Getting back to part-time flight instructing

heph224

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It's been a while since I taught anything and I will be working part time to make some extra cash as a CFI, I was looking at my notes and trying to remember how to explain lift. I know about the who bernouli crap and low and hi pressure, but that's only about 20 percent of the lift. The other 80 or so is from the downwash but I can't seem to find a good diagram/web site that explains it well. Can someone jog my memory or list a good web site.

Thanks......
 

TankerDriver

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Um, I thought it was Bernouli's "crap" that provided about 80% of lift and downwash/deflection provided the rest?
 

heph224

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TankerDriver said:
Um, I thought it was Bernouli's "crap" that provided about 80% of lift and downwash/deflection provided the rest?

I though it was the other way around... maybe im wrong......
 

hindsight2020

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It depends on what part of the flight envelope you're in. For your garden variety light single, circulation around the airfoil provides the majority of the lifting forces throughtout pretty much all of the flight envelope. Hard to get anything useful past critical AOA in the accelerated envelope on a 172...provided you can even get 2 seconds worth of it!! LOL

A delta wing planform or anything with leading edge extensions on the other hand (high performance stuff you know...), you get into substantial "newtonian lift" contribution at high/past critical AOA.

Then again you probably don't need to get that in-depth on it as it relates to general aviation private level aerodynamics. The Jeppesen book should be fine to refresh your memory. The diagrams are also very useful for the level of depth that is intended.
 

LewisU_Pilot

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Easy way to teach lift.

Newton's action/reaction law. Action is the down wash being produced by the airflow Reaction is an upward movement.

Bernoulli's. As velocity increases (air traveling more distance over the top of the wing to meet up with the air traveling a shorter distance under the wing) pressure decreases. Upper part of the wing is a low pressure. Lower part is a high pressure. High to low gives us a lift. Take a piece of paper and hold an end. Let it hang down which simulates an airfoil when looking at it from the side. Now blow on top of the paper (velocity is increased) paper should rise.
 
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