therefore closer to the higher speed that the airplane will stall  at. Because “stalling speed” is not a constant number, pilots  must understand the underlying factors that affect it in order  to maintain aircraft control in all circumstances.  feels at the slower airspeeds aids the pilot in learning that  as airspeed decreases, control effectiveness decreases. For  instance, reducing airspeed from 30 knots to 20 knots above  the stalling speed will result in a certain loss of effectiveness  of flight control inputs because of less airflow over the  control surfaces. As airspeed is further reduced, the control  effectiveness is further reduced and the reduced airflow over  the control surfaces results in larger control movements  being required to create the same response. Pilots sometimes  refer to the feel of this reduced effectiveness as “sloppy” or  “mushy” controls. Slow flight is when the airplane AOA is just under the AOA  which will cause an aerodynamic buffet or a warning from a  stall warning device if equipped with one. A small increase in  AOA may result in an impending stall, which increases the risk  of an actual stall. In most normal flight operations the airplane  would not be flown close to the stall-warning AOA or critical  AOA, but because the airplane is flown at higher AOAs, and  thus reduced speeds in the takeoff/departure and approach/ landing phases of flight, learning to fly at reduced airspeeds is  essential. In these phases of flight, the airplane’s close proximity  to the ground would make loss of control catastrophic;  therefore, the pilot must be proficient in slow flight.  The objective of maneuvering in slow flight is to understand  the flight characteristics and how the airplane’s flight controls  feel near its aerodynamic buffet or stall-warning. It also  helps to develop the pilot’s recognition of how the airplane  feels, sounds, and looks when a stall is impending. These  characteristics include, degraded response to control inputs  and difficulty maintaining altitude. Practicing slow flight will  help pilots recognize an imminent stall not only from the feel  of the controls, but also from visual cues, aural indications,  and instrument indications.  For pilot training and testing purposes, slow flight includes  two main elements: It is also important to note that an airplane flying below  L/D$_{MAX}$, exhibits a characteristic known as “speed instability”  and the airspeed will continue to decay without appropriate  pilot action. For example, if the airplane is disturbed by  turbulence and the airspeed decreases, the airspeed may  continue to decrease without the appropriate pilot action of  reducing the AOA or adding power.  [Figure 4-2] Slow flight should be introduced with the airspeed  sufficiently above the stall to permit safe maneuvering, but  close enough to the stall warning for the pilot to experience  the characteristics of flight at a very low airspeed. One way  to determine the target airspeed is to slow the airplane to the  stall warning when in the desired slow flight configuration,  pitch the nose down slightly to eliminate the stall warning,  add power to maintain altitude and note the airspeed.  When practicing slow flight, a pilot learns to divide attention  between aircraft control and other demands. How the airplane  When flying above minimum drag speed (L/D$_{MAX}$), even  a small increase in power will increase the speed of the  airplane. When flying at speeds below L/D$_{MAX}$, also referred  to as flying on the back side of the power curve, larger  inputs in power or reducing the AOA will be required for  the airplane to be able to accelerate. Since slow flight will be  performed well below L/D$_{MAX}$, the pilot must be aware that  large power inputs or a reduction in AOA will be required  to prevent the aircraft from decelerating. It is important to  note that when flying on the backside of the power curve,  as the AOA increases toward the critical AOA and the  airplane’s speed continues to decrease, small changes in  the pitch control result in disproportionally large changes in  induced drag and therefore changes in airspeed. As a result,  pitch becomes a more effective control of airspeed when  flying below L/D$_{MAX}$ and power is an effective control of  the altitude profile (i.e., climbs, descents, or level flight) Slow Flight Figure 4-2.  Angle-of-attack in degrees. 4-3 1.  Slowing to, maneuvering at, and recovering from  an airspeed at which the airplane is still capable of  maintaining controlled flight without activating the  stall warning—5 to 10 knots above the 1G stall speed  is a good target; and 2.  Performing slow flight in configurations appropriate  to takeoffs, climbs, descents, approaches to landing,  and go-arounds. Coefficient of lift C L$_{MAX}$ Coefficien of drag Lift to drag ratio L/ D$_{MAX}$ 18 16 14 12 10 8 6 4 2 0 .200 .180 .160 .140 .120 .100 .080 .060 .040 .020 0 Coefficient of drag (C D ) Lift/drag Angle of attack in degrees Separation stall 0° 2° 4° 6° 8° 10° 12° 14° 16° 18° 20° 22° 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 C L