Avionics News November 2013 - 55

BendixKing by Honeywell's KMA 30

In its simplest form, the choice should reflect what the customer wants or needs. But the range of choices can overwhelm
some shoppers - at least, compared to the "old days" of simple
audio panels.
You want one with a marker-beacon receiver? Or without?
Tomorrow's 'Anchor' Box Today
In years past, audio panels largely performed the same function: selected the radio transmitter used, the receiver monitored,
and in some instances allowed crew to hear audio broadcasts
by AM radio stations. Freight Dog pilots, over-the-road truckers and other late-night flyers often tuned their ADF receivers
to popular sports broadcasts, late-night music programs or talk
shows on high-power clear-channel frequencies.
The pilots listened to those stations received on their ADF
navigation receivers, channeled to speakers or headsets via the
audio-control box. Instrument fliers found the merger of an
audio panel with a marker-beacon receiver convenient.
Admittedly, the friend mentioned above may be one of a tiny
minority unhappy with this, but the state-of-the-art in general
aviation audio panels indeed began a sizable expansion of capabilities around the turn of the century.
And today's audio-control panels reflect the sweep of those
options, which include the technologies mentioned above, and
more.
Helping clients pick an audio panel today should involve
more than the old standard approach many pilots took in the last
century. Either go with the cheapest options or opt for avionicsbrand alignment - the better to have matching faceplates.
So you want some Bluetooth with your audio? Wi-Fi with
your tunes? Or an intercom with your comm?
Audio panel choices customers enjoy have never been so
varied. So "you can get anything you want" given the variety of
audio panels available today.
Cue the musical monologue "Alice's Restaurant Massacree"
by Arlo Guthrie.
The Genesis of the Audio Panel: Visual
Signals Versus Ambient Decibels
Early aviation struggled to deal with many challenges, and
some remain prominent today.
Airframes and engines, we can agree, are hugely more reli-

able and durable than what we flew a century ago - and even
50 years ago.
Communications and navigation took some of its greatest
leaps in stages - from the development of radio navigation to
replace fire and light beacons pilots needed to traverse the skies,
to the advent of radio voice communications to supplant light
gun signals between controllers and pilots.
Today's hardware vastly improves on what flew even a
couple of decades ago.
Sound levels, in and out of the cockpit, may be the area with
the most room for further progress. Yes, engines and props and
cabins are generally quieter, but headsets remain standard gear
for most flight crew and passengers in most propeller-driven
aircraft.
The intercom initially gave the pilot and co-pilot a communications improvement over hand signals - and bellowing to be
heard over the sounds of engines, props and exhaust pipes.
With the advent of numerous audio-oriented accessories,
the invention of the audio-control panel was part of the natural
progression - or, at least now it seems natural.
Aircraft progressed to using multiple radios that produced
audio the crew needed to hear - when they needed to hear it.
Initially the solution involved flipping open and closed different switches to route the audio into either a speaker (or speakers)
or through early headsets; the wiring was complicated by the
overlapping feeds to the speaker or speakers, necessitating a
configuration chart to show which switches should be in what
position to deliver the audio when needed.
The advent of the audio-control panel provided a moreconvenient solution, packing into one box a simpler set of connections to multiple self-contained switches.
Now a pilot or co-pilot could monitor a communications
radio, identify a VOR (VHF omnidirectional range) station's
Morse code signal and cross-check position by cross-referencing the direction of a high-power AM radio station indicated by
an automatic direction finder - through which the crew listened
to a baseball game or the like.
The audio-switching system, as some were called, also gave
the flight crew a simpler system for selecting the transmitter or
transceiver desired for communicating with air traffic control,
Continued on following page
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Avionics News November 2013

Table of Contents for the Digital Edition of Avionics News November 2013