Avionics News October 57-10 - 51

ramp and the cabin along with that avionics stack endure
the warming effects of the sun on the equivalent to a
greenhouse.
These kinds of extreme heat conditions can exist in an
airplane on a winter day with clear dry air and sunlight
warming the cabin - and its panel - well above 100
degrees. Even when it's freezing outside.
And a metal hangar, not insulated, acts like an oven
for the aircraft stored there and, in turn, the equipment
installed in the aircraft. Running a fan to circulate the
hangar air serves more to make the space like a convection
oven - with little cooling effect on the heated air.
The solutions: avionics cooling fans for behind the
panel and some form of air circulation that draws in
outside air during the hotter seasons.
Multiple options exist to plumb cooling air to flow
behind the panel. Installation of these options need
water traps and drains to prevent rain or other forms of
moisture penetrating the avionics. And for the hangar, if
not air conditioning at least a ceiling-mounted exhaust
fan to preclude the heat buildup of a closed hangar
soaking up the sun's rays and heating everything inside.
A battery of challenges
Among the most-common effects of severe cold
conditions are weakened battery output for starting
the aircraft and supporting the operation of the entire
electrical system. Lead-acid batteries - even modern
sealed recombinant-gas designs - suffer from extreme
cold.
With the advent of modern lithium-ion battery
technology for aircraft, however, that cold-soaked
starting challenge is finally starting to pick up a pasttense tone. Currently, only True Blue Power offers FAAapproved main-ship batteries for certificated aircraft,
and the range of options available under STC remains
somewhat limited - and expensive. But the longer life
cycle, reduced maintenance needs and lighter weight of
True Blue Power's batteries quickly attracted customers
in numbers encouraging the company to continue to
work on expanding its offerings.
Operators of light-sport and experimental, amateurbuilt aircraft have some options available, options worth
pursuing by operators who face cold-weather challenges.
Fortunately, because of their lighter weight, longer
life cycle and higher power density, lithium-ion battery
technology dominates the demand for standby power
integral to many avionics devices commonly offered for
flight-critical instruments.

Lithium-ion battery technology is used in virtually
all of the standby roles offered as standard or optional
equipment for PFDs, electronic flight instruments and
other safety-of-flight-critical pieces of avionics kit.
For example, the integral standby batteries in Aspen
Avionics systems is a purpose-designed lithium-ion
battery. Ditto for the optional standby battery Garmin
offers for its G5 electronic attitude indicator.
It simply makes sense to use the best option for the
job, and where power density and critical-role lines
meet, lithium-ion is the choice. And its near immunity
to cold conditions provides some assurance to pilots and
operators that the standby battery will be fully functional
when called upon.
Final analysis: Protect against excess
temperatures - but don't sweat the cold
There's little for pilots and operators to sweat outside
battery cranking power when considering the effects of
extreme cold; but more to consider from the effects of
excess heat.
Avionics OEMs test for extremes few pilots will ever
experience to assure that their avionics work properly in
the normal day-to-day swings of temperature of winter
in most of the country. And normal hot weather poses
a threat to aircraft avionics only when the aircraft is
allowed to bake unprotected from the sun.
A canopy cover offers the best line of defense against
the effects on an aircraft parked uncovered on a hot
ramp. Sitting uncovered, however, allows excessive
temperatures to build up behind the panel and in turn
approach the upper limits of many avionics tested range.
A useful accessory can be the first line of defense
against excess cabin heat: a cabin cover made of a
reflective fabric. By covering the windows, a tightly
fitted canopy or cabin cover may cut the heating effect of
direct sunlight by 20, 30, even 40 degrees.
For aircraft with tight space behind the panel or a
number of heat-producing electronics in the panel, an
avionics cooling fan can help the equipment's own
cooling fan by increasing the circulation of outside air
through the space behind the instrument panel.
Compared to what operators spend on their panels,
both of these options are inexpensive insurance against
extreme temperatures damaging sensitive electronics
pilots depend on to navigate, communicate and monitor
the health of their aircraft engine and systems.
Where weather is concerned, shielding the aircraft is
largely the most we can do about it. q
AVIONICS NEWS

OCTOBER

2020

Avionics News October 57-10

Table of Contents for the Digital Edition of Avionics News October 57-10