I wonder too was it a characteristic of the Atlas Kudu in terms of the delayed spin recovery, that one seems to be a turbine conversion which might have altered the characteristics. But lack of currency with spins might have been a factor. Later in the video, not does there appear to be some up elevator, I think I can see up aileron on the inside wing. Any aileron input would only exacerbate the situation. I have practised plenty of spins over the years but not all pilots now days are even allowed by their Instructors to carry out a spin. On that point I don't think the uniformed guy is an Instructor, just some pilot along for the ride. I often have visiting pilots beside me. Airline Captains sometimes.
I would guess the spin happened because he was a bit slow but stable only for the cameraman hanging on door and the tandem moving rearward to induce some yaw and add a bit of rearward CofG and wham, departure. I often have to correct yaw when a big guy gets out and hangs on.
The closest I came to that when early on in my diverdriving career. My bird all but stalled when all the skydivers rushed the door after I'd let it get a teeny bit slow. There was a lot of wing waving but I controlled it. Lesson learned.
