Pitot-Static System
Summary
TLDRThis script delves into the pitted static system, crucial for powering flight instruments like the airspeed indicator, altimeter, and vertical speed indicator. It explains how these instruments rely on air pressure principles, distinguishing between static, dynamic, and total pressures. The script also covers the components of the pitted static system, including the pitted tube and static port, their functions, potential errors, and correction measures, emphasizing the importance of accurate pressure measurement for safe flight operations.
Takeaways
- đ The pitted static system is crucial for providing information to three basic flight instruments: the airspeed indicator, altimeter, and vertical speed indicator.
- đ Basic flight instruments, often called the 'six pack,' include the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator.
- đ The pitted static system measures air pressure to power the airspeed indicator, altimeter, and vertical speed indicator, while the attitude, heading, and turn coordinator rely on gyroscopic principles.
- âïž Static pressure, also known as atmospheric pressure, is the pressure exerted by air on objects within the atmosphere and varies mainly with altitude.
- đ As altitude increases, static pressure decreases, which affects the readings of flight instruments that rely on air pressure measurements.
- đš Dynamic pressure is the pressure exerted by air on a moving object and is directly related to the speed of the aircraft and the air density.
- đą Total pressure, or pitot pressure, is the sum of static and dynamic pressures and is measured by the pitot tube to provide accurate airspeed readings.
- đ The pitot tube must be aligned with the aircraft's longitudinal axis and located in an area free from airflow interference to measure total pressure accurately.
- âïž Pitot tubes incorporate a heating system to prevent icing, which can cause errors in pressure measurement.
- đ§ Position errors can occur with the pitot tube during high angles of attack, affecting the accuracy of airspeed readings.
- đ The static port measures static pressure and is designed to prevent dynamic pressure from affecting its readings, but it can still be subject to position errors during skids or slides.
Q & A
What is the 'pitted static system' and why is it important for an aircraft?
-The pitted static system is a critical component in an aircraft that measures air pressure to power key flight instruments such as the airspeed indicator, altimeter, and vertical speed indicator. It is important because it provides essential information about the aircraft's speed, altitude, and vertical velocity, which are crucial for safe and effective flight operations.
What are the six basic flight instruments commonly referred to as the 'six pack'?
-The 'six pack' refers to the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator. These instruments provide vital information about the most important parameters for flying an airplane.
How do the airspeed indicator, altimeter, and vertical speed indicator operate?
-These instruments operate using air pressure. They measure different types of air pressure, such as static pressure, dynamic pressure, and total pressure, to provide readings on airspeed, altitude, and vertical velocity, respectively.
What is static pressure and how does it vary with altitude?
-Static pressure, also known as atmospheric pressure, is the pressure that air exerts on objects within the atmosphere. It is evenly distributed around all objects and is always present, regardless of whether the object is stationary or moving. Static pressure varies mainly with altitude; as altitude increases, the static pressure decreases because there is less air above exerting weight.
Can you explain the concept of dynamic pressure?
-Dynamic pressure is the pressure that air exerts on an object moving through it. It depends directly on the speed at which the aircraft is moving and the density of the air. As the aircraft's speed increases, so does the dynamic pressure, and vice versa.
What is total pressure, and how is it related to static and dynamic pressure?
-Total pressure, also known as pitot pressure, is the sum of static pressure and dynamic pressure. It corresponds to the pressure experienced by an aircraft moving through the air, combining both the pressure from the air's weight (static) and the pressure from the air's resistance to the aircraft's motion (dynamic).
What is the purpose of the pitot tube in the pitted static system?
-The pitot tube measures the total pressure of the air as the plane moves through it. It is designed to accurately measure the pressure with which the air impacts the aircraft, combining both static and dynamic pressures.
Why is the pitot tube susceptible to icing, and how is this issue addressed?
-The pitot tube is susceptible to icing because it is an exposed object that experiences airflow. Icing can block the main intake hole and cause errors in pressure measurement. To address this, the pitot tube incorporates a heating system with electrical resistances that can melt any ice when activated from the cockpit.
What is a static port, and how does it measure static pressure?
-A static port is a small hole located on the side of the aircraft's fuselage that measures the air's static pressure or atmospheric pressure. It is designed to allow only static pressure to enter, not dynamic pressure, by being positioned in a way that captures the pressure exerted in all directions by the air.
What are position errors, and how do they affect the measurements from the pitot tube and static port?
-Position errors are inaccuracies in the measurements from the pitot tube and static port due to the aircraft's orientation or maneuvers. For example, at high angles of attack, the airflow may not be parallel to the pitot tube, causing slight errors in total pressure measurement. Similarly, during a skid or slide, part of the dynamic pressure may enter the static port, affecting the static pressure measurement.
Why are there alternate static sources in aircraft, and how do they work?
-Alternate static sources are additional static ports that can be activated if the primary static port gets blocked. They are usually located inside the cabin to avoid potential blockage due to external conditions. However, they measure slightly different static pressures from the exterior, and this difference is accounted for in the calibration tables used for flight instruments.
Outlines
đ« Introduction to Basic Flight Instruments and the Pitted Static System
This paragraph introduces the basic flight instruments, often referred to as the 'six pack,' which are essential for flying an aircraft. These include the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator. The paragraph emphasizes the importance of understanding not only what these instruments display but also how they operate. It then focuses on the pitted static system, which is responsible for measuring air pressure to power three of these instruments: the airspeed indicator, altimeter, and vertical speed indicator. The concept of different types of air pressureâstatic, dynamic, and total pressureâis introduced, setting the stage for a deeper exploration of how the pitted static system functions.
đȘïž Understanding Static, Dynamic, and Total Pressure
The paragraph delves into the definitions and characteristics of static, dynamic, and total pressure. Static pressure, also known as atmospheric pressure, is the force exerted by air on objects within the atmosphere and varies with altitude. Dynamic pressure is the pressure exerted on a moving object by the air it moves through, depending on the object's speed and the air's density. Total pressure, or pitted pressure, is the sum of static and dynamic pressures. The paragraph uses the analogy of a hand out a car window to illustrate how an object in motion experiences both static and dynamic pressures. It also explains the importance of measuring these pressures accurately for flight instruments and introduces the components of the pitted static system, including the pitted tube and static port.
âïž Components and Functions of the Pitted Static System
This paragraph provides a detailed look at the components of the pitted static system, focusing on the pitted tube and static port. The pitted tube measures total air pressure and is crucial for the airspeed indicator. It is typically located on the underside of wings or the front of the fuselage and must be aligned with the aircraft's longitudinal axis to avoid errors. The paragraph discusses the potential for icing and how the pitted tube's heating system addresses this issue. It also mentions the drain hole for water removal. The static port, on the other hand, measures static pressure and is located on the side of the fuselage to ensure accurate readings unaffected by dynamic pressure. The paragraph concludes with a discussion of position errors that can occur due to the aircraft's angle of attack or other factors, and how these are accounted for in correction tables provided in aircraft manuals.
Mindmap
Keywords
đĄPitted Static System
đĄBasic Flight Instruments
đĄAirspeed Indicator
đĄAltimeter
đĄStatic Pressure
đĄDynamic Pressure
đĄTotal Pressure
đĄPitot Tube
đĄStatic Port
đĄPosition Errors
đĄCross Check
Highlights
Introduction to the pitted static system, which is crucial for measuring air pressure to power basic flight instruments.
Explanation of the 'six pack' of basic flight instruments found in any aircraft: airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator.
The importance of understanding not just what the instruments display but also the principles of their operation.
Differentiation between the three types of air pressure: static, dynamic, and total (pitted) pressure.
Definition and explanation of static pressure as the atmospheric pressure exerted on objects within the atmosphere.
How static pressure varies with altitude and the effect of gravity on air molecule density.
Static pressure measurement in inches of mercury and its standard value at sea level.
Dynamic pressure as the pressure exerted by air on a moving object and its dependence on speed and air density.
Total pressure as the sum of static and dynamic pressures experienced by an aircraft in flight.
Description of the pitted static system components: pitted tube and static port.
Function of the pitted tube in measuring total air pressure and its placement considerations.
Challenges with pitted tube design, such as susceptibility to icing and solutions like heating systems.
The role of the static port in measuring atmospheric pressure and its location strategy to avoid dynamic pressure.
Position errors associated with the pitted tube and static port during high angles of attack or skidding.
Use of correction tables in aircraft manuals to account for measurement errors.
Importance of maintaining the pitted static system free from obstructions like dirt, insects, and water.
The presence of alternate static sources in the cockpit for redundancy and error minimization.
The practice of cross-checking instruments in multi-engine aircraft for accuracy and fault detection.
Conclusion summarizing the key points about the pitted static system and its importance in aviation.
Transcripts
today
we will talk about the pitted static
system which is a system that feeds some
of the basic flight instruments
the basic flight instruments are these
six instruments that we will find in any
aircraft
since they provide information about the
most important parameters to consider
when flying an airplane
due to the fact that there are six
instruments and they are in this
arrangement
they are sometimes referred to as the
six pack
here we can find the airspeed indicator
the attitude indicator
the altimeter the turn coordinator the
heading indicator
and the vertical speed indicator however
it is not enough just to know what
information these instruments give us
and how to interpret it but also to know
how they work
that is their principle of operation in
this case
three of these instruments specifically
the airspeed indicator
the altimeter and the vertical speed
indicator use air pressure to give their
readings
while on the other hand the attitude
indicator the heading indicator and the
turn coordinator
rely on the gyroscopic principles to
work
in this particular video we are going to
focus on the system that allows to
measure the air pressure to power these
three instruments
which is known as the pitted static
system
this system then measures the air
pressure and provides the information to
the relevant flight instruments
however it is not that simple since
there are different types of air
pressure
we have the static pressure the dynamic
pressure and the total pressure
so in order to understand how the pitted
static system works
first we must see the definition of each
of these pressures
let's start with the static pressure
this is also known as the atmospheric
pressure
and it is the pressure that the air
exerts on the objects
that are inside the atmosphere this
pressure is distributed evenly around
all objects as we can see in this image
and we must also say that this pressure
is present at all times
regardless of whether the object is
stationary or moving
now having seen these basic
characteristics we could ask ourselves
what does the static pressure depend on
well
the atmospheric pressure or static
pressure varies mainly with altitude but
let's see why
here we have the surface which in this
case we are going to assume is at sea
level
and here we have a column of air above
it that spreads up into the atmosphere
as we can see the air molecules are much
closer together at the bottom
near the surface while as we go up they
separate more and more
this has an explanation quite logical
air is made of matter
and matter has weight so the gravity of
the earth makes the column of air that
is above us
exert a certain weight which causes the
particles underneath to compress more
and stay closer together
this weight that we feel from the air
column that we have above
is precisely the static pressure and at
sea level
this static pressure is approximately 30
inches of mercury
to be exact under standard conditions
this is 2992 inches of mercury
however this value may vary slightly
depending on the weather conditions
in this order of ideas as we climb in
the atmosphere
we experience less static pressure for
example
if we climb a mountain in this case the
column of air that we have above
is shorter this means that there is less
air exerting weight on us
and therefore the static pressure is
reduced
in this example in this part of the
mountain we measure a pressure of 24
inches of mercury
which is obviously less than the
pressure at sea level
now if we continue climbing the mountain
we can see that the static pressure
decreases more and more
at the top for example we can measure a
pressure of 15 inches of mercury
just because we have less air above us
in general terms
we can say that the static pressure is
reduced by one inch of mercury for every
1000 feet of altitude increase
which means that an aircraft flying at
low altitudes
will experience a higher static pressure
than one that is flying higher
and this phenomenon not only occurs with
air but also with any other fluid
such as water here we have an example of
a swimming pool
as we can observe the way in which the
water molecules behave
is quite similar to air molecules in the
atmosphere
this means that a person who is swimming
on the surface
will experience less static pressure
than one who is swimming in the depth
and we can actually feel that change in
the static pressure of the water as we
submerge deeper
especially in the ears now
since we have seen and understood the
definition of static pressure
let's move on to the dynamic pressure
this is the pressure
that air exerts on an object moving
through it so when an object
impacts the air at a certain speed that
air exerts a certain pressure on that
object
which is called dynamic pressure and
this pressure is exerted in the opposite
direction to the trajectory of the
object as we can see in this example
this dynamic pressure
depends directly on the speed at which
the aircraft is moving
and also on the density of the air which
means
that as we fly faster we will have a
greater dynamic pressure
and vice versa for example if we fly at
80 knots through the air
we will have less dynamic pressure than
if we fly at 120 knots
having already seen then the definition
of dynamic pressure
let's now see the last one which is the
total pressure
also known as pitted pressure this
corresponds to the sum of the static
pressure plus the dynamic pressure
let's see this through an example let's
suppose we are traveling on the highway
and put one hand out the window in such
a way that the palm of the hand is
exposed to airflow
in this case the hand will experience
two pressures
we have the static pressure that is
always present regardless
if we are moving or not and we will also
experience dynamic pressure due to the
air flow against which we are moving
so in this case in the palm of your hand
you will experience the sums of both
the static pressure and the dynamic
pressure
and this is exactly what happens with an
aircraft that is moving through the air
it will experience both pressures
having already understood all these
definitions let's now see what the
pitted static system consists of
this in its simplest form is composed of
a pitted tube
and a static port that feed the three
instruments that we had mentioned
previously
the static port sends information to the
three instruments
the airspeed indicator the altimeter and
the vertical speed indicator
while the pivot tube only sends
information to the airspeed indicator
we will now see each of these sensors
more in detail
so let's start with the pitted tube this
is a small tube
that allows to measure the total
pressure of the air as the plane moves
through it
we can find it typically under the wings
on small aircraft
or in the front of the fuselage on
larger aircraft
the idea of the pitted tube is to
measure precisely the pressure with
which the air impacts the aircraft
and as we had already said with the
example of the hand
the impact pressure will combine the
static pressure and the dynamic pressure
meaning that the pitted tube measures
the total pressure
now in order to ensure that this pivot
tube performs an adequate measurement
it is important that it is aligned with
the longitudinal axis of the aircraft
as we can see in this example and also
it must be located in a part where the
airflow is free from any interference
because when an aircraft moves through
the air the airflow is altered by the
parts of the plane
like for example the propeller or the
wings and this interfering flow is not
suitable for measuring the total
pressure
therefore the pivot tube should be
located in such a way
that it is exposed to the proper airflow
in other words
the free air flow however a problem with
this design
is that being an object exposed to
airflow it is also susceptible to icing
which can block the main intake hole and
thus produce errors in pressure
measurement
so in order to solve this problem the
pitted tube incorporates a heating
system
which consists of electrical resistances
that when they are turned on from the
cockpit
make the tube heat up and melt any ice
that may clog the tube
the switch by which this heating system
is turned on
is usually marked as pitted heat and is
located near the light switches
now another component of the pitted tube
is the drain hole
this is a small hole in the back of the
tube that allows water to be removed
from the system
in case of flying in rainy conditions or
when melting ice using the pitted heat
as we can see this pitted tube is
designed to eliminate any possible error
in the pressure measurement
however there are some errors that
cannot be eliminated
the so-called position errors the thing
is
that when flying at high angles of
attack the airflow that hits the
aircraft
is not parallel to the longitudinal axis
which also means that it is not parallel
to
the pitted tube let's see this through
an example
when we fly at low angles of attack we
can see that the airflow is practically
aligned with the pitted tube
which allows obtaining a fairly adequate
total pressure measurement
however if we fly at a high angle of
attack we can see that the airflow is no
longer aligned with the pitted tube
this generates slight errors in the
measurement of total pressure
these errors are taken into account by
the manufacturer
in different configurations and speeds
to publish a correction table in the
aircraft manual
in this case this calibration table
corresponds to the airspeed indicator
since it is the only instrument to which
the pitted tube is connected
however we will see this a little more
in detail in the specific video about
the airspeed indicator
but in summary we must bear in mind that
we are going to have slight errors in
the indication of airspeed
when performing maneuvers such as slow
flight flying in gusty or turbulent
conditions
or when using flaps or slats with this
being said
we finish with the pitted tube cover it
is important to keep the system free of
dirt
insects and water so on the ground a
cover is used for this tube that is
normally brightly colored
and has the inscription removed before
flight just to remind the pilot to
remove this cover before flying
since otherwise there won't be any
airspeed reading
let's now move on with the other
component of the system
the static port this consists of a small
hole normally located on the side of the
fuselage and it measures the air static
pressure
or in other words the atmospheric
pressure
this static port is located in such a
way that only the static pressure is
allowed to enter
and not the dynamic pressure let's see
how this is achieved
normally this port is located on one
side of the fuselage
where a precise pressure value can be
obtained
as we know the static pressure is
exerted in all directions
while the dynamic pressure is exerted
only in the opposite direction to the
plane's path
with this design we can see that in the
static port only enters the static
pressure
and not the dynamic thus obtaining an
adequate measurement
however this design also has some
position errors
if the aircraft performs a skid or a
slide part of the dynamic pressure will
enter the static port
thus producing errors in the measurement
this occurs because in a skidder slide
the airflow not only hits the plane from
the front but slightly on one side
if we look at the previous example but
now making a skid
we can see the following the static
pressure will not change
however the dynamic pressure will now be
exerted
slightly against a fuselage where the
static port is located
which results in that part of that
dynamic pressure will enter the static
port
apart from this effect the use of flaps
slats
landing gear or other parts of the plane
can also cause changes in the local
static pressure
so this effect must also be taken into
account in the correction tables
in this case we have a correction table
for the air speed indicator
and other for the altimeter since as we
will remember
the static port provides information to
the three instruments
now as we will remember the pivot tube
had a heating system that prevented it
from being blocked by ice
so the question now is what happens if
the static port gets blocked
well for this case we have an alternate
static source
which is basically an additional static
port that is connected to the system
and can be activated by means of a
switch in the cockpit
however this alternate static port has a
peculiarity
and it is that it is normally located
inside the cabin to avoid a potential
blockage due to external conditions
in principle this is a pretty good
design however
the problem is that the static pressure
measured inside the cabin
is slightly different from the exterior
static pressure
so then we will have a slight error in
the measurement
this error is taken into account in the
calibration tables
however make sure that the calibration
table you are using
is for alternate static source instead
of the normal one
with this we have already seen all the
information about the static port
one thing to finish is that in
multi-engine aircraft
it is common to find two independent
pitted static systems
one for the pilot's instruments and the
other for the couplets instruments
this design is quite beneficial as it
reduces measurement errors and provides
redundancy
since the instruments on one side can be
compared with those on the other side
to check how much difference they have
or if some kind of problem is occurring
this procedure is known as a cross check
i hope the information presented in this
video has been useful
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thank you for watching
you
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