Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 22000; Flight Crew Type 7500
Situational Awareness; Human-Machine Interface
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Procedure; Human Factors
The Captain was not that familiar with flying into SFO from Airport ZZZ. He also had mentioned that he had never flown this model of the 777 (I mention this because his unfamiliarity with the flap speeds became a distraction). He seemed to be new on the aircraft. During the arrival briefing; I mentioned that they usually clear us to cross OSI at 8000 feet. He asked me if that would make him low or high at OSI and I told him that would definitely make him high for the approach. He briefed that he would be doing a flaps 30 approach. We were cleared to cross OSI at 8000 and then cleared to a lower altitude once we passed OSI. Once we passed OSI; the captain descended at 250 KTS with the speed brakes full out. The autopilot was engaged at this time. Once cleared for the approach and on final; he began slowing down. When he called for flaps 5; we were too fast and I told him he needed to slow down more. After that; I don't remember the exact order of things; and at some point he disconnected the autopilot; but I did not immediately realize he had done so. He asked for 150 KTS and the gear down and once the gear was down he asked for flaps 25; therefore going from flaps 5 right to flaps 25. Since the speed brakes were still out; we got the caution message and he quickly stowed the handle which caused the airplane to balloon. Then I noticed we were slightly low on the glide path.  It was only slightly so I didn't think much of it; however; I watched to make sure he made a correction to stop the high rate of descent. I saw him make a slight change to the pitch; although it was not all the way up to the FD pitch bars. I know that the flight director tends to exaggerate the amount of correction needed and you don't want to chase them; so the fact that he showed he was aware he was low and correcting prevented me from saying anything at that time. I continued doing the landing checklist. At some point he called for target speed and I waited for him to call for Flaps 30; watching his speed closely as he was calling for flaps very close to the limit speeds.With the checklist done; I made an early 1000 FT call (@ 1080 FT) and set the missed approach altitude. I then looked outside and saw 3 red VASI lights which immediately turned to 4 red VASI lights. I told him he needed to come up. As soon as I said that; the tower issued an altitude alert and directed us to check our altitude and make an immediate correction. I thought about telling him to go-around; but since it was clear and this time he made a larger correction; I did not.  As he was correcting; I glanced at our altitude and it said 970 FT; so I'm guessing the incident occurred right at 1000 FT. We quickly reacquired the glideslope and landed without incident. However; in light of a recent mishap; which occurred in VMC; and recent reports of deviations at our company; I realize now that calling for a missed approach would have been the most conservative response and therefore the safer course of action.
B777 First Officer describes a Visual Approach to SFO by a Captain not entirely familiar with the airport or the aircraft; resulting in a slightly unstabilized approach and a low altitude alert from the Tower.