A SAAB 340B WHILE TAXIING LOST THE MAIN HYD SYS PRESSURE AND QUANTITY WHICH RESULTED IN LOSS OF BRAKE AND STEERING CTL.

Narrative

WHILE TAXIING ACROSS RWY 17R AT DFW; EXPERIENCED A PARTIAL HYD FAILURE. I STOPPED THE ACFT ON TXWY Z BTWN RWYS 17R AND 17C TO EVALUATE THE PROB. THE CTL TWR ASKED IF I COULD MAKE A L TURN BTWN THE TXWYS TO CLR 'Z.' I CHKED MY HYD PRESSURE BRAKE GAUGE AND I STILL HAD PRESSURE; SO I MADE THE L TURN. AT THIS POINT I LOST ALL PRESSURE. I LOST STEERING AND BRAKES. THE ACFT ROLLED AT A WALKING PACE PAST TXWY Y AND ONTO THE GRASS N OF TXWY Y. I SHUT DOWN THE ENGS. THERE WAS NO ACFT DAMAGE OR INJURIES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A SAAB 340B AND THE BRAKING SYS HAS BEEN A CONCERN FOR THE CREWS FLYING THIS ACFT. THE RPTR SAID THE PROB BEING THAT ALL 4 BRAKES ARE SUPPLIED BY 1 MAIN HYD SYS WITH ONLY 1 HYD ACCUMULATOR STORING PRESSURE FOR BRAKE OP WITH LOSS OF THE MAIN SYS. THE RPTR STATED DEPENDING ON THE LOCATION OF THE HYD FAILURE EVERYTHING CAN BE LOST -- FLAPS; STEERING AND BRAKES. THE RPTR SAID THIS FAILURE WAS CAUSED BY A BROKEN LINE LOCATED BEFORE THE BRAKE ACCUMULATOR.