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Quest for Performance: The Evolution
of Modern Aircraft
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- Part I: THE AGE OF
PROPELLERS
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- Chapter 7:Design Trends
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- Stalling Speed, Wing Loading,
and Maximum Lift Coefficient
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- [154] The stalling
speed, wing loading, and maximum lift coefficient are shown as a
function of years for various aircraft in figures 7.3, 7.4, and
7.5. The short, unpaved fields that served as airports in the
early 1920's, together with the relatively poor flying
characteristics of aircraft of speed. Values of the
stalling...
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- [155] Figure 7.3 - Trends in stalling speed of
propeller-driven aircraft.
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- ....speed of 40 to 50 miles per hour were
not unusual, although precise data are not shown in figure 7.3 for
the year 1920. High-lift devices were essentially unknown at that
time; hence, the wing loadings needed to give the low values of
the stalling speed were correspondingly low, as shown in figure
7.4. Values of the wing loading from 5 to 10 pounds per square
foot were typical, and the 14-pound wing loading of the DH-4 was
considered high in 1920. For a given atmospheric density, the wing
loading is, of course, related to the square of the stalling speed
by the value of the wing maximum lift coefficient. Values of the
maximum lift coefficient slightly in excess of a value of 1 were
typical of unflapped aircraft with thin airfoil sections in 1920,
as shown in figure 7.5. The demands for increased high-speed
performance resulted in increases in wing loading and, hence,
increases in the stalling speed. By the time of World War II, the
stalling speeds of high-performance military aircraft were in the
range of 80 to 100 miles per hour; wing loadings were in the range
of 40 to 60 pounds per square foot. The development and the
associated use of powerful high-lift devices, such as described in
chapter
5, resulted in aircraft maximum
lift coefficients of the order of 2.0 to 2.5 for high-performance
aircraft in the World War II period. These high-lift devices, and
consequent high maximum lift coefficient, prevented the stalling
speed....
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- [156] Figure 7.4 - Trends in wing loading of
Propeller-driven aircraft.
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- ....from increasing to an even greater
extent than that shown in figure 7.3. Since World War II, the
stalling speed of high-performance aircraft has continued to
increase and is seen in figure 7.3 to be 115 miles per hour for
the contemporary Lockheed C-130 cargo transport. The wing loading
for this aircraft is about 90 pounds per square foot, as shown in
figure 7.4, and the maximum lift coefficient is about 2.75. The
highest maximum lift
coefficient of any of the aircraft
for which data are shown in figure 7.5 is about 3.0 and was
obtained by the Lockheed Model 1049G Constellation. The
corresponding wing loading for this aircraft is about 80 pounds
per square foot. The high maximum lift coefficient of the
Constellation gave a relatively slow stalling speed of about 100
miles per hour.
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- The lower bounds in figures 7.3, 7.4, and
7.5 show modest increases in stalling speed, wing loading, and
maximum lift coefficient for aircraft of relatively low
performance. The data for current general aviation aircraft show a
wide spread in level of technology, insofar as maximum lift
coefficients are concerned, and a wide range of values of stalling
speed and wing loading. Values of maximum lift coefficient for
these aircraft vary from about 1.3 to about 2.2. The higher values
of maximum lift coefficient achieved by current high-technology
general aviation aircraft are about the same as those of military
aircraft in....
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- [157] Figure 7.5 Trends in maximum lift coefficient
of propeller-driven aircraft.
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- .....World War II. The wing loading and
stalling speeds of the high-performance general aviation aircraft
of today are also seen to be in the same order as those of World
War II military aircraft.
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