This quote intrigued me:
The full size airplane - in this case, the CV-240 - is not able to fly by itself - it must have a pilot to control it. Actually, if the airplane were designed to be so stable it would maintain itself in level flight, it would be very tiring for a pilot to fly it. The stability built into the plane is one which, when left to its own devices, will frequently cause the plane to end up in a screeching spiral dive in one direction or another, depending on which way it happens to be upset in the first place.
I thought only close to envelope fighter types were inherently unstable. Aren't most civilian planes fairy stable naturally? Or not?
I thought it took some bit of work to get a plane into a spin.
PS. I'm not at all belittling their challenges. Just exploring this bit of detail.