A330
Maintenance Powerplant; Maintenance Airframe
Maintenance Inspector 30
Confusion
Aircraft Equipment Problem Critical
General Maintenance Action
Manuals; Aircraft; Chart Or Publication; Procedure
During Operational Check of [passenger oxygen] 'Manual Mask Release'; several (more than 50) did not drop. After replacing solenoids; accomplished test again. Some dropped some didn't; with any rhyme or reason as to which ones dropped and which didn't. No single [Cabin] Zone and helter skelter on which ones dropped. Fear this may be a fleet issue and wanted to report in case anybody else had similar problems. Engineering Order (E/O) was issued.
Reporter stated the A330 was held over for three days at the hangar before they were able to fully accomplish the passenger oxygen 'Manual Mask Release' Check. Engineering had issued an Engineering Authorization (E/A); to redo the same Test; but that second test resulted in 38 Passenger Service Units (PSU) not dropping; that were not part of the previous 50 PSU units that did not drop during the first 'Manual Mask Release' Check. The aircraft is a wide body; twin aisle with a 2-5-2 passenger seat row configuration. Each PSU unit holds three or six masks. Reporter stated there is currently a belief that the small actuating rod that extends and releases the PSU door panel latch is getting dusty and the electrical signal to the actuator may not be of a high enough voltage to override and extend the dusty actuating rod to release the PSU door latch. If that is the source of the failures; that would be surprising; since he has been told the same PSU actuating mechanism is also used on the smaller Airbus A320 PSUs with very few problems. Their Engineering and Airbus are determining whether changes to the PSU mask drop check needs to be revised and just what actually contributed to the failures.
An Aircraft Inspector reports about the failure of 50 Passenger Service Unit (PSU) oxygen masks' doors that would not open on an A330 aircraft during a 'Manual Mask Release' Check. A second test noted that 38 different PSU doors failed to open. The wide body aircraft has a 2-5-2 passenger seat row configuration. Each PSU unit has either three or six masks.