Commercial Fixed Wing
Maintenance Powerplant; Maintenance Airframe
Time Pressure; Troubleshooting; Workload; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action; General Flight Cancelled / Delayed
Human Factors; Procedure; Logbook Entry; Aircraft
Aircraft X was scheduled to have a THSA (Trimmable Horizontal Stabilizer Actuator) oil inspection complete which it failed due to a leak. The THSA was then replaced by 1st and 2nd shift on Date. After installation the THSA failed the operational checks. The aircraft was then turned over to 3rd shift. 3rd shift changed parts but the ops checks were still failing. The corrective action ended by stating no fix and that position transducer on the THSA was suspected to be faulty. The aircraft was then turned over to 1st shift on Date 1. 1st shift signed the non-routine off without addressing the no fix statement. The operational checks were also stamped in the job card as being completed by a mechanic and an inspector. I came in for my 3rd shift last night Date 1 and was curious what 1st shift did to fix the problem. I found that nothing was documented on the non-routine addressing the no fix statement. another mechanic went to the aircraft and went through the ops checks in the cockpit and the checks failed exactly as they did the night before. Management was notified and the aircraft was brought back to the hangar from the gate. I was informed that the mechanic and inspector would be asked about it but the aircraft was never removed from service.  Please have another mechanic and a different inspector run through the operational checks per the THSA replacement job card. the stab control wheel does not return to zero after being placed in 13.5 up position and sec 1 is reset. The THSA stops at .4 when .3 is the limit.
Technician reported procedures were not followed during the replacement of a failed Trimmable Horizontal Stabilizer Actuator.