is it possible to answer my question

[aviatrix20]

When you lift the plane's wing in the air to 16 of the angle of attack, as what happens when the point of pressure I mean, why step up when at high angle of attack?

Please Explain to me

[muffman]

is it possible to answer my question

Actually, I don't think it is.

[aviatrix20]

Well, thank you

[muffman]

You could try rephrasing it.

[Dances With Dingoes]

Aviatrix,

Do you by chance happen to work in a call centre?

DD

[propblast]

Muffman, is that because you dont know the answer, or you don't know the question?:}

[The Green Goblin]

Anything to do with stalling is strictly the domain of Planky - Handing over :ok:

[aviatrix20]

Unnecessary because the question is very clear

[tmpffisch]

Are you asking why the center of pressure shifts forward when the angle of attack increases?

[Jabawocky]

It is school holidays again :rolleyes:

The question is about angle of attack and 16 degrees.....some of these kids are getting more cunning!

I can almost here TW or Tids go *click*

[Dances With Dingoes]

Is this a test????:eek:

[aviatrix20]

Are you asking why the center of pressure shifts forward when the angle of attack increases?
Yes, this is what I meant tmpffisch

[flying-spike]

Think of the wing in profile (leading edge left) as a clockface with the centre of pressure at 12.00. As you increase angle of attack it is the same as rotating the clockface clockwise and the centre of pressure moves to the the 11.00 position . That's the way I think of it . I may be wrong (probably am, my head hurts now, I'm going to bed)

[Ultralights]

chuck in Slats, or VG's and full span flaperons at 40 deg! 20 deg AOA...

[Wally Mk2]

......yr all fired, the bloody lot of yas!!!!:}

Go take up chicken farmin'!:)

'jaba' these kids are too smart for us:ok:

Anyway there is a heap of stuff about CP & CofG etc. To explain it all here would take more ink than my keyboard has:) Simply as AofA is increased CP moves forward by design & aerofoil shape & intersects the wings chordline at some stage of flight. Ideally if this occurred at the Cof G then the plane would be in perfect balance & not need a tailplane to keep balanced but aircraft never sustain any one position for too long. CP is the result of the lift drag vectors. Go Net surfing, these days everything known to mankind & some is right there at yr fingertips:-)

Wmk2

[apache]

is it possible to answer my question

is it possible for you to write in in intelligible english?

[D-J]

Unnecessary because the question is very clear

apparently he thought it was... :eek:


gen y oh y oh y :ugh:

[dodo whirlygig]

is it possible for you to write in in intelligible english?

hopirrently net

[ForkTailedDrKiller]

Its kinda simple actually!

Every pilot is awarded 16 degrees of Angle of Attack - when you use them up you stall!

Dr :8

[apache]

I get it now!
this is like a dungeons and dragons" question... not aviation!

[aviatrix20]

The question is very clear and requires no thought if there was a response resulting from experience and tell you again..........
why the center of pressure shifts forward when the angle of attack increases?

[propblast]

The question is very clear and requires no thought if there was a response resulting from experience and tell you again..........
why the center of pressure shifts forward when the angle of attack increases?

Yes, this question is very clear.:D

Why it shifts forward, starts to get a little complex. Pages can be written on it. And people smarter than I can offer technical explanations. Perhaps asking your lecturer is a better course of action.


When you lift the plane's wing in the air to 16 of the angle of attack, as what happens when the point of pressure I mean, why step up when at high angle of attack?

Please Explain to me


This one, is not so clear. :=

And had many baffled and bemused.:\

[ContactMeNow]

Level 6 Engrish?

I want my $100 back :{

CMN :E

[aviatrix20]

The best explanation I can think of given I'm ironing and watching the tour de france and have had no sleep...is that the centre of pressure is the "average" of the pressure differential generated by the lifting surface. As the AOA is increased, the curvature of the surface effectively increases and the greater the curvature (if using basic Bernoulli's principle) the greater the lift. For the air to flow over this greater curvature it uses up more of the energy in the air and hence the transition and separation points move forward.

That is assuming I've understood your question correctly. Frankly I wouldn't be surprised if I've not understood it at all as the standard of English is pathetic and not up to the standards I expect of a Generation Y member-must be a '90s Gen Y rather than an '80s one...



Thank you very much for the answer, and sleep peacefully cynical pilot

[muffman]

Thanks for rephrasing. The second time you asked, it made perfect sense. The first time, on the other hand....

One useful way to think about it is if we drew the pressure pattern on a diagram of the wing, the low pressure region on the upper surface would be deepest, or at its minimum pressure, near the centre of pressure.

What this means is that as the air flows past the centre of pressure, it will encounter steadily increasing static pressure called the adverse pressure gradient. Because the low pressure region (the lift) is so deep at high angles of attack, the airflow would require more energy (which it doesn't have) to overcome this adverse pressure gradient. The result is that there isn't enough energy to overcome it, and the airflow detaches from the wing. So, as the angle of attack increases, the airflow separates closer and closer to the leading edge, and an increasingly smaller section of the wing is left to produce the lift. The centre of pressure is the average of that smaller area and therefore moves forward.

[aviatrix20]

Thanks for rephrasing. The second time you asked, it made perfect sense. The first time, on the other hand....

One useful way to think about it is if we drew the pressure pattern on a diagram of the wing, the low pressure region on the upper surface would be deepest, or at its minimum pressure, near the centre of pressure.

What this means is that as the air flows past the centre of pressure, it will encounter steadily increasing static pressure called the adverse pressure gradient. Because the low pressure region (the lift) is so deep at high angles of attack, the airflow would require more energy (which it doesn't have) to overcome this adverse pressure gradient. The result is that there isn't enough energy to overcome it, and the airflow detaches from the wing. So, as the angle of attack increases, the airflow separates closer and closer to the leading edge, and an increasingly smaller section of the wing is left to produce the lift. The centre of pressure is the average of that smaller area and therefore moves forward



This is the answer that I would have liked and I think you are really intelligent pilot

[Ultralights]

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or what about the Vortex, or Lifting line theory of lift,? would that help explain how the COP moves forward with increasing AOA?

[muffman]

I didnt think the airflow actually 'detatched' from the wing as that would create a vacuum as far as I am aware.

More correctly, the boundary layer detaches from the wing.

It is important to distinguish between the separation point (where the boundary layer detaches) and the transition point/line (where the boundary layer becomes turbulent). A turbulent boundary layer is not necessarily a bad thing - hence vortex generators, etc.

[djpil]

Some light reading for you on this subject:
Noel Kruse's Book #1, Aerodynamics and Other Stuff, is a free download here. (http://www.flybetter.com.au/) Lesson 2 on page 22 is a good place to start for this topic.

[MakeItHappenCaptain]

I didnt think the airflow actually 'detatched' from the wing as that would create a vacuum as far as I am aware.



Try flow reversal?, Separation Point?