AN LTT WAS NEARLY UPSET BY THE WAKE TURB OF AN LGT IN THE NIGHT TFC PATTERN.

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APCHING DFW FROM THE NW FOLLOWING MLG TFC WHEN CTLR SAW AN OPPORTUNITY TO ALLOW US TO LAND RWY 35R. WE WERE 3000 FT MSL AT 210 KIAS ASSIGNED AIRSPD WHEN TOLD TO FOLLOW LGT OVER LOM FOR RWY 35R. CROSSED BEHIND MLG ON FINAL FOR RWY 36L STILL AT 3000 FT AND INTERCEPTED LOC FOR RWY 35R. SWITCHED TO TWR FREQ AND WERE TOLD WE HAD A 70 KT OVERTAKE ON LGT AND BEGAN SLOWING. BEGAN DSCNT FROM 3000 FT NOTING WE WERE FULL DEFLECTION ABOVE GS. I JUDGED THIS TO BE PERFECTLY ACCEPTABLE KNOWING THE NASTY REPUTATION THE LGT HAS FOR GENERATING WAKE TURB AND; IN FACT; FULLY INTENDED TO REMAIN HIGH ON FINAL. TWR ADVISED 'CLRED TO LAND FOLLOWING TFC 2 1/2 AHEAD; CAUTION WAKE TURB.' I THOUGHT WE WOULD BE SAFELY ABOVE HIS WAKE. SHORTLY AFTER; MY ACFT (LTT) ROLLED TO THE R TO AN ANGLE OF APPROX 100 DEGS (MORE THAN 90 DEGS). FULL OPPOSITE CTL INPUT DID NOT HAVE ANY AFFECT IN STOPPING THIS ROLL. IAS BEGAN DROPPING AND THROTTLES WERE THEN FIREWALLED. AS WE ROLLED R; WE HAD ALSO TURNED SLIGHTLY IN THAT DIRECTION AND I ASSUME WE FLEW OUT OF THAT VORTEX AND WERE ABLE TO RIGHT THE ACFT. THEN WE HIT WHAT I ASSUME WAS HIS R WING VORTEX AND THE ACFT (MINE) BEGAN TO ROLL L. WE FLEW THROUGH THIS VORTEX FAIRLY QUICKLY; PROBABLY DUE TO OUR NEW (UNCOMMANDED) HDG; AND OUR BANK DID NOT EXCEED 60 DEGS. WE RECOVERED FROM THIS ROLL ON A HDG OF ABOUT 080 DEGS AND DECLARED A MISSED APCH. TWR ASKED IF WE COULD ENTER A BASE FOR RWY 31R AND LAND. WE DID; AND LANDED WITHOUT FURTHER INCIDENT. THE LGT HAD OBVIOUSLY BEEN VERY HIGH ON HIS APCH FOR SOME REASON; POSSIBLY AN EARLIER TCASII RESOLUTION. OUR ATTN HAD BEEN FOCUSED ON THE MLG WE WERE ORIGINALLY FOLLOWING; THUS I WAS UNAWARE OF THE LGT'S GLIDE PATH. I FEEL SOMEONE (CTLRS) SHOULD HAVE NOTICED THIS AND REALIZED A WAKE ENCOUNTER WAS INEVITABLE. SECONDLY; I FEEL THE LGT SHOULD BE CLASSIFIED AS A 'HVY' JET AND INCREASED SPACING SHOULD BE USED.