knots with tops extending to 32,000 feet. Radar images from the Miami Weather Surveillance Radar (WSR-88D) identified multiple storm cells in the area at the time of the turbulence encounter. The radar data indicated that the core intensity of these cells was strong to intense (40 to 50 dBZ). A radar image taken about the time of the turbulence encounter shows the airplanes path came about five nautical miles from the core of one cell and three nautical miles from the core of a second cell.

The digital flight data recorder (DFDR) was removed from the airplane after the accident and sent to the NTSB Vehicles Recorder Laboratory, Washington, D.C. The recorder was in good condition, and the data were extracted normally from the recorder. The DFDR was downloaded to hard disk using NTSB readout equipment. The acquired accident data were verified for accuracy by examining take-off, cruise, and landing performance of the aircraft previously recorded on the medium. The data were found to be consistent with the normal operation of the aircraft.

The DFDR recording contained approximately 98 hours of data. The accident flight was the third from the end of the recording and began at approximately Subframe Reference Number (SRN) 292056. The duration of the incident flight was approximately 2 hours 48 minutes. The turbulence event occurred approximately 2 hours 20 minutes into the flight at approximately SRN 298456, while the aircraft was descending through an altitude of approximately 12,836 feet, on a heading of 115 degrees. During this event, the data shows the aircraft with a 2.04 g vertical acceleration load and 6 degrees of left roll. The pitch changed from -0.4º at SRN 298456 to -2.1º at SRN 298457. The autopilot remained on throughout the event and was turned off at SRN 298781. The DFDR was returned by NTSB to American Airlines on July 12, 2004.

Recorded radar data from the FAA Miami Air Route Traffic Control Center show that at about the time of the turbulence encounter the airplane was at position 25 degrees 56 minutes 50 seconds North latitude and 81 degrees 15 minutes 9 seconds West longitude, or about bearing 280 degrees at 53 nautical miles from Miami International Airport.

NTSB Probable Cause

The flight crew's inadvertent encounter with turbulence while attempting to maneuver through an area of convective activity during descent.