Dynamic stalling of delta wing a/c (wrt MiG 21)

The problem exists any time the wing does not stall rapidly with
increasing AOA.  Problem is that, if wing stalls violently, you KNOW you
have a problem and must recover.

If there is a considerable region beyond max Cl, then you may be unaware
that Cl/Cd is deteriorating rapidly.  With many planes high induced drag
can exceed max engine thrust and you will slow down even with full
throttle unless you dump nose.  Tri-pacer had such a problem (lower
aspect ratio than Cub), as did Ercoupe.

I had an Ercoupe.  Knowing about back side of power curve problem, I was
able to make short field landings okay.  Of course, the Ercoupe had no
flaps, and with two-control you couldn't slip it.  The way you made a
steep approach was to slow way down.  But, you were in that region of
reversed command.  Many people crashed Ercoupes.  When they wanted to
flare for touchdown, they brought wheel back even further, in which case
sink rate went HIGHER!

You needed to start flare twenty or thirty feet up, get nose down, pick
up airspeed, then flare when a few feet above runway.  There were many
Ercoupes around with bent/broken main spars 'cause pilots didn't do it
right.

Ercoupe had a lot of twist in wing, and extreme differential in
aileron.  It was stallproof power off (you could induce a gentle stall
power-on with practice).  However, if you kept stick back far enough,
nose would stay high, wings level, but you were falling like a rock. 
This is the region of so-called reverse command.

-- 
Don Stauffer in Minnesota
[EMAIL PROTECTED]
webpage- http://www.usfamily.net/web/stauffer