Aero-Tips!

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 together.

Aero-Tips 01.08.06

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 temperature (EGT).

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 endurance. 

Peak EGT

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.

FMI: Aero-Tips