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
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
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
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).