A300 flight crew encountered anomaly with avionics equipment during approach.

Narrative:

While descending on the OAKES2 STAR; we were cleared for the ILS to runway 30. As the PF (pilot flying); I selected 2000' on the fcp (flight control panel) and continued the descent in profile (the autopilot had already flown the entire STAR without incident). After passing the prfct fix at 5000'; the aircraft continued the descent to the next fix; parbb. But prior to reaching parbb; the aircraft failed to honor the 4;500' altitude constraint and continued to descend the approach was loaded correctly and verified by the PF and pm (pilot monitoring) prior to the start of the arrival. As the PF; I recognized the error and disconnected the autopilot to stop the descent; but we had lost approximately 800' in the process. We immediately got a call from oak approach control saying they received a low altitude alert. I had already started a climb back to 4;500 and told ATC we were correcting back to the published altitude. The rest of the approach was flown uneventfully in level change. Autopilot profile failed to honor the altitude constraint on the approach. All systems were loaded correctly and working properly up until this point in flight. The cause of the failure is unknown. This is not the first time I have seen profile miss an altitude constraint. Other pilots have commented that it has happened to them several times as well. I do not intend on using profile any more during the approach phase of flight. I simply cannot trust it anymore.

Original NASA ASRS Text

Title: A300 flight crew encountered anomaly with avionics equipment during approach.

Narrative: While descending on the OAKES2 STAR; we were cleared for the ILS to Runway 30. As the PF (pilot flying); I selected 2000' on the FCP (Flight Control Panel) and continued the descent in PROFILE (the autopilot had already flown the entire STAR without incident). After passing the PRFCT fix at 5000'; the aircraft continued the descent to the next fix; PARBB. But prior to reaching PARBB; the aircraft failed to honor the 4;500' altitude constraint and continued to descend the approach was loaded correctly and verified by the PF and PM (pilot monitoring) prior to the start of the arrival. As the PF; I recognized the error and disconnected the autopilot to stop the descent; but we had lost approximately 800' in the process. We immediately got a call from OAK approach control saying they received a low altitude alert. I had already started a climb back to 4;500 and told ATC we were correcting back to the published altitude. The rest of the approach was flown uneventfully in Level Change. Autopilot PROFILE failed to honor the altitude constraint on the approach. All systems were loaded correctly and working properly up until this point in flight. The cause of the failure is unknown. This is not the first time I have seen PROFILE miss an altitude constraint. Other pilots have commented that it has happened to them several times as well. I do not intend on using PROFILE any more during the Approach phase of flight. I simply cannot trust it anymore.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1663970
Time
Date	201907
Local Time Of Day	0001-0600
Place
Locale Reference	NCT.TRACON
State Reference	CA
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Make Model Name	A300
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT