B737-300 ENCOUNTERED WAKE TURB FROM A PRECEDING A300 IN ZLA AIRSPACE. THE B737-300 EVALUATES IT AS A SEVERE OCCURRENCE. NO INJURIES OR DAMAGE OCCURRED.

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AT CRUISE; FL330; AUTOPLT ENGAGED; ACFT BEGAN TO BUFFET. CAPT WAS PF. HE IMMEDIATELY PUT HIS HANDS ON THE CTLS. SUDDENLY; WITHOUT WARNING; ACFT ENCOUNTERED SEVERE TURB AND BEGAN TO QUICKLY ROLL L. CAPT DISENGAGED AUTOPLT AND BEGAN TO APPLY OPPOSITE CTL (TO R). ROLL L INCREASED; TURB INCREASED. CAPT STEADILY INCREASED (TO R) OPPOSITE CTL TO NO AVAIL. ACFT CONTINUED TO ROLL L. CAPT RECOGNIZED THAT HE WOULD QUICKLY RUN OUT OF OPPOSITE CTL AND BEGAN A RAPID DSCNT. I IMMEDIATELY NOTIFIED ATC OF OUR DSCNT AND WHY (AT FL328). AFTER WE STABILIZED; AROUND FL326; WE WERE CLRED TO FL290 AND CONTINUED OUR DSCNT. CONFERRING WITH ATC; WE FOUND THAT A HVY A300 WAS 10 MI AHEAD OF US AT FL330. WE THINK WE ENCOUNTERED THE A300 WAKE. NO OTHER ACFT IN THE AREA RPTED SEVERE TURB. AFTER SEVERAL MINS; WE WERE CLRED BACK TO FL330; ON A COURSE DIVERGING THE A300'S. FLT CONTINUED AND WAS COMPLETED WITH NO FURTHER INCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN THE WAKE TURB CALLBACK STUDY. RPTR STATED THE SUDDENNESS OF THE EVENT IS WHAT STARTLED THEM. ACFT WENT UP 200 FT AND ROLLED 45 DEGS L EVEN THOUGH FULL OPPOSITE AILERON WAS APPLIED. ACFT THEN DSNDED ABOUT 800 FT FROM THERE. CAPT LET IT DSND HOPING TO GET OUT OF WHATEVER WAKE THEY WERE IN. AFTER REGAINING CTL OF THE ACFT; THE FLC THEN REQUESTED LOWER ALT; AND A SHORT VECTOR TO THE SIDE OF THE AIRWAY. THEY ALSO SLOWED DOWN. AFTER THE SEPARATION INCREASED FROM THE A300; THE FLC CLBED BACK TO FLT PLAN CRUISE ALT AND THE FLT WAS COMPLETED WITH NO FURTHER TURBULENT EVENTS. SUPPLEMENTAL INFO FROM ACN 417172: SHORTLY AFTER LEVELOFF AT FL330; IN LONG RANGE CRUISE; AUTOPLT ENGAGED; ACFT BEGAN TO SHUDDER. I IMMEDIATELY REDUCED PWR AS IT FELT LIKE THE ONSET OF MACH BUFFET. AS THE BUFFETING INTENSIFIED; THE ACFT BEGAN TO ROLL L DESPITE THE AUTOPLT EFFORT TO MAINTAIN STRAIGHT AND LEVEL FLT. AS THE ROLL TO THE L INCREASED; I DISCONNECTED THE AUTOPLT; LOWERED THE NOSE AND ROLLED THE ACFT BACK TO WINGS LEVEL. WE IMMEDIATELY NOTIFIED ZLA THAT WE WERE DSNDING; HAD ENCOUNTERED EXTREME TURB; AND REQUESTED CLRNC TO FL290. AFTER DSNDING 400 FT; THE TURB SUBSIDED. WE ASKED ATC IF WE WERE FOLLOWING A HVY ACFT. WE WERE INFORMED THAT WE WERE 10 MI IN TRAIL OF AN AIRBUS 300. AN OFF COURSE VECTOR WAS ASSIGNED AND WE EVENTUALLY RETURNED TO FL330. FLT CONTINUED UNEVENTFULLY TO OUR DEST.