(7) FLT/ET Button. If ET is currently
displayed, pressing the FLT / ET button will cause the
FT to be displayed. Pressing this button again will
exchange the two timers in the display. If the standby
frequency is displayed, pressing the FLT / ET button
will cause the timer that was last displayed to reappear
in the window.
When power is first applied the flight timer
(a) Flight Timer. The flight timer is
displayed in the right portion of the display window
when the FLT message is displayed. The timer
receives power through the landing gear squat switch.
The counter will count up to 59 hours, 59 seconds. It
begins counting upon liftoff and will quit counting upon
landing. The elapsed timer may be reset back to 0 by
pressing the SET / RST button or turning the unit off.
(b) Elapsed Timer. This coupler has two
modes: count up and count down. When power is
applied, it is in the count up mode starting at 0. The
timer will count up to 59 hours, 59 seconds displaying
minutes and seconds until 1 hour has elapsed, then
displaying hours and minutes. When in the count up
mode, the timer may be reset to 0 by pressing the SET
/ RST button.
Pressing the reset button will reset the
currently being displayed.
To enter the count down mode, press the SET /
RST button for approximately 2 seconds until the ET
message begins to flash. While the ET message is
flashing, the timer is in the ET set mode. In this mode
a number up to 59 minutes, 59 seconds may be preset
into the elapsed timer with the frequency select knobs.
With the smaller knob pressed in, the 10's of seconds
digit may be changed; it will roll over from 5 to 0 and
under 0 to 5. With the knob pulled out, the 1's of
seconds digit may be changed. It rolls over for 9 to 0
and under from 0 to 9. The larger knob modifies the
minutes. It rolls over from 59 to 0 and under from 0 to
59. The timer will remain in the ET set mode (ET
message flashing) for 15 seconds after a number is
set in or until the SET / RST, FLT / ET, or FRQ button
is pressed. The preset number will remain unchanged
until the SET / RST button is pressed. When the SET
/ RST button is pressed after a number has been
preset, the elapsed timer will start counting down.
When the elapsed timer is counting down, pressing the
SET / RST button again will have no effect unless it is
held for approximately 2 seconds. This will cause the
timer to stop and enter the set mode (ET message
flashing). When the timer reaches 0, it changes to the
count up mode and continues up from 0. The elapsed
time will flash for 15 seconds, then annunciate a
(8) FRQ Button. The selected frequency is
put into the active window by pressing the FRQ button.
The standby and active frequencies will be exchanged.
(9) BFO Button. When the BFO button is
pressed, the BFO mode is activated and BFO will
display in the display window. In various parts of the
world, some L/LM stations use an interrupted carrier
for identification purposes. When in the BFO mode,
these stations are more easily identified. Pressing the
BFO button will cause a 1000 Hz tone to be heard
whenever there is a radio carrier signal present at the
(10) ADF Button. When the ADF button is
pressed, the unit is placed into the ADF mode with the
loop antenna enabled. An ADF message on the left
portion of the window will display. Indicator needles,
as selected on the RMI's, will point to the relative
bearing of the selected station.
d. Operating Procedure.
1. AVIONICS MASTER Switch On.
2. OFF / VOL Control Switch
clockwise out of detent. Adjust volume as
An audio muting feature causes the audio
output to be muted unless the receiver is
locked onto a valid station. This reduces
interstation noise and aids in identifying
3. ADF Test Select ANT mode. Verify
bearing pointers park in the 90-degree
4. Operating Mode Select as desired.
5. Frequencies Select. Ensure desired
active frequency is displayed.
6. FLT / ET Switch Operate as required.
e. Shutdown Procedures.
counterclockwise to off (detent).
2. AVIONICS MASTER Switch OFF.