Narrative:

After parking aircraft, parking brake was set and I continued with routine shutdown flow. Engines were shut down, pressurization page was checked on ECAM as well as door page prior to first officer leaving cockpit to disarm exit doors. The aforementioned took about 10 seconds and at this point I reached for the beacon switch and immediately noticed that the aircraft was moving forward. Parking brake lever was released as I simultaneously applied toe brakes bringing the aircraft to an abrupt stop. Aircraft had moved forward approximately 25 ft unnoticed and striking a tug which was attached to air stairs. Aircraft #2 engine anti-ice lip cowling struck tug just as aircraft was abruptly stopped causing sufficient damage to require replacement. Ground crew came on intercom at this time asking if parking brake had been set. Response from captain was 'yes, it was.' I did not release toe brakes until tug and tow bar were attached for pushback to parking. After parking, and chocks were in place, 3 checks of the parking brake system indicated some type of parking brake system malfunction. Parking brake system pressure now would decrease to zero within seconds. No personnel were injured. Suspect parking brake failure moments after parking brake was initially set. Maintenance found parking brake lever had failed and would not actuate parking brake hydraulic valve.

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Original NASA ASRS Text

Title: AN A310 CARGO ACFT DAMAGED AFTER HITTING TUG WHEN THE PARKING BRAKE FAILS TO MAINTAIN PRESSURE AFTER ENG SHUTDOWN ON RAMP AT ZZZ, US.

Narrative: AFTER PARKING ACFT, PARKING BRAKE WAS SET AND I CONTINUED WITH ROUTINE SHUTDOWN FLOW. ENGS WERE SHUT DOWN, PRESSURIZATION PAGE WAS CHKED ON ECAM AS WELL AS DOOR PAGE PRIOR TO FO LEAVING COCKPIT TO DISARM EXIT DOORS. THE AFOREMENTIONED TOOK ABOUT 10 SECONDS AND AT THIS POINT I REACHED FOR THE BEACON SWITCH AND IMMEDIATELY NOTICED THAT THE ACFT WAS MOVING FORWARD. PARKING BRAKE LEVER WAS RELEASED AS I SIMULTANEOUSLY APPLIED TOE BRAKES BRINGING THE ACFT TO AN ABRUPT STOP. ACFT HAD MOVED FORWARD APPROX 25 FT UNNOTICED AND STRIKING A TUG WHICH WAS ATTACHED TO AIR STAIRS. ACFT #2 ENG ANTI-ICE LIP COWLING STRUCK TUG JUST AS ACFT WAS ABRUPTLY STOPPED CAUSING SUFFICIENT DAMAGE TO REQUIRE REPLACEMENT. GND CREW CAME ON INTERCOM AT THIS TIME ASKING IF PARKING BRAKE HAD BEEN SET. RESPONSE FROM CAPT WAS 'YES, IT WAS.' I DID NOT RELEASE TOE BRAKES UNTIL TUG AND TOW BAR WERE ATTACHED FOR PUSHBACK TO PARKING. AFTER PARKING, AND CHOCKS WERE IN PLACE, 3 CHKS OF THE PARKING BRAKE SYS INDICATED SOME TYPE OF PARKING BRAKE SYS MALFUNCTION. PARKING BRAKE SYS PRESSURE NOW WOULD DECREASE TO ZERO WITHIN SECONDS. NO PERSONNEL WERE INJURED. SUSPECT PARKING BRAKE FAILURE MOMENTS AFTER PARKING BRAKE WAS INITIALLY SET. MAINT FOUND PARKING BRAKE LEVER HAD FAILED AND WOULD NOT ACTUATE PARKING BRAKE HYD VALVE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.