2) Leg Transition (LT)
a) If a fault is active at flight leg transition, and it stays active until a flight phase when it can be stored, the fault message is stored in present leg faults and in fault history with the LT flight phase code and the date and time of the flight leg transition.
3) Maintenance phases
a) The flight phases during which maintenance is usually done are defined as the maintenance phases. The maintenance phases for most systems include these flight phases: ENG SHUTDOWN (SD), POWER ON (PO), and PRE FLIGHT (PF).
4) Operational period
a) The flight phases during which maintenance on a particular system is not usually done are defined as the operational period of the system.
(e) Hard Faults 1) The message page shows the indication HRD for a hard fault. 2) The fault that caused a CMCS fault message is defined as hard if these conditions are true about the fault: a) It occurs during a flight phase when it can be stored in non-volatile memory (NVM) b) And it is generated before the maintenance phases c) And it stays active constantly until the maintenance
phases start.
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Intermittent Faults
1) The message page shows the indication INT for an intermittent fault.
2) The fault that caused a CMCS fault message is defined as intermittent if these conditions are true about the fault: a) It occurs during a flight phase when it can be stored in NVM b) And it occurs before the maintenance phases c) And it does not stay active constantly until the maintenance phases start.
Non-determined Faults
1) The message page shows no indication for a non-determined fault.
2) The fault that caused a CMCS fault message is defined as non-determined if these conditions are true about the fault: a) It occurs during the maintenance phases b) And it can be kept in NVM during the maintenance phases.
N/A Faults
1) For engine messages, N/A (for non-applicable) is used instead of hard, intermittent, or non-determined regardless of when or how often the messages occur. Because of the "Engine Shutdown" flight phase doesn't begin until the last engine shuts down, active latched HRD faults from engines shut down prior to the last engine would have shown INT even though they were latched HRD faults.
Correlated FDE
1) A FDE is defined to be correlated to a CMCS fault message if they are generated within a certain time period of each other and they are related to the same airplane system.
Latched EICAS Status Messages
1) Some EICAS status messages are latched into EIU memory when they occur. They show on the CDU with an ERASE> prompt. When the fault is corrected, the message must be erased to remove it from the auxiliary EICAS display.
Snapshots
1) A snapshot of an EICAS maintenance page is maintenance page data, stored in the EIU, that can be selected for display on the auxiliary EICAS. The CDU must be used to select a snapshot for display. Snapshots are made either manually or automatically.
2) Manual snapshots are made in two ways: a) Push the EVENT RCD switch on the EICAS control panel to make snapshots of all maintenance pages at the same time. b) Select the <RECORD prompt on the EICAS PAGE CONTROL menu on the CDU to make a snapshot of a selected maintenance page.
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3) Automatic snapshots are triggered by a system fault or engine exceedance. For more information on snapshots, refer to AMM 31-61-00/001.
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