Debunking Lift Theories Still Taught

[dazza 38]

I don't know, glider pilots look pretty cool...

Especially in their terry toweling hats, err not.

 

 

[completeaerogeek]

But the lower surface contributes zilch at zero AoA ..... probably makes it a bit harder to stay up there

True. That is another reason why supercritical wings are cambered underneath. The can create lift at low pitch angles at high speed.

 

 

[metalman]

I always thought the wings were pretty friggin important ,,,,but yeh super critical does describe them suitably!

 

 

[completeaerogeek]

Especially in their terry toweling hats, err not.

Ha Ha! But man are they good at energy management!

 

I always thought the wings were pretty friggin important ,,,,but yeh super critical does describe them suitably!

Not to helicopter pilots!

 

 

[completeaerogeek]

Why is there 2 threads on this subject? 1 . Debunking lift theories is still taught

2. Bernouli's irrelevant

 

They need amalgamating!

 

Just saying!

We could just delete Bernoulli and make it much easier!

 

 

[turboplanner]

Not so fast Einstein, let's see where this little bit of fun takes us.

 

 

[Ultralights]

so if Bernoulli's principle is irrelevant, then how do you explain the pressure drop above an upper surface cambered wing? (im not saying that the principle is whats causing the lift, but causing the pressure drop)

 

 

[Bruce Robbins]

........because the leading edge of the wing has "split" the air molecules that were just hanging around together, and forced a whole pile of them to go under the wing, leaving a large area above the wing with fewer molecules and thus lower pressure. Easier to visualise if you hold the wing at a reasonable angle of attack.

 

 

[djpacro]

Bernoulli is simply the relationship between pressures and velocities.

 

Fewer molecules = less dense air. The density doesn't change (in our simple example), just the pressure.

 

My old aerodynamics lecturer started by talking about male and female air particles .........

 

 

[fly_tornado]

The problem with that philosophy is that it is dangerous and goes against basic Aviation Human factors philosophy which says to question things that look wrong.This philosophy when employed works extremely well. When ignored is deadly. I could list many, many accidents caused by the junior pilot not challenging the captain or the pilots ingnoring a query from a flight attendant about 'strange noises'..

 

That CASA should still be teaching nonsense should not really be of any surprise to us...

No one at CASA wants to risk their career to removing Bernoulli theory from the pilot course. Student pilots are the only ones complaining.

 

 

[M61A1]

Not to helicopter pilots!

Still got wings, still supercritical for flying.

 

 

[geoffreywh]

thanks for the posts Completeaeroge, very informative and educational.....

 

 

[completeaerogeek]

so if Bernoulli's principle is irrelevant, then how do you explain the pressure drop above an upper surface cambered wing? (im not saying that the principle is whats causing the lift, but causing the pressure drop)

Have you read the first post-it's all there. It occurs with a flat plate wing. read it then come back if you are unclear.

 

 

[completeaerogeek]

No one at CASA wants to risk their career to removing Bernoulli theory from the pilot course. Student pilots are the only ones complaining.

It is ridiculous. Aviation and aerodynamics are an applied science. If you want to believe unsupportable assertions, get into religion.

 

 

[completeaerogeek]

Bernoulli is simply the relationship between pressures and velocities.Fewer molecules = less dense air. The density doesn't change (in our simple example), just the pressure.

 

My old aerodynamics lecturer started by talking about male and female air particles .........

Bernoulli is derived from Newton's 2nd Law and is used for describing behaviour in a single contiguous parcel of air not around a wing. Itt has flaws in the formula as air is assumed to be inviscid. Rather than reinterpreting something, Just use Newton's Laws. No silly explanation required.

 

 

[completeaerogeek]

........because the leading edge of the wing has "split" the air molecules that were just hanging around together, and forced a whole pile of them to go under the wing, leaving a large area above the wing with fewer molecules and thus lower pressure. Easier to visualise if you hold the wing at a reasonable angle of attack.

That's kind of correct. Push your hand through water inclined to the direction of movement and you will see this occur. The behaviour in air is exactly the same as in water.

 

 

[ianboag]

For those who want a simple explanation. The wing flies at at finite angle of attack to the air flow that hits it will get deflected down and make lift The top of the wing is cambered for drag reasons and the stuff that comes off the back of that is headed down too which all helps.

 

Think of flat wings (the desk fan) and symmetrical ones (any aerobatic plane) and you will figure out where most of the lift comes from .....

 

 

[Guernsey]

I don't know, glider pilots look pretty cool...

Unless they are Japanese.

 

Several years ago at the world gliding championships at Waikerie, South Australia on a very hot day a Japanese pilot did an outlanding in scrub country and landed near some grazing kangaroos: not knowing whether they would attack him or not, he remained in his glider with the canopy down until rescued. He didn't look very cool when the ground crew arrived. .

 

Alan.

 

 

[dazza 38]

Unless they are Japanese.Several years ago at the world gliding championships at Waikerie, South Australia on a very hot day a Japanese pilot did an outlanding in scrub country and landed near some grazing kangaroos: not knowing whether they would attack him or not, he remained in his glider with the canopy down until rescued. He didn't look very cool when the ground crew arrived. .

 

Alan.

I hope he had on a Terry toweling hat. They are standard issue to Glider pilots.

 

 

[turboplanner]

along with an aversion to using those radio thingys.

 

 

[Yenn]

the fabric on top of the wing on my Corby is concave between the ribs, aft of the spar. Proof that there is no lift from the air there, or maybe there is a theory that the inside of the wing is at lower pressure than the surrounding air.

 

 

[bexrbetter]

Interesting with all this knowledge being thrown around and challenged that wing profiles advancements haven't exactly seen anything substantial.

 

 

[Gnarly Gnu]

It is ridiculous. Aviation and aerodynamics are an applied science. If you want to believe unsupportable assertions, get into religion.

Or combine the two and become a warmie.

 

 

[bexrbetter]

Or combine the two and become a warmie.

That one left me cold.

 

 

[completeaerogeek]

For those who want a simple explanation. The wing flies at at finite angle of attack to the air flow that hits it will get deflected down and make lift The top of the wing is cambered for drag reasons and the stuff that comes off the back of that is headed down too which all helps.Think of flat wings (the desk fan) and symmetrical ones (any aerobatic plane) and you will figure out where most of the lift comes from .....

Generally correct but not quite a simple as that. The upper surface of SC wings is not appreciably cambered. The angular change of the airflow is what creates lift.

 

By the stuff off the back do you mean downwash? If you do be careful not to get caught in another myth. The wing pulls/pushes the air in its direction of movement so in effect. the air passing behind the wing from the upper surface is going 'slower' than when it encountered the wing.