Are slats shy ?

[Crumpp]

You presented a value from flaps extended polars, as you say the stall happens at ~17.5°, which is only the case with flaps extended. Good to know it wasn't intentional.

Figure it out yourself. You have no clue how to read a polar and I am not going to teach you.

AoA the slats open at.

A little basic knowledge and anyone can tell you are "out der FLAPPIN" as we used to say in the Army when somebody was completely wrong. In this case, it is quite ironic you are FLAPPIN over flaps!!



The effect of trailing edge flaps is to increase the camber of the wing.

Flaps change the airfoil pressure distribution, increasing the camber of the airfoil and allowing more of the lift to be carried over the rear portion of the section.

What is the effect of a camber increase on a lift polar??

It shifts the whole polar to the right! That means it LOWERS our Angle of Attack!! You cannot have the same Angle of Attack flaps up as you do flaps down....

Check out figure 5:

Figure 5. DC-9-30 CL vs. Flap Deflection and Angle-of-Attack

http://adg.stanford.edu/aa241/highli...liftintro.html

It is not physically possible with TE flaps to have the same general CLmax presented by the RAE in clean configuration with a polar with the TE flaps down at the same Angle of Attack.

Which incidentally also matches the 2D data from the NACA family of airfoils.

BTW you can see the data point Mtt plotted for the plain airfoil and for the slats on the polar. The Bf-109 did not have full length LE slats so it did not get a dramatic CLmax increase.