3) Because the Dufourmental modification employs a larger flap angle
and shorter arc of rotation, like the Webster modification, it results in more sharing of tension between the primary and secondary defects.
Thus, the essential features for airfoil's aerodynamics, in a 2-D framework, are described by a quasi-steady model for the lift, pitching moment and hinge moment; an aggregate aeroservoelastic model having three degrees of freedom (the plunge h, the pitch a and the flap angle
[beta]) is so obtained.
The test aircraft was flown with its experimental control surfaces at flap angles
ranging from -2 degrees up to 30 degrees.