Narrative:

At FL390 eastbound opposite/off altitude for direction of flight for hope of smoother air, we were flying in/around cirriform clouds and encountered severe air turbulence. We had avoided known radar returns by diverting north of assigned course by approximately 15 NM. Once clear we received clearance direct jst. This gave us a direct line to the south of ewc. We had flown an estimated 10 mins and were printing no returns on the x- band radar. The air was smooth and center had no reports of chop or greater in the area. The seat belt sign was turned off and a recommendation announcement made. Just south of ewc and slightly west, the aircraft pitched up violently as if we encountered a strong air current and the autoplt disengaged. I grabbed the sidestick and correct the pitch up reference the ADI. I estimate 200 ft altitude gain and 100 ft loss during the 4-5 second duration. We called for an emergency descent out of severe tbc with center and descended to FL350. Once stable I sent the first officer to check the crew. Several passenger received lacerations and several passenger and crew reported lower back and knee problems. By the time we had a good estimate of the nature of our injuries onboard, phl was as good a landing field as any, and we were planned into that field. There were no injuries reported that would required immediate emergency service. We declared an emergency and landed downwind on runway 09R. No problems were noted in the cruise, descent or landing phase. Callback conversation with reporter revealed the following: the flight crew were flying an A-320 aircraft at FL390 around areas of thunderstorms, but were in the clear when this event occurred. The onset of the severe turbulence was abrupt. Suddenly the aircraft pitched up about 4 degrees. The captain (flying) corrected by applying forward pressure on the sidestick. Then the aircraft pitched down approximately 10 degrees. During these maneuvers the aircraft climbed to FL392 and descended to FL389. The whole event lasted about 4 seconds and the peak load was approximately 2.5 G's positive according to the DFDR as read by the flight safety department. The seat belt sign was off at the time because the aircraft was in the clear and there were no reports of turbulence in this area. A number of passenger and flight attendants were injured, but not critically. The flight crew reported that they worked well together and that CRM training was very beneficial to that end. The first officer went back into the cabin after the event to assist the injured and assess the situation. He then reported to the captain and to phl operations his findings. The captain admitted that, in an effort to get on top, he may have been above the aircraft's optimum altitude when he encountered the turbulence. This certainly could have a bearing on the severity of the reaction. He further reported that, although he recovered control of the aircraft, it 'felt sluggish' during the recovery phase.

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Original NASA ASRS Text

Title: CLR AIR TURB -- THE ACR HIT SEVERE TURB IN THE VICINITY OF A TSTM AREA AND A NUMBER OF PAX AND FLT ATTENDANTS WERE INJURED.

Narrative: AT FL390 EBOUND OPPOSITE/OFF ALT FOR DIRECTION OF FLT FOR HOPE OF SMOOTHER AIR, WE WERE FLYING IN/AROUND CIRRIFORM CLOUDS AND ENCOUNTERED SEVERE AIR TURB. WE HAD AVOIDED KNOWN RADAR RETURNS BY DIVERTING N OF ASSIGNED COURSE BY APPROX 15 NM. ONCE CLR WE RECEIVED CLRNC DIRECT JST. THIS GAVE US A DIRECT LINE TO THE S OF EWC. WE HAD FLOWN AN ESTIMATED 10 MINS AND WERE PRINTING NO RETURNS ON THE X- BAND RADAR. THE AIR WAS SMOOTH AND CTR HAD NO RPTS OF CHOP OR GREATER IN THE AREA. THE SEAT BELT SIGN WAS TURNED OFF AND A RECOMMENDATION ANNOUNCEMENT MADE. JUST S OF EWC AND SLIGHTLY W, THE ACFT PITCHED UP VIOLENTLY AS IF WE ENCOUNTERED A STRONG AIR CURRENT AND THE AUTOPLT DISENGAGED. I GRABBED THE SIDESTICK AND CORRECT THE PITCH UP REF THE ADI. I ESTIMATE 200 FT ALT GAIN AND 100 FT LOSS DURING THE 4-5 SECOND DURATION. WE CALLED FOR AN EMER DSCNT OUT OF SEVERE TBC WITH CTR AND DSNDED TO FL350. ONCE STABLE I SENT THE FO TO CHK THE CREW. SEVERAL PAX RECEIVED LACERATIONS AND SEVERAL PAX AND CREW RPTED LOWER BACK AND KNEE PROBS. BY THE TIME WE HAD A GOOD ESTIMATE OF THE NATURE OF OUR INJURIES ONBOARD, PHL WAS AS GOOD A LNDG FIELD AS ANY, AND WE WERE PLANNED INTO THAT FIELD. THERE WERE NO INJURIES RPTED THAT WOULD REQUIRED IMMEDIATE EMER SVC. WE DECLARED AN EMER AND LANDED DOWNWIND ON RWY 09R. NO PROBS WERE NOTED IN THE CRUISE, DSCNT OR LNDG PHASE. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE FLC WERE FLYING AN A-320 ACFT AT FL390 AROUND AREAS OF TSTMS, BUT WERE IN THE CLR WHEN THIS EVENT OCCURRED. THE ONSET OF THE SEVERE TURB WAS ABRUPT. SUDDENLY THE ACFT PITCHED UP ABOUT 4 DEGS. THE CAPT (FLYING) CORRECTED BY APPLYING FORWARD PRESSURE ON THE SIDESTICK. THEN THE ACFT PITCHED DOWN APPROX 10 DEGS. DURING THESE MANEUVERS THE ACFT CLBED TO FL392 AND DSNDED TO FL389. THE WHOLE EVENT LASTED ABOUT 4 SECONDS AND THE PEAK LOAD WAS APPROX 2.5 G'S POSITIVE ACCORDING TO THE DFDR AS READ BY THE FLT SAFETY DEPT. THE SEAT BELT SIGN WAS OFF AT THE TIME BECAUSE THE ACFT WAS IN THE CLR AND THERE WERE NO RPTS OF TURB IN THIS AREA. A NUMBER OF PAX AND FLT ATTENDANTS WERE INJURED, BUT NOT CRITICALLY. THE FLC RPTED THAT THEY WORKED WELL TOGETHER AND THAT CRM TRAINING WAS VERY BENEFICIAL TO THAT END. THE FO WENT BACK INTO THE CABIN AFTER THE EVENT TO ASSIST THE INJURED AND ASSESS THE SIT. HE THEN RPTED TO THE CAPT AND TO PHL OPS HIS FINDINGS. THE CAPT ADMITTED THAT, IN AN EFFORT TO GET ON TOP, HE MAY HAVE BEEN ABOVE THE ACFT'S OPTIMUM ALT WHEN HE ENCOUNTERED THE TURB. THIS CERTAINLY COULD HAVE A BEARING ON THE SEVERITY OF THE REACTION. HE FURTHER RPTED THAT, ALTHOUGH HE RECOVERED CTL OF THE ACFT, IT 'FELT SLUGGISH' DURING THE RECOVERY PHASE.

Data retrieved from NASA's ASRS site as of July 2007 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.