B747-800 Advanced
Maintenance Airframe; Maintenance Inspection Authority; Maintenance Powerplant
Maintenance Inspector 5; Maintenance Lead Technician 5; Maintenance Technician 22
Confusion; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Equipment Problem Dissipated; General Flight Cancelled / Delayed; General Maintenance Action
Procedure; Manuals; MEL; Human Factors; Aircraft
While troubleshooting an audio squeal at the Captain's cockpit station; ZZZ AMT discovered the AMU in the E/E was overheated. After removing the unit and allowing it to cool off; the AMTs found the rack cooling plugs were filled with a rubber plug. Given that this aircraft was less than 2 weeks old; it was believed that the rack cooling holes were inadvertently left plugged. The ZZZ AMTs misread the plug configuration placard on the rack; and my department did as well. As the [Maintenance] Manager; I allowed the aircraft to depart with the plugs removed. Boeing confirmed on the following day that the plugs should have been installed. The aircraft operated one leg out of configuration before corrective actions were taken.
Technicians reported misidentifying aircraft configuration; resulting in the removal of aircraft equipment rack cooling plugs and the aircraft flying misconfigured.