Narrative:

Trip had an inbound squawk that #2 engine hydraulic pump was putting out 3500 psi. Being the lead mechanic I checked the system and found it to have a #2 engine green engine driven pump (edp) bad. I assigned 2 men to the job. While they opened the cowl, I pulled up the maintenance manual and brought it out to aircraft. The men removed the pump and installed pump per maintenance manual. When installing pump there was a hang up on the spine going into the gear box. By then, the supervisor came over and helped out and we got the pump on. The men connected the fittings and I had the crew set the aircraft up for engine run. I was in the cockpit with the crew, my supervisor on the headsets on ground, and 2 men by the engine to leak check, the installation. When the engine was started and running, my supervisor said it all checked normal and no leaks and I told him the pressure was good. While the mechanics closed the cowling I signed off logbook and the aircraft left for lax. The next day I found out that #2 engine lost most of its oil and the crew made an unscheduled stop in elp. They found oil coming from drain manifold and plugged the drain and released aircraft to lax. A lax mechanic removed the pump and said the o-ring on the pump shaft was missing. The lax mechanic installed the o-ring and leak checked it. Although I did not physically do all the work, our airline states in the maintenance manual 'there is no requirement that he personally inspect or observe the performance of the work accomplished provided he can adequately establish that all work was accomplished.' with the engine run, pressure good and no leaks, I was led to believe the work was finished right. Supplemental information from acn 259360: as far as the mechanic and assistant supervisor knew, o-ring was on shaft spine. It comes with edp from stock room. Due to 3 people handling pump, instead of 1 mechanic making sure all o-rings on pump, too many hands involved. Supplemental information from acn 259175: I have talked to 2 power plant maintenance controllers and 1 propulsion engineer and they all agree that if the o-ring was not installed during installation, an oil leak would have been detectable during the leak check. Also, oil quantity loss during takeoff and climb out, not 700 mi away at cruise.

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Original NASA ASRS Text

Title: REPLACED EDP HYD PUMP #2 ENG. OIL LEAK DEVELOPED DIVERT TO ELP.

Narrative: TRIP HAD AN INBOUND SQUAWK THAT #2 ENG HYD PUMP WAS PUTTING OUT 3500 PSI. BEING THE LEAD MECH I CHKED THE SYS AND FOUND IT TO HAVE A #2 ENG GREEN ENG DRIVEN PUMP (EDP) BAD. I ASSIGNED 2 MEN TO THE JOB. WHILE THEY OPENED THE COWL, I PULLED UP THE MAINT MANUAL AND BROUGHT IT OUT TO ACFT. THE MEN REMOVED THE PUMP AND INSTALLED PUMP PER MAINT MANUAL. WHEN INSTALLING PUMP THERE WAS A HANG UP ON THE SPINE GOING INTO THE GEAR BOX. BY THEN, THE SUPVR CAME OVER AND HELPED OUT AND WE GOT THE PUMP ON. THE MEN CONNECTED THE FITTINGS AND I HAD THE CREW SET THE ACFT UP FOR ENG RUN. I WAS IN THE COCKPIT WITH THE CREW, MY SUPVR ON THE HEADSETS ON GND, AND 2 MEN BY THE ENG TO LEAK CHK, THE INSTALLATION. WHEN THE ENG WAS STARTED AND RUNNING, MY SUPVR SAID IT ALL CHKED NORMAL AND NO LEAKS AND I TOLD HIM THE PRESSURE WAS GOOD. WHILE THE MECHS CLOSED THE COWLING I SIGNED OFF LOGBOOK AND THE ACFT LEFT FOR LAX. THE NEXT DAY I FOUND OUT THAT #2 ENG LOST MOST OF ITS OIL AND THE CREW MADE AN UNSCHEDULED STOP IN ELP. THEY FOUND OIL COMING FROM DRAIN MANIFOLD AND PLUGGED THE DRAIN AND RELEASED ACFT TO LAX. A LAX MECHANIC REMOVED THE PUMP AND SAID THE O-RING ON THE PUMP SHAFT WAS MISSING. THE LAX MECH INSTALLED THE O-RING AND LEAK CHKED IT. ALTHOUGH I DID NOT PHYSICALLY DO ALL THE WORK, OUR AIRLINE STATES IN THE MAINT MANUAL 'THERE IS NO REQUIREMENT THAT HE PERSONALLY INSPECT OR OBSERVE THE PERFORMANCE OF THE WORK ACCOMPLISHED PROVIDED HE CAN ADEQUATELY ESTABLISH THAT ALL WORK WAS ACCOMPLISHED.' WITH THE ENG RUN, PRESSURE GOOD AND NO LEAKS, I WAS LED TO BELIEVE THE WORK WAS FINISHED RIGHT. SUPPLEMENTAL INFORMATION FROM ACN 259360: AS FAR AS THE MECH AND ASSISTANT SUPVR KNEW, O-RING WAS ON SHAFT SPINE. IT COMES WITH EDP FROM STOCK ROOM. DUE TO 3 PEOPLE HANDLING PUMP, INSTEAD OF 1 MECH MAKING SURE ALL O-RINGS ON PUMP, TOO MANY HANDS INVOLVED. SUPPLEMENTAL INFORMATION FROM ACN 259175: I HAVE TALKED TO 2 PWR PLANT MAINT CTLRS AND 1 PROPULSION ENGINEER AND THEY ALL AGREE THAT IF THE O-RING WAS NOT INSTALLED DURING INSTALLATION, AN OIL LEAK WOULD HAVE BEEN DETECTABLE DURING THE LEAK CHK. ALSO, OIL QUANTITY LOSS DURING TKOF AND CLBOUT, NOT 700 MI AWAY AT CRUISE.

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.