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Instrument Flying Handbook Menu>Aerodynamic
Factors>Drag
Curves >Regions of Command
The drag
curve also illustrates the two regions of command: the region
of normal command, and the region of reversed command. The term
“region of command” refers to the relationship between
speed and the power required to maintain or change that speed.
“Command” refers to the input the pilot must give
in terms of power or thrust to maintain a new speed.
The “region of normal command”
occurs where power must be added to increase speed. This region
exists at speeds higher than the minimum drag point primarily
as a result of parasite drag. The “region of reversed
command” occurs where additional power is needed to maintain
a slower airspeed. This region exists at speeds slower than
the minimum drag point (L/DMAX on the thrust-required curve,
figure 2-5) and is primarily due to induced drag. Figure 2-6
shows how one power setting can yield two speeds, points 1 and
2. This is because at point 1 there is high induced drag and
low parasite drag, while at point 2 there is high parasite drag
and low induced drag.
Figure 2-6. Regions of command.
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