A320
Flight Crew Last 90 Days 270; Flight Crew Total 16600; Flight Crew Type 11000
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented
Aircraft; Human Factors
We contacted NorCal Approach descending into SFO. We were assigned the Quiet Bridge Visual to 28L. Since this approach is not in the database we asked for the FMS RNAV approach. NorCal said we could fly this but it would have to be to 28L since 28R was closed. We were high at the start of the approach but quickly got closer to the lowest altitudes on the RNAV approach. After descending to the lowest altitude on the approach; about 1;200 FT over the bridge; the Captain switched our approach to the 28L ILS to give me backup navigation since it was night time VFR. At that point the FD kept showing a descent as I was trying to level off at 1;200 FT until the last point on the RNAV (approximately over the bridge). The autothrottles were not adding power even though I was pulling back on the stick trying to level off. This resulted in us descending slightly below the last altitude of 1180 as I was trying to move over to the 28L. At that point I got a 'glideslope' alarm from the aircraft (GPWS). The FD was trying to get me to go lower even though the VASI was showing that I was below the glideslope already. I leveled off and caught both the localizer and glideslope. We landed with no further incident.
A320 First Officer reported several autoflight anomalies on a night visual approach to SFO that; if uncorrected; would have taken the flight into a CFIT situation.