NAVIGATION AND
COMMUNICATION
AIRPLANE
OPERATIONS
MANUAL
2-18-30
Page
10
Code
02
MARCH 30, 2001
IRS OPERATING PROCEDURES
POWER-ON AND ALIGNMENT
− Check the MSU switch set to OFF.
− After energizing the airplane press the AVIONICS MASTER Buttons.
− Set the MSU switch to ALIGN or NAV. ALIGN annunciator
illuminates. (ON BATT and NO AIR annunciators may illuminate
briefly). On airplanes equipped with EICAS 17 onwards, an IRS 1 (2)
ALN advisory message is displayed on the EICAS.
− Through the FMS initial position page, accept one of the present
position options.
− Wait for completion of alignment. When selecting NAV directly, the
IRU automatically enters the NAV mode after successful completion
of alignment.
NAVIGATION MODE ENTRY
− If the MSU switch was set to NAV, make sure that the ALIGN
annunciator goes out and an IRS 1 (2) ALN advisory message
disappears from the EICAS (on airplanes equipped with EICAS 17
onwards).
− If the MSU switch is set to ALIGN, set the MSU switch to NAV when
the NAV RDY annunciator lights.
− The IRU outputs inertial data to all displays and systems.
ALIGNMENT DOWNMODE (“FAST ALIGNMENT” - to be used on
through flights)
− The airplane must be stationary.
− Pull the MSU switch out of NAV detent and set it from NAV to
ALIGN. The ALIGN annunciator will illuminate and an IRS 1 (2) ALN
advisory message displayed on the EICAS (on airplanes equipped
with EICAS 17 onwards).
− If the IRU position is the same as the known position, set MSU
switch to NAV after the ALIGN annunciator illuminates (and an IRS 1
(2) ALN advisory message is presented on the EICAS, on airplanes
equipped with EICAS 17 onwards). The IRU automatically enters
NAV mode after 30 seconds.
− If the IRU position is different from the known position, re-initialize
the IRU with a new position entry through the FMS CDU.
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