Date: 201605
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Second aircraft: B757 Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Procedure; Environment - Non Weather Related; Human Factors
Primary problem: Ambiguous

Narrative: My FO and I set up for departure as normal; with a dry runway at approximately 49;000 lbs with a temperature outside of approximately 18 degrees Celsius. Our flap configuration was for flaps 8. I don't recall the winds but I believe them to be mostly calm; not requiring crosswind correction. We were close to full; and tankering fuel to the point where we landed with about 6000 lbs remaining. While we were awaiting takeoff; a group of aircraft began to collect in line on [a nearby] taxiway. These aircraft had previously landed and were awaiting taxi to their gates. They were holding short of runway while other aircraft departed. I will have to guess that there were approximately 4; maybe 5 aircraft in line to cross; while all of them were of comparable size to A321s or B757s. We completed our pre-departure checklists as normal and accepted a 'line up and wait' clearance. We were advised that traffic would be crossing downfield. We complied. More than a mile down the runway from us; traffic downfield was then cleared to cross. I never did actually see where the traffic lined up after crossing on the way to their gates but at some point after crossing; the first aircraft stopped. I am not sure; but I believe they all joined the taxiway and became blocked from continuing. Because of the size of the aircraft and the number of the aircraft; the last aircraft was only able to clear the runway; but not make the turn onto taxiway. I saw the aircraft cross; but did not notice anything besides that at the time. However; later my FO told me that he did notice that the aircraft; which was a B757; did not turn left after crossing and remained relatively close to the runway; though he appeared to be clear of the hold short lines. While holding the brakes; the FO put the power above 70 percent; then released the brakes and said 'set thrust.' The takeoff roll happened normally and while I watched outside as well as inside during the takeoff roll; I did not look as far down as the B757. However; once again; my FO did notice that aircraft and later told me that he anticipated this problem. My eyes were inside our aircraft as I called 'V1; rotate.' As the FO began pulling the yoke back; the B757 on taxiway powered up for the purpose of taxiing and we caught his jet blast right at rotation. Our rotation speed was approximately 142 knots. The FO; having been aware that this could happen; reacted immediately with a quick and hard left aileron. He did not use the rudder. After the FO's hard correction; we still banked to the right. I believe his correction to be approximately 40% of the aileron travel for a half second before immediately returning to center. The aircraft was physically moved sideways; off of the centerline by a couple of feet as we rotated. Immediately after the jet blast hit; I looked up; back and left to see what caused the aircraft to move the way it did; thinking we ran over something. It was at that time that I saw the B757 moving to its left onto taxiway Kilo. The FO and I confirmed verbally that it was the jet blast shortly after rotation and we continued on with our normal callouts and takeoff profile. Upon being assigned to departure frequency; I informed the tower controller that we had received jet blast at rotation from the taxiing traffic. The tower acknowledged my communication and we continued on with our day without further incident.Though I'm unsure of what the result would have been without a control wheel reaction from the FO; I do believe the anticipation and quick reaction of the FO potentially avoided a wing strike in this situation due to the immediate bank of the aircraft; even after the aileron correction. I would guess that there was about a one degree bank after aileron correction; maybe more. The left wing definitely came upwards as if we ran over something. I am not sure if the nose wheel was still on the ground or not at the time. I also am appreciative of the FO's experience level; professionalism and expertise throughout the ordeal because I did not anticipate this problem. I specifically did not notice that the B757 had not made the turn after crossing. As it happened; the only preventative measure to this being a bigger problem than it was; was the experience and anticipation; as well as the quick reaction by the FO. I will certainly be better aware of my surroundings about taxiing aircraft near the runway and have a better situational awareness of this issue in the future.




Synopsis: CRJ-200 Captain reported that while on the takeoff roll their aircraft was affected by jet blast from a taxiing B757.