Date: 201902
Local time of day: 0601-1200
Light: Dawn
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Reporter function: Trainee
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural MEL / CDL
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Procedure; Human Factors; Manuals; Company Policy
Primary problem: Human Factors

Narrative: Overnight maintenance is often performed at the [Company] maintenance hangar. [Company] mechanics often taxi [Company] operated [Airline] Embraer E175 aircraft from the [Company] maintenance hangar to the [Airline] terminal after the completion of overnight maintenance at the [Company] maintenance hangar.The [Airline] aircraft are repositioned from the [Company] maintenance hangar to the [Airline] terminal after the completion of overnight maintenance so the aircraft is at the [Airline] terminal in advance of when the first flight of the morning is due to depart. First flights of the morning start early. The goal of zero first flight delays is emphasized and is a primary objective and a key performance metric.At the beginning of my work shift; I asked if there would be an opportunity to taxi an (Embraer E175) aircraft (with myself as an engine run-taxi trainee) with a more senior mechanic (who is fully trained and certified to run-taxi as technician in command of the aircraft); from the maintenance hangar to the [Airline] terminal.In response to my request to participate in the aircraft run-taxi operation as a run-taxi trainee; I was told that after completion of high power engine run tests of Aircraft X; by the senior mechanic ; I could; as a trainee; participate in the taxi of Aircraft X with the more senior mechanic to terminal gate at the [Airline's terminal] so the Aircraft X would be in position at the [Airline] gate in advance of the first scheduled flight of the morning.There was a limited amount of time available to accomplish the high power engine test on Aircraft X and then taxi Aircraft X to the [Airline] terminal and still have the aircraft at the assigned gate in time for the first scheduled flight.Senior Mechanic; and I; as a run-taxi trainee; performed high power engine run tests to test the bleed 2 system. The high power engine run tests were necessary after maintenance on the bleed 2 system was performed. The maintenance of the bleed 2 system was performed and completed by mechanics on the previous shift. We completed the high power tests; leaving 30 minutes time available before the first scheduled flight.The operational (high power) check turned out good; and I was told by [the previous] shift Lead Mechanic to go ahead and sign the aircraft maintenance logbook (as inspector) and to have [Senior Mechanic] to sign the aircraft maintenance logbook as mechanic after we taxied Aircraft X to the terminal.Aircraft X was scheduled for [first] departure. We taxied Aircraft X to the [Airline] terminal gate. We remained with the aircraft and met the flight crew as the flight crew arrived at [the] gate. At this point; I noticed another deferral placard installed associated with Bleed 2 system.Once I was aware of the deferral placard; I called [the previous] shift Lead Mechanic asking why there is another deferral for bleed 2 since we were already asked to perform high power run tests.In response to my question; I was told to clear and sign this deferral as well; as [the previous] shift had completed the maintenance associated with the deferral of the bleed 2 system. [The previous shift Lead Mechanic] said there was an M-action needed to be completed prior clearing [the deferral]. The M-action requires the NPRSOV Valves to be unlocked. In response to the need to complete the M-action as quickly as possible; we divided the work needed to complete the M-Action task and each of us performed a portion of the task. I focused on reviewing the logbook and called the office for help so someone could bring the tools and help us. [Senior Mechanic] was reading the reference information [Maintenance Manual] section 36-XX-XX. [Other Mechanic] went to get the necessary tools. I focused on signing off the gear pins; wake up; engine run; and bleed 2 NPRSOV locked closed work orders. [Senior Mechanic] inspected the system and found the bleed 2 NPRSOV High Stage was locked closed and Low Stage was locked open while deferred and determined that the High Stage valve needed to be changed (to both valves closed) as he compared the valves in question with the valves on the other engine and verified his findings with a review of [Maintenance Manual] section 36-XX-XX. Then either [Senior Mechanic]; [Other Mechanic]; or both [Senior Mechanic] and [Other Mechanic] performed the M-action of actually unlocking the NPRSOV valves as [Other Mechanic] said he has performed this particular M-action before.When I was nearing completion of my portion of the task of helping with paperwork and signing previously mentioned write ups in the log book; I was told by [Senior Mechanic] that the required M-Action was completed and that the valves were put in the proper configuration. I then took pictures of the valves; and sent the photographs of the valves to [previous shift Lead Mechanic] so he could take a look at the photographs of the valves. I signed the log book; and cleared the deferral with Maintenance control. [Senior Mechanic] signed his portion of the logbook and someone else (I believe [Other Mechanic]) returned the log book to the Aircraft cockpit and closed the engines cowls. The aircraft was then taken by the flight crew and 2 hours later I received a phone call from [Senior Mechanic] that Aircraft X came back to the gate with bleed 2 problem.  After performing (as a run-taxi trainee) engine high power run tests and taxing the aircraft; we determined that an m-action needed to be completed within a short period of time in order to avoid a first flight delay. In an effort to complete the m-action as quickly as possible and avoid the first flight delay; we divided the tasks involved needed to complete the m-action. I was given the task of signing the maintenance logbook. The task of actually performing the m-action was assigned to another mechanic. As it turns out; whichever of the other mechanics ([Other Mechanic] and or [Senior Mechanic]) performed the m-action; the mechanic did not perform the m-action correctly.I trusted a more experienced mechanic; [Senior Mechanic]; an RII inspector; to verify that the m-action was completed correctly. I felt comfortable with him inspecting the work and verifying that the m-action was performed correctly; as he was reading the aircraft maintenance manual and was checking and verifying the position of the valves. The pressure to complete the mission of getting the first flight out on time played a role in the events leading up to the maintenance error. In retrospect; I should have not signed off [the deferral] until I personally verified that the valves were properly positioned (activated) and unlocked in accordance with the applicable reference data.In the future; I will be extremely vigilant to personally verify the proper completion of all maintenance I sign off; regardless of the qualifications; experience; and training of any and all other mechanics involved; and to insist that others do so as well. I will be vigilant to resist the pressure to compromise my commitment to personally verify any and all work I sign off in order to meet deadlines. I believe it is most important to make sure that I personally verify all work that I sign off is completed properly and without compromise and in accordance with all applicable reference data.




Synopsis: Mechanic reported that an aircraft returned to departure airport after engine maintenance work was done incorrectly.