Investigations on the Downwash Behind a Tapered Wing With Fuselage and Propeller Page: 5 of 52
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N.A.C.A. Technical :Memorandum No. 876
closely. But-on the "low wing with angular body" by reason
of form and incidence of the body. relative to the wing an
equal ca value of "wing alone" and "wing with body" was
not to occur until at a higher angle of attack.. This angle
lies at around a = 90 according to the polars of figure 2.
The comparatively large angle of setting of the "angu-
lar body" necessitated on the low-wing model a small cut-
away at the trailing edge which, however, could have had no
special effect on the polar and the downwash conditions.
Inversely the wing area of the "low-wing- model with ideal
body" is increased through the wing roots. The differences
in the Camax values of the polars are probably connected
The propeller is mounted approximately at 1/4 of half
the propeller diameter over the wing chord and at about 3/4
of the diameter ahead of the wing center. IThe inclination
of the propeller axis to the profile cnord on both low-wing
models is 30 in the sense of an air flow of the pressure side
of the profile through the slipstream. The propeller diam-
eter is equal to 0.2 b (b = span of model), the ratio of
swept-disk area to wing area is 1:4.5. The counter-clock-
wise rotating propeller is of the type Sx a7 A1 PI from
N.A.C.A. Technical Report No. 141 (reference 4). The pitch
is H = 0.7 D (fig. 3).. Neither the performance coefficients
nor the slipstream deflection or twist were measured on the
propeller running by itself. The characteristic curves
(fig. 4) of the propeller running alone were taken from
N.A.C.A. Report No. 141 (reference 4). The dashed curve
indicates the k values based respectively on the polar
of the "low-wing'' model with ideal fuselage and the cw
values of figure 7.
The forces with propeller running were measured at
seven anglesof attack. Lift, drag, and pitching moment
were measured at increasing r.p.m., including the r.p.m.
range between zero thrust and stopped propeller (once ver-
tical, once horizontal).
0. TEST PROCEDURE AND EVALUATION
In contrast with the earlier measurements (reference
1), which were carried out in tunnel I of 2.25 m diameter
at the AVA Gttingen, the present measurements were made
in "small tunnel" (tunnel II) of the AVA. Having enlarged
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Muttray, H. Investigations on the Downwash Behind a Tapered Wing With Fuselage and Propeller, report, September 1938; (https://digital.library.unt.edu/ark:/67531/metadc63295/m1/5/: accessed April 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.