Avionics News August 2015 - 31

At his first annual inspection, he learned that most wiring
needed considerable attention to safely power its few
components: battery, starter, the single nav/ comm, a M ode C
transponder, intercom and lights - recognition and landing.
H is A&P advised him that wiring was the only immediate
need, but to prepare because other components would soon need
attention. The owner began shopping for modern replacements.
About the same time, the P iper owner planned an upgrade
path for everything in the electrical system - like the Cessna, all
original eq uipment.
STAYING WIRED:
UPDATING AGING 'NERVE SYSTEMS'
H umans function through the connections between brain and
our bodily components through human wiring of the central
nervous system. Age brings some deterioration in how well
those connections function.

untouched thanks to a previous panel upgrade - in the 1 980s.
W ires with cotton insulation remained elsewhere in the
airframe. The P iper owner also opted to step up one gauge
instead of simply matching the gauge of the old cotton-insulated
wiring. H is avionics service provider suggested the change as a
hedge against future system demands.
Other plans to upgrade system components waited on a
" some-day" list.
NECESSITY TRUMPS
A generator failure in instrument meteorological conditions
changed the P iper owner' s plans. H is A&P was able to get the
old generator repaired - warning that the starter could be nex t.
After some research and consultations with his maintenance
shop, the Comanche owner opted for an all-in approach: A
complete system upgrade at the nex t annual inspection. M ultiple
options ex isted for each component still on the owner' s hit list:

Today's market offers opportunities to help
owners move their aircraft into modern times to better
handle pending equipment mandates - and owners'
wants for some modern systems.
A similar issue faces the wiring in older aircraft. And today,
"older" encompasses most of the fleet.
According to the Federal Aviation Administration, the
average age of the general aviation fleet is upward of 40 years.
For an aircraft still heralded as " all original," that often means
eq ually old wires - the nerve connections of the electrical
system.
U pgrading wiring arguably presents one of the most laborintensive and time-consuming elements of an electrical-system
upgrade. W iring may be a spaghetti mess behind the panel;
elsewhere, wiring runs throughout the fuselage and within the
wings.
A maj or maintenance j ob may provide an opportunity to deal
with aging wiring, such as an interior replacement or an annual
inspection during which the seats, carpet and sundry interior
components come out to allow a complete look at the airframe.
W hen the interior and the panel had to come out of the
Comanche, replacing wiring was relatively easy, presenting
the opportunity to replace and mark new wires from firewall to
tailcone, wingtip to wingtip. Only the avionics wiring remained

alternator; starter; regulator; and battery.
Y es, even the battery presented an opportunity to hit the
system-upgrade trifecta: more power, less weight and reduced
maintenance.
STARTER OPTIONS: A TRIPLE - LIGHTER, MORE
POWERFUL, LESS CURRENT
A wide range of starters ex ist for owners of aircraft with
old 1 2-volt systems from the generator era; universally, the
replacements weigh several pounds less than the originals.
V irtually all are geared starters, which produce more torq ue
from a smaller motor drawing less current when cranking.
But variations ex ist in how much current these starters draw,
and a steep current draw may interfere with the function of
electronic ignition systems flying as factory and aftermarket
installations.
The differences generally come down to the type of
magnets built into the starter; permanent magnets bring the
Continued on following page
AVIONICS NEWS

AUGUST

2015

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Table of Contents for the Digital Edition of Avionics News August 2015