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National Advisory Committee for Aeronautics, Technical Notes - Full Scale Drag Tests on Various Parts of Fairchild (FO-2W2) Cabin Monoplane

The drag due to the_various parts of a Fairchild (FC—BWB)
cabin monoplane was measured at air speeds varying from 50 to
100 m.p.h., in the Twenty—Foot Propeller Research Tunnel of the
National Advisory Committee for Aeronautics.

It was found that the largest drag was due to the radial
air—cooled engine. The measured drag due to the landing gear
was also large, being about 4/5 of that due to the engine.
Substituting Musselman type wheels for the standard wheels
caused no change in the drag due to the landing gear. A small
decrease in drag was effected by adding a turtleback to the
airplane fuselage.“

Until recently, wind tunnel measurements of the drag due
to airplane parts have been of questionable value principally
because of the small scale at which it has been necessary to
conduct the tests. The Twenty~Foot Propeller Research Tunnel
(Reference 1) of the National Advisory Committee for Aeronautics
has afforded-a means of overcoming this difficulty, for full

scale airplane parts may be tested in its air stream. Moreover,
the drag due to these parts in the presence of the rest of the
airplane can be measured, thereby determining the interference
effects.

The Fairchild (FG—BWB) cabin monoplane (Fig. l) was mounted
in the tunnel primarily to determine certain pr0pelier charac~
teristics for use in connection with glide tests to be made
with the airplane in flight. It was decided to extend the
tests and measure the drag due to the various parts of the air—
plane. This was done without the presence of a propeller slip—
stream and with the airplane at one angle of attack. Since
the air stream in the tunnel would include only 20 feet of the
airplane‘s wing, the drag values measured with the wing in I
place do not represent the total drag of the airplane. A com—
parison of the results of drag tests made on various parts of
the airplane with and without wing, does show, however, the
effect of the presence of the wing upon the drag due to these
parts.