Aeronautical Terms Defined
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The airfoil angle of attack is the angle between the chord line of an airfoil
and the direction of the relative wind. The angle of attack is a critical aspect
of aircraft performance, as it affects the lift generated by an airfoil and plays
a key role in determining an aircraft's stability and control.
The airfoil angle of attack can be either positive or negative, and each has
different effects on the lift generated by an airfoil. A positive angle of attack
refers to the angle between the chord line of an airfoil and the direction of the
relative wind when the airfoil is pitched upward. A negative angle of attack refers
to the angle when the airfoil is pitched downward.
In aircraft design, the angle of attack must be carefully considered to ensure
safe and efficient flight, taking into account the weight of the aircraft, the airspeed,
and the desired flight characteristics such as takeoff and landing performance,
cruise speed, and climb rate. The angle of attack can be adjusted by the pilot through
the control surfaces on the wing, such as flaps and slats, or through changes in
the pitch of the aircraft.
Positive Angle of Attack
A positive angle of attack results in lift generation as the air that flows over
the curved upper surface of the airfoil moves faster than the air that flows over
the flat lower surface, creating a pressure difference that lifts the airfoil. The
amount of lift generated is directly proportional to the angle of attack, up to
a certain critical angle where the air flow over the wing becomes disrupted and
results in a loss of lift, known as a stall.
Negative Angle of Attack
On the other hand, a negative angle of attack can result in a loss of lift and
increased drag. At high angles of attack, the flow separation over the airfoil can
lead to a stall, where the air flow becomes disrupted and results in a sudden drop
in lift. This can be dangerous for an aircraft, as it can result in a loss of control
and a potential crash.
Posted February 4, 2023