Narrative:

I was the captain on a boeing 777 landing sfo. I was also the pilot flying with my first officer as the pilot not flying. We were being vectored by nct from over osi VOR for a visual approach to runway 28L at sfo. We were directed to descend from 8;000 ft to 6;000 ft and speed 210 KTS while on a base leg. Approach control notified us of traffic for [runway] 28R as an airbus 320. We reported traffic not in sight. We were given a heading to intercept the final approach course for [runway] 28L; and directed to slow to 180 KTS. We still did not have traffic in sight. Approach control cleared us to 5;000 ft then gave us a rapid sequence of speed reductions to 160 KTS then to final approach speed. At this point we were getting high for a normal approach profile to the runway. My first officer then confirmed visual with the traffic and we were cleared for the visual approach to [runway] 28L. We were handed off to sfo tower controller near the san mateo bridge. We were still a little high and at minimum approach speed. Tower instructed us not to pass the airbus. We were nearly wingtip-to-wingtip at this point; around 4 to 5 miles out on final. Tower asked the A320 to speed up 10 KTS. We continued to a landing on [runway] 28L. I feel that safety margins were threatened during this approach for several reasons. The approach took place at dusk with diminished daylight. This made it difficult to make visual contact with the traffic approaching [runway] 28R. The close spacing as vectored by approach control created a heavy workload in the cockpit. There was zero room for error as we tried to maintain visual with the traffic; reduce speed to minimum speed; and then fly a steeper than normal descent profile. The converging courses of the two aircraft and our descent rate triggered a TCAS RA advisory. Our relative higher altitude over the airbus created a situation where I momentarily lost visual contact with the traffic due to visual cut-off angle from the left seat. I was relying on my first officer and TCAS to maintain separation. Our minimum approach speed was faster than the airbus and there was insufficient in-trail separation. I called the sfo tower and norcal approach by phone to discuss the issue and voice my concern and displeasure with this arrival. In retrospect; I probably should have initiated a go-around when I; as the pilot flying; lost visual with our traffic. There are; in my analysis; several causal factors that created this situation: when conducting visual approaches; it is common for us to plan a flaps 25 landing instead of using flaps 30. The approach planning takes place before top of descent. The approach speed for flaps 25 vs. Flaps 30 is approximately 7 KTS faster. I believe ATC assumed we would make visual contact earlier than we did. The altitude and speed assignments created an unacceptable lateral and in-trail spacing given the low light conditions at dusk. The lack of separation then created an undesirable approach condition for our aircraft. The arrival rate at sfo at the time was high enough that norcal was perhaps trying to 'squeeze' aircraft spacing. This may have been a different; even acceptable; situation if it involved two narrow-body aircraft. The fact that we were a 'heavy' aircraft put more limitations on us. I would offer these recommendations for consideration: our company and/or the FAA should notify all pilots that the approach flap setting for heavy aircraft should be selected to allow the slowest approach speed when conducting closely spaced parallel visual approaches. This would mitigate the potential 10 to 20 KT closure with the other traffic. Approach control should plan a minimum of 1-mile in-trail separation for heavy aircraft when paired with narrow body or light aircraft for simultaneous visual approaches to 28L/28R at sfo. This distance can easily be lost once the lead aircraft begins to slow to final approach speed. Approach control needs to be aware of the change in lighting at sunset. The visibility reported by ATIS does not necessarily translate to in-flight acuity during low light conditions. In closing; this vector to final would not have been accepted at night or in dark conditions. Any deviation left of the [runway] 28R centerline by the A320 would have put both aircraft at risk of a potential mid-air.

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Original NASA ASRS Text

Title: Air Carrier on final for Runway 28L at SFO voiced concern regarding ATC handling with regard to staying behind an A320 on final for Runway 28R.

Narrative: I was the Captain on a Boeing 777 landing SFO. I was also the pilot flying with my First Officer as the pilot not flying. We were being vectored by NCT from over OSI VOR for a visual approach to Runway 28L at SFO. We were directed to descend from 8;000 FT to 6;000 FT and speed 210 KTS while on a base leg. Approach Control notified us of traffic for [Runway] 28R as an Airbus 320. We reported traffic not in sight. We were given a heading to intercept the final approach course for [Runway] 28L; and directed to slow to 180 KTS. We still did not have traffic in sight. Approach Control cleared us to 5;000 FT then gave us a rapid sequence of speed reductions to 160 KTS then to final approach speed. At this point we were getting high for a normal approach profile to the runway. My First Officer then confirmed visual with the traffic and we were cleared for the visual approach to [Runway] 28L. We were handed off to SFO Tower Controller near the San Mateo Bridge. We were still a little high and at minimum approach speed. Tower instructed us not to pass the Airbus. We were nearly wingtip-to-wingtip at this point; around 4 to 5 miles out on final. Tower asked the A320 to speed up 10 KTS. We continued to a landing on [Runway] 28L. I feel that safety margins were threatened during this approach for several reasons. The approach took place at dusk with diminished daylight. This made it difficult to make visual contact with the traffic approaching [Runway] 28R. The close spacing as vectored by Approach Control created a heavy workload in the cockpit. There was zero room for error as we tried to maintain visual with the traffic; reduce speed to minimum speed; and then fly a steeper than normal descent profile. The converging courses of the two aircraft and our descent rate triggered a TCAS RA advisory. Our relative higher altitude over the Airbus created a situation where I momentarily lost visual contact with the traffic due to visual cut-off angle from the left seat. I was relying on my first officer and TCAS to maintain separation. Our minimum approach speed was faster than the Airbus and there was insufficient in-trail separation. I called the SFO Tower and NorCal Approach by phone to discuss the issue and voice my concern and displeasure with this arrival. In retrospect; I probably should have initiated a go-around when I; as the pilot flying; lost visual with our traffic. There are; in my analysis; several causal factors that created this situation: When conducting visual approaches; it is common for us to plan a flaps 25 landing instead of using flaps 30. The approach planning takes place before top of descent. The approach speed for flaps 25 vs. flaps 30 is approximately 7 KTS faster. I believe ATC assumed we would make visual contact earlier than we did. The altitude and speed assignments created an unacceptable lateral and in-trail spacing given the low light conditions at dusk. The lack of separation then created an undesirable approach condition for our aircraft. The arrival rate at SFO at the time was high enough that NorCal was perhaps trying to 'squeeze' aircraft spacing. This may have been a different; even acceptable; situation if it involved two narrow-body aircraft. The fact that we were a 'heavy' aircraft put more limitations on us. I would offer these recommendations for consideration: Our company and/or the FAA should notify all pilots that the approach flap setting for heavy aircraft should be selected to allow the slowest approach speed when conducting closely spaced parallel visual approaches. This would mitigate the potential 10 to 20 KT closure with the other traffic. Approach Control should plan a minimum of 1-mile in-trail separation for heavy aircraft when paired with narrow body or light aircraft for simultaneous visual approaches to 28L/28R at SFO. This distance can easily be lost once the lead aircraft begins to slow to final approach speed. Approach Control needs to be aware of the change in lighting at sunset. The visibility reported by ATIS does not necessarily translate to in-flight acuity during low light conditions. In closing; this vector to final would not have been accepted at night or in dark conditions. Any deviation left of the [Runway] 28R centerline by the A320 would have put both aircraft at risk of a potential mid-air.

Data retrieved from NASA's ASRS site as of July 2013 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.