Preliminary study of airplane configurations having tail surfaces outboard of the wing tips Page: 2 of 38
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NACA RM L58BO6 3 117601437 7965
NATIONAL ADVISORY COIt4ITTEE FOR AERONAUTICS
PRELIMINARY STUDY OF AIRPLANE CONFIGURATIONS HAVING
TAIL SURFACES OUTBOARD OF THE WING TIPS
By William C. Sleeman, Jr.
This report is concerned primarily with the concepts and applications
underlying the basic arrangement of airplane configurations having tail
surfaces outboard of the wing tips. This type of arrangement was con-
ceived to be consistent with good supersonic performance characteristics
and, also, to avoid some of the stability and trim-drag problems encoun-
tered on other supersonic configurations. The arrangements considered
both experimentally and analytically in the present study had outboard
horizontal tails and twin vertical tails mounted on slender bodies attached
to the tips of a low-aspect-ratio swept wing.
Experimental results indicated that location of the horizontal-tail
surfaces in the upwash field of the wing-tip vortices would be expected
to be favorable from the standpoint of drag due to lift and trimmed lift-
drag ratios at subsonic and supersonic speeds. Indications are that out-
board tail configurations would also be expected to have satisfactory
directional stability characteristics at both subsonic and supersonic
speeds. Pitching-moment curves for an outboard tail model showed grad-
ually increasing stability with lift up to a lift coefficient of approxi-
mately 1.0 at a Mach number of 0.60, above which a pitch-up tendency was
indicated. These and other data indicate a possible longitudinal sta-
bility problem for outboard tail configurations, which is believed to be
associated with instability caused by loss of upwash when the wing-tip
vortex becomes displaced at high angles of attack.
An analytical study at Mach number 3.0 of effects of design variables
has indicated that values of trimmed maximum lift-drag ratios were rela-
tively insensitive to the amount of stability for static margins between
0 and 10 percent mean aerodynamic chord and the trends indicated in these
estimates were verified experimentally at M = 2.01. Introduction of a
small amount of pitching moment at zero lift may be used to compensate for
losses in lift-drag ratio occurring as a result of somewhat higher sta-
bility. This analysis also indicated a gradual increase in trimmed maxi-
mum lift-drag ratio with both tail length and tail size; however, increases
with tail length were generally quite small for lengths in excess of about
one wing mean chord..1 J-M .. -
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Sleeman, William C., Jr. Preliminary study of airplane configurations having tail surfaces outboard of the wing tips, report, March 24, 1958; (digital.library.unt.edu/ark:/67531/metadc64131/m1/2/: accessed May 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.