This was Al Whiteside's FM-2. He operated Flamingo Aviation in Jacksonville, Florida in the 1950-60s and rebuilt warbirds. Had a P-63, B-25, and several others. In the late 1950s when I was 14 Al gave me the job of sweeping his hanger floor on Saturday mornings. Later I graduated to degreasing...
It has been too many years gone by and I do not remember the exact flight conditions from which we saw tumbling. But in the spin tunnel the aircraft starts out at 90 degrees angle of attack and decreases down until it reaches a spin (or in this case tumble) or if not flys out.
I was one of the participants in the 1970s P-39 tumbling study. And yes it was totally an unofficial and unfunded test. But now everyone involved is either retired or passed on, so no one can get in trouble, but it can be good lesson on how sometimes historic research gets done. At the time I...