*
Maintenance message definitions

*
Correlation information.

The fault processing sub-function receives:

*
Fault reports from airplane systems

*
Flight deck effects (FDEs) from the primary display system (PDS)

*
Discrete signals.

It isolates the failures that caused the messages to airplane LRUs and interconnects. The failure information is related or correlated to the applicable FDEs. This information is kept for use by the mechanic for troubleshooting.
The fault processing sub-function also prevents incorrect fault reports caused by transient and normal airplane conditions from being processed.
Input Processing
The CMCF fault processing sub-function can process up to 5000 fault reports per second. It can receive up to 25000 faults per second. When the fault processing sub-function receives more than 5000 faults reports per second, it stores the reports and processes them at a later time.
The CMCF fault processing sub-function also identifies if the fault reports are correct and if the LRUs sending the fault reports are currently active.
Inhibits and Special Case BITE
The fault processing sub-function removes fault reports caused by these normal airplane conditions:
*
When you first apply power to the airplane

*
When you start an engine

*
When you remove power from the airplane

*
When an engine is shutdown.

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The fault processing sub-function also makes fault reports for systems that do not monitor for faults.
Cascaded Effect Removal

The fault processing sub-function supplies software to stop fault reports that are cascaded effects of upstream failures. This prevents the mechanic from troubleshooting faults which are side effects of real faults.
Consolidation

The fault data processing sub-function puts fault reports into groups and relates them to a single maintenance message. The maintenance messages are kept and displayed for troubleshooting.
Maintenance Message and FDE Correlation

The CMCF correlates active maintenance messages to active or latched Flight deck effects (FDEs) and maintenance memos (MOs).
The CMCF has logic that makes a relation between maintenance messages and FDEs. When an FDE occurs and the CMCF receives a maintenance message that has a relation to the FDE, the CMCF correlates the FDE to the message. The CMCF correlates the maintenance message and the FDE, or MO if the two are active or latched at the same time.
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The CMCF also correlates active maintenance messages with active MOs.
The CMCF receives the airplane system maintenance message data and maintenance memo messages from these:
*
ARINC 629 buses

*
ARINC 429 buses

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Onboard local area network.

The PDF contains about 1800 FDEs. The airplane systems can supply about 200 MOs and about 15,000 maintenance message data.
The CMCF can correlate active, inactive, or latched maintenance messages to FDEs or MOs of:
*
5000 correlations for fault history

*
7000 correlations for existing faults.

Maintenance Message & FDE Storage
The CMCF keeps a fault history database that has:
*
Fault or maintenance message data

*
FDE data

*
MO data.

Fault information for each maintenance message in the fault history database includes:
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*
Message number

*
ATA chapter number

*
Symptom text

*
Activity

*
Intermittence

*
Intermittence number

*
Flight phase

*
Date and time

*
Correlated FDE, MO, MPS

*
Flight leg

*
Equipment ID.

The CMCF can store 1000 maintenance messages in fault history memory and 2000 maintenance messages for existing faults.
Each FDE and MO in the fault history database includes:
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Text

*
Level

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FRM code

*
Activity

*
Date and time

*
Flight phase.

The CMCF supplies fault correlation history storage for:
*
100 FDEs

*
100 MOs

*
50 MPSs.

The CMCF stores FDE and MO correlations only once per fault per flight leg.
The CMCF keeps the fault history database for as many legs as required to fill the database.
The CMCF manages the flight leg transitions of the fault database, where the present flight leg is leg 0.
　
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