Investigations of the damping in roll of swept and tapered wings at supersonic speeds Page: 6 of 36
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NACA RM 153A13 5
The precision of the data has been determined by estimating the
accuracies of the measured quantities and evaluating their effects on
the coefficient CZ and the parameter pb/2V. Over the range of
moments encountered in the tests, the maximum error in the strain-gage-
balance calibration factor was 1.1 percent. The resulting error in CZ
was 1.1 percent. Error in the measurement of the pertinent wing angles
gave an uncertainty in wing area such that an error of about 0.5 per-
cent was present in the values of C7. Measurements of the rolling
velocity were in error by 5 rpm in the test range and contributed a
maximum error in pb/2V of 0.1 percent. The surveyed variation of
each of the free-stream Mach numbers is about 0.01.
RESULTS AND DISCUSSION
The variations of rolling-moment coefficient with wing-tip helix
angle for the 33 wings tested are presented in figures 2 to 6. Within
the accuracy of the data, the values of. CZ for most of the wings at
the three Mach numbers varied linearly with the rolling velocity. The
parameter C;p was therefore independent of rolling velocity, as pre-
dicted by linear theory.
For several of the slender wings having highly sweptback leading
and trailing edges, the variations of CZ with pb/2V were nonlinear
(e.g., figs..2(b), 3(a), 3(e), 3(f), 3(g), and 3(i)). These nonline-
arities probably represent the net contributions to C3 of thickness
effects, separation of the flow near the tips, and aeroelastic effects.
Since the variations of C0 with pb/2V were nonlinear for some of the
wings, all slopes were estimated for that portion of the curve through
a value of pb/2V of 0.02.
The collected values of CZp are plotted in figures 7 to 12 in a
manner suggested by the linear theory for wings in steady roll. The
abscissa is the quantity P cot A, which describes the position of the
leading edges relative to the Mach cone from the wing apex. For values
of cot A greater than i, the leading edge lies ahead of the Ma.ch =
cone (supersonic leading edge); for values less than 1, the leading edge
lies behind the Mch cone (subsonic leading edge). Plotted as the ordi-
nate is the quantity BCZp. For all except the triangular wings the
values of SCZp for wings having the same taper ratio and tested at
Mach numbers giving a common value of BA are presented on the same
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McDearmon, Russell W. & Heinke, Harry S., Jr. Investigations of the damping in roll of swept and tapered wings at supersonic speeds, report, March 3, 1953; (https://digital.library.unt.edu/ark:/67531/metadc59536/m1/6/: accessed May 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.