into the engine oil. The good news is
that all it takes to keep the moisture
content low is to fly regularly and
make sure that the oil temperature
makes it over 212°F (the boiling point
of water).
Lastly, even though most of the
precipitation coming down may be
frozen, it still contains acids from
environmental pollution. So, it’s
important to give your aircraft’s exterior finish a good cleaning and waxing to protect it from the elements
during the coming months. In addition, a smooth, waxed exterior makes
clearing ice and snow much easier.
Aircraft Preheating
A cold engine can be hard to start,
and low temperatures weaken your
battery’s ability to crank the engine
for extended periods. But that’s only
the beginning. According to some
studies, winter cold starts can account
for more engine wear than years of
normal flying.
Contrary to popular belief, oil flow
is not the major reason for preheating
the engine. Modern multi-viscosity
oils such as AeroShell 15W50, Phillips
20W50, and Exxon Elite 15W50 are
designed to operate in temperatures
as low as 0 degrees. That is essentially
what the viscosity numbers in the
oils’ names mean. AeroShell 15W50
acts like 50-weight oil in hot engine
conditions and 15-weight oil in cold
engine conditions.
When the aluminum is heated, it will
expand twice as much as the steel as
well.
The bearings for the crankshaft are
an excellent example of this problem.
The crankshaft bearing is supported
by the aluminum case, while the
crankshaft itself is steel. The clearances for these parts are designed
for normal operating temperatures.
In extremely cold temperatures, the
aluminum case contracts enough to
make the bearings too tight and can
cause substantial wear and damage
upon start-up.
In the cylinder, the piston is made
of aluminum, while the cylinder barrel is made out of steel. When the
cylinder is extremely cold, the piston
shrinks much more than the barrel.
This causes the opposite problem,
at first. The piston can wobble too
much in the barrel and cause “
scuffing.” But, as soon as the engine gets
going, the piston begins to heat up
and expand rapidly—more rapidly
than the cylinder barrel. This quickly
leads to the opposite problem where
the piston expands and the piston-to-barrel clearance gets too small, also
causing wear and possible damage to
the cylinder.
