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 02.11.06

Air rebounding off the lower surface of an airplane’s wing provides a vital component of lift. When the airplane is low enough that disturbed air compresses against the ground, it dampens out many sources of aerodynamic drag. Within about one wingspan of the surface, this "ground effect" reduces wing upwash, downwash and tip vortices.

Ground effect increases as the wing is even closer to the ground. At about one-fourth a wing span above ground drag is reduced 25%; within one-tenth of a wingspan of the surface aerodynamic drag drops by about 50%.

Ground effect seems most pronounced in low-wing airplanes. This is because a low wing gets closer to the ground -- and therefore experiences a greater drag reduction—than a high wing.

Ground effect is usually taught as part of the soft-field takeoff technique. Since drag is reduced in ground effect, an airplane can fly in ground effect at a slower speed than possible even a few feet higher. Haul the airplane into ground effect at the slowest possible airspeed and you get the wheels out of the mud. But keep the wing low until you’ve reached "normal" takeoff speed—if you get just a few feet higher the drag will build and the airplane may settle back to the ground. Given that most "soft" fields are also "short," this can really ruin your day.

Ground effect indirectly contributes to many accidents at high-elevation airports. The airplane may lift off in ground effect in conditions when flight out of ground effect is not possible. The pilot has to choose between setting the airplane back down on any remaining runway or off-airport, or hitting obstacles in an inevitable (and frighteningly drawn-out) high-speed collision.

Aero-tip of the day: Recognize when ground effect is beneficial (soft fields), and when it can offer false hope of climb capability (high density altitudes).

FMI: Aero-Tips