Specifications

SECTION III
INSTRUMENTATION AND AVIONICS
MODEL 560
The SQ push button toggles the COM squelch open and closed. When the squelch is open, SQ is
annunciated in the right center port of the display.
When the EMER button is selected on the audio panel, the NAV AUDIO push button toggles the NAV
AUDIO off and on. When NAV AUDIO is on, it is summed in with the COM audio. NAV AUDIO will be
annunciated at the center left of the display.
Any time the COM transmitter is being keyed, the TX annunciator in the center of the display will
appear.
VHF COMM TRANSCEIVERS (Optional)
Dual VHF-22A transceivers are remotely located in the airplane tailcone. They are individually
controlled by CTL-22 control heads located on the right side of the center instrument panel. Each radio is a
720-channel, very high frequency (VHF) unit with a frequency range from 118.000 to 135.975 megahertz
(MHz) with 25 (KHz) and 8.33 KHz spacing.
During ground operation, radio transmissions can be blocked by surrounding terrain or structures.
This may possibly be overcome by using the other COMM, because of airplane antenna location. The
COMM 1 antenna is on the underside of the fuselage and the COMM 2 antenna is in the vertical stabilizer
fin cap. Flying through dry precipitation, it is possible for static electricity buildup to cause the VHF COMMs
to automatically squelch to a point where reception range is greatly reduced. Disabling the squelch by
selecting SQ OFF will cause background static in the speaker or headset, but normal reception range will
be restored. If the headset microphone fails to function properly, check the side console switch in MIC
HEADSET.
CTL-22 CONTROL PANEL
The CTL-22 control panel located low on the center instrument panel, uses two digital readouts to
display the controlling (active) frequency and a pilot selected preset frequency.
Tuning of the radio is by one set of dual concentric knobs which control either the active (ACT)
frequency or the preselect frequency. The active frequency is the upper readout; the lower one is
preselect. Pressing the ACT switch for approximately two seconds enables direct tuning of the active
display and of the radio itself. In direct tuning operation, dashes are shown in the preselect display.
Pressing the ACT switch again will toggle the control back to tune-preset mode and the frequency change
knob will tune the preset frequency. Both displays will again be visible.
A total of eight frequencies is available: one active, one preset, and six stored in memory. The memory
frequencies are not visible but may be selected for display by cycling the memory position (MEM) of the
XFR/MEM switch. Each time the MEM switch is pressed, the memory loop is incremented one location and
the frequency stored in that location is shown on the preselect display (it remains stored in the memory,
however). Placing the XFR/MEM switch momentarily to the XFR position, causes the active and preset
frequencies to exchange places and retunes the radio to the preset frequency.
Frequencies are stored in the memory by selecting the desired frequency in the preset frequency
display and then pressing the stow (STO) switch twice. Pressing the STO switch once displays the location
number of available memory.
A self-test system is installed which provides testing of selected COMM circuits and annunciates
results in the lower display. The self-test program is activated by pressing the TEST button on the CTL-22
control. If no trouble is found, the active display will show dashes at the end of the self-test and the preset
display will show 00. If any out-of-limit condition is found, the active display will show DIAG (diagnostic) and
the preset display will show a two-digit fault code.
I 3-20 Configuration AA 56OMB-01