How planes work.

[flying dog]

If you are argueing about Bernoulli and how planes work, try this link:

 

http://www.explainthatstuff.com/howplaneswork.html

 

 

[farri]

Well I`ll be blowed........I`ve always thought it was me that was making the aircraft fly.

 

Frank.

 

 

[pudestcon]

Well I`ll be blowed........I`ve always thought it was me that was making the aircraft fly.Frank.

Depends on how much you can blow Frank. Some people say I'd be good for keeping a hot air balloon aloft:blush:

 

Pud

 

 

[facthunter]

Kept in the Air....

 

By MONEY. Everyone knows that. Nev

 

 

[dazza 38]

By MONEY. Everyone knows that. Nev

And lots of it.

 

 

[dazza 38]

:stirring pot: I dont want to be picky, but when they say " the aerofoil is curved on the top of the wing and flatter or flat on the under side" that isnt always correct as there are full symmetrical aerofoils around .;)

 

 

[Admin]

Have you looked at John Brandon's great articles:

 

http://www.recreationalflying.com/tutorials/groundschool/index.html

 

 

[Guest davidh10]

It all depends on who is asking...

 

In RAA tests. and according to CASA, Bernoulli is king, however there's a few issues with that theory:-

 

• How do aircraft fly inverted if they have an airfoil wing? According to Bernouli theory, it would not be possible to do for any length of time, as all lift would be towards the ground.
   
   
  
• Why does the air that flows over the top of the wing have to reach the trailing edge at the same time as the air that flows under an airfoil wing. Bernouli theory assumes this is a fact, but does not test the hypothesis. In fact tests have actually shown that it is not the case.
   
   
  
• Bernouli does not explain ground effect.
   
   
  
• Aircraft with flat or symetrical cross section wings can't fly according to Bernouli. Clearly this is untrue.
   
   
  

 

 

 

While the reference you have linked, FD, is interesting and identifies the correct theory, this link is to an article that I came across when researching for my BAK and it explains the principles in more detail.

 

So, is Bernouli wrong? No, but it is only a part of the story and only contributes a minor part of the lift. There was also a good article in the RAA Magazine in May, 2010 that introduced the Neutonian explanation.

 

 

[djpacro]

If you are argueing about Bernoulli and how planes work, try this link:http://www.explainthatstuff.com/howplaneswork.html

I won't argue with the content there, thanks flying dog, however I will discuss some other points.

 

.. and according to CASA, Bernoulli is king ...

CASA's Day VFR Syllabus states:

Bernoulli's theorem

 

 

 

 

 



6.3.1 Apply Bernoulli's theorem of constant energy flow to describe how an aerofoil

 

 

 

produces lift.

 

 

 

 

 

 

Note:

 

Limited to the variation of kinetic energy (dynamic pressure) and potential

 

 

 

 

 

 

 

 

 

energy (static pressure) as air flows through a venturi or over a wing.

 

 

 

 

 

 

 

 

 



Student should also be aware that the upper surface of a wing generates the majority

 

 

 

 

 

 

of lift.

 

 

 

 

 

 

 

 

 

 

No argument with that as far as it goes. Flying dog's link would seem to be consistent with that.

 

 

 

 

 

 

 

 

 

 

 

 

How do aircraft fly inverted if they have an airfoil wing? According to Bernouli theory, it would not be possible to do for any length of time, as all lift would be towards the ground.

CASA's Day VFR Syllabus also wants pilot's to know about

 

 

 

the effect of changes in angle of attack up to the stalling angle on:

 

 

 

 

(a) pressure changes above and below the wing

 

 

 

Bernoulli's theory only relates local pressure to local velocity. On a wing surface the lift can only be manifested by a variation of pressure over the wings upper and lower surfaces. i.e. Bernoulli's Theory applies to the effects of camber, flap/control surface deflection and angle of attack.

 

 

 

 

 

 

 

 

 

 

 

Why does the air that flows over the top of the wing have to reach the trailing edge at the same time as the air that flows under an airfoil wing. Bernouli theory assumes this is a fact..

Bernoulli's Theory does not state that at all. I agree, there are some who attribute that to Bernoulli - and I agree with what you say there.

Bernouli does not explain ground effect.

• Aircraft with flat or symetrical cross section wings can't fly according to Bernouli. Clearly this is untrue....
   
   
  

 

Bernoulli states nothing on these subjects at all however his Theory applies to those situations.

 

So, is Bernouli wrong? No, but it is only a part of the story and only contributes a minor part of the lift.

Bernoulli is absolutely correct (until the flow separates), I agree, it is only part of the story and:

- Bernoulli's Theory applies to all the lift

 

 

 

- Newton's Theory also applies to all the lift.

 

 

 

That link you provided is excellent, davidh10, as is the NASA website on the same subject.

 

 

 

 

 

 

 

PS = daldy - any questions?

 

 

 

 

 

 

 

 

 

[Mazda]

There are a number of factors at work. The confusion arises I think because the CASA Day VFR Syllabus insists that Bernoulli is taught, but it does not include the other factors. So students may only be taught Bernoulli in accordance with the syllabus. The syllabus does not prevent instructors from mentioning the other factors though.

 

 

[foxy]

ps daldy...any questions...

 

mite i just say dj.......ha, bloody ha!!!

 

i like bernoulli...i can understand it easily and could as a student.....which is an important factor to be able to pass on to my own students....but i also see and agree with how newton works as well..

 

that nasa site thing is cool dj....when someones got time to read it...:big_grin:

 

 

[kaz3g]

NASA and CASA at first blush seem almost diametrically opposed whereas the truth seems somewhere in the middle!

 

Someone else who has written of such things is Jim Davis whose book I think should be on everyone's shelf despite him taking a position at the NASA end of the spectrum on this occasion http://www.jimdavis.com.au/index.php?pid=3

 

I'm not a huge fan of Wikipedia but this discussion seems to have adequate bona fides as DJP can no doubt attest from his own professional background http://en.wikipedia.org/wiki/Bernoulli's_principle

 

kaz

 

 

[dazza 38]

Nice Link DavidH. As Kaz has mentioned, JimDavis also has a great explanation in his book as well on both theories .I recommend that book.