B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 160; Flight Crew Type 4500
Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Flight Crew Took Evasive Action
Human Factors; Procedure
While on right downwind for Runway 10R 10 miles west of PDX ATC reported traffic ahead climbing and descending. The Controller stated that he had lost radar contact on the aircraft. While searching for traffic we saw what looked like a strange cloud on a clear day. It turned out to be smoke from a dark colored aerobatic aircraft doing vertical maneuvers. The aircraft came very close to us and we received a climb RA. The Captain complied with the RA and turned to the left to avoid collision. We left our assigned altitude of 4000 and climbed to about 4400 ft. We turned the aircraft 20 to 45 degrees to the south off our assigned heading. ATC apologized on frequency and we landed 10R.There is a serious safety threat having IFR aircraft vectored in that area if aerobatic aircraft will be practicing there. In the future I will be more proactive and ask for a turn away from unknown aircraft.
B737 First Officer reported taking evasive action on arrival into PDX in response to an RA that was triggered by an aerobatic aircraft maneuvering near them.