Selection Of Basic Modes And Submodes - Honeywell SPZ-8000 Maintenance Manual

MAINTENANCE
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The mode select unit (MSU) provides IRU mode selection and status
indication for three IRUS, and includes a TEST switch for the IRU. The
following paragraphs describe the MSU operation.
2. B. (1) Selection of Basic Modes and Submodes
Modes are selected by setting the MSU mode select switch as follows:
Q OFF-TO-ALIGN - The IRU enters the power-on/built-in test
equipment (BITE) submode. When BITE is complete after
approximately 13 seconds, the IRU enters the alignment mode. The
IRU remains in the alignment mode until the mode select switch is
set to OFF, NAV, or ATT.
The NAV RDY annunciator lights upon
completion of alignment.
OFF-TO-NAV - The IRU enters the power-on/BITE submode, the
alignment mode, and upon completion of alignment, the navigate
mode.
Q ALIGN-TO-NAV -
alignment mode
NAV-TO-ALIGN -
navigate mode.
The IRU enters the navigate mode from the
upon completion of alignment.
The IRU enters the align downmode from the
. NAV-TO-ALIGN-TO-NAV - The IRU enters align downmode from the
navigate mode and, after 30 seconds, automatically reenters the
navigate mode upon completion of downmode alignment.
ALIGN-TO-ATT or NAV-TO-ATT - The IRU enters the erect attitude
submode for 20 seconds, during which the MSU ALIGN annunciator
lights. The IRU then enters the attitude mode.
ATT-TO-ALIGN or ATT-TO-NAV - Once the mode select switch has been
set to ATT, the IRU remains in the attitude mode even if the mode
select switch is reset to ALIGN or NAV. The mode select switch
must be set to OFF for at least 3 seconds before the alignment or
navigate mode can be reestablished.
s ATT-, NAV-, or ALIGN-TO-OFF - After a 3-second delay, the IRU
enters the power-off submode for approximately 7 seconds. At the
end of 10 seconds, the IRU is off.
. ATT-, NAV-, or ALIGN-TO-OFF-TO-ALIGN, -NAV, or -ATT - If the mode
select switch is reset to ALIGN,
NAV, or ATT
after being in the
OFF position for 3 seconds but before the 10-second power-down
procedure has been completed, the IRU completes the power-down
procedures and then reinitiates power-on procedures.
22-14-00
Page 117
Aug 15/91
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