ON VISUAL APCH MLG EXPERIENCED SEVERE WAKE TURBULENCE.

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ENRTE FROM SAN DIEGO TO LAX. LAX APCH CALLED TFC AT 12 O'CLOCK; RIGHT TO LEFT; WDB WBOUND FOR LNDG 25L. WE WERE TO MAINTAIN VISUAL SEP FROM THE WDB AND CONTINUE FOR A VISUAL APCH TO RWY 25R. OUR YAW DAMPER WAS MEL'D INOP; WHICH CAUSES THE ACFT TO WALLOW SOMEWHAT IN THE LNDG CONFIGN. PASSING APPROX 2200' MSL ON A 7 MI FINAL TO RWY 25R; F/O FLYING; THE ACFT SUDDENLY BEGAN AN ABRUPT ROLL TO THE LEFT AND THE NOSE PITCHED DOWN. FULL DEFLECTION OF THE YOKE TO THE RIGHT DID NOT ARREST THE LEFT ROLL AND FOR A MOMENT IT APPEARED THE ACFT WAS GOING TO ROLL OVER ON ITS BACK. SUDDENLY THE ACFT BEGAN TO RECOVER AS AILERONS REGAINED EFFECTIVENESS AND THE REST OF THE APCH WAS NORMAL UNTIL 200' MSL WHEN WAKE TURB WAS ENCOUNTERED ONCE AGAIN; HOWEVER NOT TO THE EXTREME AS BEFORE. WITH A FEW LAST SECOND CORRECTIONS; THE ACFT WAS LANDED NORMALLY. THIS IS THE SECOND ENCOUNTER WITH WAKE TURB I'VE ENCOUNTERED LNDG ON RWY 25R ASSOCIATED WITH A HVY IN THE PAST 6 MONTHS. THIS ONE WAS TOO CLOSE AND FRANKLY SCARED THE HELL OUT OF ALL ON BOARD. IT IS MY OBSERVATION; BASED ON THE WIND READOUT ON OUR FMC; THAT WINDS ALOFT IN THE VICINITY OF LAX ARE USUALLY FROM LEFT TO RIGHT WHEN LNDG ON THE 25 RWYS WHICH CARRY ANY WAKE TURB VORTICES OF HVY ACFT LNDG ON RWY 25L TO DRIFT OVER TO 25R. FURTHER; LAX APCH AND TWR SEEM TO HAVE LITTLE REGARD FOR WAKE TURB SEP OF ACFT; BOTH ON APCH AND DEP. IT IS MY RECOMMENDATION THAT DUE TO LCL CONDITIONS; HVY ACFT SHOULD BE LANDED ON RWY 25R AND SMALLER ACFT ON 25L SO AS TO MINIMIZE WAKE TURB ENCOUNTERS. IT IS JUST A MATTER OF TIME BEFORE LAX EXPERIENCED A WAKE TURB RELATED INCIDENT.