Pilot's Guide to Avionics 2016-2017 - 68
AUDIO CONTROL PANELS
Continued from page 66
But by and large, the form factor most common
for an audio panel is the standard radio width and 1
inch tall .
Installation considerations ...
the task can vary widely
Installation considerations can cover the map,
given the almost infinite variety of equipment - age,
technology, functionality - installed in older aircraft .
If the job is solely to upgrade the audio panel, a
check for compatibility with existing equipment is a
common-sense step owners will well understand .
Some lucky owners of older-model BendixKing
audio panels can pick from a few models from competing companies with the benefit of being plug-andplay replacements .
Loosen the locking mechanism, remove the old
unit, slide in the new unit, lock it down - and turn on
the power . That's it . But there's no assurance this
approach will support use of all the features of the
new audio panel .
In fact, most avionics shops counsel that the first
installation question to answer concerns the wiring .
Is the old wiring in good shape? Can it support what
the new audio panel - or other new equipment - offers,
without some work updating the wiring, as well?
For example, for a stereo intercom function,
available in many audio panels, to be viable, the
monaural wiring to the monaural headset jacks can't
support stereo sound, even with stereo-capable
headsets . So even if the new panel can be plugged
into the old tray, some wiring update and new headphone jacks will be in order just to deliver the stereo
audio the audio panel offers .
Perhaps the biggest consideration, however, is
the wiring behind the panel, itself - the spaghetti
connecting the audio panel to the radios it will serve .
Installation considerations, continued ...
with digital come other sensitivities
Many avionics shop technicians consulted for
this story stressed that with newer avionics come
an increased need for shielded wiring behind the
panel - particularly for any wiring that carries sound
or digital signal .
And the more changes being made, the more im-
portant the need to make sure wiring is healthy and
up to the tasks asked of it .
Giving the aircraft owner a detailed estimate that
outlines the time involved can help avoid confusion and possible hard feelings when the invoice is
issued, as well as helping to understand why an ostensibly "plug-and-play" audio panel upgrade needs
hours of labor - perhaps the owner failed to take into
account the need to rewire the intercom connections
and install new stereo-capable headset jacks .
It's better to learn up front that the owner can
live with monaural sound if it saves the shop labor
and materials to rewire four to six intercom stations,
string new three-conductor wiring to each of the
intercom jack sites, and all the interior removal and
replacement involved to accomplish the tasks .
Add to this the hour or two of work to rewire each
radio or device changed, and leave behind any talk
of the job being just a simple audio panel replacement job .
Finding what they need ...
a shop's first service
The most important questions for aircraft owners
to answer when planning an audio panel installation
or upgrade is the most basic in aviation: What do
you need it to do for you?
The answer naturally varies owner by owner,
airplane by airplane . No two panels exactly match -
and no two pilots want exactly the same things .
For the VFR flyer using a simple panel to pilot two
or four seats, an audio panel may not even be needed - though intercoms are almost always useful .
A stand-alone intercom can handle the needs of
the simpler airplanes - ones with a single comm and
GPS . Add a single VHF nav, though, and suddenly a
way to channel the audio - to help the pilot positively
identify the station tuned - and a simple audio panel
becomes helpful .
The number of audio inputs needed provides a
definable need to help with the selection. A panel
with two comms, two navs, an ADF and another nonVHF comm (such as an HF transceiver) pushes up
the number of switched inputs required to connect
For those, a larger, more conventionally sized audio control panel delivers the needed features - from
stereo intercoms to music inputs, Bluetooth connections for phone or music devices, plus a marker-
- 68 -
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