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In fluid dynamics, angle of attack (AOA, α, or ) is 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. [1] Angle of attack is the angle between the body's reference line and the oncoming flow.
In aerodynamics, hysteresis can be observed when decreasing the angle of attack of a wing after stall, regarding the lift and drag coefficients. The angle of attack at which the flow on top of the wing reattaches is generally lower than the angle of attack at which the flow separates during the increase of the angle of attack. [8]
[1] [2] Unlike fixed-wing aircraft, of which the stall occurs at relatively low flight speed, the dynamic stall on a helicopter rotor emerges at high airspeeds or/and during manoeuvres with high load factors of helicopters, when the angle of attack(AOA) of blade elements varies intensively due to time-dependent blade flapping, cyclic pitch and ...
An angle-of-attack indicator for light aircraft, the "AlphaSystemsAOA" and a nearly identical "lift reserve indicator", are both pressure-differential instruments that display margin above stall and/or angle of attack on an instantaneous, continuous readout. The General Technics CYA-100 displays true angle of attack via a magnetically coupled vane.
Spins are characterized by high angle of attack, an airspeed below the stall on at least one wing and a shallow descent. Recovery and avoiding a crash may require a specific and counter-intuitive set of actions. A spin differs from a spiral dive, in which neither wing is stalled and which is characterized by a low angle of attack and high ...
The sessile drop contact angle is measured by a contact angle goniometer using an optical subsystem to capture the profile of a pure liquid on a solid substrate. The angle formed between the liquid–solid interface and the liquid–vapor interface is the contact angle. Older systems used a microscope optical system with a back light.
Dissymmetry of lift is also countered by cyclic feathering, i.e. a change to the angle of incidence of the rotor blades as they rotate around the hub. There is a limit to which angle of attack changes can counter dissymmetry of lift. This imposes a limit on the maximum forward speed of the helicopter.
Aircraft sideslip angle. A slip is an aerodynamic state where an aircraft is moving somewhat sideways as well as forward relative to the oncoming airflow or relative wind.In other words, for a conventional aircraft, the nose will be pointing in the opposite direction to the bank of the wing(s).