A MECHANIC WORKING ON AN A320; UNKNOWINGLY SIGNED OFF A MAINTENANCE TASK CARD HE DID NOT PERFORM THAT CHECKS THE TRIMMABLE HORIZONTAL STABILIZER (THS) PERFORMANCE AND HYDRAULIC SYSTEMS.

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THE THS CMR CHK ON ACFT X WAS MARKED 'N/A' (NOT APPLICABLE) IN 3 SIGNOFF BLOCKS OF THE THS ACTUATOR CMR CHK (MAINT TASK #2744). THESE 3 BLOCKS WERE THE ONLY BLOCKS INCORPORATED IN THE CHK. IT WAS BROUGHT TO MY ATTN BY MY DEPT'S QUALITY ASSURANCE THE PROB THAT AROSE. I EXPLAINED THAT THE DIALOGUE AND CONTEXT LED ME TO BELIEVE THAT THIS WAS THE CORRECT ACTION AT THAT CURRENT TIME. BECAUSE OF THIS; THE APPLICABLE CMR CHK WAS NOT DONE AND THE ACFT HAD TO BE GNDED UNTIL THE CHK WAS COMPLETED. I WAS ALSO INFORMED THAT A TOTAL OF 8 OTHER MECHS DID THE SAME AS ME ON OTHER ACFT. BECAUSE OF THIS THE MAINT TASK WORD CARD FOR THIS TASK HAS BEEN REWRITTEN TO INCLUDE BETTER CONTEXT AND ACFT EFFECTIVITY LAYOUT. THE END RESULT OF THIS SCENARIO WAS MYSELF UNKNOWINGLY SIGNING OFF THAT A TASK WAS COMPLETED WHEN IN FACT IT WAS NOT. AT THE TIME I WAS THINKING THAT SOMETHING WAS CORRECT DUE TO THE WORDING OF THAT TASK'S WORD CARD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED SOME OF THEIR A320'S DO NOT REQUIRE THAT PARTICULAR THS PERFORMANCE CHECK. BUT THE AIRCRAFT PAPERWORK HE APPLIED THE 'NOT APPLICABLE' (N/A) TO; WAS NOT ONE OF THEM. PART OF THE CHECK IS TO PULL CIRCUIT BREAKERS DURING A STAB OPERATION TO KNOCK OUT A SYSTEM AND VERIFY ECAM WARNINGS AND ALTERNATE SYSTEMS WILL FUNCTION AS REQUIRED UNDER DIFFERENT CONDITIONS. REPORTER STATED THAT AS A RESULT OF HIS MISUNDERSTANDING AND EIGHT OTHER MECHANICS APPLYING SIMILAR N/A'S TO THEIR PAPERWORK; THE TASK CARD HAS BEEN BROKEN OUT INTO TWO SEPARATE JOB CARDS INSTEAD OF ONE.