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Static Pressure

  • jukzizy
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jukzizy created the topic: Static Pressure

Does angle of attack affects the static pressure?

What will happen to static,dynamic&velocity if angle of attack increased?
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bobtait replied the topic: Static Pressure

No. As the name implies, static pressure is the pressure of the stationary air that is remote from the aerofoil. It is the pressure the air would have if you removed the aerofoil altogether. As the speed and angle of attack of a moving aerofoil change, the local pressure distribution across the surfaces of the aerofoil change. That has no effect on the static air remote from the aerofoil.

It is those changes in pressure distribution across the aerofoil surfaces that give rise to the forces of lift and drag.

Dynamic pressure is really the result of the speed of the aerofoil and the density of the static air. To put it simply, it is the force of 'wind'.
If you increase the speed of the aerofoil at the same angle of attack, the force of the wind will increase so lift and drag will increase.

If you increase the angle of attack at the same speed, lift and drag will increase up to the stalling angle. If the stalling angle is exceed, lift will begin to decrease and drag will continue to increase. It's all the result of those changes in local pressure across the aerofoil surfaces.
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Carello replied the topic: Static Pressure

This post raises a question that has always evaded my understanding.

If we were to take Bernoulli's theorem (below) at face value, an increase in speed should result in a decrease in static pressure as measured at the static port. This in turn should result in an erroneous increase in altitude as measure by the altimeter as speed increase.

I've always assumed the error to be minor and of no significance to typical GA aircraft.

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jukzizy replied the topic: Static Pressure

Thanks mate..I was asking because I got a question that I'm not sure about it..

As AOA increases up to the stalling angle static preasure

a) increases at the upper surface and decreases on the lower surface of the wings

b) decreases at the upper surface and increase on the lower surface of the wings

I got stuck with these question
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Carello replied the topic: Static Pressure

Here is a video that will answer your question.
Red indicates a higher static pressure and blue indicates a lower static pressure.

Ignore the end of the video

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bobtait replied the topic: Static Pressure

The fact that the airflow is flowing across the static port does indeed mean there would be an error in reading the 'true' static pressure in the air remote from the aircraft. The error is quite small and it can be reduced further by putting a lot of thought into the position and shape of the static port. Because the pitot is much more obvious to the eye, it is easy to forget the vital importance of the static port. An incorrect static reading would induce errors in all three pressure instruments.
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