13.10 and 13.22 On-board maintenance systems (ATA 45) and information systems (ATA 46)

Scope

Both sub-modules are B2 level 3 and are not part of any B2L rating.

• 13.10 On-board maintenance systems (ATA 45): central maintenance computers; data-loading system; electronic library system; printing system; structure monitoring (damage-tolerance monitoring).
• 13.22 Information systems (ATA 46): equipment dedicated to storing, updating and retrieving digital information formerly held on paper, microfilm or microfiche — air-traffic and information management, network servers, aircraft general, flight-deck, maintenance, passenger-cabin and miscellaneous information systems.

Built-in test equipment (BITE)

Each modern LRU contains BITE that:

• runs a power-up test when energised;
• runs continuous monitoring in operation (watchdog timers, checksums, wrap-around tests of inputs/outputs, power supply monitoring);
• allows initiated tests (operational/functional tests) from the maintenance computer or the LRU front panel;
• stores fault codes in non-volatile memory with flight-leg and time stamps;
• reports to the central maintenance system over a data bus.

Central maintenance computer / system (CMC, CMS, OMS)

Function	Description
Fault consolidation	Collects BITE messages from all systems and correlates them, so one root fault producing many symptoms shows as one maintenance message pointing to the most likely LRU
Flight-deck effect correlation	Links maintenance messages to the crew alerts (EICAS/ECAM messages) seen in flight
Current/present leg report and fault history	Faults per flight leg, usually for many previous legs
Interactive tests	System tests, LRU replacement tests, rigging/adjustment aids run from an MCDU or maintenance terminal
Configuration	LRU part and serial numbers, software versions
Real-time reporting	Downlinks fault reports to the operator's maintenance control by ACARS so spares/engineers can be ready on arrival
Exceedances/condition monitoring	Engine and APU reports, airframe condition monitoring (ACMS) data recorded for trend analysis

Access: maintenance pages on the MCDU, dedicated maintenance terminals, or a portable maintenance access terminal (PMAT/laptop). The maintenance messages refer to the fault isolation manual (FIM/TSM) tasks.

Key fact: The CMC does not repair anything — it isolates the fault to an LRU, reducing "no fault found" removals and turnaround time.