Narrative:

On aug/xa/99, I was working flight xyz (air carrier) from ZZZ to atl. A mechanic assisting me may have locked out the wrong valve during the course of an MEL deferral. It was near the end of my shift, and a new shift had just come on duty. Approximately 10 mins before departure, the flight crew called the maintenance department. The left engine 'bleed' light was on. Discussing the situation with the flight crew and my lead, we decided to defer the discrepancy per the MEL. This required locking closed the hp valve and deactivating the thrust reverser. At this time, at least 5 mechanics from the oncoming shift arrived to help. 1 mechanic helping went to work locking out the hp valve. It now appears he may have locked out the prsov, which is identical to the hp valve. The reverser was deactivated, all cowling closed, and I signed the logbook for the MEL deferral. With the MEL book in hand opened to the procedures section, I doublechked with the other mechanic that the valve had been properly locked closed and was satisfied with his answer. To the best of my knowledge at that time, all work was in full compliance with the MEL and maintenance manual. Not until subsequent maintenance at another station was the problem discovered.

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Original NASA ASRS Text

Title: A B767-300 WAS DISPATCHED IN NON COMPLIANCE WITH A L ENG HIGH STAGE BLEED VALVE RENDERED INOP PER THE MEL SPECIAL PROCS BUT THE PRESSURE REGULATOR SHUTOFF VALVE WAS THE ACTUAL VALVE RENDERED INOP.

Narrative: ON AUG/XA/99, I WAS WORKING FLT XYZ (ACR) FROM ZZZ TO ATL. A MECH ASSISTING ME MAY HAVE LOCKED OUT THE WRONG VALVE DURING THE COURSE OF AN MEL DEFERRAL. IT WAS NEAR THE END OF MY SHIFT, AND A NEW SHIFT HAD JUST COME ON DUTY. APPROX 10 MINS BEFORE DEP, THE FLC CALLED THE MAINT DEPT. THE L ENG 'BLEED' LIGHT WAS ON. DISCUSSING THE SIT WITH THE FLC AND MY LEAD, WE DECIDED TO DEFER THE DISCREPANCY PER THE MEL. THIS REQUIRED LOCKING CLOSED THE HP VALVE AND DEACTIVATING THE THRUST REVERSER. AT THIS TIME, AT LEAST 5 MECHS FROM THE ONCOMING SHIFT ARRIVED TO HELP. 1 MECH HELPING WENT TO WORK LOCKING OUT THE HP VALVE. IT NOW APPEARS HE MAY HAVE LOCKED OUT THE PRSOV, WHICH IS IDENTICAL TO THE HP VALVE. THE REVERSER WAS DEACTIVATED, ALL COWLING CLOSED, AND I SIGNED THE LOGBOOK FOR THE MEL DEFERRAL. WITH THE MEL BOOK IN HAND OPENED TO THE PROCS SECTION, I DOUBLECHKED WITH THE OTHER MECH THAT THE VALVE HAD BEEN PROPERLY LOCKED CLOSED AND WAS SATISFIED WITH HIS ANSWER. TO THE BEST OF MY KNOWLEDGE AT THAT TIME, ALL WORK WAS IN FULL COMPLIANCE WITH THE MEL AND MAINT MANUAL. NOT UNTIL SUBSEQUENT MAINT AT ANOTHER STATION WAS THE PROB DISCOVERED.

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.