B757-200 CREW ENCOUNTERED UNCTLABLE R TURN ON TKOF ROLL ON RWY 4L AT EWR.

Narrative

AT APPROX 120 KTS; ON THE TKOF ROLL; HAD WHAT APPEARED TO BE UNCOMMANDED R RUDDER INPUT. COULD NOT KEEP ACFT ON RWY CTRLINE; SO I ELECTED TO ABORT THE TKOF. ONCE ACFT WAS STOPPED ON THE RWY; WE RAN THE REJECTED TKOF CHKLIST. NO INJURIES OR DAMAGE TO ACFT. RPTED THE APPARENT MAINT PROB AS REQUIRED. CREW CRM BTWN FLT DECK AND CABIN CREW WAS GOOD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CREW WAS FLYING A B757-200 ACFT. THE ACFT WAS EXTENSIVELY CHKED BY MAINT. NO PROBS COULD BE FOUND. THE ACFT WAS THEN GIVEN A COMPLETE FLT TEST. AGAIN; NO PROBS COULD BE FOUND. THE FLT RECORDER WAS REMOVED AND READ. IT SHOWED AN INSTANTANEOUS LOSS OF 26 KIAS AND AT THE SAME TIME A R TURN BEGAN. IT SHOWED NO R RUDDER INPUT; AND ONLY L RUDDER TO COUNTERACT THE R TURN. THE ACFT THEN HAD AN INSTANTANEOUS INCREASE OF 12 KIAS; WHEN THE ABORT SEQUENCE STARTED. PLT RPTED HVY ACFT WERE LNDG ON RWY 4R AT THE TIME. THE COMPANY THINKS THE ACFT ENCOUNTERED THE WAKE VORTEX OF A LNDG ACFT; WHILE ON ITS TKOF ROLL; THE FAA PARTICIPATED IN THE INVESTIGATION AND CONCURS WITH THE CONCLUSION.