A319
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Other / Unknown
Flight Crew Overcame Equipment Problem
Aircraft; ATC Equipment / Nav Facility / Buildings; Human Factors
The flight was cleared to fly the standard arrival into Mexico City (MMMX) to Runway 5R.  The aircraft was flying with the autopilot and autothrottle engaged; fully configured at final approach speed; in LNAV with the ILS approach armed; turning inbound to final on the arrival and on profile. As the localizer and glideslope became active; the autopilot and autothrottle systems attempted to capture the localizer and glideslope.  The autopilot went into an aggressive bank in its attempt to capture the localizer and glideslope while the autothrottle lagged in its power application causing the airplane to enter into Alpha Floor.  The Captain intervened and disconnected the autopilot and autothrottle systems and exited Alpha Floor while continuing to fly a visual approach manually to an uneventful landing on Runway 5R.
A319 Captain reports entering Alpha Floor during localizer capture for Runway 5R at MMMX; with the autopilot initiating an aggressive bank. Both autothrust and autopilot are turned off and the approach is completed manually.