Narrative:

We were tasked with removing the right hand elevator assembly from aircraft X due to a lightning strike. We removed the assembly and on the work bench transferred the trim tab and associated hardware to the new elevator assembly. We then turned over the installation of elevator to [the day shift].at the beginning of our shift [the next day] we took a turn over from [evening shift]. Evening [shift] had installed the elevator and told us that a bushing was being aog'd (aircraft on ground) to install in the #2 hinge because it was missing or misplaced. After we received the bushing and installed it the inspector asked us if we or the previous shift had verified the trim tab balance weights. We confirmed that we didn't nor did we know if the previous shifts had verified the correct weights. The inspector then requested that we re-open the #2 balance bay panel to verify. After open up the inspector and aircraft maintenance technicians confirmed that we were taking off the correct weights per the amm (aircraft maintenance manual) illustration.we then accessed the weights and noticed that it had 3 locations with 3 weights each. The old elevator had 3 locations with 2 weights each. So we had to remove a total of three weights from the new elevator. We then closed up the access panel and proceeded on with operational checks. It was discovered [one week later] when working a left hand elevator remove and replace on [another aircraft] that the incorrect weights were removed from the elevator on aircraft X [serviced the week before]. The inspector and aircraft maintenance technicians noticed that we had removed elevator balance weights rather than trim tab balance weights which are adjacent to them on the lower side of aircraft X. Contributing factors are aircraft maintenance technicians working on an elevator remove and replace for the first time. The amm illustration was misinterpreted which caused the incorrect weights to be removed. Create a [maintenance task] so that procedures aren't missed in the future.

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Original NASA ASRS Text

Title: Air carrier Maintenance Technicians reported incorrectly removing wrong balance weights from elevator on B737-800 aircraft.

Narrative: We were tasked with removing the Right Hand elevator assembly from Aircraft X due to a lightning strike. We removed the assembly and on the work bench transferred the trim tab and associated hardware to the new elevator assembly. We then turned over the installation of elevator to [the day shift].At the beginning of our shift [the next day] we took a turn over from [evening shift]. Evening [shift] had installed the elevator and told us that a bushing was being AOG'd (Aircraft On Ground) to install in the #2 hinge because it was missing or misplaced. After we received the bushing and installed it the Inspector asked us if we or the previous shift had verified the trim tab balance weights. We confirmed that we didn't nor did we know if the previous shifts had verified the correct weights. The Inspector then requested that we re-open the #2 balance bay panel to verify. After open up the Inspector and aircraft maintenance technicians confirmed that we were taking off the correct weights per the AMM (Aircraft Maintenance Manual) illustration.We then accessed the weights and noticed that it had 3 locations with 3 weights each. The old elevator had 3 locations with 2 weights each. So we had to remove a total of three weights from the new elevator. We then closed up the access panel and proceeded on with operational checks. It was discovered [one week later] when working a Left Hand elevator remove and replace on [another aircraft] that the incorrect weights were removed from the elevator on Aircraft X [serviced the week before]. The Inspector and aircraft maintenance technicians noticed that we had removed elevator balance weights rather than trim tab balance weights which are adjacent to them on the lower side of Aircraft X. Contributing factors are aircraft maintenance technicians working on an elevator remove and replace for the first time. The AMM illustration was misinterpreted which caused the incorrect weights to be removed. Create a [Maintenance Task] so that procedures aren't missed in the future.

Data retrieved from NASA's ASRS site 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.