Does the pressure at the static ports drop as the aircraft's speed increases?

The name of the pictureThe name of the pictureThe name of the pictureClash Royale CLAN TAG#URR8PPP











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This answer by Tyler Durden explains what static ports are and how they work:




The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much [...]




Currently, the answer has a comment by Zeiss Ikon which states:




In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) [...]




Is this true? If I'm flying at a constant altitude, will the pressure at the static ports decrease as I speed up and increase as I slow down?



If so, does the altimeter have a mechanism for compensating for this?










share|improve this question

























    up vote
    2
    down vote

    favorite












    This answer by Tyler Durden explains what static ports are and how they work:




    The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much [...]




    Currently, the answer has a comment by Zeiss Ikon which states:




    In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) [...]




    Is this true? If I'm flying at a constant altitude, will the pressure at the static ports decrease as I speed up and increase as I slow down?



    If so, does the altimeter have a mechanism for compensating for this?










    share|improve this question























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      This answer by Tyler Durden explains what static ports are and how they work:




      The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much [...]




      Currently, the answer has a comment by Zeiss Ikon which states:




      In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) [...]




      Is this true? If I'm flying at a constant altitude, will the pressure at the static ports decrease as I speed up and increase as I slow down?



      If so, does the altimeter have a mechanism for compensating for this?










      share|improve this question













      This answer by Tyler Durden explains what static ports are and how they work:




      The "static ports" allow air into the instrument to provide the input for the air pressure on the side of the aircraft. They are called "static" ports because in general they take in air at the ambient pressure which does not change very much [...]




      Currently, the answer has a comment by Zeiss Ikon which states:




      In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) [...]




      Is this true? If I'm flying at a constant altitude, will the pressure at the static ports decrease as I speed up and increase as I slow down?



      If so, does the altimeter have a mechanism for compensating for this?







      aerodynamics aircraft-physics pitot-static






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      share|improve this question










      asked 5 hours ago









      Tanner Swett

      1,099720




      1,099720




















          3 Answers
          3






          active

          oldest

          votes

















          up vote
          3
          down vote













          The comment:




          In fact, the pressure at the static ports will drop as the aircraft's
          speed increases (Bernoulli principle)




          is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:



          Static Pressure distribution on a fuselage.



          [Source: NASA]



          From the same report:




          Zero static pressure error on the fuselage exists at locations 2
          through 5. One of these locations is chosen for the static port. To
          keep pneumatic lag small, the static port is normally located as near
          the airdata instruments as possible (or the other way around). (To
          determine this location precisely, several static ports are made in
          this area. The optimum location is then selected as a result of
          comparing the various ports with a reference source, such as a
          trailing cone.) This pressure distribution changes with flight
          condition, so a calibration over the flight envelope may still be
          necessary.

          ...

          Even with the selection of the best static port position, some
          pressure errors will remain, and these errors must be determined in
          flight. The difference between the locally measured static pressure
          and the ambient static pressure, which is dependent upon angle of
          attack, airspeed, and aircraft configuration, is called position
          error.




          Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.






          share|improve this answer




















          • This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
            – Tanner Swett
            2 hours ago










          • Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
            – selectstriker2
            15 mins ago










          • Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
            – selectstriker2
            9 mins ago

















          up vote
          1
          down vote













          There is a difference between the true static pressure and the measured static pressure, which varies with angle of attack, but it is generally quite small. This is called Position Error. The placement of the static port is at the spot where the Position Error is the smallest through the airplane's normal operating attitudes. Position Error has to be small enough to keep the measured pressure altitude within 30 feet of true pressure altitude, and an error of not more than 3% or +/- 5kt on airspeed.






          share|improve this answer
















          • 1




            I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
            – GdD
            4 hours ago

















          up vote
          1
          down vote













          For a basic shape, such as a sphere, the pressure on the side of the object would indeed decrease due to Bernoulli's principle. However, as Gerry's answer points out, a plane is much more complex aerodynamically. The graph in Gerry's answer shows how pressure decreases at some points, increases at others and is unchanged in some.



          For indicated airspeed, a small error could be adjusted out easily enough. After all, the pressure difference would still be mostly linear in relation to air speed, so just calibrating the scale on the airspeed indicator would suffice.



          But the static ports are also used for the altimeter. For this reason there is a strong incentive to find a location that minimizes the so called position error in the static pressure measurement. Otherwise when indicated airspeed changes, the indicated altitude could also change, which would be much more difficult to compensate for.



          So in summary: no, for a well-designed plane, the speed-induced pressure change at static ports will be minimal.






          share|improve this answer




















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            3 Answers
            3






            active

            oldest

            votes








            3 Answers
            3






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            3
            down vote













            The comment:




            In fact, the pressure at the static ports will drop as the aircraft's
            speed increases (Bernoulli principle)




            is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:



            Static Pressure distribution on a fuselage.



            [Source: NASA]



            From the same report:




            Zero static pressure error on the fuselage exists at locations 2
            through 5. One of these locations is chosen for the static port. To
            keep pneumatic lag small, the static port is normally located as near
            the airdata instruments as possible (or the other way around). (To
            determine this location precisely, several static ports are made in
            this area. The optimum location is then selected as a result of
            comparing the various ports with a reference source, such as a
            trailing cone.) This pressure distribution changes with flight
            condition, so a calibration over the flight envelope may still be
            necessary.

            ...

            Even with the selection of the best static port position, some
            pressure errors will remain, and these errors must be determined in
            flight. The difference between the locally measured static pressure
            and the ambient static pressure, which is dependent upon angle of
            attack, airspeed, and aircraft configuration, is called position
            error.




            Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.






            share|improve this answer




















            • This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
              – Tanner Swett
              2 hours ago










            • Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
              – selectstriker2
              15 mins ago










            • Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
              – selectstriker2
              9 mins ago














            up vote
            3
            down vote













            The comment:




            In fact, the pressure at the static ports will drop as the aircraft's
            speed increases (Bernoulli principle)




            is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:



            Static Pressure distribution on a fuselage.



            [Source: NASA]



            From the same report:




            Zero static pressure error on the fuselage exists at locations 2
            through 5. One of these locations is chosen for the static port. To
            keep pneumatic lag small, the static port is normally located as near
            the airdata instruments as possible (or the other way around). (To
            determine this location precisely, several static ports are made in
            this area. The optimum location is then selected as a result of
            comparing the various ports with a reference source, such as a
            trailing cone.) This pressure distribution changes with flight
            condition, so a calibration over the flight envelope may still be
            necessary.

            ...

            Even with the selection of the best static port position, some
            pressure errors will remain, and these errors must be determined in
            flight. The difference between the locally measured static pressure
            and the ambient static pressure, which is dependent upon angle of
            attack, airspeed, and aircraft configuration, is called position
            error.




            Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.






            share|improve this answer




















            • This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
              – Tanner Swett
              2 hours ago










            • Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
              – selectstriker2
              15 mins ago










            • Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
              – selectstriker2
              9 mins ago












            up vote
            3
            down vote










            up vote
            3
            down vote









            The comment:




            In fact, the pressure at the static ports will drop as the aircraft's
            speed increases (Bernoulli principle)




            is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:



            Static Pressure distribution on a fuselage.



            [Source: NASA]



            From the same report:




            Zero static pressure error on the fuselage exists at locations 2
            through 5. One of these locations is chosen for the static port. To
            keep pneumatic lag small, the static port is normally located as near
            the airdata instruments as possible (or the other way around). (To
            determine this location precisely, several static ports are made in
            this area. The optimum location is then selected as a result of
            comparing the various ports with a reference source, such as a
            trailing cone.) This pressure distribution changes with flight
            condition, so a calibration over the flight envelope may still be
            necessary.

            ...

            Even with the selection of the best static port position, some
            pressure errors will remain, and these errors must be determined in
            flight. The difference between the locally measured static pressure
            and the ambient static pressure, which is dependent upon angle of
            attack, airspeed, and aircraft configuration, is called position
            error.




            Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.






            share|improve this answer












            The comment:




            In fact, the pressure at the static ports will drop as the aircraft's
            speed increases (Bernoulli principle)




            is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316:



            Static Pressure distribution on a fuselage.



            [Source: NASA]



            From the same report:




            Zero static pressure error on the fuselage exists at locations 2
            through 5. One of these locations is chosen for the static port. To
            keep pneumatic lag small, the static port is normally located as near
            the airdata instruments as possible (or the other way around). (To
            determine this location precisely, several static ports are made in
            this area. The optimum location is then selected as a result of
            comparing the various ports with a reference source, such as a
            trailing cone.) This pressure distribution changes with flight
            condition, so a calibration over the flight envelope may still be
            necessary.

            ...

            Even with the selection of the best static port position, some
            pressure errors will remain, and these errors must be determined in
            flight. The difference between the locally measured static pressure
            and the ambient static pressure, which is dependent upon angle of
            attack, airspeed, and aircraft configuration, is called position
            error.




            Based on the measured position error, a Static Source Error Correction (SSEC) table is developed. The SSEC is loaded into the air data system when it is installed in the aircraft so that it can make the necessary corrections.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 2 hours ago









            Gerry

            9,45412845




            9,45412845











            • This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
              – Tanner Swett
              2 hours ago










            • Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
              – selectstriker2
              15 mins ago










            • Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
              – selectstriker2
              9 mins ago
















            • This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
              – Tanner Swett
              2 hours ago










            • Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
              – selectstriker2
              15 mins ago










            • Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
              – selectstriker2
              9 mins ago















            This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
            – Tanner Swett
            2 hours ago




            This is good to know! The last paragraph you quote states that position error "is dependent upon angle of attack, airspeed, and aircraft configuration"—so it does, in fact, have a dependency on airspeed. Does it depend on airspeed in a somewhat predictable way (such as "when airspeed increases, measured static pressure decreases", as Zeiss's comment suggested), or is it mostly unpredictable?
            – Tanner Swett
            2 hours ago












            Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
            – selectstriker2
            15 mins ago




            Yes, the correlation between measured airspeed and the adjustment required to the static port reading is what goes into the Static Source Error Correction table.
            – selectstriker2
            15 mins ago












            Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
            – selectstriker2
            9 mins ago




            Note that this requires the altimeter system to know the measured airspeed in order to compensate, so a stand alone altimeter will likely not adjust out any position error unless it has some way to get that from an airspeed source.
            – selectstriker2
            9 mins ago










            up vote
            1
            down vote













            There is a difference between the true static pressure and the measured static pressure, which varies with angle of attack, but it is generally quite small. This is called Position Error. The placement of the static port is at the spot where the Position Error is the smallest through the airplane's normal operating attitudes. Position Error has to be small enough to keep the measured pressure altitude within 30 feet of true pressure altitude, and an error of not more than 3% or +/- 5kt on airspeed.






            share|improve this answer
















            • 1




              I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
              – GdD
              4 hours ago














            up vote
            1
            down vote













            There is a difference between the true static pressure and the measured static pressure, which varies with angle of attack, but it is generally quite small. This is called Position Error. The placement of the static port is at the spot where the Position Error is the smallest through the airplane's normal operating attitudes. Position Error has to be small enough to keep the measured pressure altitude within 30 feet of true pressure altitude, and an error of not more than 3% or +/- 5kt on airspeed.






            share|improve this answer
















            • 1




              I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
              – GdD
              4 hours ago












            up vote
            1
            down vote










            up vote
            1
            down vote









            There is a difference between the true static pressure and the measured static pressure, which varies with angle of attack, but it is generally quite small. This is called Position Error. The placement of the static port is at the spot where the Position Error is the smallest through the airplane's normal operating attitudes. Position Error has to be small enough to keep the measured pressure altitude within 30 feet of true pressure altitude, and an error of not more than 3% or +/- 5kt on airspeed.






            share|improve this answer












            There is a difference between the true static pressure and the measured static pressure, which varies with angle of attack, but it is generally quite small. This is called Position Error. The placement of the static port is at the spot where the Position Error is the smallest through the airplane's normal operating attitudes. Position Error has to be small enough to keep the measured pressure altitude within 30 feet of true pressure altitude, and an error of not more than 3% or +/- 5kt on airspeed.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 4 hours ago









            John K

            10.1k1030




            10.1k1030







            • 1




              I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
              – GdD
              4 hours ago












            • 1




              I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
              – GdD
              4 hours ago







            1




            1




            I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
            – GdD
            4 hours ago




            I don't see how this answers the question @JohnK, the OP is asking about pressure dropping due to airspeed.
            – GdD
            4 hours ago










            up vote
            1
            down vote













            For a basic shape, such as a sphere, the pressure on the side of the object would indeed decrease due to Bernoulli's principle. However, as Gerry's answer points out, a plane is much more complex aerodynamically. The graph in Gerry's answer shows how pressure decreases at some points, increases at others and is unchanged in some.



            For indicated airspeed, a small error could be adjusted out easily enough. After all, the pressure difference would still be mostly linear in relation to air speed, so just calibrating the scale on the airspeed indicator would suffice.



            But the static ports are also used for the altimeter. For this reason there is a strong incentive to find a location that minimizes the so called position error in the static pressure measurement. Otherwise when indicated airspeed changes, the indicated altitude could also change, which would be much more difficult to compensate for.



            So in summary: no, for a well-designed plane, the speed-induced pressure change at static ports will be minimal.






            share|improve this answer
























              up vote
              1
              down vote













              For a basic shape, such as a sphere, the pressure on the side of the object would indeed decrease due to Bernoulli's principle. However, as Gerry's answer points out, a plane is much more complex aerodynamically. The graph in Gerry's answer shows how pressure decreases at some points, increases at others and is unchanged in some.



              For indicated airspeed, a small error could be adjusted out easily enough. After all, the pressure difference would still be mostly linear in relation to air speed, so just calibrating the scale on the airspeed indicator would suffice.



              But the static ports are also used for the altimeter. For this reason there is a strong incentive to find a location that minimizes the so called position error in the static pressure measurement. Otherwise when indicated airspeed changes, the indicated altitude could also change, which would be much more difficult to compensate for.



              So in summary: no, for a well-designed plane, the speed-induced pressure change at static ports will be minimal.






              share|improve this answer






















                up vote
                1
                down vote










                up vote
                1
                down vote









                For a basic shape, such as a sphere, the pressure on the side of the object would indeed decrease due to Bernoulli's principle. However, as Gerry's answer points out, a plane is much more complex aerodynamically. The graph in Gerry's answer shows how pressure decreases at some points, increases at others and is unchanged in some.



                For indicated airspeed, a small error could be adjusted out easily enough. After all, the pressure difference would still be mostly linear in relation to air speed, so just calibrating the scale on the airspeed indicator would suffice.



                But the static ports are also used for the altimeter. For this reason there is a strong incentive to find a location that minimizes the so called position error in the static pressure measurement. Otherwise when indicated airspeed changes, the indicated altitude could also change, which would be much more difficult to compensate for.



                So in summary: no, for a well-designed plane, the speed-induced pressure change at static ports will be minimal.






                share|improve this answer












                For a basic shape, such as a sphere, the pressure on the side of the object would indeed decrease due to Bernoulli's principle. However, as Gerry's answer points out, a plane is much more complex aerodynamically. The graph in Gerry's answer shows how pressure decreases at some points, increases at others and is unchanged in some.



                For indicated airspeed, a small error could be adjusted out easily enough. After all, the pressure difference would still be mostly linear in relation to air speed, so just calibrating the scale on the airspeed indicator would suffice.



                But the static ports are also used for the altimeter. For this reason there is a strong incentive to find a location that minimizes the so called position error in the static pressure measurement. Otherwise when indicated airspeed changes, the indicated altitude could also change, which would be much more difficult to compensate for.



                So in summary: no, for a well-designed plane, the speed-induced pressure change at static ports will be minimal.







                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 12 mins ago









                jpa

                1914




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