B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 148
Situational Awareness; Communication Breakdown; Distraction
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR
Flight Crew Took Evasive Action
Human Factors
We were vectored through final from an early base leg turn because we asked for S-turns (due to an early turn in and knew we would be high). So we were denied the S-turns and resequenced with gear down flaps 5 at about 160 knots. We were turned downwind and Controller asked if we had traffic (which we did at about four miles). Controller turned us from downwind straight to final (from a 150 degree heading to a 010 heading and told to follow traffic). Halfway through the turn he asked if we were still turning; which we were. However; there was a third aircraft for the parallel runway; and at our slow speed and by the time we did our almost 180 degree turn we rolled out on final next to the third aircraft. As that aircraft descended; we received a 'descend' RA (which we did) and were clear of conflict and the whole maneuver was only about 300 FT. Never did we cross our centerline. As a matter of fact; I flew left of course slightly once I saw the third aircraft and thought spacing might be close. This was a spacing issue from ATC. Our slower than normal speed (due to our aircraft configuration) probably threw off the Controllers planned spacing. The Controller should have called out the traffic for the parallel runway; which he never did. Instead; he only queried our turn; which we were in. No matter the turn or heading; that third aircraft was going to be a conflict due to our speeds. He probably should have been slowed.
B737 flight crew reported being vectored to a visual approach at SEA and responded to an RA from an aircraft on a visual to the parallel runway.