Flying — (A “How It Works” Illustration)
Flying is a commonly experienced activity in our day. However, few people, outside of pilots, know and understand what makes an airplane fly.
Learning a little about aerodynamics and/or flying an airplane can be of great illustrative value for an illustration in a speech or a message. The value is found in the fact that . . . .
- people are fascinated by airplanes
- people are curious as to how it all works
- it relates to their safety and ease while flying
- it is easy to relate flying to the Christian life . . . . lift, controls, instruments, trust, winds, flight plan, automatic pilot, etc.
History & Facts: Aerodynamics**:
What law of physics explains “lift?”
Some argue that it is explained by Bernoulli’s law. Daniel Bernoulli was born February 8, 1700, and died at the age of 82, in 1782. His work was mainly in the area of fluids.
Others argue that another law explains lift, Newton’s third law of motion.***
“Even today, there is no clear scientific position which is used to explain lift. Neither law is authoritatively cited to explain lift. Most of the time it is argued that both laws are at work. “Theories on the generation of lift have become a source of great controversy and a topic for heated arguments for many years.”
Neither man ever discussed or discovered aerodynamic “lift.” They were mathematicians and physicist, with no scientific work in the areas of flight.
If you believe that it is an airplane’s engines which are basic to flight, you would be wrong. Gliders were designed and developed before the first airplane was successfully flown by the Wright brothers. Paper planes are a commonly understood example, not to mention birds which can be seen just “floating” and “gliding” in the air. Have you seen a seagull in a stationary position in the air? — No engine necessary!
What allows an airplane to fly is the shape of the wings, which creates “lift.” The propellers or jet engines are there to move the airplane in a forward direction and speed.
It is the movement of the airplane in the “air” which creates an aerodynamic force on the top surface of the shaped wing called “lift.”
If the air can be forced to move across the wings fast enough, the result is “lift.”
The engines move the airplane through the air in order for that to happen — so that the air moves fast across the wings. Then, it is the shape of the wings which push or suck the wings upward.
What makes an airplane fly or “lift” off the ground? The answer is simple, the shape of the wing. The top surface is curved, and the bottom is flat. The wing or “airfoil” splits the wind into to two on the “leading edge” of the wing. The air moves faster across the top of the wing than the bottom according to Bernoulli’s Law. When air moves faster over one surface than another, “lift” is created.
You may not realize it, but an airplane is literally being “sucked” upward because the pressure on the top of the wings is lower than that of the bottom of that wing.
If you were to turn that airplane upside down, the wings would then be sucking the airplane downward toward the earth. No matter how much you increased the airspeed, it would not lift that plane skyward, but faster and faster to the earth.
Change the shape of the wing, and you can create more or less lift.
Disturb the airflow across the surface of the wing, and you can create turbulence.
Push the wing through the air too slowly, and you cannot lift the airplane off the ground.
Not slow down the airplane enough, and you cannot land, but will float over the runway.
Slow down the airplane over the runway too fast, and the airplane will lose lift and drop suddenly.
Takeoff into the wind and greater lift is produced. Fly away from the wind, and you will have to increase engine speed to get the needed lift — That’s the purpose of “wind socks” on runways.
Lengthen the wing (which is done during takeoff and landings), and you create a greater lift.
Add some other “wings” — such as on the tail of an airplane, which are both horizontal and vertical, and whose shape can also be changed, and you can maneuver an airplane’s other axes.
Flight revolves around the flow of air across the top and bottom surface of the “wings” or airfoils.
Key Illustrative Thoughts:
Engines are about the speed. Wings are about the lift.
Moving too slow
To get greater lift in life, change the shape of your . . . . (friendships / relationships / habits / commitment)
Fly into the wind
Turning life upside down
Change this-or-that, and you create a lot of turbulence
Flying upside down
Getting sucked into this world
There is more than one wing to maneuver in life
It’s about the flow of air in your life
We can disagree on what law of life explains it, but the reality is it flies!
* “Come Fly With Me” is also the title an excellent small book on flying an airplane as it relates to the Christian life. It was written by Lane Adams.
** Knowing and understanding various laws of physics opens up a whole different world of applications for speaking and preaching! Expand your world and find out why water can never be heated to more than 212 degrees (it changes form at 212 degrees), why cast iron is used in cooking (it stores energy), why they create valves with these big-large red circular handles (leverage), etc.
*** “Bernoulli’s principle can be used to calculate the lift force on an airfoil . . . For example, if the air flowing past the top surface of an aircraft wing is moving faster than the air flowing past the bottom surface, then Bernoulli’s principle implies that the pressure on the surfaces of the wing will be lower above than below. This pressure difference results in an upward lifting force.” — also see: https://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html