critical angle of attack


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critical angle of attack

[′krid·ə·kəl ¦aŋ·gəl əv ə′tak]
(aerospace engineering)
The angle of attack of an airfoil at which the flow of air about the airfoil changes abruptly so that lift is sharply reduced and drag is sharply increased. Also known as stalling angle of attack.
References in periodicals archive ?
The NTSB determined the probable cause(s) of this accident to include: "The pilot's exceedance of the airplane's critical angle of attack during takeoff in high density altitude conditions, which resulted in an aerodynamic stall, loss of control, and subsequent impact with terrain."
If you feel shaking through the seat of your pants, the problem is probably the wing--as redesigned by ice--ap-proaching its critical angle of attack.
Not surprisingly, amber means you're "getting close" and red is the "danger zone." There is also an audible "Geiger counter" clicking heard through the headset that increases in speed the closer the SCx shows to the critical angle of attack. Aircraft owners can mount the indicator where they want to, but Bannon recommends placing it right in the center of the pilot's field of view so the display is constantly in line of sight, even as the pilot is looking out the windshield.
Figure 5 presents the dependence [bar.[i.sub.0]] = f([bar.i']), the analysis of which demonstrates that hysteresis by critical angle of attack occurs in different values of inability to calculate the flow at [bar.i'] > 1.
In fact, a classic loss-of-control accident sequence involves slow flight and/or low-level maneuvering to the point where the wing's critical angle of attack is exceeded.
Bottom line is that if there's ice on the wing, you're flying with an airfoil where no one knows the stall speed or, more correctly, the critical angle of attack. You may get a clue from the way the airplane feels.
If there were some way I could make a series of trips back in time to change things, one of the stops on my itinerary would be to somehow infiltrate the small cadre of early pilots and airplane designers to convince them to use a word other than "stall" to describe what happens when a wing exceeds its critical angle of attack. The word obviously has numerous other applications, and using it for this purpose has confounded student pilots and television news anchors ever since.
The NTSB determined the probable cause(s) of this accident to include: "The pilot's failure to maintain adequate airspeed after becoming distracted by the open baggage door while operating in the airport traffic pattern, which resulted in the airplane exceeding its critical angle of attack and experiencing an aerodynamic stall at a low altitude.
Exceeding the critical angle of attack is the one and only cause of a stall, and that critical AoA is always the same for any given airfoil.
The NTSB determined the probable cause(s) of this accident to be: "The pilot's improper go-around procedure that did not ensure that the airplane was at a safe airspeed before raising the flaps, which resulted in exceedance of the critical angle of attack and resulted in an accelerated aerodynamic stall and spin into terrain.
Changes to the airplane's aerodynamics usually will include lowering its critical angle of attack, beyond which a stall results.

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