Date: 201810
Local time of day: 0001-0600
Location: ZTL.ARTCC, GA
Flight conditions: VMC
Light: Night
Aircraft: Regional Jet 900 (CRJ900)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZTL
ATC / advisory: Center ZTL
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Anomaly: Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Procedure
Primary problem: Procedure

Narrative: First Officer (FO) Pilot Flying (PF); I was pilot monitoring. During cruise climb Atlanta Center assigned us 270 KTS for spacing; which we complied with. While at FL210 I noticed the rear strobe of traffic at 12 o'clock so I checked the TCAS display on my MFD. The traffic was 1;000 FT above and 5 NM ahead. I inquired about our separation from the traffic with Center and they told me the separation was good and they assigned us descend via the FILPZ landing north. Early in the descent; around FL200 we felt the initial wake turbulence. I had my headset half off; talking to a [cockpit jumpseater]; but the initial bump of wake turbulence was enough for me to put my headset completely on and roll my seat forward. The second bout occurred approximately 30 seconds later - the aircraft rolled left and right; clearly not responding to the autopilot's inputs - after a few seconds it rolled hard to the left and the autopilot disconnected. I called out that I was taking controls; pitched the nose down to unload the wings and gain some roll control authority and gave it full scale deflections right and left to keep the wings level. Pitching down seemed to get us under the wake and I regained control. Once the aircraft was back under control I called approach and told them we had hit severe wake turbulence and we needed a heading and altitude to get away from it. They complied; giving us a left turn to 080 and a descent to 12;000. I called for the autopilot on and gave the controls and radios back to the FO/PF while I called the flight attendants to make sure they were okay. They said everyone was seated when we hit it so no one was hurt; but that it was the scariest turbulence they'd ever encountered. When I called approach to report no injuries they informed me that it was an A321 that we were following. This is the second time I've had an autopilot disconnect from A321 turbulence. I just saw an article about a 737 hitting wake turbulence from an A321 that caused enough of a stir in the cabin for an article to be written about it. I've had the autopilot disconnect from wake off A321s that rolled the aircraft violently. I think ATC should be made aware that A321s [generate] unusually bad wake turbulence and to give us a little extra room when we're behind them.




Synopsis: CRJ-900 Captain reported encountering 'severe' wake turbulence in trail of an A321 descending through FL210 for a CLT arrival.