Narrative:

While taxiing for departure to runway 3C on taxiway K abeam taxiway K15, the hydraulic caution light illuminated. My first officer was asked to complete the QRH checklist. My first officer did the required procedures outlined in the QRH. The end of the QRH section for this particular failure is to have the hydraulic pump switch moved from its 'automatic' position to the 'override' position. This override position didn't solve the problem. Knowing that position didn't solve the problem, I immediately stopped the aircraft. Being in the close proximity to other aircraft and ground crew members next to us adjacent to the taxiway that we were on, I had my first officer request to taxi to a place where we would not jeopardize the safety of other aircraft and terminal structures, since the brakes worked but the pressure was inadequate to set the parking brake. Once we got away from the hazards around us, I contacted our maintenance over the radio after I brought the aircraft to a complete stop. Both of us held the brake as I requested an aircraft tow back to the gate. A few seconds later, the aircraft started to move left. I tried to correct the situation by using differential power and reverse and even the brakes and nose steering tiller, but because of the failed pump, I had no nose steering and brakes. With an aircraft in front of us about 25 yards way, I had no other choice but to shut the right engine down then the left to keep away from the aircraft in front of us when it became clear that the grass adjacent to the taxiway we were on was our only option. With the ground surge by shutting down the 2 engines, we ended up speeding up towards the grass and ended up there with 3 (all) gears off the pavement. No damage to the aircraft and no injuries were reported. The passenger were escorted off the aircraft and transported back to the terminal in a shuttle bus.

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Original NASA ASRS Text

Title: LTT EXPERIENCES HYD PUMP FAILURE LEADING TO LOSS OF BRAKES AND STEERING ON TAXI OUT DTW.

Narrative: WHILE TAXIING FOR DEP TO RWY 3C ON TXWY K ABEAM TXWY K15, THE HYD CAUTION LIGHT ILLUMINATED. MY FO WAS ASKED TO COMPLETE THE QRH CHKLIST. MY FO DID THE REQUIRED PROCS OUTLINED IN THE QRH. THE END OF THE QRH SECTION FOR THIS PARTICULAR FAILURE IS TO HAVE THE HYD PUMP SWITCH MOVED FROM ITS 'AUTO' POS TO THE 'OVERRIDE' POS. THIS OVERRIDE POS DIDN'T SOLVE THE PROB. KNOWING THAT POS DIDN'T SOLVE THE PROB, I IMMEDIATELY STOPPED THE ACFT. BEING IN THE CLOSE PROX TO OTHER ACFT AND GND CREW MEMBERS NEXT TO US ADJACENT TO THE TXWY THAT WE WERE ON, I HAD MY FO REQUEST TO TAXI TO A PLACE WHERE WE WOULD NOT JEOPARDIZE THE SAFETY OF OTHER ACFT AND TERMINAL STRUCTURES, SINCE THE BRAKES WORKED BUT THE PRESSURE WAS INADEQUATE TO SET THE PARKING BRAKE. ONCE WE GOT AWAY FROM THE HAZARDS AROUND US, I CONTACTED OUR MAINT OVER THE RADIO AFTER I BROUGHT THE ACFT TO A COMPLETE STOP. BOTH OF US HELD THE BRAKE AS I REQUESTED AN ACFT TOW BACK TO THE GATE. A FEW SECONDS LATER, THE ACFT STARTED TO MOVE L. I TRIED TO CORRECT THE SIT BY USING DIFFERENTIAL PWR AND REVERSE AND EVEN THE BRAKES AND NOSE STEERING TILLER, BUT BECAUSE OF THE FAILED PUMP, I HAD NO NOSE STEERING AND BRAKES. WITH AN ACFT IN FRONT OF US ABOUT 25 YARDS WAY, I HAD NO OTHER CHOICE BUT TO SHUT THE R ENG DOWN THEN THE L TO KEEP AWAY FROM THE ACFT IN FRONT OF US WHEN IT BECAME CLR THAT THE GRASS ADJACENT TO THE TXWY WE WERE ON WAS OUR ONLY OPTION. WITH THE GND SURGE BY SHUTTING DOWN THE 2 ENGS, WE ENDED UP SPDING UP TOWARDS THE GRASS AND ENDED UP THERE WITH 3 (ALL) GEARS OFF THE PAVEMENT. NO DAMAGE TO THE ACFT AND NO INJURIES WERE RPTED. THE PAX WERE ESCORTED OFF THE ACFT AND TRANSPORTED BACK TO THE TERMINAL IN A SHUTTLE BUS.

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.