For historical reasons, Mignet’s Fleas had fixed incidence rear wings.  And it is one of the major flaws of the original design.

What happens is this:

  1. Let’s say the rear wing is fixed at 4 degrees incidence.
  2. At takeoff and landing, the front wing is inclined up to 12 degrees, producing most of the lift.
  3. However, as flight speed increases, the incidence of the front wing has to be lowered to maintain level flight.  However, the rear wing incidence is fixed, and as speed increases so does its lift.  At sufficient speed, the rear wing can actually overpower the front, and the nose of the plane begins dipping down.
  4. There comes a point where the front wing is no longer able to out-muscle the wing at the back, and the plane begins a nose-down pitch from which it is difficult to escape.  This becomes a limiting factor in the airspeed of any Pou.
  5. However, a variable pitch rear wing completely overcomes this limitation.  As the front wing incidence decreases, so does the rear wing.  The plane remains in equilibrium, and can fly as fast as it’s engine (or a dive) can propel it.
  6. Finally, when coming in to land, the rear wing can now be pivoted together with the front wing.  With both wings at (say) 12 degrees incidence, the plane now can produce far greater lift.  Which equates to slower landing speeds.
  7. One final piece of the puzzle is the “Pulga pitch control” wing on top of the tail.  With both wings inclined strongly on landing, the plane will have a tendency to pitch forward strongly.  Enter the “Pulga wing ” which acts in opposition to the two wings, producing a strong downward force to counter the forward pitch.  The result?  A smooth, co-ordinated landing at significantly lower speeds than before possible.

The blue circle in the pic below shows the bellcrank which controls the rear wing pitch.  If you prefer (for whatever reason) to keep the rear wing pitch constant, you simply set the pitch on the ground, uncouple the bellcrank from the controls and away you go.  On subsequent flights, you can adjust the rear wing incidence to suit your flying style, till you find your sweet spot.

And for the more adventurous – these will be a setting which allows left and right rear wing halves to be independently controlled.  So, for example, if coupled to the controls, the entire wing halves can be rotated in opposition to each other, so that they act as giant ailerons.  Naturally, the amount of differential deflection will need to be very small, and I am nowhere close to figuring it out.  Probably, once I’m familiar enough with the TCF in Mignet-mode, I will experiment with “Pulga” mode (i.e. with rear wing pivot).  And if/when I am confident enough, I’ll introduce differential deflection on the rear wing in extremely small increments.