Investigations on the Downwash Behind a Tapered Wing With Fuselage and Propeller Page: 2 of 52
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NATIONAL ADVISORY COMMITTEE FOR ARONAUTIOS
TECHNICAL MKORANDUM NO. 876
INVESTIGATIONS ON TEe DOWNWASH BEHIND A
TAPERED WING WITH FUSRLAG AND PROPELLER*
By H. Muttray
The new downwash measurements behind a tapered wing
with parallel center section described in the present re-
port can be brought into good agreement with theoretical
calculations if made on the basis of not-rolled-up vortex
sheet and allowance is made for the lowering of the sheet.
The test values are about 10 higher than the "upper limit"
established for it, as against approximately 0.5o in the
earlier tests behind a rectangular and elliptical wing.
The measurements on lateral axes, especially if lying be-'
low the wing on a level with the vortex train, disclosed
in accord with the lift distribution, a marked change in
angle over the span of the tail in contrast to the rectan-
gular and elliptical wing.
The downwash measurements on the low-wing model with-
out propeller running indicate only a minor effect of fuse-
lage on the downwash with "ideal" fuselage in comparison
to "wing alone." But for "angular" fuselage, the effect,
even though it also extends only over a comparatively nar-
row width, is quite pronounced, that is, in the sense of
an improvement in static longitudinal stability.
The downwash measurements on low-wing models with pro-
peller running disclose a very strongly expressed slipstream
twist in vicinity of the tail despite the rectifying effect
of the wing. There are other disturbed downwash zones to
both sides of this twist region, The prefix of the dis-
turbanoes - of different extent to left and right - is in
these sones the opposite of that of the slipstream twist.
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*"Untersuchungen aber den Abwind hinter einem TrapezflVgel
mit Rumpf und Schraube.u Luftfahrtforschung, vol. 15, no.
3, March 20, 1938, pp, 101-12,.
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Muttray, H. Investigations on the Downwash Behind a Tapered Wing With Fuselage and Propeller, report, September 1938; (digital.library.unt.edu/ark:/67531/metadc63295/m1/2/: accessed December 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.