AOPA Pilot Magazine - May 2018 - 93

address-and "VFR" instead of the aircraft's registration number-when the
associated Mode A/C transponder is
squawking the VFR 1200 code. This
ADS-B option is only available to capable
978-MHz UATs when the aircraft is operating VFR and not receiving radar services.
Garmin recommends that the anonymous
mode not be enabled in flight, to avoid
receiving an ownship shadow if you have
optional ADS-B In capabilities; instead,
activate it on the ground before takeoff.
The GDL 82 requires no pilot action
during normal operation. It is powered on
with the avionics and will automatically
begin to operate when the aircraft's Mode
A/C transponder is set to ALT and a GPS
position source is available. With ADS-B
Out, the transponder should be operated
in the ALT mode during all airport surface
operations-erroneous data may be broadcast if the transponder is switched from
Standby to ALT just before takeoff.
Sparkchasers Aircraft Services in
Smithfield, North Carolina, has installed

several GDL 82s. "When it's done right,
it's bulletproof," said Mark Huddleston,
general manager and a co-founder of the
business. "It works so well" with a digital
Mode C transponder like the Garmin GTX
327, he added. (The GDL 82 cannot be used
with a Mode S transponder.)
The only mistake an aircraft owner can
make is installing a GDL 82 with an elderly
transponder that's reached the end of its
service life, he said. "How many shops will
even fix a King KT-76A, or a [Narco] AT150
or AT150A, or a Cessna transponder?"
An operating transponder still is
required after the ADS-B Out mandate
becomes effective in January 2020, so
if your transponder has become unreliable-or unsupportable-Huddleston
recommends a new 1090ES transponder
to meet the ADS-B Out mandate. Why?
Even though a new Garmin GTX 335 or
Appareo Stratus ESG lists for $1,200 more
than the GDL 82, the installation in many
cases will cost less for the transponder
upgrade. Sparkchasers mounts a lot of

It's a computer.
It still works.

... and possibly a GNS navigator
from the same era.

the GDL 82s in the back of the airplane,
and power and ground wires have to be
run to it, he explained. If the owner wants
the optional failure annunciator or anonymous mode switch, panel modifications
and additional wiring are required.
The installation cost for either the
GDL 82 or a new transponder is going
to vary. "It depends on the airplane," he
said. "Every airplane is different-even
airplanes 100 serial numbers apart."
And there are other good reasons
for considering the transponder option,
Huddleston said. "I think you'll have
more bang for the buck-and you're
under warranty." There's a lot to be said
for that, especially if you've been paying
each year to keep an old analog transponder serviceable.
AOPA
EMAIL mike.collins@aopa.org

WEB

See AOPA's online ADS-B resources (www.
aopa.org/adsb) and ADS-B selection tool
(www.aopa.org/adsbselector).

 | 93

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AOPA Pilot Magazine - May 2018

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