• Version
• 162 Downloads
• 738.52 KB File Size
• 1 File Count
• November 4, 2016 Create Date
• November 4, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Preliminary Biplane Tests in the Variable Density Wind Tunnel

Biplane cellules using the N.A.C.A.—M6 airfoil section
have been tested in the variable density wind tunnel of the
National Advisory Committee for Aeronautics. Three cellules,
differing only in the amOunt of stagger, were tested at two air
densities, corresponding to pressures of one atmosphere and of
twenty atmospheres. The range of angle of attack was from —2°
to +480. The effect of stagger on the lift and drag, and on
the shielding effect of the upper wing by the lower at high an—
gles of attack was determined.

Confirmations of the biplane theory, and the various empir—
ical biplane corrections in general use, have for the most part
been obtained in atmospheric wind tunnels. The present series of
tests was conducted in order to find what effect the dynamic
scale has on the aerodynamic characteristics of biplane cellules
similar to those in general use, and to determine the advisabil—
ity of a,more extended biplane research in the variable density
wind tunnel. It was also desired to find the effect of positive
stagger at large angles of attack, for use in the study of
stalled flight and tail spins.

Two duralumin models of the N.A.C.A.~M6 airfoil, having 5—
inch chord and 30minch span, were assembled on duralumin N—struts
to form the biplane cellule. Three sets of N—struts, designed to
give staggers of zero, 15 degrees and 30 degrees, were used. As
will be seen in Figure l, the airfoils were made with trailing
edge flaps. The flap hinges were pinned in the neutral position
for these tests, giving the normal M6 airfoil except for the
slight groove at the hinge.

The model was mounted in a manner similar to that generally
' used in this tunnel, described in Reference 1. In order to reach
angles of attack of 48 degrees, the vertical supports were hinged
at points 15 inches below the point of attachment to the lower
wing of the cellule. Streamlined shields fastened to the tunnel
floor were placed over the part of the supports below the hinge.