EMB145 CAPT REPORTS BRAKE FAILURE AFTER PUSHBACK ALLOWING ACFT TO ROLL INTO TAXI LIGHT BEFORE CONTROL IS REGAINED.

Narrative

UNTIL PUSHBACK ALL SYS ON THE ACFT WERE COMPLETELY NORMAL. AFTER WE PUSHED BACK FROM THE GATE; THE GND CREW REQUESTED TOWBAR DISCONNECT. THE PARKING BRAKE WAS SET; THE TOWBAR WAS DISCONNECTED FROM THE AIRPLANE AND THE GND CREW WENT TO HAND SIGNALS. AT THAT TIME WE RECEIVED BOTH HYD SYS FAILURE MESSAGES ON OUR EICAS AND THE AIRPLANE BEGAN TO ROLL BACKWARDS ON THE SLIGHT HILL OF THE C CONCOURSE RAMP. WITH 2 SETS OF FEET ON THE BRAKES AND THE PARKING BRAKE ON WE WERE ROLLING. ON THE EMB145LR THE HYD PUMPS ARE NOT REQUIRED TO BE ON TO HOLD PRESSURE ON THE PARKING BRAKE AFTER THE #2 SYS HAS BEEN CHARGED. IT WAS CHARGED ON OUR MORNING FLT AND PLANE WAS NOT LEFT UNATTENDED. AFTER WE BEGAN ROLLING I REACHED UP AND TURNED ON THE ELECTRIC HYD PUMPS. THE AIRPLANE CAME TO AN ABRUPT STOP; BUT NOT BEFORE THE #2 TIRE HAD STRUCK AND BENT A TAXI LIGHT. THE AIRPLANE WAS TOWED BACK TO THE GATE AND MAINT CALLED. THE DAMAGE TO THE TIRE WAS MINIMAL; BUT STILL NEEDED TO BE REPLACED. THERE WAS NO OTHER DAMAGE TO THE AIRPLANE. THE WRITE-UPS WERE CLRED AND WE CONTINUED TO OUR DEST. CLRLY THERE WAS A HYD PROB; MAINT FIXED THAT. HOWEVER; THE GND CREWS PUSH THE AIRPLANES VERY CLOSE TO EDGE OF THE RAMP BECAUSE OF THE NECESSITY TO TURN OUT AND NOT BLOCK VEHICLE LANES NEAR THE TERMINAL. THE AIRPLANE ONLY ROLLED A SHORT DISTANCE BEFORE STRIKING THE TAXI LIGHT. A SHORTER PUSH; THUS RESULTING IN JUST A BIT MORE REACTION TIME WOULD HAVE PREVENTED THIS.