PPRuNe Forums - View Single Post - Which one to believe; which version of lift is taught for the ATPL theory exams?
Old 3rd Jan 2010, 19:13
  #15 (permalink)  
ft
 
Join Date: Oct 2000
Location: N. Europe
Posts: 436
Likes: 0
Received 0 Likes on 0 Posts
bfisk,
could you explain your reasoning for flat plates and cambered airfoils existing in different worlds from an aerodynamical point of view?

They don't, just FYI.

Without Newton, no lift. Newtons laws are laws of nature and dictate that air goes down, lift is generated. Equal and opposite reaction. 100%, always, no getting around it.

Effectively, Bernoulli's theorem tells us that there's no acceleration in a fluid without a pressure gradient, and that where there's a pressure gradient there's also acceleration. Now, that does sound familiar, doesn't it? Bet there's some annoying bloke in these forums going on and on about that relationship...

Without a pressure gradient and acceleration in a fluid (i e air, in this case), no change of direction of the airflow. Without a change of direction, no air goes down and no lift is generated.

Bernoulli and Newton co-exist, and neither is more important than the other. It is not a one versus the other situation at all. Both are 100% true, always. They both apply just the same whether the wing be a flat plate or a cambered airfoil. The latter just happens to be significantly better at generating useful lift.

Cheers,
/Fred
ft is offline