Narrative:

While taxiing across runway 17R at dfw, experienced a partial hydraulic failure. I stopped the aircraft on taxiway Z between runways 17R and 17C to evaluate the problem. The control tower asked if I could make a left turn between the txwys to clear 'Z.' I checked my hydraulic pressure brake gauge and I still had pressure, so I made the left turn. At this point I lost all pressure. I lost steering and brakes. The aircraft rolled at a walking pace past taxiway Y and onto the grass north of taxiway Y. I shut down the engines. There was no aircraft damage or injuries. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a saab 340B and the braking system has been a concern for the crews flying this aircraft. The reporter said the problem being that all 4 brakes are supplied by 1 main hydraulic system with only 1 hydraulic accumulator storing pressure for brake operation with loss of the main system. The reporter stated depending on the location of the hydraulic failure everything can be lost -- flaps, steering and brakes. The reporter said this failure was caused by a broken line located before the brake accumulator.

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Original NASA ASRS Text

Title: 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.

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.