On Sat, 12 Sep 2009 06:34:06 -0700, Ron Wanttaja
wrote:

Morgans wrote:

Interesting. I have to admit that I am intrigued by what they had to
do to tame such an unconventional wing layout.

IIRC, the problem was due to the close spacing of the two tandem wings.
The front wing is higher than the rear one, and pivots for pitch control.

On the original Flea, there was a longitudinal overlap of the front and
back wings...the trailing edge of the front wing is aft of the leading
edge of the back one.

http://collections.nasm.si.edu/media...610020000a.JPG

When the pilot pulled back on the stick, the gap between the wings would
decrease. With the closely-spaced wings of the original design, this
would start "pinching off" the gap.

With Mignet's original low-power, slow speed concept, it didn't make
much difference. But as people starting putting flying them faster and
more aggressively, the air squeezing through the gap would
accelerate...increasing the airflow over the top of the aft wing, which
would increase its lift. The plane tended to pitch down, so the pilot
would pull back on the stick, which would accelerate the air MORE, cause
MORE pitch-down, etc.

The basic cure was an increased separation between the wings...the top
wing was moved higher, and/or the aft wing was moved back further.

http://members.fortunecity.com/gvanr...ilt/pdc-10.jpg

http://www.davidandivy.co.uk/images/ac5_flying_flea.jpg

Ron Wanttaja

there are a few other things Ron.
the aerofoil(s) was changed.
the wing separation was increased.
the wing control was made a pushrod.
an elevator was incorporated in the rear wing.
the spar position was moved.

it will be interesting to read the report firsthand as a matter of
historical accuracy.
Stealth Pilot