Anonymous
Anonymous asked in Science & MathematicsPhysics · 8 years ago

# How does/can an Airplane fly?

It's always been a bit of a mystery for me...

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• 8 years ago

An airplane in flight is subject to four major forces: lift, weight, thrust, and drag.

Thrust is the force that pushes the airplane forward. It can be provided by a propeller or a jet engine.

Drag is the resistance of air as the plane moves through it. It takes energy to push air out of the way, so drag works to slow a plane down.

Weight is the downward pull of gravity. In order to get off the ground, there must be an upward force to counter the plane's weight, and that force is...

Lift. Lift acts on the wings to push the plane upward. Without sufficient lift, an airplane would never leave the ground.

In many high-school level science books, lift is attributed to the Bernoulli principle. The Bernoulli principle says that the faster a fluid moves, the less pressure it exerts. The cross-section of an airplane wing is rounded on top and flat on bottom (much like a bird's wing), which forces air moving over the top of the wing to move faster than air across the bottom. The faster moving air on the top generates less pressure than the slower moving air on the bottom, and the difference in pressure pushes the wing upward.

While Bernoulli's principle may offer a partial explanation for lift in airplanes, it's not the whole story. The most important factor in lift is something called Angle of Attack, or AoA. AoA is the angle at which the bottom of the wing meets the oncoming air. If you look at the cross-section of an airplane wing, you'll see that it slants down near the back. This forces oncoming air into a downward path. Newton's third law says that forces come in equal and opposite pairs, so when the wing forces air down, air forces the wing up.

You could theoretically fly with any shape wing, if you could move fast enough to generate the lift necessary to counter your weight. The flattened teardrop shape of most wings helps to make the experience much smoother and safer.

So that's why airplanes have to build up speed before they can take off...the air must be striking the underside of their wings fast enough to force them upward. Helicopters don't have fixed wings, but each of their rotor blades is a wing. Helicopters can hover in place without moving forward because their spinning rotors are constantly cutting through the air.

I hope that helps. Good luck!

• Anonymous
8 years ago

Something has to counter the force of gravity to stay up right?

Differences in air pressure because of the shape of its wings provide an upward force, and if that force is bigger than its weight, it stays up. Planes also tilt their nose so that the angle of attack provides lift. Look into the bernoulli principle, and newton's laws. The wing pushes the air down, air pushes the wing and thus the plane up. Engines propel the plane forward against the tremendous air drag it encounters. Pilots also tilt the plane at an angle so that the wings can initially create lift. To see why, Put your hand flat, out the window of a moving car on the freeway. When it is horizontal, there's no lift but as you raise it at an angle the air pushes ur hand up. The faster you go the greater the lift. So airplanes need to go pretty fast to generate enough lift to hold it up. This is way oversimplified though, I suggest you search further on government, aerospace sites or Nasa and the like.

• 8 years ago

A wing is a type of fin with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid. As such, wings have an airfoil shape, a streamlined cross-sectional shape producing a useful lift to drag ratio.