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Does the pressure at the static ports drop as the aircraft's speed increases?
Clash Royale CLAN TAG#URR8PPP
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?
aerodynamics aircraft-physics pitot-static
asked 5 hours ago
Tanner Swett
1,099720
add a comment |Â
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?
aerodynamics aircraft-physics pitot-static
asked 5 hours ago
Tanner Swett
1,099720
add a comment |Â
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?
aerodynamics aircraft-physics pitot-static
asked 5 hours ago
Tanner Swett
1,099720
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
aerodynamics aircraft-physics pitot-static
asked 5 hours ago
Tanner Swett
1,099720
asked 5 hours ago
Tanner Swett
1,099720
asked 5 hours ago
Tanner Swett
1,099720
asked 5 hours ago
Tanner Swett
1,099720
asked 5 hours ago
Tanner Swett
1,099720
1,099720
add a comment |Â
add a comment |Â
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:
[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.
answered 2 hours ago
Gerry
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
add a comment |Â
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.
answered 4 hours ago
John K
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
add a comment |Â
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.
answered 12 mins ago
jpa
1914
add a comment |Â
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:
[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.
answered 2 hours ago
Gerry
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
add a comment |Â
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:
[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.
answered 2 hours ago
Gerry
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
add a comment |Â
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:
[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.
answered 2 hours ago
Gerry
9,45412845
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:
[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.
answered 2 hours ago
Gerry
9,45412845
answered 2 hours ago
Gerry
9,45412845
answered 2 hours ago
Gerry
9,45412845
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
add a comment |Â
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
add a comment |Â
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.
answered 4 hours ago
John K
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
add a comment |Â
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.
answered 4 hours ago
John K
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
add a comment |Â
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.
answered 4 hours ago
John K
10.1k1030
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.
answered 4 hours ago
John K
10.1k1030
answered 4 hours ago
John K
10.1k1030
answered 4 hours ago
John K
10.1k1030
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
add a comment |Â
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
add a comment |Â
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.
answered 12 mins ago
jpa
1914
add a comment |Â
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.
answered 12 mins ago
jpa
1914
add a comment |Â
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.
answered 12 mins ago
jpa
1914
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.
answered 12 mins ago
jpa
1914
answered 12 mins ago
jpa
1914
answered 12 mins ago
jpa
1914
answered 12 mins ago
jpa
1914
1914
add a comment |Â
add a comment |Â
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