Hmm we've discussed this one before, but I tested the Spitfire out more thoroughly this time. I agree with you now that something needs to be checked out.
The flat spin itself, makes sense. No problem with that.
But I've checked the way just HOW the Spitfire enters such an aggravated flat spin so fast, and there seems to be a problem with that.
...
When a plane stalls, the weight of the plane, and the torque force pushes the plane's wings and nose to drop to one side.
Give a plane a 90 degrees left bank, pull the stick max and give full left rudder. Logically, the left bank action makes the plane side-slip towards left - in the case of a 90 degrees bank, the plane would be sideslipping downwards in the direction of the ground.
When you give full left rudder, the plane rotates on its yaw axis to the left - which in this case, with a 90d bank, it would also be towards the ground.
So, when you give max stick pull and full left rudder during a left turn, the plane stalls, and drops its nose and left wing abruptly in an action known as "snap roll", towards its left, which, is towards the ground.
Now, this is the weird part with the Spit.
When the nose/wing drops abruptly and the Spit snaprolls left towards the ground, the result of the snap roll doesn't leave the plane's nose pointing downwards. Maybe the torque force is acting too highly during a stall, but what ever the reason is, the snaproll swivels the plane 180 degrees, and causes the Spit to nose upwards when a stall develops into a spin!!
With a 90d bank and full rudder, the snaproll usually causes a plane to nose downwards - when that stall is aggravated, it develops into a spin, with the plane spinning wildly on its roll axis, and at the same time, spinning on its yaw axis, too.
But the SpitV, enters a snaproll which spins the plane 180 degrees on its yaw axis, with the nose pointing upwards.
When you check how the Spit moves during this weird spin, it's quite freaky. Imagine a yoyo when it spins downwards. The flat side of the yoyo, is the flat side of the plane. That's how the SpitV stalls - it snaprolls, spins 180degrees on its yaw axis, nose comes over the horizon and bam! immediately enters flat spin at that point.
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I think it must be looked at. I think that the momentum of the nose area in the Spit, when it enters a snap roll, is a bit exaggerated.
ps) but then again, I've never suddenly pulled the stick into max deflection while kicking full rudder, in a real life plane either.
During testing, I never had a problem with this weird snaproll developing into a flat spin if I fell into a stall gradually - which means, I enter a left turn, gradually pull the stick harder, I hear imminent stall signs, and then the plane buffets and stalls. This kind of stall didn't develop into such a fatal stall.
Only when I abruptly pulled max stick deflection as kicking max rudder, while turning, did it develop into a deadly flat spin.
Maybe that's the normal thing to happen in planes, if someone pulls max deflection of the stick. Especially, when Spitfires had so sensitive and highly responsive elevator controls, reacting quickly even with small stick input.
