Good review, but it leaves the big question unanswered: in this era of computer design, CAD/CAM, and well-known aerodynamics, how could Cessna have produced a light airplane that cannot recover from a spin? I demonstrate spins in a Cessna 150 — first produced in 1959 and the direct descendant of the 1946 140.
They used to be called tailspins in the long ago. Recovery from spins were part of flight training.
Scariest part of my training:
Instructor:
“OK, look down” (places AC in spin or other “unusual” configuration)
Followed by:
“Recover”
That's still the problem: Aerodynamics. for all our tools and understanding it still drives us, aerospace engineers, crazy.
Especially unsteady, non-linear aerodynamics; the type that drives unrecoverable spin phenomena.
There has been quite a lot of information generated on what small changes to a bodies geometry can due to it's aerodynamic performance in stall departure and spin entry that it's unbelievable that a few thousands of an inch her and there, a bug strike there or a bird "spot" there can mean the difference between recovery and continued uncontrolled flight. It's mind boggling.
There is no closed form solution to date, so that's why it's test, test, test.