Avionics News October 2016 - 17
Fortunately for aircraft owners flying the glass panels, life
Keeping the engine lubed
expectancy, repair frequency and replacement requirements all
General aviation aircraft engines - since World War II
trend toward better - less frequent repairs or replacement, fewer
overwhelmingly air-cooled - require an effective lubricationoveralls and maintenance focused more on software updates
circulation system to keep the powerplant healthy. Anything that
than mechanical needs.
reduces flow threatens an engine's health in two ways. First,
But even in their evolution from analog to glass, avionics
pressurized oil flow provides the lubrication needed to preclude
struggled with their own temperature sensitivities - and still do,
damage from metal-on-metal sliding or the kind experienced
to a lesser extent.
between pistons and cylinder, wrist pins, connecting-rod bearings and crankshaft, and main-journal bearings and the crankThe warmup
The earliest glass cockpits employed cathode ray tube techSecond, oil also carries away heat through the oil cooler
nologies - think of your parents old picture-tube television set
installed on most engines today. As the oil heats, the amount of
- and needed a warmup period just to function.
work needed to pump the oil declines as the oil thins and presThe CRT warmup delay reflected
the earlier days of aviation - before
But oil too cold to flow can congeal
transistor-based electronics. In those
in the oil cooler and possibly clog oil
days, vacuum tube radios all needed
lines and the cooler itself, where cold
COLD CAN INDUCE
time to warm up before fully funcoil gets exposed to fast-moving colder
DAMAGE TO AIRCRAFT
tioning. To merely listen, to talk, to
air. Add the chill of cold air streamnavigate, pilots waited for their radios'
ing through an oil cooler engine and
ENGINES IN MUCH
vacuum tubes to reach their minimum
lubricants may cool the oil to the point
THE SAME WAY
operating temperature - which fit well
it congeals in narrow passages.
with waiting for the engine to warm up.
Preheating the engine to warm
Transistor-based radios brought
metals and lubricants helps ward off
TRIGGER A DAMAGED
aircraft cockpits to being as instant-on
engine damage possible when cold
as we could ever expect in modern
lubricants become so viscous that they
times; then waiting was strictly an
resist the circulation efforts of the oil
engine-warmup thing ... and preparpump. Preheats that warm both metal
ing for departure, getting clearances
and lubricant greatly reduce the prosand such. With analog tuning and
pects of friction and heat damage due
frequency-selection shown through
to insufficient oil circulation.
mechanical windows, the biggest risk
from the cold was breakage of an imKeeping spin on avionics
portant mechanical part. Well, that and
Preheating the aircraft can't hurt
the speaker, which could need a brief
the avionics in cold weather. But it's
amount of time to hit its stride.
not the necessity it once was.
But the digital displays that followed CRT displays didn't
Aviation continues to steadily march toward the near obsolesexactly adapt easily to colder conditions.
cence of analog flight instruments and spinning-mass gyroLiquid-crystal displays, both monochromatic and color,
scopic indicators. Between their higher weight and shorter life
needed some warmup time to function optimally; in colder
span and the dropping costs of going glass, production numbers
weather they reacted a little like molasses in January. When
are waning in line with declining demand. As the pool of users
the image needed to change and the electronics commanded
declines, the service options fall in parallel.
a change in the crystal's polarity, the change occurred slowly
No one interviewed for this story predicted the total extinc... at least until those red, green, blue and black liquid crystals
tion of analog flight-instrument six packs; many, however,
warmed sufficiently to shift their reflectivity as quickly as the
expect analog flight instruments and gauges to become niche
items served by specialty shops.
Many repair shops report slowing repair work amid declining
Continued on following page
sales of analog instruments.
ARE AN ANATHEMA