FAA regulations cause an AD that limits TCAS usage in certain aircraft
FAA regulations have caused an Airworthiness Directive issuance requiring operating limitations on the Traffic Collision Avoidance System (TCAS) used in Collins FDSA-6500 flight display systems. These systems are installed on certain Bombardier Challenger 604, Cessna Citation CJ3, and Beechcraft King Air models. The warning is for a potential conflict between TCAS display indications and aural alerts that can occur during a resolution advisory (RA).
The problem was discovered during testing of a full flight simulator on a development program. During an RA scenario, there was a discrepancy between the TCAS fly-to/avoidance cue indication on the primary instrument displays and other TCAS system information, such as aural cues. According to the FAA, “ While the aural alert will provide the pilot with accurate information to resolve the RA, that information is not accurately represented by the TCAS fly-to/avoidance display. Specifically, the TCAS fly-to/avoidance cue is displayed relative to the aircraft horizon line instead of the aircraft symbol”.
Collins determined that the TCAS was incorrectly translated by the FDSA-6500 software. They are developing a software fix, but in the meantime, the FAA issued the AD to address the potential conflict. Be on the lookout for updates from the FAA and Collins as this software issue is addressed and corrected.