A B737-300 CAPT USING THE SELF PARK SYSTEM AT PHL TAXIED PAST THE STOP LINE WHEN THE SYSTEM FAILED TO DISPLAY A STOP MESSAGE. CAPT STOPPED WHEN THE GATE AGENT BANGED ON THE FUSELAGE.

Narrative

UNDETECTED FAILURE OF THE AUTOMATED PARKING SYSTEM ON GATE. TAXIED IN TO GATE AT PHL. AUTOMATED PARKING SYSTEM SHOWED 737 AND TO PROCEED. PARKING SYSTEM SHOWED US ON THE TAXI LINE AND PROMPTED US TO CONTINUE. PARKING SYSTEM NEVER SHOWED US APPROACHING THE STOP POSITION OR COMMANDED US TO STOP. IT JUST COMMANDED THAT WE CONTINUE. THE RAMP AGENT THEN BANGED ON THE SIDE OF THE AIRPLANE AND I STOPPED. I ESTIMATE THAT WE HAD GONE AT LEAST 10 FEET BEYOND WHERE WE WERE SUPPOSED TO STOP AND STOPPED WITHIN 4 OR 5 FEET OF THE JETWAY. IF THE RAMP AGENT HAD NOT HIT THE SIDE OF THE AIRPLANE I VERY WELL MAY HAVE MADE CONTACT WITH THE JETWAY. I APPLIED THE BRAKES AND STOPPED THE AIRPLANE. I DON'T KNOW WHAT KIND OF SELF TEST THIS SYSTEM HAS BUT IT APPEARS TO HAVE BEEN INADEQUATE TODAY. I ALSO DON'T IF THE RAMP AGENTS MEETING THE AIRPLANE TO CHOCK IT ARE TRAINED TO BE AWARE OF THIS FAILURE POSSIBILITY. HOWEVER THE AGENT ON THE GROUND THIS TIME DID AN OUTSTANDING JOB AND ALL AGENTS NEED TO BE AWARE THAT THIS COULD HAPPEN.