Narrative:

I worked on the #1 engine on aircraft X in the dock at air carrier X maintenance base. The job I was working on was to check the gap between the oil tube elbow at the 6 O'clock position on the lpt case. The clearance was ok per the job card, so I proceeded to reinstall the aft b-nut of the tube to the fitting on the case. At this time, I noticed the b-nut would not thread onto the fitting, so I informed my lead mechanic. He instructed me to remove the tube and another mechanic accomplished the required repairs. After the repairs were accomplished I reinstalled the tube starting with the forward end. I tightened the tube with my wrenches and asked the mechanic I was working if this fitting needed to be safetied. I did this because I had noticed the b-nut was not safetied upon removing it. Also, I had noticed a safety wire hole in the b-nut, but there was no place to attach the other end of the safety wire. The other mechanic told me it didn't require a safety, so I finished the installation and installed the heat shroud that covers the b-nut fitting. I then proceeded to install the aft end of the oil tube per the instructions on the job card I was working from. The engine was later dry-motored per shop procedures and checked for leaks while in the dock. This procedure was done twice on this particular aircraft. After release to the ramp, the engine was motored and checked for leaks per procedures by the ramp crew. All this was accomplished prior to the aircraft being released for revenue service. There were no leaks found at this time. After release to service, the engine developed an oil leak from the forward b-nut of the line I had been working on and signed for. This resulted in an in-flight shutdown due to low oil pressure. Upon inspection of the engine, it was found that the heat shroud had been moved aft, and the b-nut on the forward end of the tube was only hand tight.

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Original NASA ASRS Text

Title: A B737-300 SHUT DOWN #1 ENG INFLT DUE TO LOSS OF OIL. CAUSED BY #1 ENG LOW PRESSURE TURBINE CASE OIL LINE B-NUT NOT SECURED.

Narrative: I WORKED ON THE #1 ENG ON ACFT X IN THE DOCK AT ACR X MAINT BASE. THE JOB I WAS WORKING ON WAS TO CHK THE GAP BTWN THE OIL TUBE ELBOW AT THE 6 O'CLOCK POS ON THE LPT CASE. THE CLRNC WAS OK PER THE JOB CARD, SO I PROCEEDED TO REINSTALL THE AFT B-NUT OF THE TUBE TO THE FITTING ON THE CASE. AT THIS TIME, I NOTICED THE B-NUT WOULD NOT THREAD ONTO THE FITTING, SO I INFORMED MY LEAD MECH. HE INSTRUCTED ME TO REMOVE THE TUBE AND ANOTHER MECH ACCOMPLISHED THE REQUIRED REPAIRS. AFTER THE REPAIRS WERE ACCOMPLISHED I REINSTALLED THE TUBE STARTING WITH THE FORWARD END. I TIGHTENED THE TUBE WITH MY WRENCHES AND ASKED THE MECH I WAS WORKING IF THIS FITTING NEEDED TO BE SAFETIED. I DID THIS BECAUSE I HAD NOTICED THE B-NUT WAS NOT SAFETIED UPON REMOVING IT. ALSO, I HAD NOTICED A SAFETY WIRE HOLE IN THE B-NUT, BUT THERE WAS NO PLACE TO ATTACH THE OTHER END OF THE SAFETY WIRE. THE OTHER MECH TOLD ME IT DIDN'T REQUIRE A SAFETY, SO I FINISHED THE INSTALLATION AND INSTALLED THE HEAT SHROUD THAT COVERS THE B-NUT FITTING. I THEN PROCEEDED TO INSTALL THE AFT END OF THE OIL TUBE PER THE INSTRUCTIONS ON THE JOB CARD I WAS WORKING FROM. THE ENG WAS LATER DRY-MOTORED PER SHOP PROCS AND CHKED FOR LEAKS WHILE IN THE DOCK. THIS PROC WAS DONE TWICE ON THIS PARTICULAR ACFT. AFTER RELEASE TO THE RAMP, THE ENG WAS MOTORED AND CHKED FOR LEAKS PER PROCS BY THE RAMP CREW. ALL THIS WAS ACCOMPLISHED PRIOR TO THE ACFT BEING RELEASED FOR REVENUE SVC. THERE WERE NO LEAKS FOUND AT THIS TIME. AFTER RELEASE TO SVC, THE ENG DEVELOPED AN OIL LEAK FROM THE FORWARD B-NUT OF THE LINE I HAD BEEN WORKING ON AND SIGNED FOR. THIS RESULTED IN AN INFLT SHUTDOWN DUE TO LOW OIL PRESSURE. UPON INSPECTION OF THE ENG, IT WAS FOUND THAT THE HEAT SHROUD HAD BEEN MOVED AFT, AND THE B-NUT ON THE FORWARD END OF THE TUBE WAS ONLY HAND TIGHT.

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.