Normal turn  Slipping turn  Skidding turn  Centrifugal  force equals  horizontal lift  Centrifugal  force less than  horizontal lift  Centrifugal force  greater than  horizontal lift  Vertical lift Vertical lift Vertical lift  Load Load Load  Centrifugal force  Horizontal  lift  Centrifugal force  Horizontal  lift  Centrifugal force  Horizontal  lift  Lift Lift Lift  Weight Weight Weight  Figure 5-35.  Normal, slipping, and skidding turns at a constant altitude.  the lift. Lift at this moment is now greater than weight and  starts the aircraft climbing. After the flight path is stabilized  on the upward incline, the AOA and lift again revert to about  the level flight values.  If the climb is entered with no change in power setting, the  airspeed gradually diminishes because the thrust required  to maintain a given airspeed in level flight is insufficient to  maintain the same airspeed in a climb. When the flight path  is inclined upward, a component of the aircraft’s weight  acts in the same direction as, and parallel to, the total drag  of the aircraft, thereby increasing the total effective drag.  Consequently, the total effective drag is greater than the  power, and the airspeed decreases. The reduction in airspeed  gradually results in a corresponding decrease in drag until  the total drag (including the component of weight acting  in the same direction) equals the thrust.  [Figure 5-37]  Due  to momentum, the change in airspeed is gradual, varying  considerably with differences in aircraft size, weight, total  drag, and other factors. Consequently, the total effective drag  is greater than the thrust, and the airspeed decreases.  The thrust required for a stabilized climb equals drag plus a  percentage of weight dependent on the angle of climb. For  example, a 10° climb would require thrust to equal drag plus  17 percent of weight. To climb straight up would require  thrust to equal all of weight and drag. Therefore, the angle  of climb for climb performance is dependent on the amount  of excess thrust available to overcome a portion of weight.  Note that aircraft are able to sustain a climb due to excess  thrust. When the excess thrust is gone, the aircraft is no  longer able to climb. At this point, the aircraft has reached  its “absolute ceiling.”  a value lower than in straight-and-level flight at the same  power setting. Since the aircraft’s weight is acting not only  downward but rearward with drag while in a climb, additional  power is required to maintain the same airspeed as in level  flight. The amount of power depends on the angle of climb.  When the climb is established steep enough that there is  insufficient power available, a slower speed results.  As in climbs, the forces that act on the aircraft go through  definite changes when a descent is entered from straight­ and-level flight. For the following example, the aircraft  Generally, the forces of thrust and drag, and lift and weight,  again become balanced when the airspeed stabilizes but at  Figure 5-37.  Changes in speed during climb entry. Figure 5-36.  Changes in lift during climb entry.  5-24  Forces in Descents  L  L  L  L  Steady climb  normal lift  Climb entry increased lift  Level flight normal lift  W W W T  D  T  D  T  D  Steady climb forces balanced  constant speed  Climb entry drag greater than thrust speed slowing  Level flight forces balanced  constant speed  L  L  L 