Tango Whisky wrote on 12/10/2019 6:03 AM:
Le mardi 10 décembre 2019 07:31:14 UTC+1, 2G a écrit :
A thermal may not be your standard British thermal, but a confluence of
several, competing mini-thermals. I have seen up to six, or more, dust devils
converging to make a single thermal. However, in 40 years of flying, much in
the very dynamic high western desert, I have never been upset in the manner
you describe. This is not to say it can't happen, but I think the typical
glider accident is much more mundane and the direct result of poor
airmanship.

Tom

In 39 years of flying, I have once been upset by a thermal (entering at a speed
of 130 kph, 300 m over the rocks in the central Alps, 4 m/s climb after
recovery). A second time such an upset was caused by a rotor (vertical speeds
varying between -12 m/s and +12 m/s, trying to work it at 150 kph), but it
didn't really come as a surprise.

In 45 years of flying, I've never been upset by a thermal. I attribute that to
lack of exposure, as I rarely thermal below 1000' over mountains and ridges, or
below ridge top. That's where the "rogue thermals" exist, and where you are so
close to the ground that even a very capable pilot may not recover in time.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1