Narrative:

As we descended through 24;300 ft for FL200; center stated; 'there is moderate turbulence in your 12 o'clock position from 240 down to 210.' I turned the seatbelt sign on immediately and at the same time stated; 'flight attendants be seated immediately. We need everyone seated now.' the word immediately had just left my mouth when we hit severe clear air turbulence. Our altitude was 240 and it was less than 10 seconds from warning until encounter. We climbed back up to 24;300 ft with no improvement; however; that allowed our airspeed to decrease from mach .72 (280 knots) down to .67 mach (245 knots). At the lower speed; we continued the descent to FL200. The severe intensity continued down to FL200 with no relief. We requested to keep descending and found relief below FL200. I checked on the flight attendants and was told of possible passenger and flight attendant injury. We told ATC about the severe turbulence encounter seconds after it started. We soon after told ATC that we had 'possible flight attendant and passenger injuries.' we were asked by ATC if we were declaring an emergency. I said; 'yes; we are; due to precaution after severe turbulence and possible injuries onboard.' ATC asked if we needed assistance for aircraft or passengers. I responded; 'aircraft controls and systems all appear normal; so no aircraft assistance needed on ground; however; we do need paramedics for possible injuries in the cabin.' on final approach to runway 27R; in IMC; snow; ice and weather at minimums; the controller advised us that braking reported 'nil' by aircraft in front of us. We executed a go-around and shot the approach for 27L with fair to poor braking. Very slow taxi to gate due to ice on taxiways. Passengers and flight attendant were bumped around pretty badly in the cabin; however; no passengers were injured other than one man who hit the floor a couple times in aft galley. After the flight; he told me he was okay and felt good. Then he added; but I don't know how I will feel tomorrow. One flight attendant was cleared by paramedics; but wanted to go to hospital for x-rays of her arm. All tests and x-rays normal and she was released with no injuries. The passengers and crew were extremely lucky with this outcome. The flight attendants did an excellent job.as far as flight deviations; our airspeed was plus and minus 60 knots and our altitude was plus and minus 300 ft to 400 ft. We also deviated off course slightly left due to coming off LNAV/VNAV. This turbulence occurred in beautiful weather with a cloud layer below us about 10;000 ft or more.the biggest problem in this entire event; in my opinion; is the late heads up from the controller about moderate turbulence. By receiving this alert at the time of the encounter; due to being at the exact altitude being warned about; no one onboard had any time to prepare. That was information of extreme importance.

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Original NASA ASRS Text

Title: Minor to moderate injuries were reported by flight attendants and a passenger when their B737 encountered 'severe' turbulence during descent for landing.

Narrative: As we descended through 24;300 FT for FL200; Center stated; 'There is moderate turbulence in your 12 o'clock position from 240 down to 210.' I turned the seatbelt sign on immediately and at the same time stated; 'Flight Attendants be seated immediately. We need everyone seated now.' The word immediately had just left my mouth when we hit severe clear air turbulence. Our altitude was 240 and it was less than 10 seconds from warning until encounter. We climbed back up to 24;300 FT with no improvement; however; that allowed our airspeed to decrease from Mach .72 (280 knots) down to .67 Mach (245 knots). At the lower speed; we continued the descent to FL200. The severe intensity continued down to FL200 with no relief. We requested to keep descending and found relief below FL200. I checked on the Flight Attendants and was told of possible Passenger and Flight Attendant injury. We told ATC about the severe turbulence encounter seconds after it started. We soon after told ATC that we had 'possible Flight Attendant and Passenger injuries.' We were asked by ATC if we were declaring an emergency. I said; 'Yes; we are; due to precaution after severe turbulence and possible injuries onboard.' ATC asked if we needed assistance for aircraft or passengers. I responded; 'Aircraft controls and systems all appear normal; so no aircraft assistance needed on ground; however; we do need paramedics for possible injuries in the cabin.' On final approach to Runway 27R; in IMC; snow; ice and weather at minimums; the Controller advised us that braking reported 'NIL' by aircraft in front of us. We executed a go-around and shot the approach for 27L with fair to poor braking. Very slow taxi to gate due to ice on taxiways. Passengers and Flight Attendant were bumped around pretty badly in the cabin; however; no Passengers were injured other than one man who hit the floor a couple times in aft galley. After the flight; he told me he was okay and felt good. Then he added; but I don't know how I will feel tomorrow. One Flight Attendant was cleared by Paramedics; but wanted to go to hospital for x-rays of her arm. All tests and x-rays normal and she was released with no injuries. The Passengers and Crew were extremely lucky with this outcome. The Flight Attendants did an excellent job.As far as flight deviations; our airspeed was plus and minus 60 knots and our altitude was plus and minus 300 FT to 400 FT. We also deviated off course slightly left due to coming off LNAV/VNAV. This turbulence occurred in beautiful weather with a cloud layer below us about 10;000 FT or more.The biggest problem in this entire event; in my opinion; is the late heads up from the Controller about moderate turbulence. By receiving this alert at the time of the encounter; due to being at the exact altitude being warned about; no one onboard had any time to prepare. That was information of extreme importance.

Data retrieved from NASA's ASRS site 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.