A good pilot is always learning -- how many times have you heard
this old standard throughout your flying career? There is no truer
statement in all of flying (well, with the possible exception of
"there are no old, bold pilots.") It's part of what makes aviation
so exciting for all of us... just when you think you've seen it
all, along comes a scenario you've never imagined.
Aero-News has called upon the expertise of Thomas P. Turner,
master CFI and all-around-good-guy, to bring our readers -- and us
-- daily tips to improve our skills as aviators, and as
representatives of the flying community. Some of them, you may have
heard before... but for each of us, there will also be something we
might never have considered before, or something that didn't
"stick" the way it should have the first time we memorized it for
the practical test.
It is our unabashed goal that "Aero-Tips" will help our readers
become better, safer pilots -- as well as introducing our
ground-bound readers to the concepts and principles that keep those
strange aluminum-and-composite contraptions in the air... and allow
them to soar magnificently through it.
Look for our daily Aero-Tips segments, coming each day to you
through the Aero-News Network. Suggestions for future Aero-Tips are
always welcome, as are additions or discussion of each day's tips.
Remember... when it comes to being good pilots, we're all in this
Despite the fact that
fuel starvation (running a fuel tank dry) and fuel exhaustion
(running completely out of fuel) are common causes of engine
failure, and that mismanaging fuel flow contributes to engine wear
and early cylinder failure, few pilots learn how to properly lean
the fuel/air mixture. A complete discussion of leaning would
fill a large book. For now, let’s look at a concept
that forms the basis of leaning technique—peak exhaust gas
Why do we lean?
The primary purpose of mixture leaning is to derive desired
power from the engine. We can lean for a “best
power” condition (to climb or go fast), a “best
economy” condition (to go far), or somewhere in
between. Secondary reasons are to promote engine longevity,
obtain acceptable fuel flow rates, and achieve predictable flight
EGT is the indicated temperature of combustion gases as they
enter the exhaust manifold. Many airplanes do not have an EGT
gauge. Some have only a single EGT probe in the exhaust stack
of a single cylinder or in the manifold. Better equipped
airplanes have all-cylinder monitoring, providing fantastic status
and diagnostic capability that greatly enhances flight
safety. Regardless of instrumentation, however, we all use
“peak EGT” as the reference for leaning.
As fuel flow is reduced, EGT curves upward until it reaches its
maximum, or peak temperature. Continue to “lean of
peak” and EGT drops before flattening out. Horsepower
is highest somewhere before peak EGT, dropping from there through
the peak EGT point and beyond.
Aero-Tip of the day: There’s a
whole lot to learn about leaning, which we’ll explore
periodically. No matter what your leaning theory and goals,
however, technique revolves around using “peak EGT” as
an initial reference.