Figure 2.6. Angle of Attack.
The angle of attack and angle of incidence are measured angles.
Angle of incidence (fixed-wing aircraft) is the angle between the airfoil chord line and the
longitudinal axis or other selected reference plane of the aircraft.
Angle of incidence (rotary-wing aircraft) is the angle between the chord line of a main or tail rotor
blade and the plane of rotation (tip path plane). It is usually referred to as the blade pitch angle. For
fixed airfoils, such as vertical fins or elevators, the angle of incidence is the angle between the chord line
of the airfoil and a selected reference plane of the helicopter.
As the angle of attack is increased, lift is also increased up to a certain angle. Beyond this angle
airflow can no longer follow the contour of the airfoil's upper surface, as shown in the sequences in
figure 2.7. After the burble point the airfoil goes full stall.
Figure 2.7. Stall Angle.