Editing Angle of attack (section)

==Critical angle of attack==
The '''critical angle of attack''' is the angle of attack which produces the maximum lift coefficient. This is also called the "[[Stall (fluid dynamics)|stall]] angle of attack". Below the critical angle of attack, as the angle of attack decreases, the lift coefficient decreases. Conversely, above the critical angle of attack, as the angle of attack increases, the air begins to flow less smoothly over the upper surface of the [[airfoil]] and begins to separate from the upper surface.  On most airfoil shapes, as the angle of attack increases, the upper surface separation point of the flow moves from the trailing edge towards the leading edge.  At the critical angle of attack, upper surface flow is more separated and the airfoil or wing is producing its maximum lift coefficient. As the angle of attack increases further, the upper surface flow becomes more fully separated and the lift coefficient reduces further.<ref name="nasa-lc" />

Above this critical angle of attack, the aircraft is said to be in a stall. A fixed-wing aircraft by definition is stalled at or above the critical angle of attack rather than at or below a particular [[airspeed]].  The airspeed at which the aircraft stalls varies with the weight of the aircraft, the [[load factor (aeronautics)|load factor]], the center of gravity of the aircraft and other factors. However, the aircraft normally stalls at the same critical angle of attack, unless [[icing conditions]] prevail. The critical or stalling angle of attack is typically around 15° - 18° for many airfoils.

Some aircraft are equipped with a built-in flight computer that automatically prevents the aircraft from increasing the angle of attack any further when a maximum angle of attack is reached, regardless of pilot input. This is called the 'angle of attack limiter' or 'alpha limiter'.  Modern airliners that have fly-by-wire technology avoid the critical angle of attack by means of software in the computer systems that govern the flight control surfaces.<ref>{{Cite web|title=Fly-by-Wire Systems Enable Safer, More Efficient Flight {{!}} NASA Spinoff|url=https://spinoff.nasa.gov/Spinoff2011/t_5.html|access-date=2022-01-04|website=spinoff.nasa.gov}}</ref>

In takeoff and landing operations from short runways ([[STOL]]), such as Naval Aircraft Carrier operations and [[STOL]] backcountry flying, aircraft may be equipped with the angle of attack or [[Airspeed indicator#Angle of attack and Lift Reserve Indicators|Lift Reserve Indicators]].  These indicators measure the angle of attack (AOA) or the Potential of Wing Lift (POWL, or Lift Reserve) directly and help the pilot fly close to the stalling point with greater precision. STOL operations require the aircraft to be able to operate close to the critical angle of attack during landings and at the best angle of climb during takeoffs.  Angle of attack indicators are used by pilots for maximum performance during these maneuvers, since airspeed information is only indirectly related to stall behavior.