Narrative:

At the start of my shift I was informed I was going to be put on an aircraft which was OTS due to a pressurization problem. Several mechanics had already worked on the aircraft in which they had repaired several duct leaks. Myself and another mechanic were to take the aircraft out on an engine run using engine bleeds to pressurize the aircraft in order to perform a delay check per maintenance manual. In this test the forward equipment cooling fan valve located under east&east floor was to be wrenched closed. Due to the position of the valve, one has to remove the valve in order to get to the nut in order to wrench it shut. This was done by myself. The valve was reinstalled in the aircraft secured shut. We then took the aircraft out for the test run. The aircraft passed the delay check but only by 3 seconds per maintenance manual. When aircraft was returned to the gate. The sun had just gone down. I again removed the valve in order to unlock the valve and reinstalled it back into the aircraft. There were no other pressure checks done until the next morning when the aircraft took off (maintenance paper work doesn't require any further checks). At the time I installed the valve the last time, I was sure I had installed it correctly. But since no one touched the aircraft that night it would look like I had mistakenly installed it in reverse flow. I would say that the only course we could have taken to make sure this would not happen again would be to repressurize it again at the gate using the APU (which we could not do, due to a cracked APU duct) using a pillow to plug the equipment cooling vent and then remove it when aircraft had reached approximately 3 psi (note valve closes at 2.5 psi). If valve was working correctly, it would slam shut.

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Original NASA ASRS Text

Title: MECH RPT REGARDING REVERSE INSTALLATION OF COOLING FAN VALVE AFTER A TEST.

Narrative: AT THE START OF MY SHIFT I WAS INFORMED I WAS GOING TO BE PUT ON AN ACFT WHICH WAS OTS DUE TO A PRESSURIZATION PROB. SEVERAL MECHS HAD ALREADY WORKED ON THE ACFT IN WHICH THEY HAD REPAIRED SEVERAL DUCT LEAKS. MYSELF AND ANOTHER MECH WERE TO TAKE THE ACFT OUT ON AN ENG RUN USING ENG BLEEDS TO PRESSURIZE THE ACFT IN ORDER TO PERFORM A DELAY CHK PER MAINT MANUAL. IN THIS TEST THE FORWARD EQUIP COOLING FAN VALVE LOCATED UNDER E&E FLOOR WAS TO BE WRENCHED CLOSED. DUE TO THE POS OF THE VALVE, ONE HAS TO REMOVE THE VALVE IN ORDER TO GET TO THE NUT IN ORDER TO WRENCH IT SHUT. THIS WAS DONE BY MYSELF. THE VALVE WAS REINSTALLED IN THE ACFT SECURED SHUT. WE THEN TOOK THE ACFT OUT FOR THE TEST RUN. THE ACFT PASSED THE DELAY CHK BUT ONLY BY 3 SECONDS PER MAINT MANUAL. WHEN ACFT WAS RETURNED TO THE GATE. THE SUN HAD JUST GONE DOWN. I AGAIN REMOVED THE VALVE IN ORDER TO UNLOCK THE VALVE AND REINSTALLED IT BACK INTO THE ACFT. THERE WERE NO OTHER PRESSURE CHKS DONE UNTIL THE NEXT MORNING WHEN THE ACFT TOOK OFF (MAINT PAPER WORK DOESN'T REQUIRE ANY FURTHER CHKS). AT THE TIME I INSTALLED THE VALVE THE LAST TIME, I WAS SURE I HAD INSTALLED IT CORRECTLY. BUT SINCE NO ONE TOUCHED THE ACFT THAT NIGHT IT WOULD LOOK LIKE I HAD MISTAKENLY INSTALLED IT IN REVERSE FLOW. I WOULD SAY THAT THE ONLY COURSE WE COULD HAVE TAKEN TO MAKE SURE THIS WOULD NOT HAPPEN AGAIN WOULD BE TO REPRESSURIZE IT AGAIN AT THE GATE USING THE APU (WHICH WE COULD NOT DO, DUE TO A CRACKED APU DUCT) USING A PILLOW TO PLUG THE EQUIP COOLING VENT AND THEN REMOVE IT WHEN ACFT HAD REACHED APPROX 3 PSI (NOTE VALVE CLOSES AT 2.5 PSI). IF VALVE WAS WORKING CORRECTLY, IT WOULD SLAM SHUT.

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.