NTSB Says TCAS Must Warn Pilots When Offline

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Traffic alert and collision avoidance systems (TCAS) should be designed to ensure that flight crews know when they are not operating, the NTSB said in a safety recommendation issued on Wednesday. The recommendation is based on preliminary findings in the ongoing investigation into the midair collision between an Embraer Legacy bizjet and a Gol Airlines Boeing 737 in Brazil last year, which killed all 154 aboard the airliner. The NTSB said its findings indicate that, for reasons yet to be determined, the collision avoidance system in the Legacy was not functioning at the time of the accident, disabling the system's ability to detect and be detected by conflicting traffic. In addition, data from the cockpit voice recorder indicates that the flight crew was unaware that the collision avoidance system was not functioning until after the accident. "A flight crew's ability to mitigate the risk of collision is significantly degraded if the collision avoidance system becomes inoperative and the failure is not quickly and reliably brought to the crew's attention, as this accident demonstrates," the Safety Board said. Therefore, the Board wants the FAA to require, for all aircraft required to have TCAS installed and for existing and future system designs, that the airborne loss of collision avoidance system functionality, for any reason, provide an enhanced aural and visual warning requiring pilot acknowledgment.