TWO MECHANICS; ONE TOWING AND THE OTHER IN THE COCKPIT; DESCRIBE THEIR SITUATION WHEN THEIR TUG ANTI-SKID BRAKES FAILED TO STOP THEIR B777 ACFT AS THEY APPROACHED AN ACTIVE RUNWAY WITH AN MD80 LANDING.

Narrative

WHEN TOWING ACFT X FROM BLAST FENCE TO GATE; MOVED FROM BLAST FENCE TURN L ONTO TXWY '1.' WHEN I STARTED ACROSS TXWY '2;' I CAME OFF THE GAS AND APPLIED LIGHT BRAKES; THE ANTI-SKID STARTED TO CYCLE; SPD WAS 12 MPH. I CAME OFF THE BRAKES TO LET THE SYS RESET. THE ANTI-SKID CYCLES BECAME HARDER. WHEN I SAW WE WERE NOT STOPPING I APPLIED FULL HARD BRAKES. AS I ENTERED ONTO THE RWY; I TURNED R TO AVOID THE LNDG ACFT. AFTER THE ACFT HAD PASSED; I TURNED BACK ONTO TXWY '1.' THE TUG CAME TO A STOP AFTER XING RWY XXR. TUG BRAKE SYS FAILED. SUPPLEMENTAL INFO FROM ACN 782353: WHILE RIDING RADIOS; DELIVERING ACFT X WITH TUG; MR X AND MYSELF WERE CLRED UP TO AND HOLD SHORT OF RWY XXL. UPON THE ACFT CLRING THE CTR OF TXWY '2' THE ACFT SEEMED TO START PUSHING THE TUG. MR X STARTED TO APPLY THE BRAKES AND THE TUG LURCHED AND STARTED BOUNCING. THE MORE HE TRIED TO STOP; THE MORE SEVERE THE BOUNCING GOT. WE WERE PUSHED PAST THE HOLD SHORT LINE AND INTO THE RWY AREA. THERE WAS AN MD80 LNDG AT THIS TIME. THE TUG IS EQUIPPED WITH 'ANTI-SKID.' THIS SYS DID NOT APPEAR TO FUNCTION PROPERLY. INSPECT TUG BRAKING SYS.