AFH 4-6

While the elevator can assist the throttle in changing T – D and PS through changes in airspeed via energy exchange as described above, occasionally the elevator can directly increase the “D” in T – D at any given speed during a level turn, thus helping the airplane rapidly bleed off total energy. As the airplane banks, load factor (lift/weight) increases because total lift has to increase to pull the airplane into the turn while simultaneously balancing its weight. This is accomplished by pulling back on the yoke (or stick) to increase AOA which results in increased induced drag and power required at any given speed. This action will quickly slow the airplane down and decrease total energy more rapidly than by just reducing the throttle setting to idle. This additional role of the elevator is shown on the power curve. [Figure 4-5] Figure 4-5. The effect of increased load factor on total drag and power required at different airspeeds. Applying the respective role of the controls to manage the airplane’s energy state leads to a set of simple “rules” for proper throttle- elevator coordination to effectively control vertical flight path and airspeed. What are these basic rules of energy control? Rules of Energy Control The central principle encapsulating the role of the throttle and elevator for managing the airplane’s energy can be summed up as follows: coordinated throttle and elevator inputs control the airplane’s energy state. Modifying a popular adage, the principle can be restated as “pitch plus power controls energy state.” This central principle serves to guide a set of general energy control rules to achieve and maintain any desired vertical flight path and airspeed targets within the airplane’s energy envelope.