B777 flight crew on visual approach to runway 28L at sfo experiences a TCAS RA with a B757 on approa...

Narrative:

Vectors to the visual approach 28L sfo; with the captain flying the approach and myself as pm. We reported B757 in sight; who was for the right (28R). We were instructed at first to maintain 180 knots and immediately slowed to comply. We were not cleared for a visual approach until after we were vectored on a dog leg for final; where we used the ILS for lateral and vertical guidance. Shortly after joining final we were instructed to slow to 170 knots until 6 DME; as the B757 was not very far ahead of us. As the two airplanes progressed; and with myself primarily concerned with the traffic (90 percent outside); I noticed the B757 level off; or even pitch slightly up; drop their gear and obviously configure for approach. I also noticed that the B757 speed was decreasing and informed the captain; where we selected landing flaps 25 and slowed to approach speed (145 kts) so as not to pass the traffic. With eyes glued to the B757; that aircraft trend was slowly but consistently trending toward our flight vector. I glanced inside and noted that the captain was even slightly left of course; confirming that we were not the migrating culprits. The lateral closure between our two airplanes was slow but consistent; and just as the proximity was becoming uncomfortable the B757 self-initiated a go around; and seconds later we got an RA to descend. No maneuvering was required on our part as the RA pitch bar did not command action beyond our normal glide path gradient at the time. From my vantage point it appeared that the B757 vector was still migrating toward our path even after initiating the go around; and perhaps 2-4 seconds passed before the B757 noticeably turned to the right; away from our vector. We continued to a normal landing with no need at any time to execute an avoidance maneuver beyond ensuring our descent complied with the RA. Whatever was going on in the B757 cockpit; I applaud them in their decision to initiate a go around before things 'got out of hand' to the point where we would need to take more urgent action to avoid a collision.

Original NASA ASRS Text

Title: B777 flight crew on visual approach to Runway 28L at SFO experiences a TCAS RA with a B757 on approach to Runway 28R. The B757 had drifted slightly left of course and was slightly high and initiated a go around at the same time the B777 crew received their RA.

Narrative: Vectors to the visual approach 28L SFO; with the captain flying the approach and myself as PM. We reported B757 in sight; who was for the right (28R). We were instructed at first to maintain 180 knots and immediately slowed to comply. We were not cleared for a visual approach until after we were vectored on a dog leg for final; where we used the ILS for lateral and vertical guidance. Shortly after joining final we were instructed to slow to 170 knots until 6 DME; as the B757 was not very far ahead of us. As the two airplanes progressed; and with myself primarily concerned with the traffic (90 percent outside); I noticed the B757 level off; or even pitch slightly up; drop their gear and obviously configure for approach. I also noticed that the B757 speed was decreasing and informed the captain; where we selected landing flaps 25 and slowed to approach speed (145 kts) so as not to pass the traffic. With eyes glued to the B757; that aircraft trend was slowly but consistently trending toward our flight vector. I glanced inside and noted that the captain was even slightly left of course; confirming that we were not the migrating culprits. The lateral closure between our two airplanes was slow but consistent; and just as the proximity was becoming uncomfortable the B757 self-initiated a go around; and seconds later we got an RA to descend. No maneuvering was required on our part as the RA pitch bar did not command action beyond our normal glide path gradient at the time. From my vantage point it appeared that the B757 vector was still migrating toward our path even after initiating the go around; and perhaps 2-4 seconds passed before the B757 noticeably turned to the right; away from our vector. We continued to a normal landing with no need at any time to execute an avoidance maneuver beyond ensuring our descent complied with the RA. Whatever was going on in the B757 cockpit; I applaud them in their decision to initiate a go around before things 'got out of hand' to the point where we would need to take more urgent action to avoid a collision.

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	1245806
Time
Date	201503
Local Time Of Day	1201-1800
Place
Locale Reference	SFO.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Aircraft 2
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Person 1
Function	Pilot Not Flying First Officer
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 18000 Flight Crew Type 11000
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 15200 Flight Crew Type 5000
Events
Anomaly	Conflict Airborne Conflict

B777 flight crew on visual approach to runway 28L at sfo experiences a TCAS RA with a B757 on approach to runway 28R. The B757 had drifted slightly left of course and was slightly high and initiated a go around at the same time the B777 crew received their RA.