Page 93 - Airplane Flying Handbook

Visualizing the Airplane’s Ability to “Move” Between Energy States

To better understand the basic rules of energy control, a pilot needs to visualize an airplane’s energy state and its ability to switch
from one energy state to another. In other words, how does an airplane “move” from an initial altitude and airspeed to any other target
altitude and airspeed within its flight envelope, and how does the pilot control the process? A map should help, and in this case, it
charts the status of the aircraft in terms of energy.
In a navigation map, such as an aeronautical sectional chart, the geographic position of an airplane is determined by two variables—
latitude and longitude. Likewise, in an “altitude-airspeed” or “energy” map the energy position of an airplane, its energy state,
is defined by two variables—altitude and airspeed. [Figure 4-6]

Figure 4-6. The altitude-speed “map” showing lines of constant energy height.

The position of an airplane in the altitude-airspeed map represents its total specific energy or E S (which is simply the sum of its
potential and kinetic energies divided by aircraft weight) as determined by its current altitude and airspeed.

E S = h + V²
2g
Where,

g = gravitational constant
h = height (altitude)
V = velocity (airspeed)

4-7