Pilot's Guide to Avionics 2017-2018 - 68
WIRED FOR THE FUTURE?
example, swinging the landing gear on a retractable,
Continued from page 67
cycling of flap drives and more.
Ahead of starting the process, the shop needs to
the site of the short. Or two exposed wires can arc
acquire the appropriate wire and harnesses, geared to
and possibly weld together, setting the stage for other
the replacement job planned.
Vibration, chafing between wires and airframe parts,
flexing which can work-harden solid-core conductors,
With the aircraft opened for an annual inspection,
the technicians have a head start on replacing the
wiring and, if so required, other electrical components.
liquid soaked into fabric insulation - all can be the
Wiring for recognition lights, anti-collision lights - both
start of, or end of, a wiring problem.
wingtip and tail - are arguably the simplest aspect.
As one avionics shop owner put it bluntly, "Look at
Dive into the firewall-forward territory under the
the least-accessible part of the airframe, and if you
find wires with cloth insulation, the airplane is past due
for an upgrade to the wires and harnesses. The wires
cowl, components on either side of the firewall, and
wiring behind the panel and things probably get more
are, after all, the nervous system of an aircraft, and
But it's in these areas where wiring harnesses
it needs to be healthy to do its job so the rest of the
and electrical components endure the most extreme
electrical components can do theirs."
conditions they face. Every flight involves the firewall
and engine swinging from cold - possibly bone-chilling
Timing a wiring replacement mission
- to blistering heat and back again. Every flight.
When the owner or operator asks and receives an
Heat behind the instrument panel comes from the
assessment of the aircraft's wiring health, when the
electronics and avionics powered by the wiring in the
diagnosis is bad but not fatal, it's time to treat the
electrical system. And it's behind the panel where the
issue with more urgency. It's time to think about a
next best opportunity exists to update aircraft wiring.
conductor transplant by rewiring the bird.
Ditto for airframe cavities prone to collecting
Provided there are no issues so urgent as to
moisture. Water can damage wiring if exposed to
warrant an immediate wiring-upgrade visit to the shop,
freezing temperatures or if allowed to puddle and
when would work best for an owner or operator in
immerse wires and connectors.
terms of downtime, costs and convenience?
Aside from the annual inspection, other
Shop owners overwhelmingly suggest timing the job
opportunities typically come along over time.
with another major maintenance need - at a minimum,
Reupholstering the interior requires removing the
an annual inspection.
interior; repainting usually involves disassembling
"If no critical problems exist, timing the job to
happen during an annual comes closest to ideal,"
Both involve enough downtime and airframe
explained an avionics technician with experience on
exposure to tackle a wiring upgrade. Another logical
everything from Skyhawks to Global Express business
opportunity - avionics work.
jets. "What makes the timing so excellent is endemic
to the annual process."
That process necessarily includes removal of the
An opportunity in progress: Meeting
the ADS-B mandate
interior - seats and carpeting, at least - the opening
With thousands of operators still facing the
of inspection panels in the floor, in the wings and
avionics-upgrade mandate for Automatic Dependent
fuselage, and a visual inspection of the airframe
Surveillance-Broadcast Out, avionics shops have a
condition, engine inspection, compression check
perfect opportunity to help owners understand the
and other examinations specific to the airframe. For
health of their aircraft's wiring and decide what to do
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