Narrative:

#1 engine cowl anti-ice valve issue was the cause for the gate call while performing MEL special procedures. I found high stage valve lockout bolt frozen. The bolt broke off while trying to lock out valve. While I was replacing the valve; my partner; mechanic #2; worked the cowl valve and tai cannon plug. After we finished the high stage valve right&right; I did the paperwork while mechanic #2 closed the cowls for departure. It seems as though mechanic #2 disconnected the wrong cannon plug as part of special procedures and was later discovered by contract maintenance in ZZZ1. Onboard computer unit hard to work with to work special procedures. I've seen a couple of these issues. Callback conversation with reporter revealed the following information: reporter stated the B737-300/500 nose cowl anti-ice valves have a longer shape compared to the next gen series aircraft; both of which have the cfm-56 engines. The next gen aircraft nose cowl valve has a shape similar to a football. However; the confusion as to which cannon plug connector to disconnect and stow in order to satisfy their MEL procedure for the nose cowl anti-ice valve; continues. Reporter also stated he hopes a recent maintenance alert bulletin issued with better identification of the required connector to be disconnected reduces the confusion. The correct cannon plug to be disconnected is the thermal anti-ice valve pressure switch (tai) connector; not the nose cowl anti-ice valve connector.

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Original NASA ASRS Text

Title: A B737 MECHANIC REPORTS OF SIGNING OFF PAPERWORK REQUIRING AN MEL PROCEDURE THAT INCLUDED THE DISCONNECTING AND STOW OF THE #1 ENG NOSE COWL ANTI-ICE VALVE TAI PRESS SWITCH CONNECTOR; BUT WAS LATER FOUND NOT DISCONNECTED.

Narrative: #1 ENG COWL ANTI-ICE VALVE ISSUE WAS THE CAUSE FOR THE GATE CALL WHILE PERFORMING MEL SPECIAL PROCS. I FOUND HIGH STAGE VALVE LOCKOUT BOLT FROZEN. THE BOLT BROKE OFF WHILE TRYING TO LOCK OUT VALVE. WHILE I WAS REPLACING THE VALVE; MY PARTNER; MECH #2; WORKED THE COWL VALVE AND TAI CANNON PLUG. AFTER WE FINISHED THE HIGH STAGE VALVE R&R; I DID THE PAPERWORK WHILE MECH #2 CLOSED THE COWLS FOR DEP. IT SEEMS AS THOUGH MECH #2 DISCONNECTED THE WRONG CANNON PLUG AS PART OF SPECIAL PROCS AND WAS LATER DISCOVERED BY CONTRACT MAINT IN ZZZ1. ONBOARD COMPUTER UNIT HARD TO WORK WITH TO WORK SPECIAL PROCS. I'VE SEEN A COUPLE OF THESE ISSUES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED THE B737-300/500 NOSE COWL ANTI-ICE VALVES HAVE A LONGER SHAPE COMPARED TO THE NEXT GEN SERIES ACFT; BOTH OF WHICH HAVE THE CFM-56 ENGINES. THE NEXT GEN ACFT NOSE COWL VALVE HAS A SHAPE SIMILAR TO A FOOTBALL. HOWEVER; THE CONFUSION AS TO WHICH CANNON PLUG CONNECTOR TO DISCONNECT AND STOW IN ORDER TO SATISFY THEIR MEL PROCEDURE FOR THE NOSE COWL ANTI-ICE VALVE; CONTINUES. REPORTER ALSO STATED HE HOPES A RECENT MAINT ALERT BULLETIN ISSUED WITH BETTER IDENTIFICATION OF THE REQUIRED CONNECTOR TO BE DISCONNECTED REDUCES THE CONFUSION. THE CORRECT CANNON PLUG TO BE DISCONNECTED IS THE THERMAL ANTI-ICE VALVE PRESSURE SWITCH (TAI) CONNECTOR; NOT THE NOSE COWL ANTI-ICE VALVE CONNECTOR.

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