Date: 201910
Local time of day: 1801-2400
Location: ATL.Airport, GA
Flight conditions: VMC
Light: Dusk
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ATL
ATC / advisory: TRACON A80
Second aircraft: B757 Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness
Second reporter function: Pilot Flying; First Officer
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Procedure
Primary problem: Environment - Non Weather Related

Narrative: I was the pilot monitoring as we were on the ONDRE1 arrival for RWY 8L in ATL. Just passing ONDRE we were assigned 12;000' with a speed of 210kts. As we continued on the arrival we were given other descents until were in the vicinity of TRAPE at the assigned altitude of 5;000' with a speed of 180kts. About this time the plane started making an uncommanded bank to the right. The First Officer disengaged the autopilot and began making left aileron inputs to counteract the roll. At this point we realized we were suffering the effects of wake turbulence. At one point we had full left aileron input and the aircraft was continuing a roll right. During this time we lost approximately 200' altitude and while our heading did vary we remained on our correct course. When the situation stabilized we returned to 5000' and reengaged the autopilot. The first opportunity to advise ATC of the situation due to radio traffic was when they vectored us a heading of 150 and 4000' and cleared us for the visual approach. ATC then advised us to slow to 170kts for separation with a 757 we were [within] 5 miles of. As we began the [speed reduction] we encountered similar wake turbulence again and once again the First Officer disengaged the autopilot and corrected the wake turbulence effects. As we captured the localizer I broke the sterile cockpit to speak to the flight attendants to check their status. As we switched to Tower we were asked to accelerate to 180kts until SCHEL and to make first high speed turnoff due to trailing traffic with a 30kt overtake. I advised Tower that we had just suffered wake turbulence from the 757 that was approximately 4 miles ahead of us and that while we would attempt to comply we needed to keep our separation and land beyond their touchdown point. Final approach and landing occurred without further incident and we exited at 2nd high speed exit B11. Suffered 2 occurrences of wake turbulence while trailing a 757 at slow speeds for an extended time while on arrival. Sterile cockpit violation to determine if any passenger or flight attendants were injured. Need for situational awareness and ATC spacing.


Second narrative: [Report narrative contained no additional information.]


Synopsis: CRJ-900 flight crew reported encountering wake turbulence 4 miles in trail of a B757 on approach to ATL.