Flight Training - January/February 2022 - 20

PREFLIGHT WEATHER
BY DAVE HIRSCHMAN
WINTER IMC
ENJOY YOUR SUPERPOWERS
WINTER IFR FLYING PUTS A PREMIUM ON CLOUD
avoidance. That's an odd thing to say for a rating
that's all about flying in low-visibility conditions. But
few general aviation aircraft are equipped for prolonged
exposure to icy clouds, and avoiding them is
the surest way to prevent ice accumulation in flight.
Preflight weather planning should include satellite
images showing cloud coverage, freezing levels,
and pilots reports of ice encounters.
Once you get to the airplane, preheating the
engine, cabin, and avionics can reduce wear and
increase reliability of electronic and mechanical
items. If the airplane you're flying is equipped with
deice, or anti-ice systems, make sure they're serviced
(with TKS fluid or alcohol) and working properly.
TKS systems, in particular, require that the pumps are
primed, and even when they're working properly, it
can take several minutes to move fluid from the tanks
to the portions of the airplane you're trying to protect.
If you rely on a tablet computer or smartphone
for IFR charts, the cabin has to be warm enough for
your tablet to work, and cold temperatures drain battery
power faster than normal. (Bringing a separate,
external battery pack for your devices can keep them
working happily for many hours-provided that the
battery pack itself is fully charged.)
If clouds are unavoidable in flight, realize they're
not all created equal. Cumulous clouds with extensive
vertical development carry the most moisture,
and they can create clear ice that may accumulate
rapidly and present an immediate threat. Relatively
thin, stratiform clouds tend to produce lighter rime
ice that isn't such an immediate hazard.
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FLIGHT TRAINING JANUARY/FEBRUARY 2022
Pay close attention to the outside air temperature-and
realize it's likely to drop when you enter
the clouds. If you're in cruise flight in clear skies
with an outside air temperature of 38 degrees
Fahrenheit and then enter clouds, the temperature
is likely to drop to the freezing point almost
immediately. It's like stepping into the shade on
a sunny day.
Even if the airplane you're flying doesn't have
deice or anti-ice equipment, you can reduce the
hazards by making sure the pitot heat is on and
working (look for a jump in amperage when you
turn the heat on) before entering clouds, and that
should keep the pitot-static system free of ice. Also,
turn on the windshield defroster well in advance.
It's better to prevent frost from forming on the
windshield than to clear it once it's there.
When pilots encounter ice, they should report
it to air traffic control and find an expeditious way
out. Usually, that means climbing or descending. If
there's sunshine and clear air above and within the
airplane's reach, go to it-but not too quickly. It's
usually better to fly fast and make a relatively shallow
climb to avoid flying at high angles of attack.
This helps keep ice from forming behind the wing
and horizontal tail leading edges, and it provides a
greater margin over the critical angle attack where
aerodynamic stalls take place.
Winter brings cold, dense air that gives airfoils
and piston engines seeming superpowers. Enjoy the
enhanced performance the cold months bring.
dave.hirschman@aopa.org
Flight Training - January/February 2022

Table of Contents for the Digital Edition of Flight Training - January/February 2022
