Narrative:

At cruise and captain had just received an ATC report of smooth rides ahead. The seatbelt sign was turned off and he gave his announcement. 5-8 mins later; I noticed a large acceleration in the airspeed trend arrow and then the aircraft began to pitch up. I disconnected the autoplt and tried to keep the aircraft from exceeding vmax. The aircraft then began to roll to the right and with full left stick in; I was unable to prevent the aircraft from rolling farther. I believe the aircraft achieved 70-80 degrees right wing down and the aircraft defaulted into alternate law. The captain and I could hear a 'thunk' in back and we believed it was the flight attendant hitting the ground. I was able to get the aircraft somewhat level and then it rolled again which required full left stick and it also reached a high angle of bank. At this point; the captain was talking to ATC and we were descending through FL355 where I was able to control the aircraft once again. At least 2 injuries were serious enough that the customers required hospitalization. We returned to ZZZ avoiding the area that we just flew through and landed uneventfully. We had 2 electrical failures en route and both reset. I assume it was from the upset attitude that we got into. On the ground; maintenance commented that the #2 engine had a compressor stall. We had no indications from the cockpit of that happening. We called the appropriate personnel after the event and were thanked by numerous customers. I'm sure their perspective of the event was by far greater than mine.

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Original NASA ASRS Text

Title: A320 ENCOUNTERED SEVERE TURB CAUSING MOMENTARY LOSS OF ACFT CONTROL. FLT RETURNED TO DEP ARPT DUE TO PAX INJURIES.

Narrative: AT CRUISE AND CAPT HAD JUST RECEIVED AN ATC RPT OF SMOOTH RIDES AHEAD. THE SEATBELT SIGN WAS TURNED OFF AND HE GAVE HIS ANNOUNCEMENT. 5-8 MINS LATER; I NOTICED A LARGE ACCELERATION IN THE AIRSPD TREND ARROW AND THEN THE ACFT BEGAN TO PITCH UP. I DISCONNECTED THE AUTOPLT AND TRIED TO KEEP THE ACFT FROM EXCEEDING VMAX. THE ACFT THEN BEGAN TO ROLL TO THE R AND WITH FULL L STICK IN; I WAS UNABLE TO PREVENT THE ACFT FROM ROLLING FARTHER. I BELIEVE THE ACFT ACHIEVED 70-80 DEGS R WING DOWN AND THE ACFT DEFAULTED INTO ALTERNATE LAW. THE CAPT AND I COULD HEAR A 'THUNK' IN BACK AND WE BELIEVED IT WAS THE FLT ATTENDANT HITTING THE GND. I WAS ABLE TO GET THE ACFT SOMEWHAT LEVEL AND THEN IT ROLLED AGAIN WHICH REQUIRED FULL L STICK AND IT ALSO REACHED A HIGH ANGLE OF BANK. AT THIS POINT; THE CAPT WAS TALKING TO ATC AND WE WERE DSNDING THROUGH FL355 WHERE I WAS ABLE TO CTL THE ACFT ONCE AGAIN. AT LEAST 2 INJURIES WERE SERIOUS ENOUGH THAT THE CUSTOMERS REQUIRED HOSPITALIZATION. WE RETURNED TO ZZZ AVOIDING THE AREA THAT WE JUST FLEW THROUGH AND LANDED UNEVENTFULLY. WE HAD 2 ELECTRICAL FAILURES ENRTE AND BOTH RESET. I ASSUME IT WAS FROM THE UPSET ATTITUDE THAT WE GOT INTO. ON THE GND; MAINT COMMENTED THAT THE #2 ENG HAD A COMPRESSOR STALL. WE HAD NO INDICATIONS FROM THE COCKPIT OF THAT HAPPENING. WE CALLED THE APPROPRIATE PERSONNEL AFTER THE EVENT AND WERE THANKED BY NUMEROUS CUSTOMERS. I'M SURE THEIR PERSPECTIVE OF THE EVENT WAS BY FAR GREATER THAN MINE.

Data retrieved from NASA's ASRS site as of May 2009 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.