As an engineer I can explain in very technical terms exactly what makes an airplane fly, however, it isn't easily understood by non-technical people. How can I explain it to a non-technical person, or a nine year old, in a way that isn't really incorrect but is far less technical than what we learn as pilots?
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asked Dec 27, 2013 at 23:32
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$\begingroup$ I don't really think these qualify as an answer, but youtu.be/bv3m57u6ViE & youtu.be/_LXW3pHNn_U might help (the latter, a delightful 1960s video from the FAA, is also a FDA approved treatment for insomnia -- oh that voice!) $\endgroup$– voretaq7Commented Dec 28, 2013 at 0:00
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10$\begingroup$ As long as you don't say that a plane flies because of the shape of its wing. I'm still furious at my high school teacher for telling me that was the one and only reason a plane could fly. Too bad I wasn't clever enough to ask him how a plane can fly upside down. $\endgroup$– Philippe LeybaertCommented Dec 28, 2013 at 2:58
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4$\begingroup$ According to Mary Shafer, retired NASA engineer, it's all about Lift Demons and Thrust Pixies. $\endgroup$– GerryCommented Apr 26, 2017 at 15:55
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2$\begingroup$ Big Bank Accounts... $\endgroup$– DaveCommented Apr 26, 2017 at 17:01
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$\begingroup$ Lift is 100% from air-deflection by tilted wings, but confusingly, this then causes 100% of the pressure-difference blamed on "Bernoulli Effect." There's no 60%/40% here, instead it's 100% Newton's wing-tilt versus 100% Bernoulli's velocity-difference. Lift requires both. They're just two equal viewpoints. Choose whichever one is easier to explain. www1.grc.nasa.gov/beginners-guide-to-aeronautics/… $\endgroup$– wbeatyCommented Nov 3, 2023 at 8:04
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4 Answers
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The simplest explanation is the "hand out of the window" one:
Hold your hand out of the window while in a moving car and hold your hand at an angle. It gets pushed upwards. Your hand represents the wing of an airplane. The plane's engine simply makes sure the "hand" keeps moving forward against the force of the wind.
Even a 4-year old understands the concept using this explanation.
answered Dec 28, 2013 at 3:04
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21$\begingroup$ You don't need wind to fly, but you shouldn't use the word "airflow" when explaining flight to your Grandma. If people stick their head out of the window of a moving car, 99% of people will say they feel the wind in their face, not "airflow" :-) $\endgroup$ Commented Dec 28, 2013 at 15:26
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2$\begingroup$ Oh, dear, all that sticking out of limbs calls for a security briefing ;-) My gripe with wind is that fact that people often mistake "wind" for thermals when talking about gliding: "Oh, a sailplane - do you need wind for that?" $\endgroup$ Commented Dec 28, 2013 at 15:38
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2$\begingroup$ Oddly enough, this is how I explain it now (along with the requisite "you can make a plate fly this way if it is moving fast enough"), but unfortunately the lift generated by the impact of the relative wind on the body of an airplane is a very small part of the total lift generated, and I am trying to be a little more correct in my explanation (and at least cover where the majority of the lift comes from). Great answer though, and you still get a +1 from me! $\endgroup$ Commented Dec 29, 2013 at 17:00
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9$\begingroup$ Consequently, this is from where the term "airplane" comes from. The wings are the plane that deflects the air. $\endgroup$ Commented Feb 5, 2015 at 15:19
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2$\begingroup$ I only wish I had more upvotes to give... I understood this as a 4 year old, because I would stick my hand out the window and do this. I can now understand and appreciate the engineering explanations too, but it isn't as complicated as we often make it. $\endgroup$ Commented Dec 19, 2018 at 22:46
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Here's one way to do it: airplanes work by pushing air. The wings push air down, and the airplane turns by pushing air in different ways. Engines push air to the back, pulling the plane forward. Wings work by turning the air downwards--the airflow on the top of the wing follows the curve of the wing, which points it downward.
My apologies if this is too low-level--is this what you had in mind?
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$\begingroup$ This is more what I had in mind, can you think of an easy to understand way to describe how the wings push the air down? $\endgroup$ Commented Dec 29, 2013 at 17:00
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$\begingroup$ Added a sentence explaining lift. Thoughts? $\endgroup$– cmn.jcsCommented Dec 30, 2013 at 3:52
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Every pilot knows the first thing that makes an airplane fly is money.
as I tried to explain the 4 forces to my 6 year old daughter and trying to coach her I asked, what makes it fall out of the sky. I expected weight or gravity and she said lack of money. She was right.
I try to explain it like a straw. You have four straws, one in front, one in back, one above and one below. The one below the aircraft sucks at a constant rate and never stops (gravity/weight). The one in front is the prop generating thrust. It is essentially sucking its way forward. The one in back is drag and it varies by situation but it's always trying to keep you from going forward. The final one is the one on top and that is lift. Lift is generated by the wings and sucks the airplane up. The wing creates lift by moving forward. If any of the straws win other than the front one and the top one, you crash.
As for wind, no you can fly through no wind but the addition of wind coming at you effectively helps fill that forward straw so you can essentially take off at a lower ground speed. This is called relative wind. If your plane flies at 54 knots and you could essentially fly into a 34 knot headwind at 20 knots and achieve backwards flight at 14 knots.
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Blow over a sheet of paper that is lying on the table, and watch it take off. Then explain of course that there is a lot more air involved in keeping a 747 in the air, but you could make it plausible by mentioning how strong tornadoes and hurricanes are.
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3$\begingroup$ Planes don't fly because of fast-moving air above them. In particular, there is just as much fast-moving air below a plane as there is above it. $\endgroup$ Commented Apr 26, 2017 at 7:17
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$\begingroup$ I know that, but I'm not grandma. It just shows what air pressure can do. $\endgroup$– KoyovisCommented Apr 26, 2017 at 9:56
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5$\begingroup$ OK but planes don't fly because of air pressure, and planes are much bigger than a piece of paper, so what does this analogy help to explain? $\endgroup$ Commented Apr 26, 2017 at 11:15
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7$\begingroup$ @DavidRicherby why you say that planes don't fly because of air presure? This answer is based on the Bernoulli's principle. Wikipedia "From Bernoulli's principle, the pressure on the upper surface where the flow is moving faster is lower than the pressure on the lower surface where it is moving slower. This pressure difference creates a net aerodynamic force, pointing upward." $\endgroup$– RobertCommented Apr 26, 2017 at 15:00
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2$\begingroup$ You're intentions are right but you're explication is lacking. $\endgroup$– Notts90Commented Apr 26, 2017 at 16:15