Spit IIa

Originally Posted by Crumpp

Aerodynamically the Spitfire could easily out-turn a Bf-109E series. A pilot dealing with the real world stability and control issues would leave the contest much closer than the aerodynamic analysis on paper.

I agree that the fighter pilots would have driven their kites closer to the limits than tought at flight school. As you indicate yourself by your phrase, aerodynamic calculations are never as accurate as to predict reproducable stall speeds. But this may go both ways that is that calculations are either pessimistic (stall would occur later than calculated) or also optimistic (stall would occur sooner than calculated). So it may be the way you stated it (the pilots drove their plane closer to the limits than what calculations would have predicted) but it may also be the other way around.

Principally I would guess that stall speeds taught to the cadets were obtained experimentally. And keep in mind that pilots appreciated when they got a feedback from the plane (e.g. buffeting) when they got close to the stall limit.

[Kurfürst]

I wonder, is there a clear definition of stall at all...?

[CaptainDoggles]

Originally Posted by Kurfürst

I wonder, is there a clear definition of stall at all...?

Stall is defined as the point where the airfoil's critical angle of attack is exceeded.

[Crumpp]

I wonder, is there a clear definition of stall at all...?

Captain Doggles gives a good definition:

Stall is defined as the point where the airfoil's critical angle of attack is exceeded.

The question is not when does the stall occur but rather how much warning the aircraft gives.

That is the conundrum faced by designers. Today stability and control is a well defined science. Aircraft designers have many more tools to take advantage and flying characteristics are a consideration almost from conception. For example, today designers build aircraft with no stall warning at all, these airplanes can be flown at maximum performance right up to CLmax without aerodynamic penalties of a buffet. To warn the pilot he is nearing a stall, an artificial device called a "stick shaker" is used.

To understand that stall warning, one must understand what buffeting is aerodynamically. It is a rapid secession of flow separation and reattachment.

When that boundary layer is not attached to a portion of the wing that portion is stalled, an airplane in turn is no longer turning at maximum rate. If you read the Spitfire Mk I pilots notes it expressly warns the pilot to ensure he experiences no buffeting in a turn. First of all when the airplane is buffeting, the turn rate is reduced even though the airfoil is not at CLmax. Secondly, the Spitfire has an extremely nasty stall that will spin and the aircraft is susceptible to airframe destruction in an aggravated spin.

[Skoshi Tiger]

If the spitfire's stability was unacceptable why would Werner Molders have written

"It handles well, is light on the controls, faultless in the turn and has a performance approaching that of the BF109."

All very subjective I know, but i can only assume that he would have been comparing it to the 109 he flew.

Just because something doesn't comply to a standard doesn't mean it lacks merit, it just means it doesn't comply to a standard.

It's just like if you get a Porche intended for the German market ands try to licence it in Australia, it would fail to meet the Australian safety standard and you wouldn't be able to legaly drive it on our roads. The same car with minor altertations to meet the Australian standards (and given an appropriate compliance plate) would be fine in Australia but in the process render it non-compliant in Germany.

Cheers!