Pitot-Static System

Summary

This 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

• 😀 The pitted static system is crucial for providing information to three basic flight instruments: the airspeed indicator, altimeter, and vertical speed indicator.
• 📚 Basic flight instruments, often called the 'six pack,' include the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator.
• 🔍 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.
• ⚖️ Static pressure, also known as atmospheric pressure, is the pressure exerted by air on objects within the atmosphere and varies mainly with altitude.
• 📉 As altitude increases, static pressure decreases, which affects the readings of flight instruments that rely on air pressure measurements.
• 💨 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.
• 🔢 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.
• 🛠 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.
• ❄️ Pitot tubes incorporate a heating system to prevent icing, which can cause errors in pressure measurement.
• 🚧 Position errors can occur with the pitot tube during high angles of attack, affecting the accuracy of airspeed readings.
• 🔄 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

00:00

🛫 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 pressure—static, dynamic, and total pressure—is introduced, setting the stage for a deeper exploration of how the pitted static system functions.

05:00

🌪️ 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.

10:02

✈️ 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.

Keywords

💡Pitted Static System

The Pitted Static System is the focus of the video and refers to the mechanism that measures air pressure to power certain flight instruments. It is integral to the operation of the airspeed indicator, altimeter, and vertical speed indicator, which rely on air pressure readings. The script explains that this system is not as straightforward as it seems due to the different types of air pressure involved, making it central to understanding how aircraft measure and respond to changes in atmospheric conditions.

💡Basic Flight Instruments

Basic Flight Instruments are the six essential instruments found in any aircraft, often referred to as the 'six pack.' They include the airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator. The script emphasizes the importance of not only knowing how to interpret these instruments but also understanding their underlying principles of operation, which is crucial for safe flight navigation.

💡Airspeed Indicator

The Airspeed Indicator is one of the basic flight instruments that measures the speed of the aircraft relative to the air. It uses air pressure to provide readings, specifically dynamic pressure. The script explains that the pitted tube, a part of the pitted static system, sends information to the airspeed indicator, making it a critical component for pilots to monitor flight speed and ensure safe and controlled flight.

💡Altimeter

The Altimeter is a flight instrument that measures the aircraft's altitude above a reference level, typically mean sea level. It uses static pressure to provide an altitude reading. The script describes how the static port, another component of the pitted static system, feeds information to the altimeter, allowing pilots to be aware of their height in the atmosphere, which is vital for collision avoidance and navigation.

💡Static Pressure

Static Pressure, also known as atmospheric pressure, is the pressure exerted by the air on objects within the atmosphere. The script explains that it is constant regardless of whether an object is moving or stationary and varies primarily with altitude. This pressure is crucial for the operation of the altimeter and is measured by the static port in the pitted static system.

💡Dynamic Pressure

Dynamic Pressure is the pressure exerted by the air on a moving object, such as an aircraft, and is directly related to the aircraft's speed and the air's density. The script uses the example of a hand out of a car window to illustrate how dynamic pressure is the pressure felt due to the airflow against the direction of motion. It is a critical factor for the airspeed indicator to function correctly.

💡Total Pressure

Total Pressure, also referred to as pitot pressure, is the sum of static pressure and dynamic pressure. The script explains that the pitot tube measures total pressure, which is essential for calculating airspeed. It is a composite pressure that reflects both the force of the air due to its weight (static) and its motion (dynamic) relative to the aircraft.

💡Pitot Tube

The Pitot Tube is a component of the pitted static system that measures the total pressure of the air as the aircraft moves through it. The script describes its placement on the aircraft, typically under the wings or in front of the fuselage, and its importance in aligning with the longitudinal axis to avoid measurement errors. It also mentions the heating system to prevent blockage from ice, which is crucial for accurate airspeed readings.

💡Static Port

The Static Port is a small hole that measures static pressure and is part of the pitted static system. The script explains that it is designed to allow only static pressure to enter, ensuring accurate altitude readings for the altimeter. However, it also discusses the potential for position errors if the aircraft skids or slides, which can allow dynamic pressure to affect the measurement.

💡Position Errors

Position Errors refer to inaccuracies in the measurement of air pressure due to the aircraft's orientation or angle of attack. The script explains that when flying at high angles of attack, the airflow is not parallel to the pitot tube, leading to slight errors in total pressure measurement. Similarly, position errors can occur with the static port if the aircraft performs a skid or slide, allowing dynamic pressure to affect the static pressure measurement.

💡Cross Check

Cross Check is a procedure mentioned in the script where pilots compare the readings of flight instruments on one side of the aircraft with those on the other side. This is particularly relevant in multi-engine aircraft with independent pitted static systems for the pilot and co-pilot. The cross check helps to identify discrepancies and potential problems, ensuring the reliability of the flight instruments.

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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