B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 220; Flight Crew Type 21000
Communication Breakdown
ATC Issue All Types; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; General Declared Emergency; General Physical Injury / Incapacitation
Weather
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.
Several aircraft had reported turbulence up to moderate in the descent; most reporting improvements out of FL210. No precipitation was depicted on the scope. I reported this to the controller at sector 12 and asked that she not assign high speeds to the arrivals. Pireps were also entered into ERIDS and the supervisor notified of each report.When the B737 checked on; I reported moderate turbulence in the descent reportedly improving below FL210 and cleared them to descend to FL200. They read back the clearance and began the descent. A moment later they reported that they were returning to FL240 due to the turbulence to reduce speed. They subsequently climbed to FL241 for at least one hit. One of the pilots stated that they had encountered 'let's call it borderline severe'. I cleared the aircraft to...15000 and gave them speed their discretion and the aircraft began descending.I reported the turbulence to the supervisor and the A side entered the pirep. When I returned my attention to the scope; I noted that the 737 had deviated north of course. They had descended to approximately FL205 and requested lower. I again cleared them to cross JAYBO at 15000; then amended the clearance to cross HEDGE at 15000 and direct HEDGE. At this point the pilots reported that it was severe turbulence they encountered and that there were passenger injuries. I reported this to the supervisor and asked the pilots for any more information they had. The pilots did not give any further information before the next sector requested communications with them and I shipped them.One more aircraft flew through the affected area before all arrivals were rerouted and did not report either moderate or severe turbulence.
Minor to moderate injuries were reported by flight attendants and a passenger when their B737 encountered 'severe' turbulence during descent for landing.