IRS Present Position
Displays latitude and longitude of IRS present position.
Data is from the “on–side” IRS (L or R).
All displays on this ANCDU are based on inputs from this IRS.

IRS LEGS
Allows selection of IRS LEGS page 1.

Cross–Track Error (XTK ERROR)
Displays present deviation (NM left or right) from the DSRTK flight plan course.

WIND
Displays present IRS true wind direction and speed in knots.

IRS Waypoint Data (WPT DATA)
Allows line selection of IRS WPT DATA page 1.
IRS Legs
The IRS LEGS page displays details of the ANCDU flight plan (20 waypoints

maximum). It has no required entries.
The page allows review of the crossloaded FMC flight plan, or it may be used to
enter or modify a unique ANCDU flight plan.

The flight plan is cleared at flight completion.

Page access is as shown. The page is also displayed automatically upon FMC
failure when IRS inputs are valid and an active ANCDU flight plan does not exist.

Flight Management, Navigation -Alternate Navigation System (ANS)

IRS Legs Page

Leg Direction
Applies to the leg going to the waypoint identified on the line below.
Copyright . The Boeing Company. See title page for details.
11.50.8  December 1, 2000

Flight Management, Navigation -Alternate Navigation System (ANS)
737 Operations Manual
Displays the IRS computed great–circle course. For the active waypoint, the displayed course is the present magnetic course to be flown. For all downpath waypoints, displayed course is the initial true course for that leg.

Waypoint Identifier (lines 1L–4L)
Used for entry and/or display of any valid waypoint identifier.

Entry may be made via the keyboard or propagated from either the RTE LEGS
page or IRS WPT DATA page.
Entries are propagated to the IRS WPT DATA pages.
The active waypoint identifier is highlighted in reverse video. It cannot be deleted,

but it can be overwritten.

Crossload
Used to crossload (copy) the FMC flight plan into the ANCDU.
If there is no flight plan in the ANCDU, initial lines selection displays the FMC
flight plan which is proposed to be stored in the ANCDU.

If an ANCDU flight plan already exists, line selection changes the page title to

MOD.
Line selection “arms” the execution function, and the EXEC light illuminates.
Subsequent execution activates the ANCDU flight plan (page title change to
ACT).

Upon FMC failure, the CROSSLOAD prompt is replaced by the LAST FMC
PLAN prompt.

IRS Progress
Allows selection of the IRS PROGRESS page.

Estimated Time En route
Applies to the leg going to the waypoint identified on the line below. Displayed
only when ground speed exceeds 210 knots.
For the active waypoint, displays time–to–go to the active waypoint.
For all downpath waypoints, displays estimated time en route for that leg.

Leg Length
Applies to the leg going to the waypoint identified on the line below.
For the active waypoint, displays computed distance–to–go from present position
to the waypoint.

Flight Management, Navigation -Alternate Navigation System (ANS) 737 Operations Manual

For all downpath waypoints, displays flight plan leg length.
Blank if distance–to–go is greater than 9,999 NM.
Displayed values are in tenths of miles if the leg length is less than 10 NM.

IRS Waypoint Data
Allows selection of the corresponding IRS WPT DATA page.

Last FMC Plan
Displayed upon FMC failure.

Line selection displays the FMC flight plan which existed at the time of FMC
failure. The EXEC key illuminates.
Subsequent execution activates the ANCDU flight plan.

IRS Waypoint Data
The IRS WPT DATA page displays latitude and longitude for each waypoint in the
ANCDU flight plan (20 waypoints maximum). It has no required entries.
The page can be used to enter or modify the ANCDU flight plan.
Page access is from IRS PROGRESS page or IRS LEGS page.

IRS Waypoint Data Page

Waypoint Line (lines 1L–4L)
Used for entry and/or display of any valid waypoint identifier and the associated latitude and longitude.
Copyright . The Boeing Company. See title page for details.
11.50.10  December 1, 2000

Flight Management, Navigation -Alternate Navigation System (ANS)
737 Operations Manual
Entry may be via the keyboard or propagated from either the RTE LEGS page or
the IRS LEGS page.
Entries are propagated to the IRS LEGS pages.
The active waypoint cannot be deleted, but it can be overwritten.
　
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