WAKE ENCOUNTER - ACR B757-200 HITS THE WAKE OF A B727 AS IT APCHS TOUCHDOWN AND MAKES A FIRM LNDG.

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I WAS FLYING A B-757-200 ON AN APCH TO RWY 22L AT EWR ON APR/THU/94. THE WIND AT THE TIME WAS RPTED AT 190 DEG 10 KTS. WE HAD BEEN FOLLOWING A B-727 BY ONLY APPROX 2 1/2 MI AS MEASURED BY TCASII. THIS DID NOT SEEM TO BE A PROB AS WE DID NOT FEEL ANY UNUSUAL TURB DURING THE APCH. THE B-727 LANDED AND TURNED OFF THE RWY. AT APPROX 50 FT AGL (ON SPD AND GS) THE ACFT SUDDENLY BEGAN A HARD; RAPID ROLL TO THE L. I TRIED TO COUNTERACT WITH R AILERON INPUT BUT IT TOOK ALMOST FULL R AILERON TO STOP THE ROLL. THE ROLL STOPPED AT APPROX 10 DEGS L WING DOWN AND; AFTER A SLIGHT HESITATION; THE ACFT BEGAN TO RESPOND AND ROLL BACK TOWARD THE R. I STARTED TO RELEASE THE R AILERON INPUT SO AS TO STOP THE ROLL AT THE WINGS LEVEL POS. HOWEVER; AS SOON AS THE R AILERON PRESSURE WAS EASED (AILERON MOVEMENT OF NO MORE THAN 3 INCHES FROM FULL R); ANOTHER RAPID L ROLL BEGAN. I AGAIN TRIED TO COUNTERACT THE L ROLL BUT SOON REACHED FULL R AILERON INPUT JUST PRIOR TO L WHEELS GND CONTACT. AS THE L WHEELS HIT THE GND; A RAPID ROLL TO THE R BEGAN AND THE L WING ATTEMPTED TO LIFT FROM THE GND. I PUSHED THE NOSE FORWARD IN N ATTEMPT TO GET; AND KEEP; BOTH WHEEL TRUCKS ON THE GND. THIS ACTION WORKED AND THE NOSE WHEEL WAS LOWERED NORMALLY. THE ACFT WAS ON CTRLINE. TOUCHDOWN WAS AT APPROX XA10 LCL TIME. ROLLOUT WAS UNEVENTFUL. I CAN THINK OF NO PHENOMENA THAT COULD HAVE CAUSED THIS EVENT EXCEPT POSSIBLY THE VORTICES FROM THE B-727 THAT LANDED JUST AHEAD OF US. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE FO SAID THAT THE WX CONDITIONS WERE GOOD; OCCASIONAL LIGHT TURB WITH THE WINDS AT 180 DEG 8 KTS. HE WAS FLYING THE B757-200 AT 'BUG PLUS 5 KTS AND EVERYTHING WAS PERFECT UNTIL THE ROLL STARTED.' THE B727 AHEAD OF THEIR ACFT DID NOT RPT ANY DISTURBANCES. AT ABOUT 50 FT THE INITIAL ROLL BEGAN. THEN JUST PRIOR TO TOUCHDOWN THE SECOND ROLL STARTED (ABOUT 1 FT AGL). THE FIRST ROLL TOOK 'ALL OF THE AILERON AUTH I HAD AND WHEN THE SECOND ONE BEGAN; I DECIDED THAT I HAD BETTER PUT THE ACFT ON THE RWY.' THE TOUCHDOWN WAS FIRM. THE FO; WHO HAD BEEN A HIGHLY EXPERIENCED CAPT AT ANOTHER ACR; STATED THAT HE HAD NOT EXPERIENCED SUCH PERSISTENT ROLL IN A WAKE BEFORE THIS.