Narrative:

Air carrier aircraft left ZZZ from maintenance hangar after completing a heavy check jul/xa/00. It arrived in XXX the same day with a loss of hydraulic quantity. On investigation, it was found that the a and B system hydraulic lines were crossed over the rudder PCU, which was removed and replaced during the above maintenance check. Data I am aware of: on jul/xb/00 I was the assigned inspector on the rudder PCU replacement of air carrier aircraft xyz. I was on a 16 hour shift. When this occurred, had a partial inspection of another aircraft the previous shift. On the above aircraft, I noticed that air carrier engineering order wxwx was not the same as the one I had been working on the earlier shift. I did question it to my lead and was told they were different engineering orders on the above aircraft. I inspected the attached points of the PCU and witnessed the required torques of PCU hardware at the attached points only. This was accomplished at the end of my 16 hour shift. I wrote a write-up explaining what had been done, and I irreversible-stamped off the completion block. I did not get involved with the hydraulic attachments or operations checks which are attached to this block that I stamped. As hydraulics were off the system at this time and the standby rudder actuator was also removed, this stand-by rudder actuator has another job card to it that I wasn't involved with. I did get involved with the jack screw removal and replacement on the same aircraft during the same work assignment. Callback conversation with reporter revealed the following information: the reporter stated 3 different job cards are required to accomplish the engineering order and the card being worked was to check the attach points of the rudder power control unit and torque setting of the hardware. The reporter said the crossed lines were flexible high pressure lines with no visible identify. The reporter said a second job card checks the lines for installation and leakage but this was not accomplished at the time the PCU was installed as several system were open and no hydraulic power could be applied. The reporter said when the aircraft was pushed out of the check several days later and run, a hydraulic loss was observed and was reported fixed. The reporter stated when the aircraft was delivered to the gate, the hydraulic quantity indicators showed a loss of fluid and the system were svced. The reporter stated the loss of hydraulic fluid the crew reported was investigated and it was then found the rudder power unit pressure lines crossed but the return lines were in the normal position but the different capacities of the reservoirs caused the dumping of the fluid.

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Original NASA ASRS Text

Title: A B737-300 WAS DISPATCHED IN NON COMPLIANCE WITH THE RUDDER PWR UNIT HYD PRESSURE LINES CROSSED 'A' FEEDING 'B' AND 'B' FEEDING 'A.'

Narrative: ACR ACFT LEFT ZZZ FROM MAINT HANGAR AFTER COMPLETING A HVY CHK JUL/XA/00. IT ARRIVED IN XXX THE SAME DAY WITH A LOSS OF HYD QUANTITY. ON INVESTIGATION, IT WAS FOUND THAT THE A AND B SYS HYD LINES WERE CROSSED OVER THE RUDDER PCU, WHICH WAS REMOVED AND REPLACED DURING THE ABOVE MAINT CHK. DATA I AM AWARE OF: ON JUL/XB/00 I WAS THE ASSIGNED INSPECTOR ON THE RUDDER PCU REPLACEMENT OF ACR ACFT XYZ. I WAS ON A 16 HR SHIFT. WHEN THIS OCCURRED, HAD A PARTIAL INSPECTION OF ANOTHER ACFT THE PREVIOUS SHIFT. ON THE ABOVE ACFT, I NOTICED THAT ACR ENGINEERING ORDER WXWX WAS NOT THE SAME AS THE ONE I HAD BEEN WORKING ON THE EARLIER SHIFT. I DID QUESTION IT TO MY LEAD AND WAS TOLD THEY WERE DIFFERENT ENGINEERING ORDERS ON THE ABOVE ACFT. I INSPECTED THE ATTACHED POINTS OF THE PCU AND WITNESSED THE REQUIRED TORQUES OF PCU HARDWARE AT THE ATTACHED POINTS ONLY. THIS WAS ACCOMPLISHED AT THE END OF MY 16 HR SHIFT. I WROTE A WRITE-UP EXPLAINING WHAT HAD BEEN DONE, AND I IRREVERSIBLE-STAMPED OFF THE COMPLETION BLOCK. I DID NOT GET INVOLVED WITH THE HYD ATTACHMENTS OR OPS CHKS WHICH ARE ATTACHED TO THIS BLOCK THAT I STAMPED. AS HYDS WERE OFF THE SYS AT THIS TIME AND THE STANDBY RUDDER ACTUATOR WAS ALSO REMOVED, THIS STAND-BY RUDDER ACTUATOR HAS ANOTHER JOB CARD TO IT THAT I WASN'T INVOLVED WITH. I DID GET INVOLVED WITH THE JACK SCREW REMOVAL AND REPLACEMENT ON THE SAME ACFT DURING THE SAME WORK ASSIGNMENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED 3 DIFFERENT JOB CARDS ARE REQUIRED TO ACCOMPLISH THE ENGINEERING ORDER AND THE CARD BEING WORKED WAS TO CHK THE ATTACH POINTS OF THE RUDDER PWR CTL UNIT AND TORQUE SETTING OF THE HARDWARE. THE RPTR SAID THE CROSSED LINES WERE FLEXIBLE HIGH PRESSURE LINES WITH NO VISIBLE IDENT. THE RPTR SAID A SECOND JOB CARD CHKS THE LINES FOR INSTALLATION AND LEAKAGE BUT THIS WAS NOT ACCOMPLISHED AT THE TIME THE PCU WAS INSTALLED AS SEVERAL SYS WERE OPEN AND NO HYD PWR COULD BE APPLIED. THE RPTR SAID WHEN THE ACFT WAS PUSHED OUT OF THE CHK SEVERAL DAYS LATER AND RUN, A HYD LOSS WAS OBSERVED AND WAS RPTED FIXED. THE RPTR STATED WHEN THE ACFT WAS DELIVERED TO THE GATE, THE HYD QUANTITY INDICATORS SHOWED A LOSS OF FLUID AND THE SYS WERE SVCED. THE RPTR STATED THE LOSS OF HYD FLUID THE CREW RPTED WAS INVESTIGATED AND IT WAS THEN FOUND THE RUDDER PWR UNIT PRESSURE LINES CROSSED BUT THE RETURN LINES WERE IN THE NORMAL POS BUT THE DIFFERENT CAPACITIES OF THE RESERVOIRS CAUSED THE DUMPING OF THE FLUID.

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.