Angle of attack (AOA) is a term used in fluid dynamics and aerodynamics to describe the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving. In aerodynamics, AOA specifies the angle between the chord line of the wing of a fixed-wing aircraft and the vector representing the relative motion between the aircraft and the atmosphere. The angle of attack can be simply described as the difference between where a wing is pointing and where it is going.
An increase in angle of attack results in an increase in both lift and induced drag, up to a point. Too high an angle of attack (usually around 16 degrees) and the airflow across the upper surface of the aerofoil becomes detached, resulting in a loss of lift, otherwise known as a stall. If you reduce airspeed (thrust) and want to maintain your current altitude, the angle of attack must be increased. As the aircraft slows down, it will be necessary to continually increase the amount of backpressure exerted on the controls to maintain level flight.
It is important to note that AOA is sometimes confused with pitch angle or flight path angle. Pitch angle (attitude) is the angle between the longitudinal axis (where the airplane is pointing) and the horizon, while flight path angle is the angle between the airplanes flight path and the horizon.
