Date: 202004
Local time of day: 0001-0600
Flight conditions: VMC
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Normal Brake System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown; Time Pressure; Workload; Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Environment - Non Weather Related; Procedure; Human Factors
Primary problem: Procedure

Narrative: We were told that our assigned aircraft had changed. We now had Aircraft X [on the ground] and [an inspection aircraft] still scheduled to arrive [a few hours later]. We went to Aircraft X and started with completing the Maintenance Visit inspection before starting the FIM [Fault Identification Manual] for brakes dragging. During the inspection we found the L/H aft Position light inop and an MEL for galley drawer we needed parts for. We went to grab parts for Mel and light. During this time [another aircraft] returned to a gate for PSEU [Proximity Switch Electronic Unit] light on. The Lead asked for anyone available to answer the call. After the second request AMT2 [Aircraft Maintenance Tech 2] and I decided to answer the gate return. We were able to fix the PSEU light and [the] aircraft was able to continue its flight though it took a little longer than planned. We got back to Aircraft X; we fixed the L/H position light and galley MEL and began working the FIM. The FIM asked us to apply brakes and observe the piston actuation and retractions if no problems were observed the fault was transitory. We called Maintenance Control to clear the MEL and report our findings on the brake dragging. Maintenance Control asked us to perform an additional task of jacking both gears of the aircraft and physically spin all 4 Main Landing Gear tires. So we went to get the landing gear jack and brought it to the aircraft and jacked the R/H landing gear first. While spinning the wheels we found the #3 grinding and not spinning freely. I started to prep for tire and brake removal. AMT2 went to go get the torque wrenches and thread/axle protectors we would need to change the #3 brakes. We felt we had to have the brake changed and aircraft ready to fly before our [next] check aircraft arrived because we did not know how long it would take to complete the check and if we could make it back out to Aircraft X. We changed the brake [about 10 minutes before the next aircraft was scheduled to arrive] and when we torqued the tire back on and we still needed to jack the LH side as soon as the tire was on and secured. We lowered the gear and I went to jack the left side while AMT2 installed dust cover. I jacked and spun the left gear and found them spinning freely. Over the radio we heard that [our next assigned aircraft] was on the ground and taxiing to [the] gate. I remember worrying about making it to debrief the crew and completing the check package before morning launch. I lowered the left gear while AMT2 picked up the old brake and filled out PCT [Parts Control Tag]. AMT2 loaded the tire cart while I set the brakes and grabbed the log book. We split up; AMT2 went to finish the log book and turn in the tire equipment while I met [the next] aircraft and started the check. The rest of the night proceeded normally from there. Completing the inspection and the remainder of the shift.[Later] during my fact finding I was informed that the brake hydraulic line was not installed and was found after 3 flight legs.If assigned a high stress job like Aircraft X; the team members should not be assigned another high stress job like completing a check before first launch on a late landing aircraft. I will focus more on the job I am currently working instead of worrying about the next job.




Synopsis: Technician reported not installing a main wheel brake hydraulic line after troubleshooting a dragging brake and replacing the brake assembly.