A Study of the Effects of Radii of Gyration and Altitude on Aileron Effectiveness at High Speed Page: 4 of 12
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3
RESULTS AND DISCUSSION
The results are presented in figures 1 to 3.
Figure 1 includes three types of variation with alti-
tude: one variation at constant true airspeed, another at
constant Mach number, and a third at constant indicated
airspeed. Cases for constant true airspeed and constant
Mach number are chosen to be identical at 20,000 feet and
oases for constant indicated airspeed and constant Mach
number are chosen to be identical at 50,000 feet.
Figure 1(a) shows the variation with altitude of the
rolling-moment coefficient that must be applied by aile-
rons to perform two banking maneuvers; namely, the attain-
ment of an angle of bank of 45 at the end of the first
half second and 90 at the end of the first second.
Figure 1(b) shows the variation with altitude of the
time to bank to 45 and 90.0 The rolling-moment coef-
ficients applied at all altitudes are those that produce
an angle of bark of 450 at the end of the first half
second and of 90 at the end of the first second at zero
altitude.
The rolling-moment coefficient necessary to bank to
450 in one-half second is greater than that necessary to
bank to 90 in 1 second. This difference in reauired
rolling-moment coefficient is due to the fact that the
airplane accelerates in roll during all or a large part
of the time intervals considered. The moment of inertia
in roll therefore has an important influence on very short
rolling maneuvers. The rolling-moment coefficient re-
quired to bank to any other angle in the same time is
directly proportional to the angle; that is, to bank to
450 in 1 second requires half the rolling-moment coef-
ficient necessary to bank to 900 in 1 second.
The decrease in reouired rolling-moment coefficient
shown for increasing altitude with indicated airspeed con-
stant is caused by the large increase in true airspeed
that is required to maintain a given indicated airspeed.
(See table I.) The rolling-moment coefficient necessary
to bank the airplane in a given time is not a function of
velocity alone, however, as is shown by the variation of
rolling-moment coefficient with altitude when true air-
speed is constant (fig. i).
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Fehlner, Leo F. A Study of the Effects of Radii of Gyration and Altitude on Aileron Effectiveness at High Speed, report, April 1943; (https://digital.library.unt.edu/ark:/67531/metadc61620/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.