AN A320 HAD PARKING BRAKE SET AFTER PUSHBACK PRESSURES CHK OK. TOW BAR DISCONNECTED; STEERING PIN PULLED. THE ACFT ROLLED FORWARD; BRAKES APPLIED NO HELP. ANTI-SKID NOSE STEERING SWITCHED 'ON' ACFT STOPPED.

Narrative

BRAKES SET NORMALLY AFTER PUSHBACK/PRESSURES CHKED OK. AS SOON AS TOW BAR DISCONNECTED AND NOSEWHEEL STEERING PIN PULLED; THE ACFT STARTED ROLLING FORWARD. GND CREW CALLED ON HEADSET THAT ACFT WAS ROLLING. CAPT APPLIED BRAKES WITH PEDALS FOLLOWED BY FO. DID NOT NOTICE BRAKE PRESSURES AT THE TIME. ACFT CONTINUED TO ROLL FORWARD ABOUT 10 FT PARKING BRAKE CYCLED ON-OFF-ON WITH NO HELP. WHEN ANTI-SKID/NOSEWHEEL STEERING SWITCH TURNED TO THE 'ON' POS (WITH BRAKE PEDALS APPLIED) THE BRAKES IMMEDIATELY APPLIED AND THE ACFT STOPPED. NO INJURIES TO FLT ATTENDANTS/GND PERSONNEL/OR EQUIP. ACFT RETURNED TO THE GATE WITH WHAT APPEARED TO BE NORMAL STEERING AND BRAKES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED WHEN THE GND CREW ADVISED THE FLT CREW THE AIRPLANE WAS ROLLING THE BRAKES WERE APPLIED AND THE ACFT CONTINUED TO ROLL; BRAKES WERE CYCLED NO HELP. ANTI-SKID NOSE STEERING SWITCH TURNED TO 'ON' AND WITH BRAKES ALREADY APPLIED THE ACFT STOPPED. A CONTRACT TECHNICIAN WAS CALLED AND THE TECHNICIAN ARRIVED AND ADVISED THE CAPT OF HAVING PREVIOUS EXPERIENCE WITH A320 EQUIP. THE BRAKE PROB WAS RPTED BY THE CONTRACT TECHNICIAN TO THE MAINT CTLR AND A BRAKE SYS TEST AND CHK WAS ACCOMPLISHED AND THE SYS CHKED OK. THE AIRPLANE WAS DISPATCHED AFTER MAINT AND OPERATED THE REMAINDER OF THE DAY WITH NO PARKING BRAKE PROBS.