Avionics News April 2013 - 66

WHAT RADIAL ARE WE ON?
Continued from page 64

Of course, all the usual concerns
about old cables and antennas apply
– even more than usual since these
are critical for IFR flight. Ed Maher,
in his book Avionics Troubleshooting

and Repair, advocates a simple
approach to VOR debugging: listen
to the audio on the VOR frequency.
Noisy audio, particularly on dual
receivers, almost always indicates an
antenna problem. Maher also noted
at times, nav and comm cables can
be switched – leading to performance

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66

avionics news

•

april

2013

problems for both systems.
An expert I interviewed on this
topic added some additional information: “We live in an analog world…
but it’s converted to digital and then
back to analog for the CDI display.”
I asked if this might explain why the
KX-155 in our Skylane sometimes
seems to give an ILS glideslope
before the GNS 530, and he said
“probably.” He added that “heat and
time take their toll” whether in analog or digital systems.
One more point bears repeating.
It’s common for people in this field
to write that VOR is on its way out,
due to be replaced by GPS navigation
systems.
With all due respect, that’s bunk.
As this article went to press, the
FAA released a major update on the
Aeronautical Information Manual.
On page 1-1-22, it notes that air carrier and commercial operators must
have dual navigation systems, only
one of which can be GPS based. With
inertial navigation systems beyond
the budget of most nonairline operators, and alternatives like long-range
navigation and NDB/ADF either
decommissioned or on the way out,
VORs will be with us for quite some
time.
Meanwhile, don’t be surprised if
a confused pilot asks why his stateof-the-art glass panel reports him far
from where he should be on VOR
navigation. Take a long look at his or
her antennas and cables. Odds are the
position shown is accurate – within
the limits of the hardware.
For a slightly dated, but still helpful review of VOR (and ILS) receiver
test procedures, see Brad Primm’s
“Troubleshooting VHF NAV/ILS
Problems” from the October 2003
issue of Avionics News. The NAV401 test set he described has been
superseded by the more sophisticated
NAV-4000. You can download the
complete manual for it (and a number of application notes) from the
Aeroflex website. q
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Avionics News April 2013

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