The chart may be subject to what is called collinearity, which is a relationship between two variables that may not be causal in nature.
Probably multiple collineararities.
So why would FAA (CAA) not notice this in their original data used to determine they should stop spin training?
And why would a modern organization like AOPA even publish that graph?
You’re “on” to the answer. Agenda and statistical manipulation. Seeing that fatal spins mostly “went away” for the most part statistically, doesn’t seem to sink in much when spin training threads come up now...
And remember I’m in the camp that says we should still do them.
It because of some accident statistic, more because spins are a completely normal thing for an airplane to do. Wholistic teaching. Airplanes are three dimensional operating machines, often being taught like they’re more two dimensional than they are.
Example: Phrasing. How many times is proper application of rudder taught as an afterthought to the bank dimension... do this, THEN that... no, do both. Simultaneously.
The helicopter pilots will chuckle at this example. Try applying controls in a heli as reactions to the others and see how bad that hover gets, and how fast it gets out of hand.
Aileron requires simultaneous rudder, not “now look at the ball and fix the rudder input”, if you see what I mean. No delay, they’re simultaneous.
Spin training forces the recognition of this better than many other ways to show it. The “make a good coordinated turn back to centerline” technique mentioned above would also highlight it really well. (And wasn’t one that I’d thought of, but it makes sense.)
The pilot who’s behind on the rudder input is going to make a dog’s breakfast out of that little two turn sequence nice and low over a nice straight ground reference for instant feedback on their feet not being connected to their brain nor instantly and simultaneously connected to aileron movements.
The pilot who’s behind on rudder inputs can be “set up” to let the airplane start spinning.
Same root cause underpinning problem.
Toss in the “taildraggers make better pilots” argument too, while we’re focusing on what feet need to do.
Fun stuff, talking about this.
That graph, is a total mess of assumptions leading somewhere that gives a lot of wrong impressions, if not thought carefully about.
Like a lot of graphs.