On Sunday, June 24, 2018 at 7:28:17 AM UTC-5, Waveguru wrote:
He was on base, made several circles and climbed a little, and then broke into a spin. The standard cirus did about 2 revolutions before it hit the ground. This was no freak atmospheric event, except that the air is more turbulent near the ground. Don’t f*#~k around down low...

Boggs

Thanks for this note. I've been thinking about this accident all week.
Obviously, whenever the airplane does something unplanned, there are 3 categories of adverse influences:
- something wrong with the aircraft
- something wrong with the pilot
- something wrong with the air.
A big problem is that air is invisible. Yet it sometimes takes on small transient wrinkles that cause aircraft to move awkwardly.
I noticed in the video the bushes tossing and the pilots' clothing fluttering, and that it was sunny. This means that there were big and little wrinkles in the air.

Back when I thought I had to keep the yaw-string straight in a turn, thermal turbulence induced incipient spins more often than I could count.

On windy days, the vertical or horizontal torque in the air can be pretty strong. When thermaling low, all it takes is a momentary backwards-moving gust to stall a wing and induce a spin.

Can't see it, can't prove it, but I've felt it often.

My condolences. This is a risky sport.

Danl J