Quest for Performance: The Evolution of Modern Aircraft
Chapter 7:Design Trends
Stalling Speed, Wing Loading, and Maximum Lift Coefficient
[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...

chart illustrating the trends in stall spedd from 1920 to 1980
[155] Figure 7.3 - Trends in stalling speed of propeller-driven aircraft.

....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....

chart illustrating the trens in wing loading from 1920 to 1980
[156] Figure 7.4 - Trends in wing loading of Propeller-driven aircraft.

....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.
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....

chart illustrating the trends in lift coefficient from 1920 to 1980
[157] Figure 7.5 Trends in maximum lift coefficient of propeller-driven aircraft.

.....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.