Narrative:

Event: open static line on captain's side in electrical and electronics compartment of an medium large transport aircraft. I was troubleshooting an autoplt writeup of which was deferred. During the process of troubleshooting as per the maintenance manual I suspected the air data causing the problem. I have a repair man's certificate for another local airline which does not allow me to use or interrupt the pitot-static systems west/O being accompanied by an inspector or mechanic who is pitot-static authority/authorized. The problem arose when the auxiliary static system was disconnected after a leak check had been performed and the air date computer out of stock had failed the self-test. I made the decision to remove the newly installed air data computer and replace with another one. It was getting late by this time and the inspectors that were with me had 2 other aircraft to perform tests on pitot-static systems. I decided to help speed things up and route the pitot-static lines from the test box and disconnect the static line to what I thought was the auxiliary system. I did this while the inspectors were away at the time. I never questioned myself or the inspectors if they had connected to the line I had disconnected for them. The air data computer operations and the auxiliary system leaks checked good. The aircraft took off on its scheduled flight and that's when the pilot noticed his altimeter was not responding. The paperwork covering the information on what was done to the aircraft previous of the flight was used as reference, and a quick phone call to my home. We were able to direct the maintenance crew to the problem and rectify the situation quickly. I had the maintenance manual with me for the troubleshooting of the autoplt system but not the pitot-static system, which was my initial mistake. I believe by trying to speed things upon my first midnight shift back on duty impaired my decision on disconnecting the wrong static line west/O communicating through the maintenance manual or the inspectors I was working with at the time. These items will be adhered to more strictly from now on.

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Original NASA ASRS Text

Title: AFTER RECEIVING CORRECTIVE MAINTENANCE ON ITS PITOT STATIC SYSTEM, AN ACR MLG RETURNS TO LAND AFTER ITS ALTIMETER FAILS TO OPERATE PROPERLY AFTER TKOF.

Narrative: EVENT: OPEN STATIC LINE ON CAPT'S SIDE IN ELECTRICAL AND ELECTRONICS COMPARTMENT OF AN MLG ACFT. I WAS TROUBLESHOOTING AN AUTOPLT WRITEUP OF WHICH WAS DEFERRED. DURING THE PROCESS OF TROUBLESHOOTING AS PER THE MAINT MANUAL I SUSPECTED THE AIR DATA CAUSING THE PROB. I HAVE A REPAIR MAN'S CERTIFICATE FOR ANOTHER LCL AIRLINE WHICH DOES NOT ALLOW ME TO USE OR INTERRUPT THE PITOT-STATIC SYSTEMS W/O BEING ACCOMPANIED BY AN INSPECTOR OR MECH WHO IS PITOT-STATIC AUTH. THE PROB AROSE WHEN THE AUX STATIC SYS WAS DISCONNECTED AFTER A LEAK CHK HAD BEEN PERFORMED AND THE AIR DATE COMPUTER OUT OF STOCK HAD FAILED THE SELF-TEST. I MADE THE DECISION TO REMOVE THE NEWLY INSTALLED AIR DATA COMPUTER AND REPLACE WITH ANOTHER ONE. IT WAS GETTING LATE BY THIS TIME AND THE INSPECTORS THAT WERE WITH ME HAD 2 OTHER ACFT TO PERFORM TESTS ON PITOT-STATIC SYSTEMS. I DECIDED TO HELP SPD THINGS UP AND RTE THE PITOT-STATIC LINES FROM THE TEST BOX AND DISCONNECT THE STATIC LINE TO WHAT I THOUGHT WAS THE AUX SYS. I DID THIS WHILE THE INSPECTORS WERE AWAY AT THE TIME. I NEVER QUESTIONED MYSELF OR THE INSPECTORS IF THEY HAD CONNECTED TO THE LINE I HAD DISCONNECTED FOR THEM. THE AIR DATA COMPUTER OPS AND THE AUX SYS LEAKS CHKED GOOD. THE ACFT TOOK OFF ON ITS SCHEDULED FLT AND THAT'S WHEN THE PLT NOTICED HIS ALTIMETER WAS NOT RESPONDING. THE PAPERWORK COVERING THE INFO ON WHAT WAS DONE TO THE ACFT PREVIOUS OF THE FLT WAS USED AS REF, AND A QUICK PHONE CALL TO MY HOME. WE WERE ABLE TO DIRECT THE MAINT CREW TO THE PROB AND RECTIFY THE SITUATION QUICKLY. I HAD THE MAINT MANUAL WITH ME FOR THE TROUBLESHOOTING OF THE AUTOPLT SYS BUT NOT THE PITOT-STATIC SYS, WHICH WAS MY INITIAL MISTAKE. I BELIEVE BY TRYING TO SPD THINGS UPON MY FIRST MIDNIGHT SHIFT BACK ON DUTY IMPAIRED MY DECISION ON DISCONNECTING THE WRONG STATIC LINE W/O COMMUNICATING THROUGH THE MAINT MANUAL OR THE INSPECTORS I WAS WORKING WITH AT THE TIME. THESE ITEMS WILL BE ADHERED TO MORE STRICTLY FROM NOW ON.

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.