(6) AP ENGAGE Push Button. The engage
switch is used to engage the autopilot. Engaging the
autopilot automatically engages the yaw damper. The
autopilot may be engaged with the airplane in any
reasonable attitude. The autopilot is normally
disengaged by momentarily pressing the control wheel
AP DISC switch. The autopilot may also be
disengaged by any of the following actions.
1. Actuation of the control wheel AP
DISC button. Disengagement is
confirmed by five flashes of the AP
2. Pressing the respective vertical gyro
FAST ERECT button.
3. Actuation of respective compass
INCREASE / DECREASE switch.
Disengagement is confirmed by the
AP ENG annunciator flashing five
times and illumination of the GA
5. Pulling the autopilot AP CONTROL
6. Pressing the autopilot AP ENGAGE
7. When transferring between pilot and
copilot flight directors.
Any of the following malfunctions will cause the
autopilot to automatically disengage.
1. Vertical gyro failure.
2. Directional gyro failure.
3. Autopilot power or circuit failure.
(7) Elevator Trim Annunciator. The elevator
trim annunciator indicates UP or DN when a sustained
signal is being applied to the elevator servo. The
annunciator should not be illuminated before the
autopilot is engaged.
3C-21. VHF NAVIGATION RECEIVERS.
Receiver provides 200 50-kHz spaced VOR/LOC
channels from 108.00 through 117.95 MHz and 40 GS
channels automatically paired with localizer channels.
It also provides a marker beacon receiver.
The digital VIR-32 provide VOR, LOC, and GS
deviation outputs, high and low level flag signals,
magnetic bearing to the station, to/from information,
marker beacon lamp signals, and VOR and marker
beacon audio outputs.
passage, always listen for marker beacon
audio. Do not rely solely on the marker
b. Operating Controls. All operation controls
for the VIR-32 are located on the CTL -32 NAV control.
Refer to Figure 3C-15.
(1) Compare Annunciator (ACT). ACT
momentarily illuminates when frequencies are being
changed. ACT flashes if the actual radio frequency is
not identical to the frequency shown in the active
(2) XFR / MEM Switch. This switch is a 3-
position, spring-loaded toggle switch. When held to
the XFR position, the preset frequency is transferred to
the active display and the receiver re-tunes. The
previously active frequency becomes the new preset
frequency and is displayed in the lower window. When
this switch is held to the MEM position, one of the four
stacked memory frequencies is loaded into the preset
display Successive pushes cycle the four memory
frequencies through the display (
2, 3, 4, 1, 2 ,3
(3) Frequency Select Knobs. Two concentric
knobs control the preset or active frequency displays.
The larger knob changes the three digits to the left of
the decimal point in 1-MHz steps. The smaller knob
changes the two digits to the right of the decimal point
0.05-MHz steps. Frequencies roll over at the upper
and lower limits. The two frequency select switches
are independent of each other such that the upper and
lower limit rollover of the 0.1-MHz digit will not cause
the 1.0-MHz digit to change.
(4) ACT Button. Push the ACT button for
approximately 2 seconds to enable the frequency
select knobs to directly retune the receiver. The
button window will display dashes and the upper
window will continue to display the active frequency.
Push the ACT button a second time to return the
control to the normal two-display mode.
(5) TEST Button. Press the TEST button to
initiate the radio self-test diagnostic routine. (Self-test
is active only when the TEST button is pressed.)