What a “Stall” is in aerodynamics and why it’s an emergency for airplanes
In: 7
Take a spoon and open the tap,
Do what you see in this video, you can just hold the spoon with your hand https://youtu.be/AvLwqRCbGKY
What you see is the Coanda effect, air on top of a wing does the same as water on the back of the spoon.
A stall is when the angle between the wing and the air direction before the wing (angle of attack) is too big so -the air stops to follow the wing profile-.
Try with the spoon. You will see that as long as water sticks to the spoon, it will affect the spoon, as soon as it separates, the spoon is no more affected by the water.
With a wing stall you get two big problems:
1 you completely lose wing lift, you fall.
2 a deep stall may affect your ailerons, and trying using ailerons in a stall will make the wing you want to lift to stall even more, and opposite, may recover the wing you wanted to lower, so that wing will stop stalling and lift up. The result is that you left or right wing drops more than the other wing and you will spiral down uncontrollably.
The only way to get out of a stall is to change the angle of attack, usually by a dive nose down. Now, you can imagine that going nose down until the stall ends is already scary, but if the stall happens close to ground, you are left with the choice to 1fall to the ground, 2nose down to the ground, or if you use the alieron or you are already in a turn: 3you will spiral into the ground.
Good news: planes are fitted with stall detectors, a trained pilot will prevent the stall by reacting to the warning. In training, pilots also purposely stall the plane and recover it to practice with how it feels and how to do it best. Stall is one of the basic bricks to build a pilot. Also, pilots know their plane performances and fly always a good margin away from stall conditions.
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