P-47 flaps

[RTHolmes]

just for comparison the RAF manual for the Mustang III has the following limits:

Flaps down 10^o     400mph
Flaps down 20^o     275mph
Flaps fully down   165mph

[2bighorn]

You do increase your Clmax though, hence more lifties. 

Yes, that's what I've said.  And if your wing has more lift, your max achievable AoA will be higher.

To illustrate that better, look in publication you posted link to, specifically figures PF 6.2 and PF 6.3

[Stoney]

Yes, that's what I've said.  And if your wing has more lift, your max achievable AoA will be higher.

To illustrate that better, look in publication you posted link to, specifically figures PF 6.2 and PF 6.3



"

Look at those two graphics.  The x-axis is AoA.  When flaps are used, Clmax increases, but stall AoA decreases.  Just underneath PF 6.3, you'll find this excerpt:  Wings with deflected flaps usually stall at a lower AoA than wings without flaps

Flaps do not increase your "max achievable AoA".

[hitech]

Look at those two graphics.  The x-axis is AoA.  When flaps are used, Clmax increases, but stall AoA decreases.  Just underneath PF 6.3, you'll find this excerpt:  Wings with deflected flaps usually stall at a lower AoA than wings without flaps

Flaps do not increase your "max achievable AoA".

Hence why flaps are put in the wing root not the wing tips. Makes the root stall before tips and hence makes a more docile stall.

HiTech

[2bighorn]

Look at those two graphics.  The x-axis is AoA.  When flaps are used, Clmax increases, but stall AoA decreases.
Flaps do not increase your "max achievable AoA".

Yes they do. Look at the right portion of PF 6.3.  As you lower the flap, you increase the effective camber and change the effective chord line. See how effective alpha has changed (increased). Look also at PF 6.4.

 

Just underneath PF 6.3, you'll find this excerpt:  Wings with deflected flaps usually stall at a lower AoA than wings without flaps

Yes, but this in reference to the geometrical chord line of the main airfoil, as depicted on PF 6.4. which is clearly mentioned just bellow:

The lower stall AoA is here measured to the chord line of the main aerofoil. The stall AoA measured from a chord line from the leading edge of the main aerofoil to the trailing edge of the flaps can be higher.

[Charge]

"Yes, but this in reference to the geometrical chord line of the main airfoil, as depicted on PF 6.4. which is clearly mentioned just bellow:
Quote: The lower stall AoA is here measured to the chord line of the main aerofoil. The stall AoA measured from a chord line from the leading edge of the main aerofoil to the trailing edge of the flaps can be higher."

Of course. As the camber of the wing changes it usually tolerates more AoA. However, the observable AoA by the pilot is less with flaps down than with flaps up, as I stated earlier and with which you disagreed, i.e. as the camber of the wing changes it happens in relation to the fuselage. That causes that you observe that the whole airframe tolerates less AoA with flaps down than with flaps up.

-C+

[dtango]

...However, the observable AoA by the pilot is less with flaps down than with flaps up, as I stated earlier and with which you disagreed, i.e. as the camber of the wing changes it happens in relation to the fuselage. That causes that you observe that the whole airframe tolerates less AoA with flaps down than with flaps up.

-C+

2bighorn: Alpha is generally referenced from the geometric chord as per what Charge (quoted above) and Stoney say.  Otherwise you wouldn't be comparing apples to apples and any comparartive discussion becomes meaningless.

[2bighorn]

Of course. As the camber of the wing changes it usually tolerates more AoA. However, the observable AoA by the pilot is less with flaps down than with flaps up, as I stated earlier and with which you disagreed, i.e. as the camber of the wing changes it happens in relation to the fuselage. That causes that you observe that the whole airframe tolerates less AoA with flaps down than with flaps up.

Yes, I missed your "in relation to the fuselage"

2bighorn: Alpha is generally referenced from the geometric chord as per what Charge (quoted above) and Stoney say.  Otherwise you wouldn't be comparing apples to apples and any comparartive discussion becomes meaningless.

Well, in that specific article we talked about, they made distinctive difference between geometric chord line of the main airfoil and effective chord line (when high lift devices are deployed) to illustrate the difference in pressure at critical AoA. So, I didn't compare apples to oranges, article did.

If you'd go by that article, than effective chord line is equal to geometric chord line of airfoil with no high lift devices deployed. Which is true. After you deploy flaps and airfoil geometry changes (increased camber), you could say that geometric chord line changes (if you measure from flaps trailing edge), or you could made distinction (effective chord line) as they did. Which terminology is right, whether theirs or yours, is matter of semantics.

It doesn't change the fact how Cl and AoA are correlated.

[dtango]

2bighorn: I'm not trying beat you up over semantics brother .  Why someone would choose a frame of reference to measure aoa other than the angle of an airfoil's fixed chord line relative to airflow is beyond me, so I'll stick with the usual aero definition of aoa vs. some wonky effective aoa with respect to the modified camber chord line .

[bozon]

Typically, your stall AoA decreases.  Or, to be more precise, the effective AoA of the wing increase because the chord line slope increases when flaps are deployed (the trailing edge of the wing is lowered, hence the chord line is "steeper").  So, no, you don't increase your max AoA.  You do increase your Clmax though, hence more lifties. 

That is because of the poor definition of AoA that is commonly used (what is zero AoA?). If you define AoA=0 when zero lift is generated then you can get a higher achievable max AoA, but true, not necessarily. The addition of slots often contribute much to the higher acheiveable AoA. I don care about the angle at which the wing is attached to the fuselage or the instantaneous angle at the moment of deployment. The change in the shape of the wing redefines the point of L(AoA)=0 and the current AoA.

[2bighorn]

Why someone would choose a frame of reference to measure aoa other than the angle of an airfoil's fixed chord line relative to airflow is beyond me

Baffles me as well. Why simple when they can make it complicated 

[STEELE]

Hence why flaps are put in the wing root not the wing tips. Makes the root stall before tips and hence makes a more docile stall.

HiTech

Dosen't washout do the same exact thing?  Incidentally the fw 190 series all have a few degrees washout. With a notch of flaps, I can see where all the pilot accounts of slow speed turnfighting in even the heavier, late model A series
would be highly possible. (without violently flipping over to the left). Actually, most 190 pilots say with some flaps out, the stall when it finally does come, is  reversed, or to the right.

[Stoney]

That is because of the poor definition of AoA that is commonly used (what is zero AoA?). If you define AoA=0 when zero lift is generated then you can get a higher achievable max AoA, but true, not necessarily. The addition of slots often contribute much to the higher acheiveable AoA. I don care about the angle at which the wing is attached to the fuselage or the instantaneous angle at the moment of deployment. The change in the shape of the wing redefines the point of L(AoA)=0 and the current AoA.

I apologize if the article I linked was confusing.  I was merely looking for a resource that had images that would illustrate was I was talking about.  I suppose I should have taken the time to draw my own graphics.

Typically, the AoA = 0 means that the chord line is parallel to the relative wind.  You can't say AoA = 0 when the lift = 0 because on most airfoils in use, which have camber, the actual angle of attack would have to be negative in order to be at zero lift.  The definition of angle of attack in most aerodynamic texts is the angle between the chord line and the relative wind.  Using that definition, you cannot increase the stall AoA of a flapped area of wing by lowering flaps.

Neither incidence or pitch angle of the aircraft change the stall AoA of an airfoil/wing.

[Stoney]

Dosen't washout do the same exact thing?  

Its supposed to help low-speed handling, yes.  But, merely including washout doesn't mean that an aircraft won't exhibit nasty stall characteristics.

[2bighorn]

Using that definition, you cannot increase the stall AoA of a flapped area of wing by lowering flaps.

That would depend on type of flaps, wouldn't it? For example type of flaps which can maintain boundary layer a bit longer and delay flow separation at high AoA.