Maintenance Avionics; Maintenance Repairman
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
General Maintenance Action
Software and Automation; Procedure; Manuals; Chart Or Publication
On Aircraft X [a Boeing 737-900ER] I installed two serviceable Flight Control Computers (FCCs) and performed the Line Replacement Unit (LRU) replacement test in [the] Digital Flight Control System (DFCS) bite in accordance with the manual. While finding the correct software for the FCCs the mechanics ran a test on the elevator tab control.  The test failed step 5 resulting in the trim tabs split when pushing the control forward or aft instead of them going the same direction like the test calls out for. All breakers were in and no flight deck effect showed. I found out that the preloaded software was 737 MAX. As soon as I installed the correct software the tabs worked correctly in accordance with the test. My concern is that if someone misses loading the software like the manual tells them to do that there might be a safety of flight issue that could result in loss of life. I know its not supposed to happen because the manual tells you to check it but in a high pressure situation or with low experience it could and I don't want to see something like that happen.
Maintenance technician conducting a line replacement test after installing two Flight Control Computers on a Boeing 737-900 discovered that the installed software was for the B-737 MAX.