Stability
Letter by Ron Ligeti.
In November 2003 I got in contact with Ron Ligeti, the son
of the designer of the Stratos. I asked him to explain a bit more
about the stability of this concept. He sent me this letter:
"If the max angle of attack of the airfoil is greater than the
angle between the wings, The wings stall before the turbulent wash
of the canard will hit the main wing.
Difference in angle of attack = upwash angle (canard) +
downwash angle (main wing)
On a BADLY designed tandem wing aircraft the stall may
create a uniform turbulent wash over the rear wing causing a deep
stall. Research has shown that you might even get the
aircraft in a condition where you can not get the rear wing back
out of a stall once you are in it.
A GOOD design usually has the wing loading on the canard
higher than that of the main wing. The vertical /horizontal
distance between the wings is set so that the wings stall before
the turbulence of the canard effects the main wing. The incidence
angles of the two wings can be different so the main wing is at a
lower angle of attack. The main wing can have extended tips that
are in clean air just in case.
*There are a couple really good tandem wing aircraft out
there.
