A Line Mechanic reports he failed to notice a Passenger Seat Inspection Operational Check Taskcard for the right cabin seats on a B737-800 was actually a stand alone Jobcard for Inspection only. He had included the Inspection Card with other 'A' Check Interior jobcards and signed all them off.

Narrative

'A' Check task cards were issued as usual. I divided the task cards into the aircraft areas to be worked. I took the Interior 'A' Check Cards to the B737-800 aircraft and reviewed them noticing there was a new stand alone task card added to the night's check that required a check of the passenger seats on the right side of the aircraft. I read Task Card XXXX; PASSENGER SEATS INSPECTION/OPERATIONAL CHECK-RIGHT; task instructions in its entirety and realized that it was very similar to our [Technician] Seat Inspection done as part of the 'A' Check Interior Card. I placed the task card with my other task cards after reviewing them all and went about my work for the night. During completion of my night's work; I stamped-off the completed tasks until fully complete; not realizing that Task Card XXXX was an Inspection Card. I reviewed the task cards looking for missing blocks; found none and turned in my paper work. On my following work night; a co-worker was completing the same card and was talking about some of the discrepancies he found. I spoke to him about completing the task card the night before and realized upon looking at his paperwork that his was an Inspection Card. I went to my Supervisor and asked him if I could check if the card being worked that night was the same as I had worked on the previous night. I realized my mistake and again let the Supervisor know about the problem with the previous B737-800 paperwork. Task Card XXXX; PASSENGER SEATS INSPECTION/OPERATIONAL CHECK-RIGHT; was a task card I did not recognize. In my review of the card; although I read thoroughly thru the task instructions; I did not recognize that this was an Inspection Card. I understand the different sign-off locations; indicating Technician and Inspection stamp areas on our task cards. However; Task Card XXXX is so similar to our other [Technician] Seat Inspection cards that are already done as part of the 'A' Check Interior Card (not an Inspection Card); that I wrongfully assumed it was a Technician's card. Also; I always look for items that may require Inspection due to being RII Required Systems and ETOPS critical systems that would normally [be] red flagged for multi-system maintenance; and a Seat Check did not set me in that line of thought. Finally I should have seen the Inspection blocks I stamped; on Final Review but I was tired that night and during the Final Review I saw no blank areas of paperwork signoffs (since I had already reviewed and read all task instructions at the beginning of the night); I assumed all was correct and turned in my paperwork. Supervisor verified that the [Inspection] Card was a stand alone card and that the aircraft had not over flown [the Inspection Card] scheduled due date. The card was re-issued for completion on the aircraft. Supervisor counseled me on the problem and its effects. My mistake was in complacency and fatigue/lack of sleep. Both are problems that I know and recognize. The initial failure to not recognize the Inspection Task; complacency; believing that because it was similar to the other 'A' Check card (non-Inspection); and fatigue/lack of sleep in not recognizing my mistake on final paperwork review. In order to prevent a recurrence I will have to try to maintain better focus before; and after work completion; in order to slow down; reassess and re-focus for initial and final paperwork review.