TM 1-1520-238-10
3-46
Change 3
NOTE
Throughout this procedure, range, time-to-
go, bearing, and left/right steering data are
computed and displayed for the destination
selected via the FLY TO DEST thumbwheel.
1. DISPLAY selector switch – DEST-TGT.
2. DEST DISP thumbwheel – 7.
3. KYBD pushbutton – Press.
4. DEST DISP thumbwheel – 2.
5. ENT key – Press.
f. Transferring Variation From One Location to
Another.
The procedure to transfer variation data to the
same location where the associated stored target coordi-
nates have been transferred is the same as in para
3.14.8.e, except that the DISPLAY selector switch is
placed at SPH-VAR.
g. Dead Reckoning Navigation.
As an alternate
BACKUP mode, dead reckoning navigation can be done
using ground speed and track angle estimates provided
by the operator.
1. MODE selector switch – BACKUP.
2. DISPLAY selector switch – GS-TK.
3. Best estimate of ground speed and track angle –
enter via keyboard.
4. MODE selector switch – Set to any other posi-
tion to abort procedure.
h. Operation During and After Power Interrup-
tion.
During a dc power interruption, the random access
memory (RAM) (stored destination and present position)
data is retained by power from a 9-volt dc dry nicad bat-
tery. This makes it unnecessary to reenter any navigation-
al data when power returns or before each flight. If the bat-
tery does not retain the stored destination data during
power interruption, the display will indicate an EN when
power returns. This indicates to the pilot that previously
stored data has been lost and present position (spheroid/
variation) and destinations must be entered. The comput-
er, upon return of power, resets present position variation
to EO 00.0-degree destination, and associated variations
to a non-entered state, and remembers wind to zero and
spheroid to CL6. The following data must be entered fol-
lowing battery failure:
1. Enter spheroid.
2. Enter present position variation.
3. Enter present position.
4. Enter each destination and its associated varia-
tion.
i. Stopping Procedure.
1. MODE selector switch – OFF.
3.15 AN/ASN-137 DNS CONTROLS AND DISPLAYS.
The AN/ASN–137 DNS uses the IP–1552G CDU to com-
municate for data entry and display. The CDU (fig 3-12)
has a full alphanumeric keyboard for data entry, 13 special
purpose fixed action buttons (FAB), and 8 variable action
buttons (VAB). In the non integrated navigation system
only 6 of the FABs are active: NAV, FDLS, STR, SPC,
CLR and FLPN. The CDU display architecture is orga-
nized in page formats. Each page can display information
on 8 separate lines. The bottom line is always the data
entry scratchpad, which is 22 characters wide. The 8
VABs are arranged 4 on each side of the CDU display.
The function performed by the VAB depends on the partic-
ular page displayed. VABs may be used to transfer data to
or from the scratchpad to a specific location on the display
or select another page to perform other functions. The
CDU IP–1552G is located in the CPG right–hand console.
The function of each is described in table 3-14.
