Figure 3C-25. CDU Standard Display Symbols
(2) Data Entry and Display Formats. The
acceptable entry formats, valid data ranges, and
display formats are discussed in the following
paragraphs. They are applicable to all CDU pages
unless stated otherwise. On many CDU pages,
configuration settings and entered data are maintained
through each power cycle to maintain continuity
between aircraft sorties. Also, a lot of data is
maintained in the event of a bus controller swap.
(a) Valid Data Ranges and Units for
Entry and Display. Data entry valid ranges for a given
field are generally limited by the display resolution with
assumption of a fixed decimal point and positive
entries (i.e., a four-digit numerical field with no decimal
point will accept entries from 0 to 9999). Some
entered data is limited by operational considerations,
e.g., VNAV angle of 6.0° or 3500 fpm maximum. For
values which cannot be computed due to insufficient
data, the CDU will display dashes ( ); e.g., if
gross weight cannot be computed by the FMS
because total fuel has not been specified. Asterisks
(****) are displayed if the value is too large for its
respective display field.
(b) Entry and Display of Waypoints.
Flight plan waypoints and other locations are entered
in three basic formats.
1. Position Coordinates. Latitude-
longitude waypoint pair.
2. Waypoint Identifier. Up to a five-
The appropriate data is extracted
from an on-board ICAO waypoint
waypoint list of navigation aids,
airports, intersections, etc.
3. Identifier / Bearing / Distance.
Position defined at the specified
bearing and distance from a data