Flight Crew Air Transport Pilot (ATP)
Confusion
Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Regained Aircraft Control
Weather
On the RNAV Arrival into Chicago; we encountered severe turbulence in the descent. We were in the descent at approximately 14000ft over PAITN when we started to feel turbulence. The aircraft violently rolled into a 40 degree right bank which caused the autopilot to disengage. The Captain took controls and leveled the wings. As he got the LNAV set back on the turbulence started again and the aircraft violently rolled into a 40 degree left bank. The Captain continued to hand fly the plane while I contacted ATC. I informed them of the severe turbulence and queried if we were following a heavy aircraft since we saw nothing visually or on TCAS. ATC allowed us to offset to the right; so I set up the autopilot in HDG mode and 30 degree right turn off course. ATC responded that we were following a 737 which was 2000ft below us approximately 12 miles ahead. After flying on the heading for about 2 minutes; I asked ATC for instructions to rejoin the arrival. We never saw any aircraft pass overhead nor were told about any traffic passing overhead. Once the plane was under control; the Captain rang the Fight Attendant (FA) to check on her and passengers. No injuries were reported. ATC queried about injuries and/or aircraft damage to which I replied there were none; but the aircraft would be inspected on the ground. We landed without incident. The Captain wrote up the severe turbulence encounter and had maintenance inspect the aircraft. No deformations were found on my walk around. Maintenance found the Captain side piano hinge rod broken through the safety wire. It was unclear if it was caused by the turbulence. Maintenance re secured the piano hinge. The Captain took himself off the trip to get his wrist looked at since he twisted it during the turbulence encounter.
Embraer First Officer reported encountering severe turbulence while on descent into ORD.