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How Do Airplanes Stay Up?

An airplane's engine provides thrust.
Members of an air crew work together to make sure an aircraft stays within its flight envelope for a given altitude.
The Boeing 747, a wide-body jetliner, can maintain flight even if it loses power in three engines.
The nose of an aircraft is designed to create as little drag as possible.
Thrust provided by the airplane's engines moves it forward, while drag slows it down.
Though a biplane configuration provides more lift than a monoplane arrangement, it generates increased drag.
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Though airplane flight may appear miraculous, there is science behind it. Airplanes stay up in the air because of the aerodynamic force referred to as lift. Airplane lift, generated by each part of an aircraft, is a force that works in direct opposition to the weight of an aircraft. It has to do with the movement of air, which is typically referred to as a fluid in aerodynamic descriptions. This fluid acts on the plane to allow it to rise into the air and stay there, as long as several conditions are met.

Lift is present when a solid object deflects or turns a moving flow of fluid. Flow turns in one direction, while lift is produced in the opposite direction. Solid surfaces of all types are able to cause the flow to turn aside, ensuring that airplanes stay up in the air. For example, both the upper and lower portions of an airplane’s wing surface are important in deflecting the flow of fluid.

Motion is also vital in ensuring that airplanes don’t come crashing down. Without movement, lift is not generated. There must also be a velocity difference between the plane and the fluid. Airplane lift is generated perpendicular to motion, so as the plane moves forwards, lift is generated upward. Motion does not act alone when airplanes fly through the sky, however; drag opposes motion, contributing to the science of flight as well.

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Besides lift, motion, and drag, weight and thrust are also important in making sure airplanes stay in the sky. The weight of an airplane is spread out, keeping it balanced. It is this force that pulls a plane toward the ground. Thrust, provided by the airplane’s engines, moves it forward and drag slows it down. Without these forces, each working in its own way, an airplane could not fly.

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anon306902
Post 10

The Coriolis effect explains why planes fly in curved paths.

anon189352
Post 8

I agree with Posts 2 and 7. That the wing's shape creates lower density of molecules on top of the wing and higher density on the top.

anon168481
Post 7

I like a challenge. Having no understanding of physics, whatsoever, I do know how lift is created. It's basically the same explanation as post number 2, except I think I'll give a better visual.

Picture a wing from the side. While the front of the wing cuts the airstream in two, the curvature of the wing makes the molecules on the underside of the wing travel a shorter distance to reach the other end. The ones that flow over the top of the wing travel a longer distance over the wing to end up at the same point as the ones on the bottom.

The molecules over the wing are thinner spread because of this, or one could also say that the molecules under the wing are packed denser. De denser packed molecules can bear more weight, and are able to lift the moving wing.

This only works if the wing moves. The faster the motion, the bigger the capacity to lift. Hence: airplanes are both fast, and have big wings. The bigger the wings, the faster the plane needs to be.

anon119156
Post 6

Ok, so if lift is caused by the fluid air being redirect perpendicular to the plane in a downward motion then it still doesn't explain why a plane can stay in the sky. Wouldn't the top of the plane deflect air perpendicularly up? wouldn't this counteract the force of the air deflecting down?

And for the pressure/wing shape explanation well, the Wright brothers flew a plane with wings that were the same shape on both sides. so what happened there? Or the fact that planes going fast enough can fly upside down. How does that happen?

anon89731
Post 5

Going to make this post short. Comment #2 below gives the most common but incorrect or incomplete explanation of what creates lift on a wing.

The discussion of the Bernoulli principle is all correct, however only plays a small part in creating lift. It is actually Newton's third law of motion that states for every action there is an equal and opposite reaction. Simply put, a wing (airplane, bird, rotor, etc.) redirects or pushes air down and the opposite reaction is the wing goes up!

Maybe the best way to envision this is to stand underneath a rotary wing (helicopter) and the huge amount of air being "pushed" down. The opposite reaction is up!

anon81801
Post 4

Just look up 'drag.' there are plenty of definitions available.

anon74669
Post 3

Wanted to teach the kids this - need someone to teach it to me first!

anon59653
Post 2

Bernoulli's Principle states that fluid (air) moving rapidly creates less pressure than slower moving fluid (air).

The design of the aircraft wing forces the air (fluid) over the top of the wing to move faster and therefore creates less pressure on the wing. The air underneath the wing has more pressure and pushes up- therefore "lift" has occurred.

Simple, really. For an example you can do at home, take a sheet of paper and hold it flat in front of you, blow across the top of it and you will see the paper rise up.

anon57421
Post 1

i love the brevity of wise geek explanations, but i just have to say that this one sucks! what on earth is drag? i think this could have been explained with a lot less jargon.

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