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Wind-Tunnel Investigation of a Fowler Flap and Spoiler for an Advanced General Aviation Wing

An investigation has been conducted in the Langley Research Center V/STOL tunnel
to determine the effects of adding a Fowler flap and spoiler to an advanced general avia-
tion wing. The wing was tested without fuselage or empennage and was fitted with approx-
imately three -quarter-span Fowler flaps and half-span spoilers. The spoilers were
hinged at the 70-percent chord point and vented when the flaps were deflected. Static
longitudinal and lateral aerodynamic data were obtained over an angle—of—attack range
of -80 to 220 for various flap deflections and positions, spoiler geometries, and vent-lip
geometries.

Lateral characteristics indicate that the spoilers are generally adequate for lat-
eral control. However, the spoilers do have a region of low effectiveness when deflected
less than 100 or 15°, especially when the flaps are deflected 30° or 40°. In general, the
spoiler effectiveness increases with increasing angle of attack, increases with increas-
ing flap deflections, and is influenced by vent- lip geometry. In addition, the data show
that some two-dimensional effects on spoiler effectiveness are reduced in the three-
dimensional case. Results also indicate the expected significant increase in lift coeffi—
cient as the Fowler flaps are deflected; when the flap was fully deflected, the maximum
wing lift coefficient was increased about 96 percent.

The development of new, thick, high-lift airfoil sections has had a profound effect on
the general aviation community because these sections offer the possibility of improved
performance on several new light aircraft designs. These airfoils provide higher maxi-
mum lift coefficients than the conventional 64-Series airfoils used on many general avia-
tion aircraft. This increase in maximum lift coefficient allows the use of a smaller,
more highly loaded wing with less wetted area. These developments can increase cruise
performance and improve ride quality. The increased thickness of these airfoils also
provides the opportunity for wing structural weight savings.