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 better pilots, we're all in this together.

Aero-Tips 05.14.06

We've been looking at planning to avoid fuel exhaustion—is mishap that's common and often fatal. It's absolutely vital to know how to predict fuel requirements, monitor fuel use in flight, and safely arrive with a substantial fuel reserve remaining.

Advisory Circular 61-23C, the Pilot's Handbook of Aeronautical Knowledge tells us:

Fuel Consumption

The rate of fuel consumption depends on many factors... [including] richness of the mixture...

Mixture

Mixture setting is the ratio of fuel to air in combustion. We're taught in primary flight training that optimal mixtures run at about 15 parts air for every part of fuel. What we don't learn is that is a theoretical fuel/air ratio, and operating requirements almost always dictate a different mixture setting.

If the engine does not have an Exhaust Gas Temperature (EGT) gauge usual technique is to lean until the engine runs rough, then enrichen until it's smooth. This is imprecise at best because it is highly dependent on the individual engine's condition and even outside environmental factors. Consequently getting anything that looks like "book" fuel flow is mere coincidence.

If the engine is equipped with an EGT gauge, we use EGT as our primary leaning reference. But mixture setting is also key to cylinder temperature management. We may have to sacrifice some efficiency rich of peak EGT, or (if the engine can take it) choose to run lean of peak EGT to keep cylinders cool (usually with a power loss as tradeoff). And as we change mixture setting the resulting horsepower changes, also.

Fuel burn information from cruise performance charts are always predicated on a specified mixture technique. Sometimes it takes effort to locate the prescribed technique in the Pilot's Operating Handbook (POH). Any deviation from "book" technique provides non-book results.

Aero-tip of the day: Any change in mixture setting from "book" will render POH performance charts nearly useless—requiring you to recalculate fuel requirements.

FMI: Aero-Tips