737 MAX Flight Crew Operations Manual
Flight Management, Navigation -
Navigation Systems Description
MN-FLT-OH-201
11.20.9
Fast Realignment - During transit or through-flight stops with brief ground times,
a thirty (30) second fast realignment and zeroing of ground speed error may be
performed while the airplane is parked by rotating the MSU switches from NAV
to ALIGN and back to NAV without rotating the switch to the OFF position.
Present position should be simultaneously updated by manually entering latitude
and longitude.
Automatic Navigation Realignment (ANR) - ANR is another alignment function
that is performed while the IRS is in NAV mode. The purpose of the ANR function
is to automatically perform realignment corrections and navigation reset to fine
tune the navigation solution (i.e. trim velocities to zero, correct attitude and
heading errors, etc.) while the IR is in NAV mode and the aircraft is motionless on
ground. These resets allow navigation accuracy to be maintained over long
periods of time without performing a normal full alignment. A long segment of no
detected motion (7.5 to 15 minutes) is required before the first reset is performed.
Resets are then performed at 1-minute intervals until aircraft motion is detected.
A subsequent stop for another long segment will again allow resets to occur.
Multiple automatic realignments can occur prior to a flight or following a flight.
Loss of Alignment for ADIRU with Hybrid GPS-Inertial
1B402 - 1B786, 1B807 - 1J594
The hybrid GPS-inertial reference has the additional capability to completely
recover from an in-flight loss of alignment due to a power interruption or
inadvertent shutdown. It's called Align In Motion (AIM). When power is restored
to the IRS while in flight, maintain straight and level flight for approximately 30
seconds or until the align light extinguishes; attitude information should become
available within a few seconds and full navigation capability is restored
automatically within about 10 to 30 minutes. This capability relies on GPS data
and is therefore not available if the GPS receivers are not functioning.
Note:
During Align In Motion mode, the align times are longest during a
continuous straight flight trajectory (up to 30 minutes) and shortest if there
are significant changes in airplane heading. With extreme heading
changes, such as a complete course reversal, it is possible to complete
alignment in less than 5 minutes.
Loss of Alignment for ADIRU
1B401, 1B801 - 1B806
If an IRS loses both AC and DC power, the alignment is lost. Alignment can also
be lost if the MSU switch is moved out of the NAV position.
March 1, 2021
