Analysis of Wind-Tunnel Tests to a Mach Number of 0.90 of a Four-Engine Propeller-Driven Airplane Configuration Having a Wing With 40 Degrees of Sweepback and an Aspect Ratio of 10 Page: 7 of 171
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NACA TN 3790
p angle of local wing chord relative to the wing-root chord, posi-
tive for wasbhn, measured in planes parallel to the plane of
tail effectiveness parameter, measured at a constant angle of
trim indicates condition of Cm or Cmcg = 0
SELECTION OF MODEL
Design of the model was based on some of the requirements of an
assumed airplane capable of long-range operation at a cruising speed of
550 miles per hour at an altitude of 40,000 feet (M = 0.83) with wing
loadings of the order of 75 to 100 pounds per square foot (c = 0.4
to 0.5). This section of the report will be devoted to a brtef discussion
of the factors which were considered in the design of the model. More
detailed discussion of this subject will be found in reference 1 (wing,
fuselage, fences), reference 2 (all-movable tail), reference 4 (nacelles),
and reference 5 (flaps).
A semispan model was used in preference to a sting-mounted, full-span
model primarily because of the larger size permissible with the semispan
model, which resulted in increased Reynolds number as well as more space
within the model for oil, water, electric, and air lines. Limitations
of this arrangement are that only longitudinal characteristics can be
determined and that the direction of rotation of the propellers of the
image wing is always opposite to that on the semispan wing itself. The
semispan model was designed to represent to 1/12 scale the right-hand
side of a hypothetical four-engine airplane having right-hand propellers
on the right wing and left-hand propellers on the left wing. Details of
the model are presented in figure 1 and in table I. Photographs of the
model mounted in the wind tunnel are presented in figure 2.
The wing incorporates a number of features designed to alleviate the
longitudinal stability difficulties usually associated with flow separa-
tion on sweptback wings of high aspect ratio. These features include
cambered wing sections having NACA four-digit thickness distribution
(comparatively large leading-edge radius), twist to reduce the load on
the outer portions of the wing, and chordwise fences on the upper surface
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Edwards, George G.; Buell, Donald A.; Demele, Fred A. & Sutton, Fred B. Analysis of Wind-Tunnel Tests to a Mach Number of 0.90 of a Four-Engine Propeller-Driven Airplane Configuration Having a Wing With 40 Degrees of Sweepback and an Aspect Ratio of 10, report, September 1956; (https://digital.library.unt.edu/ark:/67531/metadc56014/m1/7/: accessed May 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.