B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 163
Situational Awareness
Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Human Factors; Airspace Structure
We were cleared for the ILS 28L in San Francisco. Passing 5000 feet on glideslope; ATC was vectoring a 777 to join us for a 'side by' for 28R. We were 18 miles out when we got a TA; and my First Officer commented he was going to change the Transponder from TA/RA to 'TA only' per our procedures in SFO and DEN. As the 777 approached the localizer; we noticed he would not be able to join his localizer but fly through ours as well. He was probably at 4000 feet.Although we never received another TA; he was underneath us as we descended on the glideslope. I realized it wasn't going to work so I climbed from approximately 4500 feet to 5500 feet. Meanwhile; ATC was trying to send us around; but the call was blocked. I believe he flew directly under us less than 500 feet. We were vectored for another ILS with no further complications. Before we were handed off to Tower; Approach apologized and said that the 777 didn't turn in; in time. The next day I decided to review the Transponder policy and realized we are supposed to switch to 'TA only' inside of eight miles. We were 18 miles out.I failed to brief the eight mile point for TA only. Without a brief of eight miles; I'm concerned most would switch from TA/RA to TA only further than eight miles when another aircraft pulls alongside.
B737 Captain reported executing a go-around from the SFO ILS Runway 28L after experiencing an NMAC with a B777 on parallel approach to Runway 28R.