Narrative:

Upon arrival in stl all hydraulic pressures were normal and quantities were approximately 12-13 quarts. Landing gear and flaps extended normally. It was my approach and landing. Both reversers operated normally. I decelerated the aircraft and brought both reversers to forward idle at 80 KTS. At 90 KTS I started braking and braking was normal. At just under 80 KTS, the captain took the aircraft and slowed to 5-10 KTS. As he started turning off runway 30R onto taxiway B, about 1/2 way through the turn, I noticed he was having a hard time turning the nosewheel steering. We were now headed at a 45 degree angle off the runway. At this time everything on the aircraft appeared normal. The captain used 2 hands on the steering and full left rudder to keep from going off the taxiway. We had made the turn onto taxiway B now and at this time we noticed we had no hydraulic pressure in either system. Both quantity gauges were off scale high. We are now still rolling and headed off taxiway B at a 45 degree angle to the left. With no brakes, the captain elected to try reverse thrust but neither reverser opened. We departed the taxiway and went into the grass. We shut down both engines and the captain notified emergency equipment and told the passenger to follow the directions of the flight attendants. I notified the company and maintenance and ran the after landing checklist. Maintenance pushed us back onto the taxiway and towed us into the gate. None of the passenger were injured and there was no damage to the aircraft. Preliminary investigations indicated a crack in the transfer pump case which caused both system to dump directly to the reservoirs causing both system to foam up. It seems to me that there must be a design flaw in this system for something like this to happen. These were supposed to be 2 independent system. Callback conversation with reporter revealed the following: the reporter states that he has heard of no other incidents of this type. His air carrier, the FAA, NTSB, and the manufacturer are all working on a solution to a 'problem that cannot happen,' but did. The air carrier and pilot's union put out a bulletin to warn all pilots of this possibility. There was no fluid lost overboard, both fluid gauges read full when the aircraft came to rest. There was no crack in the case of the transfer pump, but some kind of internal failure that allowed the pumps to circulate fluid through the tanks without producing any pressure and therefore power. The reporter states that he now has been informed that if he had turned off the transfer pump electrically, operation would have returned to normal.

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Original NASA ASRS Text

Title: AN ACR MLG RAN OFF THE TXWY AFTER LOSING ALL HYD PWR.

Narrative: UPON ARR IN STL ALL HYD PRESSURES WERE NORMAL AND QUANTITIES WERE APPROX 12-13 QUARTS. LNDG GEAR AND FLAPS EXTENDED NORMALLY. IT WAS MY APCH AND LNDG. BOTH REVERSERS OPERATED NORMALLY. I DECELERATED THE ACFT AND BROUGHT BOTH REVERSERS TO FORWARD IDLE AT 80 KTS. AT 90 KTS I STARTED BRAKING AND BRAKING WAS NORMAL. AT JUST UNDER 80 KTS, THE CAPT TOOK THE ACFT AND SLOWED TO 5-10 KTS. AS HE STARTED TURNING OFF RWY 30R ONTO TXWY B, ABOUT 1/2 WAY THROUGH THE TURN, I NOTICED HE WAS HAVING A HARD TIME TURNING THE NOSEWHEEL STEERING. WE WERE NOW HEADED AT A 45 DEG ANGLE OFF THE RWY. AT THIS TIME EVERYTHING ON THE ACFT APPEARED NORMAL. THE CAPT USED 2 HANDS ON THE STEERING AND FULL L RUDDER TO KEEP FROM GOING OFF THE TXWY. WE HAD MADE THE TURN ONTO TXWY B NOW AND AT THIS TIME WE NOTICED WE HAD NO HYD PRESSURE IN EITHER SYS. BOTH QUANTITY GAUGES WERE OFF SCALE HIGH. WE ARE NOW STILL ROLLING AND HEADED OFF TXWY B AT A 45 DEG ANGLE TO THE L. WITH NO BRAKES, THE CAPT ELECTED TO TRY REVERSE THRUST BUT NEITHER REVERSER OPENED. WE DEPARTED THE TXWY AND WENT INTO THE GRASS. WE SHUT DOWN BOTH ENGS AND THE CAPT NOTIFIED EMER EQUIP AND TOLD THE PAX TO FOLLOW THE DIRECTIONS OF THE FLT ATTENDANTS. I NOTIFIED THE COMPANY AND MAINT AND RAN THE AFTER LNDG CHKLIST. MAINT PUSHED US BACK ONTO THE TXWY AND TOWED US INTO THE GATE. NONE OF THE PAX WERE INJURED AND THERE WAS NO DAMAGE TO THE ACFT. PRELIMINARY INVESTIGATIONS INDICATED A CRACK IN THE TRANSFER PUMP CASE WHICH CAUSED BOTH SYS TO DUMP DIRECTLY TO THE RESERVOIRS CAUSING BOTH SYS TO FOAM UP. IT SEEMS TO ME THAT THERE MUST BE A DESIGN FLAW IN THIS SYS FOR SOMETHING LIKE THIS TO HAPPEN. THESE WERE SUPPOSED TO BE 2 INDEPENDENT SYS. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR STATES THAT HE HAS HEARD OF NO OTHER INCIDENTS OF THIS TYPE. HIS ACR, THE FAA, NTSB, AND THE MANUFACTURER ARE ALL WORKING ON A SOLUTION TO A 'PROB THAT CANNOT HAPPEN,' BUT DID. THE ACR AND PLT'S UNION PUT OUT A BULLETIN TO WARN ALL PLTS OF THIS POSSIBILITY. THERE WAS NO FLUID LOST OVERBOARD, BOTH FLUID GAUGES READ FULL WHEN THE ACFT CAME TO REST. THERE WAS NO CRACK IN THE CASE OF THE TRANSFER PUMP, BUT SOME KIND OF INTERNAL FAILURE THAT ALLOWED THE PUMPS TO CIRCULATE FLUID THROUGH THE TANKS WITHOUT PRODUCING ANY PRESSURE AND THEREFORE PWR. THE RPTR STATES THAT HE NOW HAS BEEN INFORMED THAT IF HE HAD TURNED OFF THE TRANSFER PUMP ELECTRICALLY, OP WOULD HAVE RETURNED TO NORMAL.

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.