Autopilot/Flight Director (AP/FD) TCAS capability

An AP/FD Airborne Collision Avoidance System (ACAS) capability is a guidance mode designed by Airbus which allows the aircraft to automatically fly the Resolution Advisories if the autopilot is engaged, or the pilot to manually fly the RA by following the Flight Director commands. The AP/FD capability is currently available for all Airbus aircraft (except the A340s).

Broadly speaking, when an AP/FD aircraft receives an RA, the aircraft will automatically change its vertical speed to the vertical speed prescribed by the current RA plus 200 ft/min (in order to help the flight crew's monitoring of the RA response), unless the RA prescribes a null vertical speed (e.g. a Level Off RA) - in which case the aircraft will change its vertical speed to the vertical speed of 0 ft/min. The manoeuvre starts within 3 – 5 sec. and accelerations of 0.15 – 0.25g. When the RA is terminated, the AP/FD function will guide the aircraft to the selected altitude. All low level TCAS inhibitions are applicable.

The AP/FD functionality has been specified in the Minimum Aviation System Performance Specification (MASPS) for Flight Guidance System (FGS) coupled to ACAS published by European Organisation for Civil Aviation Equipment (EUROCAE) (ED-224).

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