Sign In | Sign Up | Help | Invite    
Advanced Search Ask A Question Community Recent Changes
My:             Contributions   
Contributors
{for ul in pageInfo.page}
${ul.nickName}
{var al = toBreakWord(ul.adUrl,18)} {if ul.adSentence !=''}${ul.adSentence}
{/if} {if ul.adUrl !=''}${al}
{/if}
 
{/for}
Earn Free Advertising   +   Earn Money By Writing What You Know at WISTEME.COM
Question Discussion History

Edit
    Question ID:   4891         Current Version: 2
Question: How do airplanes fly?
Category: Automotive & Transportation > Aircraft
Keywords: air, pressure, fly, airfoil, airplane, plane
Type: how
Rating:(1 ratings)    Views: 750    Discussions: 0   In Watch Lists: 2  

 
    Answer:
Most of us have probably seen or felt wind blowing things like flags or kites around. But how is it possible that heavy airplanes (some weighing almost half a million pounds, or more than 200,000 kilograms) are able to be supported by air high above the ground?

The answer may sound strange at first, but it's actually the air that is pushing the airplane's wings and the rest of it up. The air under the wings pushes up more than the air on top of the wings pushes down. This "pushing" by the air is called air pressure. We can think of air pressure as air "press"-ing down or up against something else. On a windy day, you can actually feel the air pressure push against your body. The wings of an airplane "feel" a similar pushing, but there happens to be a bigger pressure under the wings and a smaller pressure on the top.

What's really amazing is why this happens. The special shape of an airplane's wing makes the air moving around it behave in a certain way. If we look at an airplane's wing from the side, we can see that the wing is a special shape called an airfoil.

An airfoil is curved on the top and flat on the bottom, causing some of the air to go over the top and the rest of the air to go along the bottom. This shape looks simple, but it is the main reason airplanes can fly at all. Because of the airfoil's curved shape, the air moving under the airfoil moves at a slower speed than the air going over the top.

A scientist named Daniel Bernoulli (Ber-NEW-lee), who lived more than 200 years ago, did work that proves slow-moving air causes a high pressure and fast-moving air causes a low pressure. Because there is a higher pressure "pushing" on the underside of the wing than on the top, the bottom pressure wins out overall and the wings (and the airplane attached to it) are pushed up, making the entire thing fly!

You can actually see this for yourself. If you take a strip of paper and blow over the top of it, the paper will rise.

What happened? You lowered the pressure that was pushing down on the top of the paper, causing the pressure on the bottom side of the paper to push the paper strip up. The same thing happens when air pushes on the bottom side of an airplane's wing. The pressure that is pushing the airplane up creates a force called lift in the upwards direction.

Forces act on an airplane 

There are four forces acting on an airplane in flight: lift, weight, thrust and drag.

We already know that lift comes from the wings. What about the other forces?

Weight is a force caused by gravity. You've felt gravity every time you jump. Gravity is what pulls you and everything else back down to the ground. This "pulling down" by gravity is what causes you to have a "weight" that you measure when you step on a bathroom scale. An airplane's weight also pulls downward on it - directly opposite to the lift force that is pulling the airplane up. It's like the lift and weight forces are playing a game of tug-of-war. One pulls in one direction and the other pulls in the opposite direction. For level flight, lift and weight must balance each other out.

Thrust, caused by the airplane's engines, is the force that moves the airplane forward. If an airplane did not keep moving, air would stop moving over and under the wings. Without this movement of air, the wings could not create lift, and the airplane would start to fall back to the ground!

Drag is the force that tries to slow down a moving object. To lessen the drag that an airplane feels, most airplanes are made more aerodynamic, or streamlined, to reduce the amount of drag they feel. A streamlined airplane has smooth surfaces and no bumpy sections, causing as little resistance to the air as possible. Just like lift and weight are opposite forces, thrust and drag are opposites to each other too. For an airplane to keep flying, its thrust must be bigger than its drag.

Read more questions from WISTEME through
     Add to MSN Add to My AOL
 Rate this Question
   Add to Groups   Add to Watch Lists   Share Question
                          
     Question ID:  ${question.id}         Current Version:  ${question.version}

{for qh in questionHistory} {if qh.status == 'r'} {else} {/if} {/for}
Version Contributor Date (ET) Voting
${qh.version} ${qh.nickName} ${qh.date} Rejected
${qh.version} ${qh.nickName} ${qh.date} {if qh.status != 'c'} {if qh.status == 'a'} Approved {else} {if qh.rstatus == 'c'} On-going {else} Pending {/if} {/if} {else}   {/if}
Start a New Topic
ID Topics Replies Latest Post (ET)
{if dlist!=null} {for d in dlist} {/for}
${parseInt(d_index)+1} ${d.sentence} ${d.replyNum} ${d.lastestDate}
{else}
No discussion topic.
{/if}
Label Name:
 
Group Name:
 
 
{else}
     You have no group.
{/if}
Advertisements
{if advertisements.length > 0} {else} {/if}
{for ad in advertisements}
${ad.adTitle}
${ad.adSentence}
${ad.adUrl}
{/for}

Home | About Us | Terms of Use | Privacy Policy | Browse Questions | RSS Feed

Copyright ©2010 WISTEME LLC. All Rights Reserved.