Flight Crew Air Transport Pilot (ATP)
Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Procedure; Environment - Non Weather Related
We were on the GIBBZ2 arrival into IAD; between SIYOB [and] MIKEJ intersections. My hands were on the controls and aircraft was steady at 210 knots assigned and 4000 feet. The auto-pilot was on. We were already briefed and ready for the ILS 01C. All check lists were completed and we were waiting for a vector to final to intercept the ILS. This entire event was over maybe an 8-10 second period. We encountered wingtip vortices from a B737 that was 6 miles in front of us. I had my hands on the controls at the time it started. When all of a sudden the right wing was automatically forced down. I turned the yoke to the left and seemed to regain control of the aircraft. When we were back to level; the wing took another dip. At this point; I thought the autopilot was malfunctioning and quickly hit the trim switch to disengage it quickly. Then when the wing dipped again and with more force and a little further down. This time I had almost full left aileron in to keep the aircraft up right. We were never over 45 degrees at any point. I estimate it to be in the 30-35 degrees. But when it is uncommanded; it was startling; and I was having trouble maintaining 100% control of the aircraft. Then once I would gain control again; it would start again. So; it was an intermittent event; as it would start and stop. By the 3rd time the aircraft was bumped around. We had figured we were hitting a vortex off another aircraft. First officer (F/O) ask if we were following anybody. ATC replied with a B737; 6 miles in front of us. I told him to request an immediate climb; as vortices go down and out. F/O was on the ball and requested it; the controller responded with a climb to 6000 feet. I started an immediate climb and we seemed to be clear of it; after we had climbed maybe 75 feet. Then the controller revised the clearance to maintain 5000 feet. We leveled at 5000 feet and he then turned us east bound on a left base leg. The F/O had 2 or 3 direct transmissions with ATC with no delays or other aircraft talking. He reported the turbulence; asked about traffic; requested a climb; all in a few seconds and it seemed to work out very well. This was maybe a 10 second time period. But; it was very quick; very abrupt; then we were out of it and turning left to intercept and starting a descent back down to 3000 for the approach. I ask him to check on the passengers. They said they were ok; and we would explain once on the ground. Once on the ground; engines shut down. I jumped up to greet them and explain with a big apology for the turbulence. The passenger explained his wife was in the lav and that was a great thing as she was fearful of flying. I explained to them the vortices of airplanes. They were thankful for of our work in the process. At one point; he thought we might actually end up rolling it completely over. I assured him we were not even at the 45 degree mark; but I understand his position being in the back and having a view that would maybe make him think that. They seemed happy and satisfied with the flight and went on their [way]. I briefed [Company] of the incident as well and they noted it on their files too.
BAE-125-850XP Captain reported encountering wake turbulence in 6-mile trail of a B737 on approach to IAD.