EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
ATC Issue All Types; Conflict NMAC; Inflight Event / Encounter Unstabilized Approach
Flight Crew FLC complied w / Automation / Advisory
Human Factors; Airport; Procedure
While the Seattle Airport was reporting visual conditions; a smoke layer from forest fires in Canada were restricting visibility and making it difficult to see traffic or the Airport. Not being able to clearly Identify the airfield due to this haze; the aircraft was assigned to maintain 3000 ft until established on the approach and cleared ILS 34L. As we were setting up for the approach; I heard ATC talk to another flight regarding a EMB175 on final and if this aircraft was able to see us and the airport. I heard him acknowledge both but was too concerned with our approach to hear what he was assigned. Just outside the FAF was when we picked up our first descending RA with the Aircraft 800 ft above us. I notified ATC of this yet the controller did not tell us where the traffic was or what it was. We received a second RA as the controller was sending us over to the tower. I told him that we received a second RA but not sure if he acknowledged. We were visual at this time and the FO was descending on the Glideslope when the third descending RA occurred and I noticed that the Aircraft in question was 400 feet above us. I switched to tower and told the tower that we were visual for Runway 34L and to pass on to approach that we received 3 descending RAs. The FO was stable by 1000 ft and we landed without incident. While I realize that I may have fumbled my verbiage during the event due to the speed that everything occurred at; I am still shocked that the controller allowed a plane to fly over at such a distance. Especially since we were on an Instrument Approach due to the hazy conditions.
EMB175 Captain reported three descending RAs during an ILS approach to Runway 34L at SEA caused by an aircraft on approach to the parallel runway. The reporter believed that ATC was remiss in allowing the other aircraft to get so close.