Position update can be effected by depress-
ing the ENT key. The computer updated the present posi-
tion at the time the KYBD key was depressed by using the
stored destination coordinates, and adding to them the
distance traveled between the time the KYBD key was
depressed and the ENT key was depressed. In addition,
if an associated variation for the stored destination ex-
ists, the present position variation is also updated.
If a present position update is unnecessary
(as indicated by an appropriately small value of DIS-
TANCE to go on overflying the destination), set the DIS-
PLAY switched to some other position - this action aborts
the update mode.
b. Updating Present Position from a Landmark.
There are two methods for updating present
position from a landmark. Method 1 is particu-
larly useful if the landmark comes up unex-
pectedly and the operator needs time to de-
termine the coordinates. Method 2 is useful
when a landmark update is anticipated.
Method 1 (Unexpected update)
Set DISPLAY switch to PP position.
Overfly landmark and depress KYBD key.
The present position display shall freeze.
Compare landmark coordinates with those
If the difference warrants an update, enter
the landmark coordinates by depressing the KYBD key
to blink the field to be changed, enter coordinates, then
depress the ENT key. The computer updates the present
position (from the time the KYBD key was depressed) to
the landmark coordinates, and adds to the updated pres-
ent position the distance traveled between the time the
KYBD key was depressed and the ENT key was de-
If an update is not desired, set the DISPLAY
switch to some other position. This action aborts the
Method 2 (Anticipated update)
1. Set DISPLAY switch to WP/TGT position.
2. Access P by depressing the LTR LEFT key
followed by the 6 key, entering destination
00 then depressing the DEC key, or enter-
ing destination 99 then depressing the INC
3. Depress KYBD key. Observe that the dis-
4. Manually enter the landmark coordinates
by depressing the KYBD key to blink the
field to be changed and enter the coordi-
5. When overflying landmark, depress ENT
6. If an update is not desired, set the DISPLAY
switch to some other position. This action
aborts the update mode.
3-3-52. Fly-To Destination Operation.
a. Initialization of Desired Course.
When a fly-to destination is selected such as at the start
of a leg, the present position at the time is stored in the
computer. A course is then computed between the se-
lected point and the destination. If the aircraft deviates
from this desired course, the lateral offset or crosstrack
distance error is computed.
Distance and bearing to destination, actual track angle,
and track angle error correction are computed from pres-
ent position to destination. See figure 3-3-8 for graphic
definition of these terms.
b. Procedure for Selecting One of 100 Possible Fly-
To Destinations (Direct Mode).
The Doppler/GPS navigation set has the capability of
selecting a fly-to destination from 100 destinations (num-
ber 00 through 99).
As an example, consider selecting Fly-To destination
Set MODE switch to MGRS (LAT/LONG or
GPS LDG may also be used).
Set DISPLAY switch to XTK/TKE. Observe
e standard Cross Track (XTK) and Track angle error
(TKE) display. (DIST/BRG/TIME may also be used)
To display Fly-To destination 43 depress the
INC or DEC keys, or depress keys 4 then 3. This is a
direct key entry action.
Left-Right Steering Signals
There are two methods the pilot may use to fly-to destina-
tion, using left-right steering signals displayed on the
computer-display unit. Left-right steering signals may be
used when flying the shortest distance to destination
from present position (Method 1) or when flying a ground
track from start of leg to destination (Method 2).