Three Contributions to Angle of Attack

　

As mentioned earlier, it is difficult to directly perceive angle of attack. Fortunately, there are three other quantities that can be perceived, and together they determine the angle of attack. They are:

•Pitch attitude, which is defined to be the angle that the fuselage makes relative to the horizontal.

•Angle of climb, which is just the angle between the flight path and the horizontal.

•Angle of incidence, which is the angle at which the wings are attached to the fuselage.

These quantities are related to the angle of attack by a very simple formula

                 Pitch Attitude + Incidence = Angle of Climb + Angle of Attack

This relationship is illustrated in figure 2.2. Perhaps the simplest case is straight and level flight at cruise airspeed. In this case, the pitch attitude is zero, the angle of climb is zero, and the angle of attack is equal to the angle of incidence..

Figure 2.2: Pitch + Incidence = Climb + Attack


Extending the flaps has the effect of increasing the incidence by several degrees. You need to be always aware of what flap setting you are using, and to recognize the distinction between ``pitch attitude'' and ``pitch attitude plus incidence''. For any given flap setting, you can take the incidence to be constant, whereupon angle of attack depends only on pitch attitude and direction of flight.

　

　

Next page -Making Changes in Angle of Attack