(2) BITE operating principles
 -
The BITE is capable of memorizing, while making the distinction between internal and external faults, over a period of one or several flights (depending on the system).

 -
The fault data memorized during the flight(s) are not affected by the various ground maintenance operations.

 -
The BITE enables the memorization of faults in flight and on the ground, by means of different memory zones.

 -All LRU input buses (ARINC 429) are monitored according to the configuration of each system.
 -The faults are memorized following confirmation over several cycles (intermittent faults).
 -Faulty LRUs are identified by their ATA 100 reference and sometimes by their Functional Item Number (FIN).
 -The BITE permanently transmits maintenance messages in real time (in flight). These maintenance messages cover internal and external faults of the current flight or of the last flight.
 System BITEs operate in 2 modes : NORMAL MODE and MENU MODE.
 (3) The various fault classes detected by the system BITEs. The faults detected by the system BITEs are classified in 3 categories with respect to their consequences on aircraft safety and availability.
 (a) Class 1 faults These are faults detected by the systems, which may have an operational consequence (safety aspect) on the current flight. These faults are indicated to the crew in flight:
 -
by the ECAM system (upper and/or lower display unit)

 -
by local warning in the cockpit.

 NOTE : The FWC receives the class 1 faults from the aircraft
____
 systems which are connected to it.

 (b) Class 2 faults These are faults detected by the systems and which do not have any operational consequences (safety aspects) on the current flight or on the following flight(s) but which may have consequences if a second fault occurs. These faults are indicated to the crew in flight on the ECAM STATUS page after manual selection and are the subject of an ECAM report on the ground after shut down of the engines.
 NOTE : The warning messages (class 1 and 2) presented to the crew
____ are transmitted in real time by the FWC to CFDIU which memorizes them and constitutes the ECAM REPORT (only
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 messages corresponding to primary and independent faults
 are transmitted).
 (c) Class 3 faults These are faults detected by the systems which have no consequences on aircraft safety or availability.
R The operator may have these faults corrected at his convenience. R These faults are not indicated to the crew.
 (4) Various types of systems and BITE connected to the CFDS
 (Ref. Fig. 006)
 (a) Type 1 systems
 Systems with an ARINC 429 input and output bus, the input being specific to the CFDS.
 These constitute the majority of aircraft systems.
 Type 1 systems are capable of memorizing data concerning faults detected on a maximum of 64 flights.
 Schematically, a Type 1 system BITE consists of 5 zones of non-volatile memory:
 1 Zone 1
_
 This zone is used for storing the identity of the LRU declared faulty during the current or the last flight. It is also used for storing the identity of LRUs declared faulty during the last 63 flights (background over 64 flights). The capacity is approximately 30 failures.
 2 Zone 2
_
 This zone is used for storing complementary data (e.g. : aircraft configuration, ...) concerning faults occured during the last 64 flights. The capacity is approximately 30 failures.
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 CFDIU - Connection With Different System Types Figure 006
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 3_ Zone 3
 This zone is used to store the identity of faulty LRUs and the complementary data concerning these fault, for faults that occurred on the ground during the last line stops. The capacity is approximately 3 failures.
 Zone 3 access:
 a_ On the center pedestal, on the MCDU, get access to the MCDU page.
 b_ On the MCDU MENU page, push the line key adjacent to the SYSTEM REPORT/TEST indication.
 c_ On the SYSTEM REPORT/TEST page, push the line key adjacent to the related system.
 d_ On the SYSTEM REPORT/TEST page of the system that you have selected, push the line key adjacent to the related computer indication.
 e_ Push the line key adjacent to the trouble shooting function indication (if the computer has this function).
 4_ Zone 4
 This zone is used for storing more detailed data concerning the faults (parts of the LRU). This zone is only accessible in the workshop (test bench).
　
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