Date: 201206
Local time of day: 1801-2400
Location: ATL.Airport, GA
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: Descent
Airspace: Class B ATL
ATC / advisory: TRACON A80
Second aircraft: B757 Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: Moderate wake turbulence encounter passing 7;500 FT at 180 KIAS flaps 8 degrees on downwind to 8L in ATL. Light to moderate chop followed by an abrupt roll into 45 degrees of left bank. Captain; pilot flying; disconnected autopilot and smoothly recovered to wings level. Flight Attendant reported her right shoulder impacted the service door. No aircraft damage or flight attendant injury was evident. All passengers were securely belted in. During debrief Flight Attendant said that she had one foot off the floor stowing the trash can when the incident occurred. She did not exactly fall down; it was almost as if the airplane rotated around her to the point of the service door striking her shoulder and then smoothly rolled back to wings level. Passengers seemed more amused than alarmed at our mutual show of agility.ATC did not notify us that we were following a B757 on downwind. This was probably due to frequency congestion; however we could see him and thought he probably was a B757. As a precaution I attempted to remain above his descent path (apparently unsuccessfully) and kept the engines spooled to a minimum of 45% N1. The Flight Attendant could have been injured but fortunately reported no significant injuries. The greatest threat was the temptation to correct too abruptly and inadvertently perform a control reversal causing structural failure. Another threat on the CRJ-200 is engine flameout due to disrupted airflow associated with the turbulence. That is why many captains who encounter moderate wake turbulence have trained themselves to place one hand on the yoke and the other hand turns on the IGNITION CONT. Another threat is the possibility of stall due to vertical gust loads imposed by the wake turbulence. For this reason I keep my engines spooled to 45% N1 minimum when following a heavy. Also; during recovery my technique is to unload slightly and add at least a little power to increase airspeed and improve stall margins. These techniques worked well during this event. If you like the techniques described above include them in training and publications. Another thing you might want to add to SIM training if possible is to get a wake turbulence encounter that has several cycles of roll and yaw to see if the pilot will perform a control reversal; then debrief it if he does. Having a caution in the Operating Manual to avoid rapid and large alternating control inputs is helpful but giving pilots a chance to experience it in the SIM would be better as long as the SIM provides a realistic simulation.




Synopsis: A CRJ-200 Captain reported encountering significant wake turbulence following a B757 into ATL.