AFH 4-16

As illustrated in the airplane's power required and available curves [Figure 4-14], the airplane slows down, going from speed 1 where it is climbing (A: power available greater than power required), to speed 2, where it stops climbing (B: power available equal to power required), and continuing to speed 3 where the stall horn sounds (C: power available less than power required). The energy map [Figure 4-15] tells the same story from a total mechanical energy standpoint: the airplane has positive PS at point 1 and climbs to point 2 where it stops climbing since PS = 0, then continues to point 3, where the PS < 0 and the stall horn sounds. Figure 4-15. The energy depletion scenario viewed in the energy map. Specific excess power (PS) contours are labeled in units of feet per minute. The question then is: what does the pilot do to recover from this predicament? The answer is proper energy management. The airplane needs to move to a different place on the energy map that will allow the airplane to begin climbing. So, what does that mean? ⦁ As can be seen in Figure 4-12, the pilot is in a scenario akin to that at the desired altitude, but with cautions when very slow. ⦁ The pilot then has to do something that is not intuitive; consider gaining speed at the expense of some altitude initially to improve climbing performance with full throttle. ⦁ Once the airplane accelerates to an airspeed in which the PS > 0, it can begin to climb again. The above recovery scenario is shown in the energy map Figure 4-16, which illustrates the important role of the elevator in assisting the pilot to recover from unintentional and dangerous deceleration and/or sink rate (refer to Additional Role for the Elevator section).