engine as the engine cools and the
air in the engine contracts.
The problem with this is that it
makes the engine breathe in moist
air. The moisture can then condense
out on the inside of the engine,
promoting corrosion on any surface
where the oil film has left the steel
parts of the engine unprotected.
This can cause excessive corrosion of
the interior of the engine. As such,
the recommendation is to keep the
heater on when in use, except when
the airplane will be flown.
Most of the professional-grade
heaters for aircraft engines are
internally thermostatically controlled
and will cycle to maintain the proper
temperature. Since the temperature
band maintained is fairly tight, while
some change in the air does take
place, it generally is not enough to
promote excessive corrosion, since
the engine does not generally cool
down to ambient temperatures.
No matter how you look at it,
if you intend to fly your plane
when the mercury dips toward the
freezing range, it is very important
that you take the necessary steps
to preheat your engine. Failing
to properly preheat your engine,
whether using a light bulb, a heater, a
propane blower system, or a custom-designed engine heater, can expose
your engine to problems that can
substantially shorten your engine life,
or even damage the engine, requiring
expensive repairs. The cost of avoiding
these problems is fairly minor, when
compared with the cost of the repairs
necessary if the engine is not properly
preheated prior to being started!
George Wilhelmsen holds a
commercial certificate, airplane single-
engine land, with an instrument
rating, and he has more than 1,000
hours of flight experience. He has
a bachelor’s degree in engineering
technology with a background in DC,
analog, and digital controls. He flies a
Beech Debonair.
