Section 7
Description of the Airplane and Systems
Columbia 400 (LC41-550FG)
RC050002
Initial Issue of Manual: November 10, 2004
7-120
Latest Revision Level/Date: A/12-01-2004
GARMIN GMA 340 AUDIO PANEL
General
– The Garmin GMA 340 VHF Communication Transceiver/VOR/ILS Receiver/GPS
Receiver is frequently referred to as the audio panel. The system is a fully integrated panel-
mounted instrument, which contains audio and microphone switching and amplification, a
marker beacon receiver, and an intercom system. The audio panel is located in the top of the
radio rack panel assembly and a picture of the unit is shown in Figure 7 - 46.
The
GMA 340 Pilot’s Guide
is included as part of the delivery kit with the airplane and is the
primary source document for operation of the unit. The discussion below is taken from the
GMA
340 Pilot’s Guide
and is intended to provide the pilot with a brief overview of the unit’s
operation.
Abnormal Procedures –
If the GMA 340 fails to function as expected, turn the left volume
control fully counterclockwise to switch the GMA 340 off. When the GMA 340 system is turned
off, the pilot’s headphone and microphone are connected directly to the No. 1 GNS 430 Com. If
either Com 1 or Com 2 seem to be functioning abnormally, the GNS 430 display may show the
Coms are transmitting when they are not. In this situation, reset the Com 1 or Com 2 circuit
breakers.
PICTURE OF THE GMA AUDIO PANEL
Figure 7 - 46
On/Off and Fail-safe Feature
– Unit power is turned off by rotating the left small knob
counterclockwise into the detent. To turn the unit on, rotate the knob clockwise past the click.
The small knob also functions as the pilot or copilot’s ICS volume control on the appropriate
unit. A fail-safe circuit connects the pilot’s headset and microphone directly to Com 1 in case the
power is interrupted or the unit is turned off.
Transceivers –
Selection of Com 1, Com 2, or Com 3 for both MIC and audio source is
accomplished by pressing COM 1 MIC, COM 2 MIC, or COM 3 MIC. The active com audio is
always heard on the headphones. Each audio source can be selected independently by pressing
COM 1, COM 2, or COM 3. When selected in this way, they remain active as audio sources
regardless of which transceiver has been selected for microphone use. When a microphone is
keyed, the active transceiver’s MIC button LED blinks approximately once per second to
indicate the radio is transmitting.
Split Com –
Pressing the COM 1/2 button activates the Split Com function. When this mode is
active, Com 1 is dedicated solely to the pilot for MIC/audio while Com 2 is dedicated to the
copilot for MIC/audio. The pilot and copilot can simultaneously transmit in this mode over
separate radios and only hear his or her own radio. Both pilots can still listen to Nav 1, Nav 2,