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National Advisory Committee for Aeronautics, Report - Pressure Distribution Over a Rectangular Airfoil with a Partial Span Split Flap

Pressure-distribution tests of a Olarlc Y wing model
with a partial-span split flap were made to determine
the distribution of air loads over both the wing and the
flap. The model was used in conjunction with a re-
flection plane in the N. A. 0’. A. 7- by 10-foot wind
tunnel. The 20-percent—chord split flap contended over
the inboard 60 percent of the semispan. The tests were
made at various flap deflections up to 45° and covered
a range of angles of attack from zero lift to approximately
maximum lift for each flap deflection.

The results are given as airfoil section, or rib, pressure
diagrams for the wing with flap neutral. Increments of
airfoil section pressures are given for various amounts
of flap deflection so that combined wing and flap sec-
tion pressure diagrams may be obtained by a simple
addition. Calculated coeficients of section loads and
moments and of wing loads and moments are also given
for the wing and flap combination and for the flap alone.

It was found that deflecting a partial-span split flap
affected the pressures and the section normal—force and
pitching—moment coefl'icients over the entire wing span.
The flap loads and moments were almost constant over
the span of the partial-span flap for a given angle of
attack and jlap deflection. The maximum normal—force
and-hinge-moment coeflicients were about the same for
the partial-span split flap of the present tests as for a
full-span split flap previously tested.

A considerable amount of aerodynamic and air-load
data is available for simple split flaps extending along
the entire span of the wing. (See references 1 to 3.)
However, because of the general use on present-day
airplanes of the outer portion of the wing span for
ailerons, most of the installations of split flaps have
been limited to the inner 40 to 60 percent portion of
the wing span. Some aerodynamic information on
partial-span split flaps is available from wind-tunnel
force tests of both rectangular and tapered wings
equipped with such flaps (references 4 and 5).