Incident Overview
Approximately 20 minutes prior to landing, a passenger sustained a serious in-flight injury during an evasive maneuver executed in response to a Traffic Alert and Collision Avoidance System (TCAS) warning. The incident occurred while the aircraft was descending into Chicago.
TCAS Warnings and Maneuver
According to a written statement from the copilot, the flight crew received an aural 'TRAFFIC, TRAFFIC' warning from the TCAS, accompanied by a visual warning on the Electronic Horizontal Situation Indicator (EHSI). Almost immediately after the initial Traffic Advisory (TA), a subsequent 'CLIMB, CLIMB, CLIMB' aural warning was issued at approximately 14,000 feet, along with visual warnings on both the EHSI and the Electronic Attitude Director Indicator (EADI). The TCAS Resolution Advisory (RA) commanded a pitch attitude of approximately 5 degrees nose up. Within one minute, the TCAS 'CLEAR OF CONFLICT' aural warning was issued, after which the captain reestablished a descent. The copilot notified Air Traffic Control (ATC) of the RA and the resumption of the descent.
Passenger Injury
After the maneuver, the captain contacted the flight attendants to ascertain the condition of the passengers and cabin crew. He was informed that one passenger had hurt his ankle during the avoidance maneuver but was not in need of immediate medical assistance. The doctor who later treated the passenger stated that radiographs taken on 01 August 2000 revealed a left fibular fracture.
Weather Conditions
Meteorological conditions at the time did not support the presence of clear air turbulence, indicating that the injury was not caused by turbulence but by the evasive action taken in response to the TCAS warning.