Mark James Boyd wrote:

Some aircraft have a very nose low spin (Blanik), others have a much
flatter spin (Katana). The Katana, which spins very flat on the horizon,
is going North at 30 knots. I stall it and spin. Over the course of
a second, the nose is now pointed South.

Why do you think it takes only one second? Even a aerobatic glider can't
reverse direction that quickly - that would be such a violent manuever.
Think about it: a 60 knot change in one second takes over 3 gs, and a
spin entry produces nothing like that.

Try timing a spin entry sometime with stopwatch or a recorder on board.

Is the Katana moving
South with an airspeed of 30 knots? No, it is not.

It's probably still got about 30 knots airspeed (do they really stall at
such a low speed?), but because it is pointed down, the southerly
component is less than 30 knots.

snip

Except for that 1 in 10 case, I'd guess aft CG is just a contributing
factor, not a cause. But I'd like to see data. When I hear of
a winch launch by an experienced pilot during the first
flight of the season, ending in a fatality, I have to wonder if
he took something out of the nose, or put something in the
tail, and so his stick pressure feel and initial trim setting
were off... Of the stall spin fatalities on record, I'd
bet most, if not all, had CG further back than the 60-70%
forward that Eric described...

Just to be clear here, the convention is: 0% is at the front of the
range; 100% is at the aft end of the range. It sounds like you have it
backwards.

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Eric Greenwell
Washington State
USA