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 01.10.06

You learned it by rote—pull the carb heat knob and note an rpm loss as part of your Before Takeoff check, and when reducing power below about 1500 rpm for landing.  If anybody asks (not likely since your last checkride or flight review) you mutter something about “venturi effect” and “carburetor ice.”  But do you really understand why we need carb heat and how to properly use it?

The big chill

The venturi-shaped internal design of carburetors cools air as much as 40° Fahrenheit.  This means moist air as warm as 70°F can freeze in the carburetor, strangling combustion.  

Use carb heat:

1. At the first sign of power loss -- if too much ice forms or engine exhaust cools too much, carb heat might not melt out all the ice.
2. When humidity exceeds about 80% and/or there’s a three degree or smaller temperature/dew point spread.
3. When operating at low power settings, especially during extended glides.
4. Any time recommended by the aircraft or engine manufacturer.

(Note: After applying carb heat you may be able to get the engine to run more smoothly by leaning the mixture slightly.  The object is to adjust fuel flow to compensate for the reduced oxygen density of carb-heat combustion air).

All or nothing?

If flying with a carburetor temperature gauge, you can apply just enough carb heat to get the temperature out of the freezing range, minimizing power loss.  Without such instrumentation the conventional wisdom is to apply full carb heat whenever carb ice is likely, accepting the power loss that results.

Aero-Tip of the day:  Know the conditions requiring carb heat; use it how and when needed.

FMI: Aero-Tips