A Fowler Flap System for a High-Performance General Aviation Airfoil

As part of a general aviation airfoil development program being carried out under the direction of the NASA Langley Research Center, a 30% chord Fowler flap has been developed for the GA(W)-1 airfoil.. Wind tunnel tests at Wichita State University have demonstrated a c_1max value of 3.80 for 40 deg flap deflection at a Reynolds number of 2.2 × 10⁶. Effects of flap slot geometry have been systematically tested and optimum flap settings for any flight c₁ have been obtained. Modification of the reflexed lower surface contour resulted in a reduced c_1max with flap nested. Vortex generators provided an increase in c_1max of 0.2 for flap nested and 40 deg flap along with a drag penalty at low c₁ values. Flow visualization studies show that the stalling patterns for the new airfoil are characterized by an absence of leading edge separation for both the flap-nested and the 40 deg flap cases.