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 five
character alphanumeric string. The appropriate data is
extracted from an on-board ICAO waypoint database
or user defined waypoint list of navigation aids,
airports, intersections, etc.
3 Identifier / Bearing / Distance.
Position defined at the specified bearing and distance
from a database waypoint with the indicated identifier.
Longitude Waypoints. Latitude-longitude waypoints
are entered in the form of degrees and minutes
followed by optional decimal minutes or seconds and
decimal seconds. The required format is an N or S
followed by four or six digits, with a decimal point and
up to three additional digits optional. Then followed by
E or W with five or seven digits, with a decimal point
and up to three additional digits optional.
Latitude-longitude waypoints are displayed as
whole minutes on all CDU pages except in the
scratchpad when the value is copied and on the
Position, Integrated Navigation, Start 1, or Data pages
where thousandths of minutes are displayed.
Waypoints. Identifiers are entered as up to five
alphanumeric. Identifier waypoints are displayed left
justified, with alphabetic characters always written as
capital letters. Crew-entered identifiers are limited to
between two and five characters. Single character
identifiers cannot be entered by the crew and are only
accessed by inserting a SID, STAR, or approach that
includes such a waypoint in the procedure.
distance waypoints are entered as an identifier
followed by a / , followed by the bearing, followed by a
/ , followed by distance. Bearings are entered as three
digits optionally followed by a decimal point and an
additional digit. Bearing is displayed as three digits
rounded to the nearest degree. An entry of 145.3° will
be displayed as 145°. In the case of a number such
as 145.5°, the CDU always rounds up to the nearest
whole number. Distances are entered as up to four
digits optionally followed by a decimal point and one
When a bearing/distance is applied to a
waypoint, the waypoint will appear as one of the
999 nm or less, the waypoint will
be displayed as identifier/bearing/
distance (e.g. EDW/350/45).
2. If the waypoint is not a way point
identifier or the distance is greater
than 999 nm, the waypoint will be
displayed as latitude/longitude.
Declination. Magnetic variation is used in converting
most azimuth angles from true to magnetic reference.
Courses into navaid waypoints and any offset
waypoints described relative to these waypoints use
variation in the computations, so that they match those
on published Instrument Flight Rules (IFR) charts.
(g) Entry and Display of Time and Date.
Time is entered with no delineators between hours,
minutes, and seconds. Seconds are optional, so that
three to six digits are acceptable. If no time or date is
available for a given field, blanks are displayed. All
times are entered and displayed as Coordinated
Universal Time (UTC). Dates are entered and written
using the military convention of day, month, year (six
digits total). Example would be 16/12/97 (December
The FMS-800 system has been designed to
avoid date and time rollover problems. The operator
will not see problems if a current date and time are
entered into the CDU prior to initializing GPS modules.