Narrative:

Aircraft X arrived with 1 write-up. Amber tai indication illuminated during flight on #2 engine. Upon arrival at gate; the engine was opened and inspection/troubleshooting was started. The engine anti-ice valve was operated 6 complete cycles with no abnormal indications. Because no root cause was found; the decision was made between myself and maintenance control to MEL the engine anti-ice valve in the open position so as not to incur icing restrs using MEL. This also required the use of another MEL to lock the high stage valve closed. As I was already in the flight deck operating the valve and bleed switches; I started the MEL paperwork while mr X complied with the departure deviation guide procedures under the direction of maintenance controller; mr Y. During the time mr X was being given direction; I was explaining to the oncoming flight crew what we were doing so they could begin their initial flight planning. I did not hear all the details given to mr X but assumed that all the procedures were relayed and followed. The aircraft departed after a short delay with no further incident. I was informed that aircraft had an air turn-back because of an over-pressure related flight deck indication on takeoff. This was found to be attributed to the fact that the cannon plug for this pressure switch was not removed; capped and stowed as should have been done per the requirements of MEL. The aircraft made an air turn-back because the amber 'cowl anti-ice' light illuminated on climb out. This light is directly connected to the pressure switch which should have been disconnected. I should have relayed the departure deviation guide requirements; myself; to mr X and verified that the full procedure was completed prior to releasing the aircraft to service. Had the full procedure been followed; this event would not have occurred. I should have verified that all the departure deviation guide procedures were followed. This should be common practice as 2 sets of eyes are better than one. I will also remove myself from the flight deck during MEL procedures such as this to alleviate the distrs that caused me to not hear all the relayed instructions to my fellow mechanic. This will help to ensure that instructions are not missed. Supplemental information from acn 780038: log item; #2 amber light; came on with switch turned to the 'on' position. Mr Z and I opened reverser for access to pressure regulating shutoff valve to allow us to operate the anti-ice valve to check it. Mr Z went to the flight deck; I stayed at the engine to watch valve and listen for air flow into the cowl. Since it operated with no difficulties; I thought we were going to sign off the discrepancy. Mr Y and mr Z were talking about which light was coming on and mr Y said to be on the safe side we should MEL the anti-ice valve in the 'open' position and lockout the high stage valve. I do not remember what the actual words were about taking the cannon plug off. I know mr Y said be sure to take the cannon plug off. I don't remember if he said valve or not but I know I was not told to take the plug off the pressure switch. It's possible that part of the transmission was dropped as our radios have lots of static and break up at times. Possible dropped communication. My thinking the cannon plug on the valve when in fact it was supposed to be the pressure switch.

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Original NASA ASRS Text

Title: A B737-800 ACFT REQUIRED AN AIR TURN BACK DUE TO #2 ENGINE AMBER 'COWL' ANTI-ICE LIGHT ILLUMINATED ON CLIMB-OUT. CANON PLUG FOR NOSE COWL ANTI-ICE VALVE PRESSURE SWITCH NOT REMOVED AS PART OF MEL REQUIREMENT.

Narrative: ACFT X ARRIVED WITH 1 WRITE-UP. AMBER TAI INDICATION ILLUMINATED DURING FLT ON #2 ENG. UPON ARR AT GATE; THE ENG WAS OPENED AND INSPECTION/TROUBLESHOOTING WAS STARTED. THE ENG ANTI-ICE VALVE WAS OPERATED 6 COMPLETE CYCLES WITH NO ABNORMAL INDICATIONS. BECAUSE NO ROOT CAUSE WAS FOUND; THE DECISION WAS MADE BTWN MYSELF AND MAINT CTL TO MEL THE ENG ANTI-ICE VALVE IN THE OPEN POS SO AS NOT TO INCUR ICING RESTRS USING MEL. THIS ALSO REQUIRED THE USE OF ANOTHER MEL TO LOCK THE HIGH STAGE VALVE CLOSED. AS I WAS ALREADY IN THE FLT DECK OPERATING THE VALVE AND BLEED SWITCHES; I STARTED THE MEL PAPERWORK WHILE MR X COMPLIED WITH THE DEP DEVIATION GUIDE PROCS UNDER THE DIRECTION OF MAINT CTLR; MR Y. DURING THE TIME MR X WAS BEING GIVEN DIRECTION; I WAS EXPLAINING TO THE ONCOMING FLT CREW WHAT WE WERE DOING SO THEY COULD BEGIN THEIR INITIAL FLT PLANNING. I DID NOT HEAR ALL THE DETAILS GIVEN TO MR X BUT ASSUMED THAT ALL THE PROCS WERE RELAYED AND FOLLOWED. THE ACFT DEPARTED AFTER A SHORT DELAY WITH NO FURTHER INCIDENT. I WAS INFORMED THAT ACFT HAD AN AIR TURN-BACK BECAUSE OF AN OVER-PRESSURE RELATED FLT DECK INDICATION ON TKOF. THIS WAS FOUND TO BE ATTRIBUTED TO THE FACT THAT THE CANNON PLUG FOR THIS PRESSURE SWITCH WAS NOT REMOVED; CAPPED AND STOWED AS SHOULD HAVE BEEN DONE PER THE REQUIREMENTS OF MEL. THE ACFT MADE AN AIR TURN-BACK BECAUSE THE AMBER 'COWL ANTI-ICE' LIGHT ILLUMINATED ON CLBOUT. THIS LIGHT IS DIRECTLY CONNECTED TO THE PRESSURE SWITCH WHICH SHOULD HAVE BEEN DISCONNECTED. I SHOULD HAVE RELAYED THE DEP DEVIATION GUIDE REQUIREMENTS; MYSELF; TO MR X AND VERIFIED THAT THE FULL PROC WAS COMPLETED PRIOR TO RELEASING THE ACFT TO SVC. HAD THE FULL PROC BEEN FOLLOWED; THIS EVENT WOULD NOT HAVE OCCURRED. I SHOULD HAVE VERIFIED THAT ALL THE DEP DEVIATION GUIDE PROCS WERE FOLLOWED. THIS SHOULD BE COMMON PRACTICE AS 2 SETS OF EYES ARE BETTER THAN ONE. I WILL ALSO REMOVE MYSELF FROM THE FLT DECK DURING MEL PROCS SUCH AS THIS TO ALLEVIATE THE DISTRS THAT CAUSED ME TO NOT HEAR ALL THE RELAYED INSTRUCTIONS TO MY FELLOW MECH. THIS WILL HELP TO ENSURE THAT INSTRUCTIONS ARE NOT MISSED. SUPPLEMENTAL INFO FROM ACN 780038: LOG ITEM; #2 AMBER LIGHT; CAME ON WITH SWITCH TURNED TO THE 'ON' POS. MR Z AND I OPENED REVERSER FOR ACCESS TO PRESSURE REGULATING SHUTOFF VALVE TO ALLOW US TO OPERATE THE ANTI-ICE VALVE TO CHK IT. MR Z WENT TO THE FLT DECK; I STAYED AT THE ENG TO WATCH VALVE AND LISTEN FOR AIR FLOW INTO THE COWL. SINCE IT OPERATED WITH NO DIFFICULTIES; I THOUGHT WE WERE GOING TO SIGN OFF THE DISCREPANCY. MR Y AND MR Z WERE TALKING ABOUT WHICH LIGHT WAS COMING ON AND MR Y SAID TO BE ON THE SAFE SIDE WE SHOULD MEL THE ANTI-ICE VALVE IN THE 'OPEN' POS AND LOCKOUT THE HIGH STAGE VALVE. I DO NOT REMEMBER WHAT THE ACTUAL WORDS WERE ABOUT TAKING THE CANNON PLUG OFF. I KNOW MR Y SAID BE SURE TO TAKE THE CANNON PLUG OFF. I DON'T REMEMBER IF HE SAID VALVE OR NOT BUT I KNOW I WAS NOT TOLD TO TAKE THE PLUG OFF THE PRESSURE SWITCH. IT'S POSSIBLE THAT PART OF THE XMISSION WAS DROPPED AS OUR RADIOS HAVE LOTS OF STATIC AND BREAK UP AT TIMES. POSSIBLE DROPPED COM. MY THINKING THE CANNON PLUG ON THE VALVE WHEN IN FACT IT WAS SUPPOSED TO BE THE PRESSURE SWITCH.

Data retrieved from NASA's ASRS site as of May 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.