Narrative:

The aircraft was in the 4TH and last day of an 'a' check. We were under heavy pressure to complete the 'a' check and return the aircraft to revenue service. A problem with a pressurization outflow valve was thought to have been corrected the previous day by replacing the automatic pressure controller. The fault had returned, technicians now believed the problem was being caused by the outflow valve itself, and had placed an order for the valve assembly. As the technical representative, I was informed that there were no valve assemblies in stock, or readily available other than by direct purchase at a cost of over $40,000.00. With knowledge that most such problems are attributable to the actuator on the valve, I was certain that we didn't need the entire assembly, but only the actuator assembly which is easily replaced via instructions in the maintenance manual. I ordered an actuator assembly of a part number correct for an outflow valve assembly directly compatible with the one installed in the plane. When the new actuator arrived, it was noted that the shell covering one of the electric motors had been clocked in such a way as to prevent installation without interfering with adjacent structure, and preventing the electrical connector from being installed. Believing the problem to simply be with the installation of the shell, I removed the 3 self locking screws securing the cover, rotated it 120 degrees counterclockwise, and reinstalled them using standard torque. The unit was installed without any problems and the functional check was carried out successfully. My concern is that I had no ready access to the component maintenance procedure for the part. Such component manuals are available to operators, but my company doesn't have them. I think requiring commercial operators to have at least 1 set of such manuals either at or available to mechanics at locations where heavy maintenance is routinely performed would at least inform technicians of maintenance actions that could only be performed in a shop environment.

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Original NASA ASRS Text

Title: A B747-200F OUTFLOW VALVE ACTUATOR MOTOR WAS ROTATED 120 DEGS TO AVOID STRUCTURE INTERFERENCE. MOTOR POS CHANGED WITHOUT USE OF COMPONENT MANUAL.

Narrative: THE ACFT WAS IN THE 4TH AND LAST DAY OF AN 'A' CHK. WE WERE UNDER HVY PRESSURE TO COMPLETE THE 'A' CHK AND RETURN THE ACFT TO REVENUE SVC. A PROB WITH A PRESSURIZATION OUTFLOW VALVE WAS THOUGHT TO HAVE BEEN CORRECTED THE PREVIOUS DAY BY REPLACING THE AUTOMATIC PRESSURE CONTROLLER. THE FAULT HAD RETURNED, TECHNICIANS NOW BELIEVED THE PROB WAS BEING CAUSED BY THE OUTFLOW VALVE ITSELF, AND HAD PLACED AN ORDER FOR THE VALVE ASSEMBLY. AS THE TECHNICAL REPRESENTATIVE, I WAS INFORMED THAT THERE WERE NO VALVE ASSEMBLIES IN STOCK, OR READILY AVAILABLE OTHER THAN BY DIRECT PURCHASE AT A COST OF OVER $40,000.00. WITH KNOWLEDGE THAT MOST SUCH PROBS ARE ATTRIBUTABLE TO THE ACTUATOR ON THE VALVE, I WAS CERTAIN THAT WE DIDN'T NEED THE ENTIRE ASSEMBLY, BUT ONLY THE ACTUATOR ASSEMBLY WHICH IS EASILY REPLACED VIA INSTRUCTIONS IN THE MAINT MANUAL. I ORDERED AN ACTUATOR ASSEMBLY OF A PART NUMBER CORRECT FOR AN OUTFLOW VALVE ASSEMBLY DIRECTLY COMPATIBLE WITH THE ONE INSTALLED IN THE PLANE. WHEN THE NEW ACTUATOR ARRIVED, IT WAS NOTED THAT THE SHELL COVERING ONE OF THE ELECTRIC MOTORS HAD BEEN CLOCKED IN SUCH A WAY AS TO PREVENT INSTALLATION WITHOUT INTERFERING WITH ADJACENT STRUCTURE, AND PREVENTING THE ELECTRICAL CONNECTOR FROM BEING INSTALLED. BELIEVING THE PROB TO SIMPLY BE WITH THE INSTALLATION OF THE SHELL, I REMOVED THE 3 SELF LOCKING SCREWS SECURING THE COVER, ROTATED IT 120 DEGS COUNTERCLOCKWISE, AND REINSTALLED THEM USING STANDARD TORQUE. THE UNIT WAS INSTALLED WITHOUT ANY PROBS AND THE FUNCTIONAL CHK WAS CARRIED OUT SUCCESSFULLY. MY CONCERN IS THAT I HAD NO READY ACCESS TO THE COMPONENT MAINT PROC FOR THE PART. SUCH COMPONENT MANUALS ARE AVAILABLE TO OPERATORS, BUT MY COMPANY DOESN'T HAVE THEM. I THINK REQUIRING COMMERCIAL OPERATORS TO HAVE AT LEAST 1 SET OF SUCH MANUALS EITHER AT OR AVAILABLE TO MECHS AT LOCATIONS WHERE HVY MAINT IS ROUTINELY PERFORMED WOULD AT LEAST INFORM TECHNICIANS OF MAINT ACTIONS THAT COULD ONLY BE PERFORMED IN A SHOP ENVIRONMENT.

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.