P-40 spin characteristicsThe late Erik Shilling posted the following on a Usenet news group in answer to a flight simmers question about how the P-36 differed from the P-40. (They are essentially the same airplane, the 36 with a radial engine and the 40 with a liquid-cooled, in-line Allison.) Comments in brackets  are mine. -- Dan Ford
The spin characteristic of the P-36 was entirely different from that of the P-40; the spin/ snap roll of the P-36 was quite violent. I was unable to snap or spin any of the P-40B's that I had flown although I tried without success. The difference was due to a cuff place [placed] on the wing root of the P-40, but absent on the P-36.
Spin recovery for the P-36 was the standard NACA recovery. Flat spin recovery was pro spin: full aileron into the spin, stick full back, and rudder into the spin. When the [nose] dropped and normal spin developed, [standard] NACA recovery was used. [I reckon this is the spin recovery I was taught: power off, neutralize the stick, and kick full opposite rudder to the airplane's rotation. Once the plane stops spinning, be ready to counteract if it begins to spin in the other direction. Then pull back hard to recover from the dive.--DF]
However the P-40 had a vicious tumble (end over end) if a stall was entered into at a nose high position of about 60 degrees above the horizon. To recover from the tumble you reduced power and went along for the ride with all controls in neutral. After about 12,000 feet the nose settled into a vertical dive from which recovery was normal.
[It's that last paragraph that made me want to post this memoir for the ages. The notion of a plane revolving around its pitch axis, and of going "along for the ride" while it dropped more than two miles, makes me happy that I did my spin training in a Great Lakes trainer and not a P-40.--DF]