Narrative:

This report addresses an aircraft encounter with severe turbulence. The event occurred in clear air during descent into ord. Recent convective activity and a strong frontal gradient were in the area during the descent. There were no reported injuries as a result of the incident. The crew was briefed on the weather and ride situation into ord. We were familiar with each other as we had flown together for 3 legs over two days; and had left ord the previous evening during convective activity. The crew was prepared and anticipated turbulence; but severe turbulence was not forecast or reported recently. We had a lengthy discussion about spring weather and preparedness; especially since we had a rough ride leaving ord the night before. I believe the briefing; preparation and awareness of the crew was instrumental in avoiding injury during this incident. The aircraft was flying to jvl VOR to intercept the BULLZ1 arrival and beginning the initial descent. There was no recent report of turbulence in the area; though we were wondering when it would begin. We saw clouds in front of us while in the descent through FL260. This is when we anticipated the turbulence would begin. As [we] continued our descent; the airspeed began to increase inside the limits of the managed descent bracket; approaching mmo/vmo. The autopilot was disengaged to prevent an overspeed; and the descent rate was arrested from the 6000 FPM range. The aircraft began to slow; and we quickly discussed getting the flight attendants down when the first wave of turbulence hit. The plane encountered moderate turbulence for about 15 seconds; and the seatbelt sign was turned on and the flight attendants were told to be seated. After a break of about 30 seconds; we began to encounter severe turbulence passing FL220 and continuing down to 17;000 ft. The autopilot; which had since been selected back on; was turned off again; as the slow response seemed to make things worse. The aircraft was marginally controllable at times with vvi variations between +2500 to -6000 FPM; +/- 20 to 30 KTS airspeed variation; and at one point had idle thrust; full speed brakes and a +1000 FPM vvi. We had been attempting to descend through the turbulence and slow to the taps (turbulence auto-PIREP system) airspeed during that event. There was un-commanded roll and pitch which was violent; but within normal aircraft pitch and roll limits. The aircraft left the turbulence at about 16;000 ft. We noticed that the wind vector had shifted from 250/115 at FL260 to 170/65 at 17;000. At the end of the incident; the lead flight attendant was called to see if anyone was injured. She had told us no one was hurt and that the two of the flight attendants were in their jumpseats and one stayed on the floor. The flight attendants then prepared the cabin for landing; and after a short lull; the remainder of the flight concluded in light to moderate chop. During the incident; chicago center controllers seemed to be in disbelief as to the severity of the turbulence. They continued to give instructions and crossing restrictions even after receiving information that our control of the aircraft was diminished due to the severe turbulence. They were reluctant to inform other aircraft of the severe turbulence. I was disappointed with the performance of the typically elite controllers in the chicago center. With two jumpseating pilots in the cockpit; everyone agreed this was unquestionably severe turbulence and for the majority; the worse clear air turbulence encountered. Chicago center seemed unresponsive in this situation; and though we can all get reluctant to use the phrase 'severe turbulence'; this doesn't appear to be a mis-characterization of the situation. We listened and it seemed that other aircraft followed us through the area. After landing; we taxied to the gate; informed maintenance; and conducted a crew debrief. Upset passengers had to wait 20 minutes for a jetway so theycould de-plane; and people were again asked if anyone was injured. No one indicated any injuries. Though this was an unfortunate and unexpected clear air turbulence encounter; the preparation and training of the crew played an important role in avoiding serious injury. We had expected some turbulence in the descent; but associated with the front and convective activity; not the clear air shearing that was encountered. Continued contact and updates from dispatch and especially chicago center could have helped to mitigate the circumstances even further. Nonetheless; for our situation; we are fortunate that the outcome was positive.

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Original NASA ASRS Text

Title: An A320 flight crew reported encountering severe turbulence on descent into ORD.

Narrative: This report addresses an aircraft encounter with severe turbulence. The event occurred in clear air during descent into ORD. Recent convective activity and a strong frontal gradient were in the area during the descent. There were no reported injuries as a result of the incident. The crew was briefed on the weather and ride situation into ORD. We were familiar with each other as we had flown together for 3 legs over two days; and had left ORD the previous evening during convective activity. The crew was prepared and anticipated turbulence; but severe turbulence was not forecast or reported recently. We had a lengthy discussion about spring weather and preparedness; especially since we had a rough ride leaving ORD the night before. I believe the briefing; preparation and awareness of the crew was instrumental in avoiding injury during this incident. The aircraft was flying to JVL VOR to intercept the BULLZ1 arrival and beginning the initial descent. There was no recent report of turbulence in the area; though we were wondering when it would begin. We saw clouds in front of us while in the descent through FL260. This is when we anticipated the turbulence would begin. As [we] continued our descent; the airspeed began to increase inside the limits of the managed descent bracket; approaching Mmo/Vmo. The autopilot was disengaged to prevent an overspeed; and the descent rate was arrested from the 6000 FPM range. The aircraft began to slow; and we quickly discussed getting the flight attendants down when the first wave of turbulence hit. The plane encountered moderate turbulence for about 15 seconds; and the seatbelt sign was turned on and the flight attendants were told to be seated. After a break of about 30 seconds; we began to encounter severe turbulence passing FL220 and continuing down to 17;000 FT. The autopilot; which had since been selected back on; was turned off again; as the slow response seemed to make things worse. The aircraft was marginally controllable at times with VVI variations between +2500 to -6000 FPM; +/- 20 to 30 KTS airspeed variation; and at one point had idle thrust; full speed brakes and a +1000 FPM VVI. We had been attempting to descend through the turbulence and slow to the TAPS (Turbulence Auto-PIREP System) airspeed during that event. There was un-commanded roll and pitch which was violent; but within normal aircraft pitch and roll limits. The aircraft left the turbulence at about 16;000 FT. We noticed that the wind vector had shifted from 250/115 at FL260 to 170/65 at 17;000. At the end of the incident; the Lead Flight Attendant was called to see if anyone was injured. She had told us no one was hurt and that the two of the flight attendants were in their jumpseats and one stayed on the floor. The flight attendants then prepared the cabin for landing; and after a short lull; the remainder of the flight concluded in light to moderate chop. During the incident; Chicago Center Controllers seemed to be in disbelief as to the severity of the turbulence. They continued to give instructions and crossing restrictions even after receiving information that our control of the aircraft was diminished due to the severe turbulence. They were reluctant to inform other aircraft of the severe turbulence. I was disappointed with the performance of the typically elite controllers in the Chicago Center. With two jumpseating pilots in the cockpit; everyone agreed this was unquestionably severe turbulence and for the majority; the worse clear air turbulence encountered. Chicago Center seemed unresponsive in this situation; and though we can all get reluctant to use the phrase 'severe turbulence'; this doesn't appear to be a mis-characterization of the situation. We listened and it seemed that other aircraft followed us through the area. After landing; we taxied to the gate; informed Maintenance; and conducted a crew debrief. Upset passengers had to wait 20 minutes for a jetway so theycould de-plane; and people were again asked if anyone was injured. No one indicated any injuries. Though this was an unfortunate and unexpected clear air turbulence encounter; the preparation and training of the crew played an important role in avoiding serious injury. We had expected some turbulence in the descent; but associated with the front and convective activity; not the clear air shearing that was encountered. Continued contact and updates from Dispatch and especially Chicago Center could have helped to mitigate the circumstances even further. Nonetheless; for our situation; we are fortunate that the outcome was positive.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.