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National Advisory Committee for Aeronautics, Technical Notes - Full Scale Wind Tunnel and Flight Tests of a Fairchild 22 Airplane Equipped with a Fowler Flap

Full- scale wind-tunnel and flight tests w_ere made of , g
a Fairchild 22 airplane equipped _with a Fow_1er flap to de—
termine the effect of the flap on the performance and con-
trol characteristics of the airplane. In the wind» tunnel
tests of the airplane with the horizontal tail surfaces
removed, the flap was found to increase the maximum lift
coefficient from 1.27 to 2.41. In the flight tests, the
flap was found to decrease the minimum speed from 58.8 to
44.4 miles per hour. The required take-off run to attain
an altitude of 50 feet was reduced from 935 feet to 700
feet by the use of the flap, the minimum distance being
obtained with five—sixths full deflection. The landing
run from a height of 50 feet was reduced one-third. The
longitudinal and directional control was adversETy_affect—
ed by the flap, indicating that the design of the tail
surfaces is more critical with a flapped than a plain wing

At the request of the Bureau of Aeronautics, Navy
Department, the Committee is conducting a series of tests
of different types of flapped wings on a Fairchild 22 air—
plane. The tests consist of the measurement of the—pri—
mary aerodynamic characteristics of the airplane with each
type of flap in the full—scale wind tunnel and of the
measurement of control and other characteristics, not
readily determined in the tunnel, in flight. The tests
of the Fowler wing, the first of the’series, have been
completed and are herein reported.

The Fowler wing has a variable area and camber, and
consists of two separate airfoils of different chords.

The larger airfoil is the basic wing and the smaller one
is the'Fowler flap. which in its retracted position fits
into a. recess in the lower _surfa_c_e of the basic wing at
its trailing edge. The flap is operated by moving it
downward and to the rear along a circular are, thereby ~
increasing both the chord and camber of the wing combina—
tion. In the extended positiOn the flap is situated with
its leading edge approximately under the trailing edge of
the“baeic wing_and with its chord line 29° relative to

the chord line of the basic wing. The flap is a slight
distance below the trailin_g edze of the basic wing so that
a slot is formed between the mai_n wing and the nose of the
flap.