Pitot Static System is hugely used in aviation sector. Even almost all modern aircrafts use this ancient technology to calculate their airspeed, altitude, and vertical speed.
The system is briefly but exquisitely presented in this slide.
a slideshow about the pitot static and gyroscopic instruments. this slideshow has review slides as well as stuff about the asi like the errors and other important things like that. I hope you find this
Airports Authority Of India:The Airports Authority of India (AAI) under the Ministry of Civil Aviation is responsible for creating, upgrading, maintaining and managing civil aviation infrastructure in India. It provides Air Traffic Management (ATM) services over Indian airspace and adjoining oceanic areas.
It manages a total of 125 airports, including 11 International Airports, 8 Custom Airports, 81 Domestic Airports and 25 Civil enclave at Military Airfields.
introduction:The Airports Authority of India provides air traffic services as per AAI Act 1995. These services are - air traffic control service, flight information service, and alerting service. In order to achieve the objectives of air traffic services there is a need to specify procedures necessary for the safety of air navigation for uniform application throughout India.
Powered Flight explained from First Principles. Starts with Sir Issac Newton's Laws of motion. Explains concepts of Weight, Lift, Drag and Thrust. Controlling the flight using concepts of Pitch, Roll & Yaw explained with illustrations.How this is explained with the help of Ailerons, Rudder and Elevators explained. Clear visuals provided.
Avionics Unit V Study Material
Air data quantities – Altitude, Air speed, Vertical speed, Mach Number, Total air temperature, Mach warning, Altitude warning – Auto pilot – Basic principles, Longitudinal and lateral auto pilot.
a slideshow about the pitot static and gyroscopic instruments. this slideshow has review slides as well as stuff about the asi like the errors and other important things like that. I hope you find this
Airports Authority Of India:The Airports Authority of India (AAI) under the Ministry of Civil Aviation is responsible for creating, upgrading, maintaining and managing civil aviation infrastructure in India. It provides Air Traffic Management (ATM) services over Indian airspace and adjoining oceanic areas.
It manages a total of 125 airports, including 11 International Airports, 8 Custom Airports, 81 Domestic Airports and 25 Civil enclave at Military Airfields.
introduction:The Airports Authority of India provides air traffic services as per AAI Act 1995. These services are - air traffic control service, flight information service, and alerting service. In order to achieve the objectives of air traffic services there is a need to specify procedures necessary for the safety of air navigation for uniform application throughout India.
Powered Flight explained from First Principles. Starts with Sir Issac Newton's Laws of motion. Explains concepts of Weight, Lift, Drag and Thrust. Controlling the flight using concepts of Pitch, Roll & Yaw explained with illustrations.How this is explained with the help of Ailerons, Rudder and Elevators explained. Clear visuals provided.
Avionics Unit V Study Material
Air data quantities – Altitude, Air speed, Vertical speed, Mach Number, Total air temperature, Mach warning, Altitude warning – Auto pilot – Basic principles, Longitudinal and lateral auto pilot.
AbstractGenerally, the wind tunnel experiment is used to gauge .docxbartholomeocoombs
Abstract
Generally, the wind tunnel experiment is used to gauge the drag and lift forces affecting an aircraft. The current experiment measured the drag and lift forces of a small wing at different angles of attacks with an increment of 2 degrees from -10. The results indicated a minimum and maximum lift coefficient of 0.14 and 0.65 respectively. Likewise, the maximum and minimum drag force was 0.24 and 0.05 respectively. On the calculation of the drag and lift coefficients, the stall angle occurred during the 12th angle of attack at a lift force of 0.38 and drag force of 0.17
Introduction
Generally, all atmospheric flying objects such as aircraft, ships, and vehicles need to undergo several Computational Fluid dynamics (CFD) simulations and wind tunnel tests in order to improve their designs. Accordingly lift and drag force tests are some of the most critical tests that such bodies go through. The phenomenon of Lift and drag is quite complicated and is hypothesized for better understanding by potential flow and boundary layer theory which has good agreements with experimental results. Generally, lift and drag forces are derived from two equations:
Lift Force FL= CL A V2/2
Drag force FD = CD A V2/2
Where, A is the projected area of the object, V is the freestream air velocity, ρ is the air density, and Cl and CD are the lift coefficients and drag coefficients respectively. Notably, the lift and drag of a wing is a function of multiple variables such as the angle of attack, airspeed, and cross-sectional geometry. An increase in the angle of attack raises the lift and drag up to a critical value upon which any increase leads to a sharp decrease in lift. Typically, this is referred to a stalling. Accordingly, this experiment measures the lift and drag of a model wing in order to determine its lift and drag coefficients at a specific speed.
Description of Work
In completing the experiment, three main pieces of equipment were used: the wind tunnel (see figure 1), pilot tube, and a small wing. Accordingly, the experiment was designed to gauge the lift and drag that were measured using the gauges. On the other hand, the pilot tube was used to measure the dynamic pressure. Typically, the pilot tube uses a manometer to measure pressure as air pushes the wing. Prior to beginning the experiment, the wing was mounted in the wind tunnel and the lift and scale readings confirmed to be zero. The wind tunnel was then adjusted for maximum velocity. The dynamic pressure was then measured changing the angle of attack with +/- 2 degrees after each measurement. This step was repeated until the stall angle was exceeded.
Figure 1. Wind Tunnel Device
Results and Discussion
Following the completion of the experiment, all the data was tabulated in excel for the purposes of calculating the lift coefficient and drag coefficient. Table 1 below summarizes the values for lift and drag coefficients for each angle of attack used in .
Advanced Anti surge Control System for Turbine Driven Centrifugal CompressorsArslan Ahmed Amin
Advanced Anti surge Control System for Turbine Driven Centrifugal Compressors
Please subscribe to my YouTube Channel for best training lectures:
https://www.youtube.com/channel/UCRkUJFOsyZG1E1LDWzUr_hw/playlists?view_as=subscriber
Preclusion of High and Low Pressure In Boiler by Using LABVIEWIJSRD
Pressure is an important physical parameter to be controlled in process boiler, heat exchanger, nuclear reactor and steam carrying pipeline. In the article the issue has been face in boiler operation due to pressure is handled. In boiler, the problem is due to maximum and minimum range of pressure. Due to the issues there is a chance to causes the hazop. To avoid such the problem the high and low pressure in boiler has to control. In the paper such the problem has sorted out by implementing ON-OFF control. Here the proposed control action for pressure control is implemented with the help of LabVIEW (Laboratory Virtual Instrument Engineering Workbench) software and NI ELVIS hardware. In the idea the boiler’s low range and high is monitored and controlled valve desirably. And also the high range and low range of pressure in the boiler is signified to plant operator by alarm signal.
Preclusion of High and Low Pressure In Boiler by Using LABVIEWIJSRD
Pressure is an important physical parameter to be controlled in process boiler, heat exchanger, nuclear reactor and steam carrying pipeline. In the article the issue has been face in boiler operation due to pressure is handled. In boiler, the problem is due to maximum and minimum range of pressure. Due to the issues there is a chance to causes the hazop. To avoid such the problem the high and low pressure in boiler has to control. In the paper such the problem has sorted out by implementing ON-OFF control. Here the proposed control action for pressure control is implemented with the help of LabVIEW (Laboratory Virtual Instrument Engineering Workbench) software and NI ELVIS hardware. In the idea the boiler’s low range and high is monitored and controlled valve desirably. And also the high range and low range of pressure in the boiler is signified to plant operator by alarm signal.
For Video Lecture of this presentation: https://youtu.be/8sMbl6pJpd0
The topics covered in this session are, Primary flight instruments: Altimeter, ASI (Airspeed Indicator ), VSI (vertical speed indicator) , Turn-bank indicator. The session is categorized into two portions namely, pitot-static system based and gyroscopic instrument based.
Attention! "Gate Aerospace Engineering aspirants", A virtual guide for gate aerospace engineering is provided in "Age of Aerospace" blog for helping you meticulously prepare for gate examination. Respective notes of individual subjects are provided as 'Embedded Google Docs' which are frequently updated. This comprehensive guide is intended to efficiently serve as an extensive collection of online resources for "GATE Aerospace Engineering" which can be accessed free of cost. Use the following link to access the study material
https://ageofaerospace.blogspot.com/p/gate-aerospace.html
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Fundamentals of Electric Drives and its applications.pptx
Pitot static system
1. May 24 , 2015
1
Pitot-Static System
Prepared and to be presented by
MD. ATAUL MAMUN
Bangladesh Airlines Training Center Biman
2. Objectives
May 24 , 2015
2
Topic Objectives:
To have idea on earth atmosphere and its impact on
instruments
To learn what is pitot-static system
To learn basic working principles of instruments that use
pitot-static system
To understand the limitations of the system
Bangladesh Airlines Training Center Biman
3. Introduction
May 24 , 2015
3
Within an aircraft the flight crews need to know airspeed,
aircraft altitude, vertical speed etc. for a safe flight.
They get these data from corresponding instruments (airspeed
indicator, altimeter, vertical speed indicator) in the cockpit.
The above mentioned instruments collect data from
environment through pitot probes, static ports etc.
Thus the atmosphere provides much of the basic information
required by a pilot. Before we study pitot-static system
instruments we must first, therefore, understand the properties
of the atmosphere these instruments utilize.
Bangladesh Airlines Training Center Biman
4. Atmospheric Physics
May 24 , 2015
4
The earth’s atmosphere is the surrounding envelope of air (mostly
Nitrogen, 78.09% and Oxygen, 20.95% gas).
The envelope is divided into several layers extending from the
earth’s surface.
The lowest layer is the troposphere, extending to a height of
about 28,000ft (11km) at the equator.
This is the start of the tropopause, which goes on up to about
66,000 ft (20km).
Above this is the stratosphere, extending to the stratopause at
an average height of between 60 and 70 miles.
As all aircraft fly in the troposphere or lower levels of the
stratosphere we will not concern ourselves with other higher layers.
Bangladesh Airlines Training Center Biman
5. May 24 , 2015
5
Atmospheric Pressure:
The atmosphere is held in contact with the earth's surface by
gravity, producing a pressure within the atmosphere.
Gravitational effects decrease with increasing distance from the
earth's center, so that atmospheric pressure decreases steadily
with altitude.
The standard sea-level pressure is 14.7 lb/𝑖𝑛2
and is equal to
29.92 in Hg or 1013.25 mbar.
The rate at which the pressure falls with height is termed as ‘the
lapse rate’. The pressure lapse rate is not linear, but exponential.
Bangladesh Airlines Training Center Biman
Atmospheric Physics cntd.
Standard Pressure Lapse Rate:
1 in Hg per 1000ft. of altitude.
6. May 24 , 2015
6
Atmospheric temperature:
The air in contact with the earth is heated by conduction and
radiation, and as a result its density decreases and the air starts
rising. As it rises its pressure falls, allowing the air to expand,
the expansion in turn causing a fall in temperature.
The air temperature decreases by 1.98°C for every 1,000 feet
increase in altitude from +15°C at MSL to -56.5°C at 36,089
feet (i.e. up to tropopause)
In the stratosphere the temperature at first remains constant at
-56.5°C, then it increases again to a maximum at a height of
about 40 miles
Bangladesh Airlines Training Center Biman
Atmospheric Physics cntd.
7. May 24 , 2015
7
Bangladesh Airlines Training Center Biman
Figure: ICAO standard atmosphere
Atmospheric Physics cntd.
8. What is Pitot-Static System
May 24 , 2015Bangladesh Airlines Training Center Biman
8
A pitot-static system is a system of pressure-sensitive
instruments that is used to determine an aircraft's
airspeed, vertical speed, altitude, and Mach number.
It uses the principle of air pressure gradient i.e. it
measures pressures/pressure differences and uses
these values to determine the speed and altitude.
9. May 24 , 2015
9
Static Pressure:
Static pressure, as the name suggests, is the absolute pressure
(pressure referenced to a vacuum) of the air surrounding the
aircraft.
This is easily obtained whilst the aircraft is stationary on the
ground, but will be affected as the aircraft moves through the
air, giving rise to errors. Modern aircrafts sample static pressure
through pairs of Static Vents.
Bangladesh Airlines Training Center Biman
Basics of Pitot-Static System
10. May 24 , 2015
10
Pitot Pressure:
The pitot pressure is a measure of ram air pressure (the total air
pressure created by aircraft motion)
To understand this, let us consider a probe placed in a flowing
fluid. When the fluid flows at a certain velocity, v over the
probe, it will be brought to rest at the nose
known as the stagnation point.
The stagnation pressure of the fluid,
also known as the total pressure or the
pitot pressure.
Bangladesh Airlines Training Center Biman
Basics of Pitot-Static System cntd.
11. May 24 , 2015
11
Bangladesh Airlines Training Center Biman
At the stagnation point, kinetic energy of the fluid is
converted into pressure energy.
Kinetic energy=pressure energy
1
2
m 𝑣2
= 𝑃𝑉
»
1
2
ρ 𝑣2
= 𝑃
» 𝑣α 𝑃
So, by measuring dynamic pressure we can determine
the fluid velocity.
(P=dynamic pressure=difference
between pitot and static pressure)
Basics of Pitot-Static System cntd.
12. May 24 , 2015
12
Bangladesh Airlines Training Center Biman
Figure: Measuring airspeed by using pitot and static pressures
Basics of Pitot-Static System cntd.
13. May 24 , 2015
13
Bangladesh Airlines Training Center Biman
Air Speed Indicator
14. Airspeed indicator measures the difference between the pitot
and static pressures in terms of the 1/2ρV2 formula i.e. it
measures a differential pressure which varies with the square of
the airspeed.
Air Speed Indicator cntd.
May 24 , 2015
14
Bangladesh Airlines Training Center Biman
15. May 24 , 2015
15
Pointer movement means capsule deflection. At low speeds
small pointer deflection means large speed variations and vice
versa.
So direct magnification of deflection would give a non-linear
scale reading which is inconvenient to read.
To make the dial linear an arrangement needed so that the
pointer movement is increased for small deflections and
decreased for large deflections i.e. a variable magnification
which is called, in this case, the square-law-compensation
Bangladesh Airlines Training Center Biman
Air Speed Indicator cntd.
16. May 24 , 2015
16
Bangladesh Airlines Training Center Biman
Figure: Square-law-compensation by rocking lever/sector-arm mechanism
Square-law-compensation
Air Speed Indicator cntd.
17. Vertical Speed Indicator
May 24 , 2015
17
VSI is a very sensitive differential pressure gauge, designed to
indicate the rate of altitude change from the change of static pressure
alone.
This indicator consists basically of three main components,
I. a capsule,
II. an indicating element and
III. a metering unit with an orifice/
calibrated leak
The orifice is opened to the interior of the
case to apply static pressure to the
exterior of the capsule. It has a time-lag
response characteristic.
Bangladesh Airlines Training Center Biman
18. May 24 , 2015
18
Bangladesh Airlines Training Center Biman
Level flight: zero differential
pressure across capsule
aircraft descending: metering unit maintains
case pressure lower than capsule pressure
aircraft ascending: metering unit maintains
case pressure higher than capsule pressure
Vertical Speed Indicator cntd.
19. Altimeter
May 24 , 2015
19
Bangladesh Airlines Training Center Biman
Figure: Aneroid Barometric altimeter
An altimeter operates on the aneroid barometer principle, i.e.
it responds to changes in atmospheric pressure.
The Altimeter has a sealed evacuated capsule inside a sealed
case.
20. Altimeter cntd.
May 24 , 2015
20
The air pressure on the outside of the capsule tends to squash it,
this being opposed by the leaf spring and the spring action of
the corrugated metal itself. As barometric pressure increases or
decreases, the capsule will be compressed or expanded
respectively.
By the use of an amplifying lever and chain linkage the expansion
and contraction of the capsule is transmitted to a pointer that
moves over a scale, calibrated to show barometric pressure, with
the leaf and tensioning springs maintaining tension in the linkage.
Bangladesh Airlines Training Center Biman
The aneroid comes from the Greek aneros, 'not wet‘.
21. Altimeter errors due to changes in atmospheric pressure
May 24 , 2015
21
The basis for the calibration of altimeters is the standard atmosphere.
If the atmospheric pressure at MSL is not standard, the altimeter will
be in error.
If an aircraft were on the ground on an airfield at sea level with
standard pressure (1013.25 mb, 29.92 in Hg) the altimeter would
indicate zero feet.
If the atmospheric pressure now falls to say, 1012.2 mb (29.89 in Hg)
the altimeter would indicate +30 feet.
If atmospheric pressure had risen to 1014.2 mb (29.95 in Hg) it would
have indicated -30 feet. Similar errors would occur in flight.
There is a Baro correction knob to set the pressure of the day in
millibars, (or inches of Hg), so that the altimeter displays the correct
height.
Bangladesh Airlines Training Center Biman
22. May 24 , 2015
22
Bangladesh Airlines Training Center Biman
Altimeter errors due to changes in atmospheric
temperature cntd.
The standard atmosphere assumes certain temperature values at
all altitudes and consequently non-standard values can also cause
errors in altimeter readings.
Figure: Effect of atmospheric temperature on an altimeter
23. Altimeter Dial
May 24 , 2015
23
Bangladesh Airlines Training Center Biman
Altimeters used to have three
pointers rotating at different rates,
one revolution of a pointer indicating
one thousand, ten thousand and one
hundred thousand feet of altitude
respectively.
24. ‘Q’ Code for altimeter setting
May 24 , 2015
24
It is essential for maintaining adequate separation between aircraft
and for terrain clearance during take-off and landing. Meteorological
data is transmitted from ATC, forming part of the ICAO “Q" code of
communication. The three code groups used in connection with altimeter
setting procedures are QNH, QFE and QNE.
QFE Setting the pressure prevailing at an airfield to make the
altimeter read zero on landing and take-off.
QNE Setting the standard sea-level pressure of 1,013.25 mbar
(29.92 in Hg) to make the altimeter read the airfield elevation.
QNH Setting the pressure scale to make the altimeter read airfield
height above sea-level on landing and take-off
Bangladesh Airlines Training Center Biman
25. May 24 , 2015
25
Mechanical or conventional altimeters suffer from friction in their
bearings and mechanical linkages; this leads to the indication lagging
actual altitude by as much as 10% (called ‘hysteresis’). As the aircraft
climbs hysteresis error increases. These limitations can be overcome by
replacing the mechanical linkage between the capsules and pointer
with an electrical servo mechanism.
In servo altimeter a two-phase drag-cup type motor is coupled by a
gear train to the pointer and counter assembly, and also to a
differential gear which drives a cam. The reference phase of the motor
is supplied with a constant ac voltage from the main source, and the
control phase is connected to the amplifier output channel.
Bangladesh Airlines Training Center Biman
Servo Altimeter
26. May 24 , 2015
26
Bangladesh Airlines Training Center Biman
Servo Altimeter cntd.
27. May 24 , 2015
27
When the aircraft altitude changes the capsule respond that and the
displacement of the capsules in transmitted to the I-bar, changing its
angular position w.r.t. the E-bar. The ‘E and I Bar’ converts capsule
movement into an electrical signal; amplitude being proportional to
the amount and phase the direction of that movement. This signal is
amplified and fed to a servomotor to drive the pointer and height
counters in the correct direction. It also, via the worm gear, cam and
cam follower, drives the E bar back to a null position. Indication is
similar to the mechanical altimeter.
The ‘set ground pressure’ knob puts a bias on the E bar, which is then
driven to a null by the servo as before, with the bias appearing as a
change of indicated altitude.
Bangladesh Airlines Training Center Biman
Servo Altimeter cntd.
28. Typical pitot probes, static ports and their locations
May 24 , 2015
28
A pitot probe consists of a pipe
facing into the airflow, with
electrical heating to prevent
icing and a water drain at its
lowest point.
The static vents are cross
connected, by pipework,
in pairs to balance out any
pressure difference caused
by sideslip of the aircraft.
Bangladesh Airlines Training Center Biman
29. May 24 , 2015
29
If failure of the primary pitot-static pressure source occurs, for
example, complete icing up of a probe due to a failed heater
circuit, then it is obvious that errors will be introduced in the
indications of the instruments
As a safeguard against failure, therefore, a standby system may
be installed in aircraft employing pitot-static probes whereby
static atmospheric pressure and/or pitot pressure from alternate
sources can be selected and connected into the primary system.
The required pressure is selected by means of selector valves
connected between the appropriate pressure sources and the
flight instruments, and located in the cockpit within easy reach of
the flight crew.
Bangladesh Airlines Training Center Biman
Alternate Pressure Sources
30. May 24 , 2015
30
Bangladesh Airlines Training Center Biman
Alternate Pressure Sources
Figure: Alternate pitot pressure and static pressure system
31. Pitot-Static Heating
May 24 , 2015
31
To prevent icing, the pitot tubes and static ports have an
arrangement of heating (usually electrical heating.) The
heating elements require 28V DC or 115V AC.
The heating circuit has a control switch as well as an indication
light to know whether or not the circuit is functioning correctly.
In the circuit shown, K1 and K2 are current sensing relays. If
the Pilot has failed to switch the heating on; or a heater
element has gone open circuit; no current will flow through the
relay coil. The relay will de-energise, connecting 28 VDC
from the left essential bus to the Master Caution Logic; thus
illuminating the appropriate Pitot Heat Caution lamp.
Bangladesh Airlines Training Center Biman
(The loss of A330 flight AF 447 in mid-Atlantic, June 2009 was due to icing of the pitot probes. )
33. May 24 , 2015
33
In order for a pitot-static system to operate effectively under all flight
conditions, provision must also be made for the elimination of water
that may enter the system as a result of condensation, rain, snow, etc.,
thus reducing the probability of `slugs' of water blocking the lines.
Such provision takes the form of drain holes in probes, drain traps and
drain valves in the system pipelines.
Drain holes are drilled in probe pitot tubes and casings, and are of
such a diameter that they do not introduce errors in instrument
indications.
Bangladesh Airlines Training Center Biman
Drains
34. Pipelines
May 24 , 2015
34
Pitot and static pressures are transmitted through seamless and
corrosion-resistant metal pipelines. The diameter of pipelines is related
to the distance from the pressure source to the instruments to eliminate
pressure drop and time -lag factors.
It is very important to ensure that there are no leaks in the pipework,
as this would give rise to inaccurate readings. Even though they don't
have to handle high pressures, the instruments are very sensitive to
small changes in pressure so that even very small leaks can cause
errors in the instruments.
The tubing and hoses that are used are not very strong and should be
inspected carefully for damage. The fittings and connections should be
installed with care and torqued to specified values as stated in the
AMM.
Bangladesh Airlines Training Center Biman
35. Pressure (Position) Error
May 24 , 2015
35
Measuring airspeed and altitude by pitot and/or static port has two challenges:
1. to design a probe which will not cause any disturbance to the airflow over it
2. To find a suitable location on the aircraft where the probe will not be affected
by the disturbance due to aircraft movement itself.
A pressure error is introduced in the instrument due to this problem.
Pressure or position error (PE) is defined as the difference between the local static
pressure and the free-stream static pressure.
Altimeter and airspeed indicators suffer from PE most.
By using pressuring error correction transducers, we can minimize the pressure or
position error.
Bangladesh Airlines Training Center Biman