What are the static and dynamic stalls on the aircrafts wing? When would we encounter static and when dynamic one? What is the difference between them?
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2 Answers
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Static stall is what we typically think of, when we think of stall. Slowly increasing AOA and then loss of lift as the flow separates.
But pitch rate (rate of increase of AOA) has an impact too. At high pitch rates, the wing can go beyond normal stall AOA and still provide significant lift, but for just a short period of time. After that, the bottom falls out. This is dynamic stall.
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2$\begingroup$ yup, got my +1 now. Minor one, "google it" on SE often results in a catch 22 loop, as Google will likely show this question as one of the top results now, it likes stack exchange answers, so best to make answers as complete as possible. $\endgroup$– Notts90Commented Mar 29, 2019 at 21:37
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These may be regional terms, I have not heard of static vs dynamic stall, I am a pilot in the USA. Airplane flight (heavier than air, lifted mainly by reaction of wings not engine thrust.) is inherently dynamic and so a stall must be as well.
I assume the question is actually asking about a typical low speed stall compared to an accelerated stall? An accelerated stall occurs when the wing load is increased substantially above the airplane gross weight due to acceleration along the vertical axis(the airplane's vertical axis, not earth's); examples are pulling up sharply at cruise speed or while in a steep turn. Both types of stall happen at the same effective angle of attack but at different forward speeds.
Accelerated stalls can have a more sudden effect but generally recovery is also quick because the plane only needs to reduce the wing load; in a non-accelerated stall the forward speed is so slow that maximum lift is less than the weight of the airplane and some speed must be recovered before altitude can be maintained.
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3$\begingroup$ You are right, even a static stall is a bit dynamic. Maybe "quasi-static" would be a better word for it, but it is too long. Both the static and the accelerated stall are the same if entered with a slow speed decrease or load factor increase. At higher load factors, the asymmetry of the turn will make the accelerated stall differ more and more from the static stall. And a dynamic stall is yet another thing, as @MikeY correctly explains. This answer has more on this. $\endgroup$ Commented Mar 29, 2019 at 17:16