is descending at the same power as used in straight-and­ level flight.  As forward pressure is applied to the control yoke to initiate  the descent, the AOA is decreased momentarily. Initially,  the momentum of the aircraft causes the aircraft to briefly  continue along the same flight path. For this instant, the AOA  decreases causing the total lift to decrease. With weight now  being greater than lift, the aircraft begins to descend. At the  same time, the flight path goes from level to a descending  flight path. Do not confuse a reduction in lift with the inability  to generate sufficient lift to maintain level flight. The flight  path is being manipulated with available thrust in reserve  and with the elevator.  To descend at the same airspeed as used in straight-and­ level flight, the power must be reduced as the descent is  entered. Entering the descent, the component of weight  acting forward along the flight path increases as the angle  of descent increases and, conversely, when leveling off, the  component of weight acting along the flight path decreases  as the angle of descent decreases.  An aircraft stall results from a rapid decrease in lift caused by  the separation of airflow from the wing’s surface brought on  by exceeding the critical AOA. A stall can occur at any pitch  attitude or airspeed. Stalls are one of the most misunderstood  areas of aerodynamics because pilots often believe an airfoil  stops producing lift when it stalls. In a stall, the wing does  not totally stop producing lift. Rather, it cannot generate  adequate lift to sustain level flight.  Since the C$_{L}$ increases with an increase in AOA, at some  point the C$_{L}$ peaks and then begins to drop off. This peak is  called the C$_{L-MAX}$. The amount of lift the wing produces drops  dramatically after exceeding the C$_{L-MAX}$ or critical AOA, but  as stated above, it does not completely stop producing lift.  In most straight-wing aircraft, the wing is designed to stall  the wing root first. The wing root reaches its critical AOA  first making the stall progress outward toward the wingtip.  By having the wing root stall first, aileron effectiveness is  maintained at the wingtips, maintaining controllability of  the aircraft. Various design methods are used to achieve  the stalling of the wing root first. In one design, the wing is  “twisted” to a higher AOA at the wing root. Installing stall  strips on the first 20–25 percent of the wing’s leading edge  is another method to introduce a stall prematurely.  The wing never completely stops producing lift in a stalled  condition. If it did, the aircraft would fall to the Earth. Most  training aircraft are designed for the nose of the aircraft to  The stalling speed of an aircraft is also higher in a level turn  than in straight-and-level flight.  [Figure 5-39]  Centrifugal  force is added to the aircraft’s weight and the wing must  produce sufficient additional lift to counterbalance the load  imposed by the combination of centrifugal force and weight.  In a turn, the necessary additional lift is acquired by applying  back pressure to the elevator control. This increases the wing’s  Low speed is not necessary to produce a stall. The wing  can be brought into an excessive AOA at any speed. For  example, an aircraft is in a dive with an airspeed of 100  knots when the pilot pulls back sharply on the elevator  control.  [Figure 5-38]  Gravity and centrifugal force prevent  an immediate alteration of the flight path, but the aircraft’s  AOA changes abruptly from quite low to very high. Since  the flight path of the aircraft in relation to the oncoming air  determines the direction of the relative wind, the AOA is  suddenly increased, and the aircraft would reach the stalling  angle at a speed much greater than the normal stall speed.  One way the aircraft can be stalled in straight-and-level flight  by flying too slowly. As the airspeed decreases, the AOA  must be increased to retain the lift required for maintaining  altitude. The lower the airspeed becomes, the more the AOA  must be increased. Eventually, an AOA is reached that results  in the wing not producing enough lift to support the aircraft,  which then starts settling. If the airspeed is reduced further,  the aircraft stalls because the AOA has exceeded the critical  angle and the airflow over the wing is disrupted.  There are three flight situations in which the critical AOA is  most frequently exceeded: low speed, high speed, and turning.  The stalling speed of a particular aircraft is not a fixed value  for all flight situations, but a given aircraft always stalls at  the same AOA regardless of airspeed, weight, load factor, or  density altitude. Each aircraft has a particular AOA where the  airflow separates from the upper surface of the wing and the  stall occurs. This critical AOA varies from approximately 16°  to 20° depending on the aircraft’s design. But each aircraft  has only one specific AOA where the stall occurs.  drop during a stall, reducing the AOA and “unstalling” the  wing. The nose-down tendency is due to the CL being aft of  the CG. The CG range is very important when it comes to  stall recovery characteristics. If an aircraft is allowed to be  operated outside of the CG range, the pilot may have difficulty  recovering from a stall. The most critical CG violation would  occur when operating with a CG that exceeds the rear limit.  In this situation, a pilot may not be able to generate sufficient  force with the elevator to counteract the excess weight aft of  the CG. Without the ability to decrease the AOA, the aircraft  continues in a stalled condition until it contacts the ground.  Stalls  5-25 