AOPA Pilot Magazine - November 2019 - 86

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In Episode 6, Lippisch starts with a simple propeller, increases its efficiency by
enclosing it with a shroud, and then ultimately motivates the modern jet engine.
In Episode 12, he explains why the smooth
wings on a bird and the rough wings on an
insect each minimize drag. These are just
a few of the topics guaranteed to fascinate
student pilots and aerodynamicists alike.
The Secret of Flight is indeed a time
capsule produced when color films were
rare. I chuckled when Lippisch predicted that "rocket engines will someday
take man to space." But while the age of
the series is evident in quaint ways, the
laws of aerodynamics are timeless; it's our
attempts to model and understand them
that evolve over time. These smoke tunnel videos and simple demonstrations are
as valuable as instructional tools today as
ever. I have watched the series several
times and I glean new facts with each
86 | AOPA PILOT November 2019

INDUCED DRAG is an inevitable

byproduct of lift and can be
visualized through wingtip
vortices. In this sequence of
frames, we see from above a wing
in the smoke tunnel with negative,
zero and positive angles of attack.
A wing with a symmetric airfoil at
a zero angle of attack produces
no lift and, therefore, no induced
drag (above). With a positive angle
of attack, the higher-pressure air
below the wing seeks the lower
pressure environment on top as
is evidenced by the streamlines
curling around the wing tips (left).
WIth a negative angle of attack,
the higher-pressure air atop the
wing curls to the lower side around
the wing tips (above left).

viewing.
In recent years, The Secret of Flight
became unavailable for purchase after
the supply of DVDs was exhausted. But in
August of this year, the University of Iowa
bestowed upon the aviation community an
incredible gift by uploading the series in
its entirety on YouTube (bit.ly/2Pcstp3).
No money, anxious waiting times, nor
impending disappointment is necessary.
Just sit back, relax, and enjoy as the secret
of flight is revealed.
AOPA
CATHERINE CAVAGNARO is an aerobatics

instructor (aceaerobaticschool.com) and
professor of mathematics at Sewanee: The
University of the South.
Check out more images from
The Secret of Flight and access
the full series.
aopa.org/secretofflight

http://www.AOPA.org/creditcard http://www.bit.ly/2Pcstp3 http://www.aceaerobaticschool.com http://www.AOPA.org/creditcard http://www.aopa.org/secretofflight

AOPA Pilot Magazine - November 2019

Table of Contents for the Digital Edition of AOPA Pilot Magazine - November 2019