How Do Airplane Wings Produce Lift?
■ H OW D O A IRPLANE W INGS P RODUCE L IFT ?
The following demonstration speech was presented by a student in the basic
speech course. Mark Yingling was a licensed private pilot and aviation student who
wanted to share his passion for flight with the members of his audience. The speech
not only represents effective research, organization, and delivery, it also illustrates
how a speaker used PowerPoint software to develop an effective slide show that
was shown with a computer projector.
An Informative Speech to Demonstrate
Mark Yingling
1. (slide 1) Good afternoon. My name is Mark Yingling. Today I’d like to talk to you
about airplane wings, but more specifically, how airplane wings produce lift. I’d like to
begin with a quote from Leonardo da Vinci (slide 2): “For once you have tasted flight,
you will walk the earth with your eyes turned skyward, for there you have been, and
there you long to return.” Da Vinci was fascinated with flight five hundred years ago,
and Jeppesen wrote a book called the Private Pilot Manual, and it describes him as having a manuscript with sketches and drawings of flying machines.
2. To fly, you need a force called “lift,” and that’s what I’m going to talk about today.
(shows slide 3) We’re going to talk about three components of lift: We’re going to talk
about airfoil design, we’re going to talk about Sir Issac Newton’s Third Law of Motion,
and we’re going to talk about Daniel Bernoulli’s principle.
3. So let’s begin and examine the airfoil. (slide 4) What is an airfoil? An airfoil is any surface that is designed to produce lift when it is interacting with air. On an airplane, a
wing is an airfoil and a propeller is an airfoil. If you ever get a chance, look at a propeller: It looks very similar in shape and design to a wing. Now I brought my little
model here. (displays a model airplane) The parts of an airfoil: We have a leading edge,
and we have a trailing edge, and this curvature here is called “camber.” Now when the
air is moving over the wings, it has to follow this camber, and it is directed downward
Slide 1
Slide 2
1. The speaker begins
his introduction. Since
Mark’s classroom audience already knows
him, it is not necessary
to begin with a personal greeting. It would
be more effective to
start with the quote,
“For once you have
tasted flight . . .”
2. The speaker presents
his three-point thesis
statement. It is not necessary to “announce”
the thesis with “I’m
going to talk about.”
3. Mark introduces the
first numeral of the
body.
He uses a model airplane to demonstrate
the different parts of
the wing.
CHAPTER
11 Using Audiovisual Aids
Slide 3
Slide 4
Slide 5
Slide 6
Mark uses an effective
analogy to a garden
hose.
4. The external transition is clear, if somewhat abrupt.
5. The speaker supports
his speech with a credible source.
to increase (slide 5 ) what we call downwash, and it is this downwash that helps to produce lift. The best analogy I can give you is to take a garden hose and hold it at an
angle at the ground and let it go full blast, and you can feel that it wants to push up.
4. Okay, next let’s talk about Sir Isaac Newton’s Third Law of Motion. (slide 6 )
5. Isaac Newton was a seventeenth-century physicist-mathematician, and his Third Law
states that for every action there is an equal and opposite reaction—everybody has
heard of this one before. Irvin Gleim wrote a book called the Pilot Handbook, and he
best describes this as the deflection of air. Now to understand this, let’s see how the
wing is attached to the plane (slide 7 ). Let’s begin by drawing a line through the longitudinal axis of the plane and then let’s draw a line through the leading edge and trailing edge of the wing. When you bring those lines together (slide 8), you can see that
they are slightly different, and it forms a small angle; and this angle is called the “angle
How Do Airplane Wings Produce Lift?
Slide 7
Slide 8
Slide 9
Slide 10
of incidence” and basically it is the way the wing is attached to the plane—it’s got a
slightly upward slant to it compared to the longitudinal axis of the plane. So as air is
coming (slide 9), it hits underneath the wing and deflects downward. That is the action
(slide 10). The reaction is the upward force. So you have action, deflection of air, and
reaction, the lifting of the plane.
6. Next, let’s talk about Bernoulli’s Principle (slide 11).
7. Now Daniel Bernoulli was an eighteenth-century Swiss mathematician, and he studied
the movements of fluid. He also studied the pressure differences with velocity.
Bernoulli’s Principle states that as the velocity of a fluid such as air increases, its pressure decreases. Now this is a little bit difficult to understand, but Jeppesen wrote a
6. A better external
transition might be,
“Now that you know
how Newton’s Law
applies to flight, let’s
consider Bernoulli’s
Principle.”
CHAPTER
11 Using Audiovisual Aids
Slide 11
Slide 12
Slide 13
7. The speaker cites
another source to verify
the credibility of his
research.
8. Mark begins his conclusion with a summary of the three main
numerals of his speech.
book called the Instrument/Commercial Manual, and they best describe how the wing
takes advantage of Bernoulli’s Principle by differences in pressure (slide 12). Now as air
is moving over the wing as the velocity is increasing, it has to travel a longer distance to
get over this camber so the velocity is increasing, which decreases the pressure. The
pressure underneath the wing is increasing. So this high pressure underneath the wing
wants to get on top of here because pressures are always trying to equalize, and the
golden rule is, high pressure always goes to low pressure. So in essence this high pressure wants to get on top of here and pushes the plane.
8. So as a (slide 13) result of Newton’s Third Law of Motion, we have the deflection of air,
which is the action/reaction of the lifting of the airplane. We have Bernoulli’s Principle,
1
which is the difference in pressure. We have the high pressure underneath the wing,
the lower pressure on top of the wing, and the higher pressure pushes the plane up and
tries to get on top of this lower pressure. And we have the shape of the airfoil. The air,
moving over the wing, has to follow the camber downwards creating that downwash,
helping the airplane produce lift. So lift is accomplished, and flight is made possible by
these three components. Now I’d like to conclude by saying that like da Vinci, I’m also
fascinated with flight, and I long to return to the sky as soon as possible.6
The speaker ends by
referring briefly back to
his introduction and
making a personal
comment about flying.
❘❙❚ Summary
The term audiovisual aid refers to a device that may appeal to any of the senses: mechanical
media (including the useful PowerPoint program); graphs (line, pie, and bar); drawings,
photographs, and pictures; posters, flipcharts, and chalkboards; physical objects; and you,
the speaker. The computer projector, often used with graphics software such as PowerPoint,
is a popular visual.
Here are six guidelines to help you use the PowerPoint(tm) program successfully:
1.
2.
3.
4.
5.
6.
Know your options.
Keep visuals simple.
Know how to use the program during the speech.
Be sure that the technology is set up and working properly.
Have a backup plan if the media fails.
Consider your audience at all times.
Other mechanical media—such as digital, video, and audio; overhead, slide, or film
projectors; as well as audio- and videotape-recording equipment—are useful in different
situations. Posters, either hand-drawn or produced with a computer, can reinforce ideas
effectively, and the chalkboard is useful for brief or incidental support of a speech. You can
also include scale models, partial objects, or life-size objects in a speech. As a speaker, you
are also a visual aid. You can incorporate your own body movements and actions into a
speech, and you can ask someone to help you.
Observe five general guidelines to use visual aids effectively:
1. Talk to the audience, not to the visual.
2. Don’t pass objects around during the speech.
3. Be sure listeners can see your visuals.
4. Use visuals at the right psychological moment.
5. Be clear at all times.
❘
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