Date: 201912
Local time of day: 0001-0600
Flight conditions: IMC
Aircraft: A300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Aircraft component: FMS/FMC
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: IMC arrival. After several vectors for spacing; and speed changes; we were given a heading of 320 degrees to join the LOC; maintain 3;000 ft. and cleared the ILS. Sometimes; an Airbus Flight Director does not like large turns to join a LOC; this was one of those cases. Our aircraft indicated 'LOC STAR' meaning it was joining the LOC; yet the aircraft continued a right turn through the LOC course and a further 20 deg right. I immediately noticed the deviation; and directed the First Officer to disconnect the autopilot and turn left back on course. Our CDI indicated a max deviation of 1.5 dots right of course. When; while hand flying; we were centered on the LOC once again; we re-automated the aircraft. Remainder of the ILS was normal. Later that same night; I got a phone call from the [Chief Pilot] stating that TRACON wanted to speak with me; saying we had left an ILS and returned without clearance. I called TRACON and explained the situation above. Once I told him that our max deviation was 1.5 dots (meaning we were on the LOC at all times while correcting back to centerline) he was relieved and stated 'ok that's all I need to know.'I have experienced this problem with Airbus Flight Directors before and written them up; and the clearing action is always 'cannot duplicate the error'. Even the [Chief Pilot] said he has experienced this same problem.


Second narrative: While being vectored for an approach; a speed of 190 kts. and a heading of 310 degrees was given approximately 20 miles away from the runway. Subsequently; a clearance was given to intercept the localizer. Shortly after; A clearance was given to 'maintain 170 kts.; 3;000 ft. until established; cleared for the ILS.' The crew noticed the aircraft make excessive roll inputs while it was intercepting the localizer (LOC star). As the pilot flying; I placed my hands on the control wheel as it was now oscillating back and forth in a rolling fashion. A decision was made to disengage the autopilot and suppress the rolling tendencies. I quickly took control and noticed that the localizer deviation indexer was 1 1/2 dot off the localizer. This was corrected immediately and once corrected; I asked that the Captain re-automate the FCP. Once the runway was in sight (about 800 ft. AGL) the autopilot was disengaged and the remainder of the approach was hand flown; without incident.The parameters built into the A300 Honeywell suite are at times; overly sensitive. This creates over correcting/over controlling of the auto flight system. Generally; when this minor malfunction is written up; it results in a 'cannot duplicate' resolution or sign off.Flight crews are always ready to intervene and remove the automation on the Airbus.


Synopsis: A300 flight crew reported that an autopilot malfunction resulted in a course deviation.