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Space Shuttle Avionics: Difference between revisions
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While critical systems all have a hardware fault detection and never rely on software running, less important systems send backup warning messages to the software in case of off-nominal situations. | While critical systems all have a hardware fault detection and never rely on software running, less important systems send backup warning messages to the software in case of off-nominal situations. | ||
These appear as flashing messages below the DPS display in the so-called fault line. In case of multiple faults, only the latest message is displayed. Pressing <b>MSG ACK</b> once on the keypad ends the flashing of the message and allows to inspect it, a second press clears the fault line and brings up the next message from the stack (if there is any). A record of the last 15 fault messages is kept in the FAULT display (DISP 99), see below. | These appear as red flashing messages below the DPS display in the so-called fault line. In case of multiple faults, only the latest message is displayed. Pressing <b>MSG ACK</b> once on the keypad ends the flashing of the message and allows to inspect it, a second press clears the fault line and brings up the next message from the stack (if there is any). A record of the last 15 fault messages is kept in the FAULT display (DISP 99), see below. | ||
C/W messages may include a pointer to the utility function which allows to inspect the problem in more detail. Users should consult the Space Shuttle Crew Operations Manual for the procedures to deal with faults beyond acknowledging the message. | C/W messages may include a pointer to the utility function which allows to inspect the problem in more detail. Users should consult the Space Shuttle Crew Operations Manual for the procedures to deal with faults beyond acknowledging the message. | ||
=== MEDS fault messages === | |||
The MEDS system produces its own set of fault messages which only deal with failures of the MEDS system itself, not with problems elswhere in the Shuttle. These are displayed in the lower portion of the display, above the title of the current menu page. | |||
Like the CWS messages, they need to be acknowledged, can be deleted from the line, and are available as a summary on the IDP FAULT SUMMARY page. However, unlike the CWS messages, they are not acknowledged by keyboard entries but by edgekey options. | |||
MEDS messages are specific for one IDP and are preferentially shown on any DPS screens this IDP commands. Any MDU not commanded by the IDP which has detected the fault will not show the message in either the fault line or its summary page. | |||
As the following example shows, it is possible to have CWS and MEDS fault messages on-screen simultaneously. | |||
[[File:Shuttle avionics meds menu.jpg|600px|MEDS menu layer of the Space Shuttle avionics]] | |||
=== Illegal entry === | === Illegal entry === | ||