the SET/RST button is pressed. When the SET/RST
While the FLT or ET are displayed, the in use frequency
button is pressed after a number has been preset. the
may be changed with the frequency control knobs.
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
(a) FLT/ET button. If elapsed time (ET)
approximately 2 seconds. This will cause the timer to
stop and enter the set mode (ET message flashing).
is currently displayed pressing the FLT/ET button will
When the timer reaches 0 it changes to the count up
cause the flight timer (FT) to be displayed. Pressing this
mode and continues up from 0. The elapsed time will
button again will exchange the two timers in the display.
flash for 15 seconds, then annunciate a steady display.
If the standby frequency is displayed. pressing the
FLT/ET button will cause the timer which was last
(10) FRQ button. The selected frequency is
displayed to reappear in the window.
put into the active window by pressing the FRQ button.
The standby and active frequencies will be exchanged.
(11) BFO button. When the BFO button is
When power is first applied the flight
timer is displayed.
depressed, the BFO mode is activated and BFO will
display in the display window. In various parts of the
(b) Flight timer. The flight timer is
world, some L/LM stations use an interrupted carrier for
identification purposes. When in the BFO mode these
displayed in the right portion of the display window when
stations are more easily identified. Pushing the BFO
the FLT message is displayed. The timer receives
button will cause a 1000 Hz tone to be heard whenever
power through the landing gear squat switch. The
there is a radio carrier signal present at the selected
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
(12) ADF button. When the ADF button is
the SET/RST button or turning the unit off.
depressed. the unit is placed into the ADF mode with
(c) Elapsed timer. This counter has two
the loop antenna enabled. An ADF message on the left
portion of the window will display. Indicator needles. as
modes: count up and count down. When power is
selected on the RMI's, will point to the relative bearing of
applied it is in the count up mode starting at 0. The timer
the selected station.
will count up to 59 hours, 59 seconds, displaying
minutes and seconds until one hour has elapsed, then
d. Operating Procedures.
displaying hours and minutes. When in the count up
mode. the timer may be reset to 0 by pressing the
1. AVIONICS MASTER switch - ON.
2. OFF VOL control switch - Turn
clockwise out of detent.
volume as required.
Pressing the reset button will reset
the elapsed timer regardless of what
is currently being displayed.
An audio muting feature causes the
audio output to be muted unless the
To enter the count down mode, the SET/RST button
receiver is locked onto a valid
is held depressed for approximately 2 seconds until the
This reduces interstation
ET message begins to flash. While the ET message is
noise and aids in identifying
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.
3. ADF test - Select ANT mode. Verify
With the smaller knob pressed in, the 10's of seconds
bearing pointers park in the 90-
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
4. Operating mode - Select as desired.
seconds digit may be changed. It rolls over for 9 to 0
5. Frequencies - Select.
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
switch - Operate as
message flashing) for 15 seconds after a number is set
in or until the SET/RST. FLT/FT or FRQ button is
pressed. The preset number will remain unchanged until
Change 5 3-27