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You've probably seen the small wedge-shaped strips on the front of your wings. They're called stall strips, and they're a pretty important part of an aircraft's design.
Stall strips create a more controlled stall across the wing, and they also increase wing buffeting before a full stall happens. So how do they work? It starts with something called the stagnation point.
When air approaches the leading edge of your wing, it divides. Some air flows on top of the wing, and some flows under it. The spot where the airflow splits is called the "stagnation point."
When your wing is at a low angle-of-attack (AOA), the stagnation point is on the leading edge, and when your wing is at a high angle of attack, the stagnation point moves below the leading edge.
Stall strips start working when your wing is at a high angle-of-attack. Because the stagnation point is on the underside of the wing at a high AOA, air flows up and around the leading edge, making its way over the top of the wing. With no stall strip, airflow can stay attached to the wing when this happens.
But since stall strips are sharp, airflow can't stay attached as easily, and it starts to separate from the wing before your wing reaches the critical AOA. The result? An "early" stall, directly behind the stall strip.
Stall strips are typically fairly small, and placed near the root of the wing (next to the fuselage). The idea behind their location is simple: you want your wing to begin stalling in a desirable location, which is typically the root. When the root of the wing stalls first, you still have aileron roll control in the stall's early stages. (Wing washout also contributes to this, but we covered that in another article).
There's an added benefit to stall strips: wing buffeting. Because the small section of wing directly behind the strip stalls before the rest of the wing, you'll feel a buffet from airflow separation several knots before you actually stall. It's a good addition to your stall warning horn, because it helps you feel the stall approaching.
The next time you head out the airport, check out the leading edges of the airplanes on the ramp. You'll find almost every kind of aircraft with stall strips, from training airplanes to corporate jets. When you see them, you'll know exactly what they're used for.
Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at email@example.com.