AEA Pilot's Guide 2021-2022 - 53

atmospheric conditions. Few things produce the
degree of temperature changes, however, that aircraft
experience in a typical day's use.
Unarguably, summers provide jet aviation with its
most dramatic temperature swings through the course
of an otherwise routine flight. The aircraft experiences
a temperature swing from the oven-roasting heat of
a 120-degree airport ramp to a minus 60 degrees
or colder in the bone-chilling-cold-soaking at Flight
Level 510 - and back again at
landing.
Less severe are the
temperature swings
experienced by aircraft typical
of the piston-powered set.
Normally aspirated pistonpowered
aircraft rarely fly at
altitudes where summertime
temperatures fall to the same
degree. It may be 120 on the
ramp, but at typical cruising
altitudes, temperatures still
remain comfortably above
freezing.
A spin around the past
A friend and fellow aviator recently regaled a novice
pilot about the advances in aviation over the past three
decades.
COLD CAUSES FEW
PROBLEMS FOR MODERN
DIGITAL ELECTRONICS
COMPARED TO THE
ELECTRONICS USED 30
YEARS AGO AND MORE,
ACCORDING TO INPUT
FROM SEVERAL AVIONICS
MAKERS. HEAT, HOWEVER,
IS AN ENEMY OF
But inside the heat-soaked
cabin during summer, avionics
temperatures easily reach
into triple digits. In the winter,
avionics in a cold-soaked
cabin may fall well below
freezing levels until power
starts to warm the electronics.
So extreme temperature
swings should be considered
a routine part of flying any time of year. Dealing with
this reality can help the avionics reach operating
temperatures more quickly and help reduce any delay
from waiting on display screens to fully warm and
reach their optimal operating temperature range, with
more-responsive, more-colorful displays happening
sooner.
ELECTRONICS IN GENERAL
- AND MORE SO FOR
THE FINE CONNECTIONS
EMBEDDED IN THE TINY
DIGITAL CIRCUITRY
INSIDE CHIPS.
Composite airframes; digital engine controls;
airframe-recovery parachutes; and light-emitting diodes
for everything from anti-collision and wingtip position
lights, landing and taxi lights. LEDs can be excellent
for saving weight, reducing current draw and long lives,
reducing maintenance needs. But
nowhere in aviation do we see
more progress than in our avionics
stacks. Digital electronics long
ago started supplanting transistorbased
electronics, which replaced
radios using tubes.
Within the transition to
electronic displays, the industry
first moved to cathode ray tubes
for displays before advancing into
liquid-crystal and LED displays.
" Something you should never
experience flying your aircraft is
the grinding sound of a failing
attitude indicator approaching
failure because of worn bearings
- the source of the sound, " the
veteran explained to the rookie.
The rookie seemed puzzled.
" You mean my primary fight
display has bearings? " The
rookie's voice reflected his
incredulity. The rookie never flew
even a trainer with analog flight
instruments with spinning-mass gyroscopic instruments
for attitude, turn indication or gyro compass; electronics
were all he's flown. A fact which prompted a series
of hangar-flying tales of failed directional gyros and
attitude indicators - typically prefaced with the warning
signs of failing bearings grinding themselves into
seizure.
Certificated avionics endure testing to establish their
operating-temperature ranges - data published in the
documents accompanying them from their respective
factories. Consider these conditions for dealing with
temperature extremes in the care and feeding of
aircraft avionics.
Cold weather, the veteran explained, taxed the
bearings most, as the air pump strained to bring those
spinning-mass gyroscopes up to a functional speed.
" In the summertime, " the veteran pilot added, " the
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