AN ACR MD83 FLC HIT THE WAKE OF A B747 AND ROLLED TO THE L TWICE BEFORE THE FLC COULD ESCAPE BY CLBING. THE FIRST ROLL WAS TO AT LEAST 45 DEGS AND THE SECOND TO 60 DEGS. THE B747 WAS 7 MI AHEAD AND THE PROPER WAKE ADVISORIES HAD BEEN GIVEN BY THE APCH CTLR.

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WHILE BEING VECTORED FOR A VISUAL APCH TO RWY 24R AT LAX; OUR ACFT ENCOUNTERED THE WAKE OF A B747 WHICH WAS BEING VECTORED FOR AN APCH TO THE S COMPLEX (RWY 25L/R). OUR ACFT ABRUPTLY; BUT SMOOTHLY; ROLLED ABOUT 45 DEGS TO THE L. I APPLIED IMMEDIATE CTL INPUT TO LEVEL THE ACFT ONLY TO EXPERIENCE THE SAME SIT ABOUT 5-7 SECONDS LATER. AT THIS POINT; I INITIATED AN IMMEDIATE CLB TO GAIN 500 FT ALT TO PRECLUDE ENCOUNTERING THE WAKE AGAIN. AT THE TIME OF THE ENCOUNTER; THE B747 WAS ABOUT 6-7 MI AHEAD OF US ON A DOWNWIND LEG. SINCE HE WAS VECTORED FOR A WIDER PATTERN AND SUBSEQUENTLY A LONGER DOWNWIND; I ASSUME THAT HIS ALT WAS ABOVE OURS AND WE ENTERED HIS DSNDING WAKE. WHEN THE ILS IS BEING FLOWN; IT'S GENERALLY EASY TO AVOID THIS SIT BY BEING ON OR SLIGHTLY ABOVE THE GLIDE PATH TO AVOID THE DSNDING WAKE; BUT WHILE MANEUVERING FOR VISUAL APCHS THERE MUST BE MORE RELIANCE ON ATC TO AVOID XING A LIGHTER ACFT BEHIND AND BELOW A 'HVY' ACFT. THIS IS PARTICULARLY CRITICAL WHEN COMMON ARR RTES ARE FLOWN (IE; DEPART SMO ON HDG 070 DEGS). IN RETROSPECT; ALTHOUGH THE ENCOUNTER WAS RANDOM; THE PROBABILITIES APPEAR TO BE HIGHER WHEN USING THE ARR RTES COMMON AT LAX. IF ACFT ARRIVING FROM THE S WERE TO LAND ON THE S COMPLEX AND N ARRS WERE TO UTILIZE THE N COMPLEX; THERE WOULD BE LESS XOVER (IE; ALTHOUGH WE ARRIVED OVER SMO AS DID THE B747; IT WAS NECESSARY FOR HIM TO CROSS THE FINAL APCH COURSE OF BOTH RWYS 24L&R TO LINE UP WITH RWY 25L). ADDITIONALLY; IT WAS NECESSARY FOR US TO BE AT A LOWER ALT IN ORDER TO EXECUTE A VISUAL APCH TO THE NEAR COMPLEX. CURIOUSLY; HAVING CONSIDERABLE EXPERIENCE OPERATING INTO AND OUT OF MANY 'HVY' HUBS -- ATL; BOS; DEN; ORD; MIA; ETC; THE ONLY WAKE TURB ENCOUNTERS I'VE HAD WERE AT LAX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR IS AN MD83 CAPT AND HE SAID THAT; AS FAR AS HE KNEW; THE CTLR FOLLOWED THE WAKE SEPARATION PROGRAM. HE SAID THAT HE HAS HAD MANY ENCOUNTERS WITH WAKE AT LAX AND HE SUSPECTS THAT THE CAUSE MAY BE THE FACT THAT THE SAME GND TRACK IS USED BY A NUMBER OF ACFT OF DIFFERING WTS. IN THIS CASE; HE SAID THAT THE B747 THAT WAS GOING TO RWY 25L CROSSED SMO AT 7000 FT ABOUT 7 MI IN FRONT OF HIS MD83 AND STARTED A DSCNT TO 3500 FT. HE THEN CROSSED SMO AND WAS CLRED TO 2500 FT. SHORTLY AFTER HIS LEVELOFF; THE MD83 ROLLED SMOOTHLY TO THE L; REACHING AT LEAST A 45 DEG ANGLE OF BANK EVEN THOUGH HE HAD APPLIED FULL AILERON TO THE R TO COUNTER THE ROLL. SHORTLY AFTER THE ACFT RECOVERED FROM THIS; IT ROLLED TO THE L AGAIN AND THIS TIME IT REACHED 60 DEGS OF BANK WITH BOTH PLTS ATTEMPTING TO COUNTER WITH THE CTL WHEEL FULL TO THE R. AS THEY RECOVERED FROM THIS ROLL THE CAPT STARTED A CLB TO AVOID FURTHER ENCOUNTERS AND HE ADVISED THE APCH CTLR OF THE ROLLS AND OF HIS CLB TO ESCAPE. AFTER LNDG; HE SAID THAT HE BRIEFED THE PAX ABOUT THE ENCOUNTERS AND AS THEY LEFT THE ACFT; A NUMBER OF PAX SPOKE TO HIM ABOUT THE EVENT AND ALL OF THEM WERE UPSET. APPARENTLY HE SAID; THERE HAD BEEN SOMETHING ON TELEVISION ABOUT WINDSHEAR AND OTHER UPSET CAUSES AND MANY OF THE PAX HAD SEEN THE PROGRAM. 1 PAX WROTE A LETTER TO THE COMPANY AND THE CAPT WAS ONE OF THE SEVERAL RESPONDENTS.