Narrative:

As a result of a duct split discrepancy on a B-400 aircraft; I and a co-worker were tasked to right&right (remove and replace) #2 engine prsov (pressure regulator shutoff valve). Following the right&right I short-signed the paperwork that I had done the right&right only. Because the aircraft was still in the hangar; I verbally communicated with my co-worker that he would do the post installation and operations checks required as the aircraft was taken outside. In my short-sign; I also failed to specify in writing what I had communicated verbally; that per maintenance manual 36-11-15 page 401-420 I had only done the strict right&right of the prsov and not the post installation test. I was completing this short-sign as the aircraft was out doing the operations check engine run. As I came in on my shift the following evening I was told that the aircraft experienced an air-turnback because of a failure to get duct pressure on the #2 engine side. Swing shift claimed the manual override on the prsov was secured in the closed position. I was concerned because; even though I was not directly involved with the operations check; it was my understanding that the operations check following installation of the new prsov was normal. My co-worker performed this test and completed the sign off of the deferral. I have assisted with the right&right of a prsov one other time and felt comfortable performing the task. I believe this situation may have been the result of miscom between my co-worker and myself that a post installation test and an operations check were necessary for the prsov. The post installation test would have essentially leak checked the new prsov and related air connections. I still do not fully understand how the prsov could be secured in the closed position and still passed the operations check. Supplemental information from acn 710170: observed engine run qualified tech perform prsov operations check. Observed 40 psi at below 50% N2. I was satisfied with the results and requested return to hangar. I proceeded to sign off discrepancy. The following shift it was mentioned to me that there had been a problem with the prsov valve and the aircraft made an air turnback. It appears that I misunderstood a procedure I felt I understood.

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Original NASA ASRS Text

Title: A B737-400 RETURNED TO THE DEP ARPT DUE TO #2 ENG BLEED INOP. FOUND PRESSURE REGULATOR AND SHUTOFF VALVE SECURED CLOSED.

Narrative: AS A RESULT OF A DUCT SPLIT DISCREPANCY ON A B-400 ACFT; I AND A CO-WORKER WERE TASKED TO R&R (REMOVE AND REPLACE) #2 ENG PRSOV (PRESSURE REGULATOR SHUTOFF VALVE). FOLLOWING THE R&R I SHORT-SIGNED THE PAPERWORK THAT I HAD DONE THE R&R ONLY. BECAUSE THE ACFT WAS STILL IN THE HANGAR; I VERBALLY COMMUNICATED WITH MY CO-WORKER THAT HE WOULD DO THE POST INSTALLATION AND OPS CHKS REQUIRED AS THE ACFT WAS TAKEN OUTSIDE. IN MY SHORT-SIGN; I ALSO FAILED TO SPECIFY IN WRITING WHAT I HAD COMMUNICATED VERBALLY; THAT PER MAINT MANUAL 36-11-15 PAGE 401-420 I HAD ONLY DONE THE STRICT R&R OF THE PRSOV AND NOT THE POST INSTALLATION TEST. I WAS COMPLETING THIS SHORT-SIGN AS THE ACFT WAS OUT DOING THE OPS CHK ENG RUN. AS I CAME IN ON MY SHIFT THE FOLLOWING EVENING I WAS TOLD THAT THE ACFT EXPERIENCED AN AIR-TURNBACK BECAUSE OF A FAILURE TO GET DUCT PRESSURE ON THE #2 ENG SIDE. SWING SHIFT CLAIMED THE MANUAL OVERRIDE ON THE PRSOV WAS SECURED IN THE CLOSED POS. I WAS CONCERNED BECAUSE; EVEN THOUGH I WAS NOT DIRECTLY INVOLVED WITH THE OPS CHK; IT WAS MY UNDERSTANDING THAT THE OPS CHK FOLLOWING INSTALLATION OF THE NEW PRSOV WAS NORMAL. MY CO-WORKER PERFORMED THIS TEST AND COMPLETED THE SIGN OFF OF THE DEFERRAL. I HAVE ASSISTED WITH THE R&R OF A PRSOV ONE OTHER TIME AND FELT COMFORTABLE PERFORMING THE TASK. I BELIEVE THIS SIT MAY HAVE BEEN THE RESULT OF MISCOM BTWN MY CO-WORKER AND MYSELF THAT A POST INSTALLATION TEST AND AN OPS CHK WERE NECESSARY FOR THE PRSOV. THE POST INSTALLATION TEST WOULD HAVE ESSENTIALLY LEAK CHKED THE NEW PRSOV AND RELATED AIR CONNECTIONS. I STILL DO NOT FULLY UNDERSTAND HOW THE PRSOV COULD BE SECURED IN THE CLOSED POS AND STILL PASSED THE OPS CHK. SUPPLEMENTAL INFO FROM ACN 710170: OBSERVED ENG RUN QUALIFIED TECH PERFORM PRSOV OPS CHECK. OBSERVED 40 PSI AT BELOW 50% N2. I WAS SATISFIED WITH THE RESULTS AND REQUESTED RETURN TO HANGAR. I PROCEEDED TO SIGN OFF DISCREPANCY. THE FOLLOWING SHIFT IT WAS MENTIONED TO ME THAT THERE HAD BEEN A PROBLEM WITH THE PRSOV VALVE AND THE ACFT MADE AN AIR TURNBACK. IT APPEARS THAT I MISUNDERSTOOD A PROC I FELT I UNDERSTOOD.

Data retrieved from NASA's ASRS site as of January 2009 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.