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: 3 of 171
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NACA TN 3790
Estimates of the stability with nacelles moved 0.1 of the semispan out-
board of their original position are shown, along with estimates of roll-
ing and yawing moments resulting from loss of thrust on an outboard engine.
A study of the high-speed data indicates that the. effects of oper-
ating propellers on the longitudinal characteristics of the model were
comparatively small at high subsonic speeds.
The propulsive characteristics of the model are presented and com-
pared with those of the isolated propeller for both low-speed and high-
speed conditions of operation.
The potentialities of the turbine-propeller propulsion system, par-
ticularly with regard to take-off and range characteristics of multiengine
airplanes, have stimulated interest in the long-range turboprop airplane
designed to fly at high subsonic speeds. A practical airplane configura-
tion for this application appears to be one utilizing a sweptback wing of
high aspect ratio in combination with tractor-mounted supersonic propel-
lers. The effects of these highly loaded propellers on the flow over the
swept wing and tail surfaces and the consequent effects on the longitudi-
nal characteristics of the airplane cannot be estimated with confidence on
the basis of existing experimental data or by theoretical methods. Appli-
cable experimental data are meager, and existing theoretical methods,
developed for airplanes with low propeller-disc loadings and unswept wings,
are of doubtful validity for the arrangement considered.
An investigation has been conducted in the Ames 12-foot pressure wind
tunnel to determine the longitudinal characteristics of a representative
multiengine airplane configuration with sweptback wing of high aspect
ratio. The investigation included wind-tunnel tests of a model with and
without supersonic-type propellers. The power-off longitudinal character-
istics of several combinations of the components of this airplane configu-
ration have been presented in references 1 to 4. The results of power-on
tests at low and at high subsonic speeds have been presented without anal-
ysis in reference 5.
The present report is concerned with an analysis of the data pre-
sented in reference 5. The sources of the large effects of operating pro-
pellers indicated in the low-speed data are traced in an effort to indi-
cate those design features which would reduce adverse effects of operating
propellers on the longitudinal characteristics of this type of airplane.
Calculated static longitudinal stability characteristics are presented for
a revised airplane configuration. Also investigated is the propulsive
efficiency of the configuration tested and its relation to the efficiency
of the isolated propeller.
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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/m1/3/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.