Why do Spitfires turn better than Hurricanes?!

[TomcatViP]

Originally Posted by Sternjaeger II

I hate to insist on a topic that I'm not well prepared in, but I believe compressibility shows on your tail surface first simply because the surface itself is smaller than the wing one, and proportionally the control surface is bigger, so the transonic and supersonic effects happen there earlier. But then again I'm happy to be proven wrong..

No problem. The ultimate fighter Pilot is the utmost finest Engineer (this is an awfully wrong statement )

Do you remember the Venturi effect when the air is accelerated through a narrower section ?
Now take a wider look at a wing section. If you focus either on the upper or the lower surface, you will see that regarding to the free stream of air unperturbed by the airfoil, there is a section increase as the thickness of the airfoil increase and the a similar decrease after the point of inflexion.

The direct effect of this (appart from the direct generation of LIFT) is that the air is accelerated and then as the section increased, expended with a rather brutal Pressure increase.

Now imagine that (I am actually singing it) you are flying at a speed nearly 2/3 of the speed of sound.

Due to the imaginary geometry described above, you can understand that the air is accelerated trough this partially materialized venturi. The increase in speed being directly proportional the the section decrease. Hence the more thickness the more the air flow is accelerated

When the speed and the wing's thickness are high enough, the airflow ard the wing reach Mach 1, the speed of sound. As the air goes further back along the chord, the air is expended (the distance btw the free airstram and the airfoil increase) and the air is decelerated bellow Mach one trough a pressure shock. This pressure shock is what we call a shock wave.

Now let say simply that due to he fact that the pressure distribution is modified because of both the shock waves above and bellow the wing, the LIFT moment is modified with a negative upward (relative to the chord) pitch down moment.
What you can see is that the more the wing is thick, the earlier the air ard the airfoil section reach the critical mach number.

Hence the thin airfoil series of the 50's fighters (Starfighter, F105, Mig 21 etc..).

This is why the compressibility affect the wing and not so much the generally thinner tail section.

Interestingly too this is what makes the Spitfire so fast in a dive. What you can see now is the sublime irony of mother nature that turned a wrong design assumption (the elliptical wing) in a wining parameter. I tell you Germany cldn't hve win !

Note : The 47 had an elliptical wing too. And it was also awfully fast in a dive!

~S!