Maintenance Powerplant; Maintenance Airframe
Distraction; Situational Awareness; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Incorrect / Not Installed / Unavailable Part; Procedure; Chart Or Publication; Human Factors
I was the Lead Mechanic of the gearbox change at ZZZ on an MD-80 aircraft #2 engine. On a final inspection; the Inspector and I missed an oil line that was not safetied; or the bolts were not installed. The engine run-up and leak check was good. The aircraft flew for nine flights before the line leaked oil. We drove our shop truck to and from ZZZ. It's approximately a six-hour drive each way.
During [engine] gearbox installation; Mechanic A [(there were four mechanics total)] did not install the bolts to the oil return line to the gearbox. I suggested to him; not to forget to install the bolts and continued with the installation of the fuel pump and Controller. Mechanic A did not install the bolts; nor did he advise any of the other mechanics or Lead Mechanic that he left these bolts out. The leak check on [engine] run-up was OK; no leaks were apparent. Lead Mechanic and Inspectors [approved] the engine gearbox [change]; no leaks were found.
A Lead Mechanic and two other mechanics report on their involvement with a N2 gearbox change and oil return line installation on a Pratt-Whitney JT8D engine at the #2 engine position. The MD-80 aircraft flew nine flights before the return line leaked oil.