WAKE TURB ENCOUNTER.

Narrative

WHILE BEING VECTORED IN-TRAIL FOR LAX; AN ACR 747-400 WAS VECTORED OVER TOP OF US AND DSNDED IN FRONT. SPACING WAS NEVER LESS THAN 8 MI. WE RECEIVED BUFFET AND ROLL FROM PREVIOUS ACFT THAT WAS STRONG ENOUGH AT ONE POINT TO INDUCE 45 DEG BANK AND DISCONNECT AUTOPLT. CORRECTIVE ACTION: REQUESTED SLOWER SPD AND MORE SPACING BEHIND ACFT. ATC REPEATEDLY STATED THAT PRECEDING ACFT WAS 8 MI AHEAD. CONTRIBUTING FACTORS: NEWER WING DESIGNS PRODUCE WAKE THAT IS POTENTIALLY HAZARDOUS TO LARGER ACFT AND IN- TRAIL SPACING BEHIND THESE NEWER ACFT NEEDS TO BE REEVALUATED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AS RPTR AND FLC WERE DSNDING THROUGH 8000 FT THEY ENCOUNTERED WAKE TURB FROM A PRECEDING B-747-400 THAT WAS 8 MI AHEAD OF THEM. THE TURB WAS STRONG ENOUGH TO ROLL THE ACFT INTO A 45 DEG BANK. RPTR'S ACFT WAS BEING FLOWN BY AUTOPLT WHICH DISENGAGED AS THE ACFT APCHED 45 DEGS OF BANK ANGLE. FLT PATH DISPLACEMENT WAS 200 FT. EVENT WAS DISTURBING TO FLC AND PAX. AFTER THE 5 SECOND EVENT THE ACFT WAS RIGHTED AND CONTINUED UNEVENTFULLY FOR A LNDG. PRECEDING ACFT WAS ALWAYS ANNOUNCED AS 8 MI AHEAD. THIS DISTANCE WAS VERIFIED BY TCASII.