B757-200
Confusion; Workload; Training / Qualification
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Human Factors; Manuals; Procedure
We were reviewing the paperwork for [a Boeing 757 Leading Edge Slat Trailing Edge Wedge Skin Inspection (AD 91-22-51)] for a verifying signature just before noon. We recognized in reading this that we made two mistakes on [the previous] aircraft pertaining to the entries and signoffs: 1) The part number 012N8812-53 that was recorded for #5 Leading Edge Slat was not a valid part number in the B757 IPC search. This may need to be inspected as though it had no Data Plate. 2) The part number 012N8892-22M was recorded for #6 Leading Edge Slat. After reviewing the Table on 5.A and foot note at the bottom of Card 14; we found that the Slat needed to be inspected. I notified my Lead. He reviewed the paper with us and had me contact our Manager; who instructed me to call the Boeing Desk. I called and they explained how to re-inspect the slats. There should be a note that states that the part number should start with 114N3002- or 012N8892- and you are looking for these - numbers to inspect. Foot notes are not clear. It read to me; at the time; that Alpha (A) was the only end letter that applied; not all letters at the end; like (M). First time seeing this inspection (for our crew as well) and having other inbound flights to work. Noise level; arriving flight and ground equipment. [We need] clearer notes. Double check P/N's and S/N's [and] compare them to what was documented. Review the numbers with the Lead or better yet with [a Maintenance Technician] that has done the inspection before. Review the paper work inside before and afterwards with your co-worker(s).
While performing a complex inspection with paperwork that was unfamiliar; two Maintenance Technicians did not properly perform the required tasks. This was not recognzied until working on the second aircraft; one week after the improperly inspected aircraft was released for service.