and the flap 40 and as a result permits the boundary layer to remain thin and attached longer to the flap surface the resulting curvilinear configuration of the upper surface 42 of the trailing edge flap 40 during periods when the flap is stowed in the main airfoil in effect the leading end portion 44 of the flap 40 is retracted into the cove 26 at the trailing edge 24 of the airfoil 12 evidences a somewhat raised or 34 bumplike 34 surface configuration which may be generally referred to as an 34 out of contour 34 shape different aspects of the inventive 34 out of contour 34 concept may be clearly ascertained from the airfoil and trailing edge flap assemblies as illustrated in the various embodiments of fig6 through 9 of the drawings thus fig6 illustrates in a manner somewhat similar to the representation of fig1 the fragmentary rear end portion of a main airfoil 12 and with the trailing edge flap 40 being that as represented in fig5 hingedly articulated thereto as may be clearly ascertained the upper aerodynamically curvilinear surface 42 of the flap 40 forms a 34 bump like 34 configuration or out of contour surface relative to the airfoil upper surface 20 when the flap 40 is stowed in the airfoil i e retracted into the cove 26 of the latter fig7 shows a single slot configuration for the wing and whereby a trailing edge flap 50 is shown in a deployed condition through solid lines while the stowed condition thereof is represented by the dash lines the flap 50 incorporates an articulating trailing edge portion.