This document provides an overview of the study conducted by two students of the Metallurgical Department at NED University of the engine overhaul shop at Pakistan International Airlines (PIA). It describes the various sections observed in the shop including CNC machining, electroplating, thermal spraying, welding, heat treatment, and non-destructive testing. The goal was to learn about the latest methods used by PIA to protect aircraft parts and extend their usable lifetime through maintenance and repair.

1. STUDY OF ENGINE OVERHAUL SHOP AT
PIA
GROUP A:
NED UNIVERSITY
METALLURGICAL DEPARTMENT
(THIRD YEAR 2014)
 AZEEM BIN USMAN (MY-069)
 SHAHROZ AHMED (MY-056)

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ACKNOWLEDGEMENTS
Since undertaking the task of writing this report, instructors and management, too numerous to mention,
have guided us in the best of their health and have shared their experience and input and contributions on
how to make this work more effective as a learning tool .To all those who have helped by any means, we
express our sincere thanks.
Appreciation is expressed to those who have made our tour easy and provided us assistance, so we can
explore and learn more. We are especially indebted to Mr. Nadeem , who provide us the easiest route of
exploring and advised us the best instructors in the respective section. We are sincerely thankful to Mr.
Najeeb, who granted us permissions to visit respective sections of our interest and helped in every aspect
of our visit. Mr. Ather (in charge of plasma section)for his continual encouragement and support.
In the end, our sincere thanks to all those who have made our journey to PIA successful and free of
worries , their contribution is deeply and sincerely appreciated.

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PREFACE
In this report, we have discussed our learning experience at Pakistan International Airlines(PIA).The
report has main considerations at the engine overhaul and its subdivisions .some of which includes
cleaning, electroplating, plasma spray areas, non-destructive testing sections, pneumatic areas etc.
Being as metallurgical engineers, we have tried to get most of our focus to the latest methods followed in
PIA related to metals and materials which includes protective coating of metals such as anti-corrosive
coatings, thermal barrier coatings, electroplating etc., cutting of parts through CNC machining, crack
detection by best of methods available, heat treatment, welding etc.
Our primary objective was to submit and share the maximum knowledge to the reader about the latest
methods adopted by PIA to give strict attention for the maximum protection of the parts of aircraft, their
usage period, cleaning through proper method, ensuring the parts dimensions from time to time,
maintenance, flaw detection and scrap in a way that it cannot be used for future by any means.
We hope that our work would be successful in accomplishing our goal.

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S.NO. CONTENTS PAGE NO.
01 CNC MACHINE 05
02 EROM AREA 06
03 MACHINE SHOP 06
04 ELECTROPLATING 11
05 THERMAL SPRAY CLASES 14
06 PAINT SHOP 16
07 WELDING 17
08 HEAT TREATMENT 17
09 AERO FILE SECTION 18
10 STRIPPING AND ASSEMBLY SECTION 18
11 CLEANING SHOP 20
12 NON DESTRUCTIVE TESTING 21
13 VIEW ROOM 23
14 PLANNING 23
15 STANDARDS ROOM 24
16 PNEUMATIC SECTION 25
17 TEST BENCH 26
18 QEC BUILDUP 26
19 LANDING GEAR SHOP 27
20 WHEEL BAY 27
21 HYDRAULIC SYSTEM AND REPAIR 28
22 HYDROSTATIC TEST 28
23 EXPERIENCE 29

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ENGINE OVER HALL SECTION
After certain life engine is subjected to over haul section weather it is accessible or not to investigate it
and finish parts to enhance or increase the life of engine and as well as other parts.
STATES OF ENGINE OVERHALL SECTION:
Some states in which the parts of plane get subjected for increasing the life of parts are
1. CNC Machine
2. Erom area
3. Machine shop
4. electroplating
5. Electroplating
6. Thermal spray shop
7. welding
8. Heat treatment
9. Aerofile section
10. Stripping and engine assembly section
11. NDT testing
12. Planning room
13. Standard room
14. Pneumatic
15. Test bench
16. QEC buildup
17. Landing gear
18. Wheel bay
19. Hydraulic system and repair
20. Hydraulic test
1. CNC MACHINE:
CNC stands for “computer numeric control”. In CNC machines data is feed in machine which can
regulate the whole process automatically without need any labour or manual work.
There are several CNC machines which can frequently used in Pakistan international airline
which increases the quality of engine parts.

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2. EROM AREA:
Erom is a largest machine which is found in Erom area. It is vertical multiple operated machine
where lathe machine process take place. It is computer numeric control and a highly automated
machine.
It is a manufacturing and as well as repairing machine use for cutting, chipping and many other
purpose.
3. MACHINE SHOP:
Some machine used in PIA are CNC and as well as manually operated machine.
 Lathe machine
 CNC lathe machine
 Milling machine
 Horizontal boring machine
 Grinding machine
3.1. LATHE MACHINE:
 Lathe machine are considered as the mother of all machines. It can be vary in sizes. For large
parts large lathe machines used such as fixture plates etc. the sizes of lathe machine depend upon
the bed length and height from the center. Higher the distance the larger diameter products can be
produces.

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 working mechanism:
The mechanism of lathe machine is similar to metal forming and shaping techniques. In lathe
machine the work piece is dynamic and holds in a die which moves the part and the tool is
stationary. Tools can be change with specified material.
 Coolants:
Coolants must be use in machine to remains the work piece cool to prevent the excessive heat
distortions. Domes can be used as coolant.
 Application:
Lathe machine is used for drilling and formation of threads in parts, some sort of cuts can also be
produced with lathe machine.
 Limitations:
The limitation of lathe machine is that it can only operate with the parts having only circular cross
section. It cannot be used for rectangular or any polygonal parts.
 Precautions:
Job should be hold lightly in a die.
Care should be taken properly where scrap can be produced

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Eye shields, hand gloves properly used
3.2. CNC LATHE MACHINE:
 CNC lathe machine is vertical lathe machine in which tool is positioned in vertical direction. It is
a manufacturing and as well as repairing machine.
 Data is feed in machine then the machine process automatically to make parts. CNC lathe
machine is vertical in position, a chunk which hold work piece can be rotated. For large parts,
having a high weight so it can be made vertical to carry machining operation easily.
 Application:
Landing gear, jaws can also be produced with this machine which are highly irregular in shape.
3.3. MILLING MACHINE:
 The mechanism of working of milling machine is inverse of lathe machine in which the tool is
moving where as the work piece is stationary and hold tightly in a die.
 In milling machine, milling cutters are used. The benefit of using milling machine is that any type
of job in shape can be practice in milling machine.
 In milling machine the position of tool is either vertical or horizontal

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3.4. CNC MILLING MACHINE:
 In CNC milling machine tool is place vertically. The main advantage of CNC milling machine is
that drawing can be made by using different softwares such as autocat and feed in a machine
which can work automatically by single command without need of labour.
 Use of milling machine:
Perforated parts holes in parts can be produced by milling machine.

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3.5. HORIZONTAL BORING MACHINE:
 This machine is considered to be as one of the largest machine in PIA. It is a CNC machine.
Horizontal boring machine is comprises of both lathe and as well as milling machine where both
machine’s process can be performed in a single machine.
 This machine has multiple axis of rotation. Machine which is present in PIA five axis of rotation.
 It can rotate longitudinally transverse, rotational about its axis and left right and up and down.
These movements can be take place after a specified time which is mentioned in manual provided
by the manufactures
 Bushes can be used in this machine which prevent the tearing wearing of parts and degrade by
itself.
 This machine is horizontal in position and data is feed in codes such as G and M codes are used G
stand for geometric and M stands for machining.
3.6. GRINDING MACHINE:
 Grinding machine is commonly used for surface parts. Hard materials such as tungsten carbide is
very difficult tube machined so in place of machining operation grinding of surfaces is carried
out.

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 Parts before service are plated in order to prevent from oxidation rusting, scaling when these
coating degrades, so obsolete skins of coating (e.g.: chromium plating) can be removed by
grinding upto optimum thickness with high accuracy.
4. ELECTROPLATING:
 Plating means coating of some other material in engine parts.
 Plating can be carried out either by providing current is a solution known current is a solution
known as electroplating or either without providing electricity.
 After the repairing of part work piece it is subjected to difficult sections according to the
requirements. Parts are inspected which are required to be coated and then transfer to plating
section.
Electroplating shop
4.1. COATING METALS:
There are several metals used in PIA for coating purpose these are
 Copper plating
 Nickel plating
 Chromium plating
 Cadmium plating
 Silver plating
4.2. PRINCIPLE OF ELECTROPLATING:

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 The electroplating process is based on a principle in which the ions present in a solutions moving
towards their respective electrodes.
 Parts which going to be plated is hang vertical with wire and dipped in a tank.
 Current is passing in work piece part either connected with negative terminal known as cathode
or with as positive one known as anode.
 Ions in solution move towards their respective electrode and deposition on part, which can
resulting a coating of metal on work piece. Part remains in a solution until a required thickness is
achieved.
4.3. MASKING / WAXING:
This step is carried out before the plating. In this step the regions where plating is not required are
left and rest of the regions covered with masking sticky sheet. The part is then dipped in wax tub
where the wax coated in exposed areas. Making can be removed so that wax remains only a
region where metal coating is not required after plating process the war is then removed.
4.4. PURPOSE OF PLATING:
Plating of some other material on engine parts is carried out to prevent the part from corrosion,
scales formation, wearing and tearing, and to increase the life of parts.
4.5. LABORTARY TESTING:
Solution in tanks for plating purpose are first compose in labs according to the manual provided
by manufacturers.
Solution is tested after a certain period of time in order to retain the proper composition and
elemens are added.
Solution testing is carried out by means of titration process to check the acidity and basicity of
solution.
Tukore (centrifugal rotater) is used to check the amount of sulphate in solution.
4.6. TYPES OF PLATING:
4.6.1.ALCHROME PLATING:
In alchrome plating process the solution contains aluminum and chromium ions. In this technique
there is no need to supply current. Initially parts dipped in hot water to remove paints, coatings,
grease etc .then dipped in alchrome tank, and there is no need of thick layer.

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4.6.2.CHROME PLATING:
To make the parts more resistive to corrosion and rust chrome plating is usually done.
Parts to be plate is hanged on a tank, since the chromium is positively charged ion so it attracts
towards the cathode and deposited on parts. Tank usually use for chromium plating filled with
several balls. In order to prevent the toxic fumes in atmosphere. One of the hazards of chromium
plating is that chrome is positively charge ion and hydrogen from water is also a positively charge
so hydrogen also entrapped it cathode this will result in generation of cracks at high pressure
avoid. This type of failure must be backed for several times to remove the entrapped hydrogen.
4.6.3.COPPER PLATING:
The procedure is similar to all other types of plating. Copper plating is a protective coating. The
solution in a tank containing copper ion which deposition on part with the passage of electric
current.
4.6.4.CADMIUM PLATING:
Cadmium coating is also a protective coating. Since the solution contains cadmium and as well as
hydrogen ions which are deposition on cathode so parts must be baked later. There are two types
of cadmium plating.
 Low hydrogen plating:
Low hydrogen plating done on high strength parts made up of steel, iron, alloys because these
parts subjected to high forces so hydrogen is necessary to remove.
 High hydrogen plating:
High hydrogen plating for low strength parts which are not subjected to high forced.
4.6.5.NICKLE PLATING:
Nickel plating is a protective coating. Nickel plating is primary plating. For highly damaged
parts initially it is nickel plated and then chromium plated for protective purpose.
4.7. DEPLATING TECHNIQUE:
After a certain life time different parts of plane are disassemble and transfer to engine over
haul in order to repair parts and increase its life.

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The initial step is to clean the plate from any type of coating. Electroplating is usually
removed by reversing the current in parts so the ions deposited part leave the part and remain
in solution.
Other methods are by dipping the part in different chemical solution.
4.8. SKIN ROUGHNESS TECHNIQUE:
Rough surface are generated in some parts to increase the resistance and then it is
electroplated. Some methods to increase roughness are as follows.
 DRY BLAST:
In dry blast technique the metallic powder in microns is blasted through gun on parts with
tremendous amount of velocity.
This phenomenon is also used for relieving the residual stresses on parts known as short
pinning.
 REVERSING CURRENT:
By reserving the current on part plating is removed which resulting the rougher surface.
 ETCHING:
Rough surface can be generate by etching the part is dipped in acid which resulting the rough
surface.
5. THERMAL SPRAY CLASES:
There are three classes of thermal spray these are.
 Plasma spray
 Thermo spray
 Metal spray

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5.1. PLASMA SPRAY:
 Plasma is considered to be as a fourth state of matter having a highly oxidized ions and it is a
state lies between the gases and liquids.
 Why some materials are plasma coated?
Some parts of engine are highly expensive and high cost effective so the degradation of such
parts must be prevented in order to increase the life of parts. This can be achieved by coated
the part with plasma.
 Mechanism:
Plasma spray is just only a method to produce heat.
Heat is required to heat the powder or red hot the powder and soften it rather liquefy.
5.2. PLASMA TESTING LABORTORY:
To check the quality of work piece after plasma coating several equipment used.
5.2.1.TENSILE BOND STRENGTH:
Equipment is similar to the tensile strength equipment. In this test the part is joint with the
bonding agent such as some thermo resin (epoxy). Now this test piece is subjected under tensile
load and due to stress concentration part can be broken at the bonded region, so this equipment
helps us to determine the tensile bond strength of a material.
5.2.2.CUTTING MACHINE:

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After the plasma spray part is then cut by using the cutting machine. Work piece must be hold
tightly at same side of blades in between jaws. The coolant is used to cool the blade and work
piece during cutting. Now this work piece is mounted to check the quality control of work piece.
5.2.3.POLISHING:
The mounted part is being polished by using different emly papers in order to get a finished and
polished surface.
5.2.4.ROCKWELL SUPERFICIAL (HARDNESS TESTER):
Rockwell superficial is used to check the hardness of thin parts. Brale indenter or sometimes ball
indenter may be used to check the hardness. Scale N and T is used for ferrous material and W, X,
Y scale is used for non ferrous material.
Initially minor load is applied and to set the dial at zero now applied major load. Hardness
reading can be read from the scale.
For heat generation first plasma is generating by involving two gases.
5.3. THERMO SPRAY :
Thermal spray is similar type of coating as plasma coating only differ in the heat generation
technique.
Heat can be generated by burning the gases at very high temperature at about 18000 to 20000 °C.
In thermo spray wire and powder both can feed in gun.
6. PAINT SHOP:
Paint shop in PIA s considered to be as a part of repair process where the parts after cracks
detection and further processes subjected to paint shop to make the finish product.
Initially the part is being cleaned and by means of chemical, mechanical, and electro refining
process. Now the clean product if required it is masking to prevent the application of the paint in
unwanted regions.
Paint is applied in two steps firstly primer is applied to prevent the part from being corrosion and
degradation it is somehow absorb in a part to provide better coating then in final step enamel is
applied it is finish coat applied for the finishing purpose.

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7. WELDING:
Welding is a joining process. It is a process in which two parts of metal weather similar or
dissimilar atoms join together by generating high amount of heat in between the two parts.
Welding is also considered to be as a repair process in which the broken parts of aircraft being
welded. There are several type of welded conducted to join the parts such as Argon welding,
electric welding, gas welding.
Argon and electric welding welded only similar type of metals.
Gas welding is used to weld the dissimilar metals.
8. HEAT TREATMENT:
Heat Treatment is the controlled heating and cooling of metals to alter their physical and
mechanical properties without changing the product shape. Heat treatment is sometimes done
inadvertently due to manufacturing processes that either heat or cool the metal such as welding or
forming. Heats Treatment is often associated with increasing the strength of material, but it can
also be used to alter certain manufacturability objectives such as improve machining, improve
formability, and restore ductility after a cold working operation. Thus it is a very enabling
manufacturing process that can not only help other manufacturing process, but can also improve
product performance by increasing strength or other desirable characteristics.
Vacuum furnace heat treatment furnaces

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9. AERO FILE SECTION:
Aircraft is lifted in the air due to its shape. Aero file is a shape due to which air smoothly flow
and causes the aircraft to be lifted. Wings of aircraft is made in aero file shape in order to
produce thrust , wings are bulgy at upper surface and straight at lower surface which helps the air
flow most faster at lower surface then above which causes the production of thrust.
Moreover in engine parts turbine blades are also made aero file in shape which moves through
the smooth flow of air.
10. STRIPPING AND ASSEMBLY SECTION
The engine and APU of the aircraft is an assembly of many complex parts and these parts needs
to be replaced or requires maintenance after a certain amount of time. Sometimes, the engine
encounters problems before its maintenance period. This is often due to failure of single part or
some parts present in the engine.
For unlocking these parts from the engine or APU, stripping area provides the needful; when the
maintenance or replacement is complete assembling is also done in this area. This area is
basically used for two functions.
 stripping or disassembling
 assembling the engine parts
10.1. STRIPPING:
Engine parts are disassembled in this section; this requires expert and skillful people having the
complete knowledge of optimum tool selection. When the required parts are stripped, these are
sent to different areas for detection of flaws, maintenance and replacement.

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Aircraft’s APU present in stripping section
10.2. ASSEMBLY AREA:
When the stripped parts are replaced or serviced, the same section is used for assembling these
parts to make a workable engine, but the routes of both stripping and assembling are different.

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11. CLEANING SHOP:
Before the inspection disassembles parts are firstly cleaned. Cleaning process is carried out in
several cleaning steps.
 Hand cleaning
 Chemical cleaning
 Mechanical cleaning
 Electrical cleaning
11.1. HAND CLEANING:
It is an initial step it is a hand cleaning process in which different components cleaned by means
of cloth by means of labor. It is cleaned by different oils and chemicals such as MEK, acetone,
and kerosene oil.
11.2. CHEMICAL CLEANING:
Scales, corrosion, rusting all can be cleaned by chemical cleaning. In chemical cleaning part is
dipped in some chemical solution for cleaning.
11.3. MECHANICAL CLEANING:
In this step cleaning is carried out by machining. Dry blast, vapor blast, sweco processes are the
methods for mechanical cleaning. In short by this method Al2O3 powder is pressurized on parts.

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11.4. ELECTRO CLEANING:
In electro cleaning method tank is filled with non ionic water and is connected with ultrasonic
machine which produce swirling effect due to resonance, component is placed in a tank for
specific time and temperature usually turbine blades cleaned by this method. Water daglocked the
holes and increase the life of part. For assurance we use back flesh machine.
12. NON DESTRUCTIVE TESTING:
Non destructive technique is a technique use to determine the cracks, flaws, leap, and inclusions
without damage to impair its future usefulness.
There are several types of non destructive test carried out at aircraft parts at PIA these are,
 Radiography testing
 Magnetic particle inspection
 Fluorescent penetrant
 Ultrasonic testing
 Eddy current testing
 Radiography:
12.1. RADIOGRAPHY TESTING:
It is a technique use to detect the surface, sub surface and as well as internal flaws. In this
technique X-rays or gamma rays generated to detect the flaws. X-rays generated by the
bombardment of electrons on to the metal this will generate a stream of x-rays which penetrate in
a part to detect the cracks and flaws.
12.2. MAGNETIC PARTICLE INSPECTION:
This technique is usually used to detect the surface and sub surface cracks. It is only applicable
for ferromagnetic components. This test does not detect the internal cracks.
First the component is being magnetized by induction principle. Current passing through a coil
which generates magnetic field part is being place as a core in a coil and magnetizes through
induction. Now iron fillings are sprinkle on surface, iron filling forming a pattern around the
crack because of the N and S poles generated at crack tip and leak magnetic field.

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Magnetic particle inspection
12.3. FLUORESCENT PENETRANT:
In this technique only surface flaws can be detected. Component being tested is first dipped in
fluorescent penetrate and the developer is applied to enhance the crack now the part is examined
under a black light so the cracks appear as bright at dark background.
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Detection of Crack through Fluorescent Inspection
12.4. ULTRASONIC TESTING:

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This is a technique use for several years for detection of flaws by hammering the part and detect
by the sound generated.
There are two types of method used in ultrasonic testing these are,
 Pulse echo method
 Trough transmission method
In pulse echo method two transducer used and in through transmission method only a transducer
used. Piezoelectric transducer is used which convert the electrical signal into sound energy and
the signal display in oscilloscope. If flaws detected so small signal produced.
12.5. EDDY CURRENT TECHNIQUE:
This technique is used to detect the cracks and composition of component this test conducted in
electrical conductive materia .Eddy current is produce by the induced current in part.
13. VIEW ROOM:
View room is just a place where decision is been taken with the help of component history.
Manual provided by manufacturer and the cycles of aircraft. Cycle is a term used in aircraft, cycle
means take off and landing of aircraft is a one cycle. Cycles or life of aircraft engine is provided
but the manufacturer and after the specified life times the aircraft disassemble and send to
different repairing shops. In view room it is decided that which part is first send to in which
section such as plasma shop. NDT testing, CNC machining. Tags are placed along with
component; yellow tag indicates that this part is repaired
14. PLANNING:
There are several function which are conducted in planning room. These are
 Spare provisioning
 Quantity of material being used
 Projects planning
 Labour required
All the above factors are conducted in planning room of engine overhaul shop. Problems occur in
aircraft are also considered in planning room. Planning is actually documentation which is
planned by skilled planners.

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15. STANDARDS ROOM
This room is basically associated with the calibration of instruments .which is used to ensure the accuracy
of instruments. From time to time this practice is repeated depending on the instruments.
Various instruments are calibrated in this section .for example
1. Pressure gauges
2. Screw gauges
3. Hardness testers
4. Torque meters
5. Profilometers
6. Verneir calipers
Pressure gauge torque meter

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Hardness tester
PRINCIPLE AND CALLIBRATION OF PRESSURE GUAGE AND TORQUE METER:
For calibrating pressure gauges and torque meters there is a main(on which accuracy of instruments is
checked) the instrument is connected to the main and then force or pressure is applied if the reading on
the main and instrument is same then there is no error, if there is variation in the readings the instrument
has errors.
PRINCIPLE OF CALIBRATION FOR HARDNESS TESTERS, VERNIER CALLIPERS,
PROFILOMETERS AND SCREW GAUGES:
For ensuring the accuracy of these devices standard test blocks are provided with the instruments by the
supplier.
The standard test block have the value of hardness, depth ,length or roughness etc known, by measuring
the respectable parameters of the test block on the respective instruments we can check the accuracy of
the instruments.
16. PNEUMATIC SECTION:
Pneumatic is a term used in engineering means the movement of different components through
air. To make the pneumatic system properly working three basic things are required these are

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pressure, vacuum and air flow. Pneumatic system in an aircraft is required for air conditioning
system and for bleed purposes.
Basic operation:
Pneumatic system in an aircraft is pretty straight forward. The heart of this system is a pressure
and vacuum creating engine driven air pump.
The air pump draws air into the system through a filter. The fasts moving stream of air passes
over the vanes and power the autopilot and de icing system.
17. TEST BENCH:
In test bench shop whole engine is placed on bench for testing purpose. It is tested and compare with
standard engines provided by manufacture. To prevent the metal particles during oil refining all oil
refining process conducted in test bend shop.
18. QEC BUILDUP:
QEC stands for quick engine change. It is a shop where the internally completed engine is
subjected in order to complete the engine externally. Only internally completed engine does not
meet with all the requirements in aircraft external equipments are necessary to run the aircraft
safe and sound. Only engine can just produce thrust which help aircraft to lift up in air but engine
become a power plant in QEC buildup shop. QEC buildup also generates the tendency of engine
for de icing and anti icing purposes.

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Air compresses which resulting in increase in pressure and temperature which heated air and
apply in different chambers with the help of valves to suspend the ice formation. With the help of
QEC buildup shop the pressure inside the aircraft equal to the atmospheric pressure for the safe
and sound journey of passengers. Furthermore in pneumatic system ducts, valves, exhaust system
are built by QEC shop.
19. LANDING GEAR SHOP:
Landing gear in general term considered to be as the legs of aircraft. It helps aircraft to land
smoothly. It size varies from very small to very huge depending on the size of aircraft. For small
aircraft two gears are enough where as in larger ones more than gears are used. Main gear, nose
gear, wings gear are used in large aircrafts.
These gears come in overhaul shop and disassemble then it is transfer to any repairing section
according to the requirement either for heat treatment process or any other. Gear must be made up
of such material so it should be a shock resistance. For shock absorbance nitrogen and hydraulic
oils are used, it consist of two chambers upper and lower chamber. There is a certain life of gears
and after its life it subjected to engine overhaul shop, for example the life of 747 is 24000 cycles
and for 310 it is 15000 cycles or 8 years.
Main gear and nose gear
20. WHEEL BAY:

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For testing of aircraft wheel are subjected to wheel bay shop. Pressure of wheels and other testing of
wheels tested in this shop.
21. HYDRAULIC SYSTEM AND REPAIR:
A hydraulic system uses a fluid under pressure to drive machinery or move mechanical
components.
Virtually all aircraft make use of some hydraulically powered components. In light, general
aviation aircraft, this use might be limited to providing pressure to activate the wheel brakes. In
larger and more complex aero planes, the use of hydraulically powered components is much more
common. Depending upon the aircraft concerned, a single hydraulic system, or two or more
hydraulic systems working together, might be used to power any or all of the following
components:
 Wheel Brakes
 Nose Wheel Steering
 Landing Gear Retraction/Extension
 Flaps And Slats
 Thrust Reversers
 Spoilers/Speed Brakes
 Flight Control Surfaces
 Cargo Doors/Loading Ramps
 Propeller Pitch Control
A hydraulic system subjected to hydraulic repair shop after the completion of its cycles for
repairing purpose.
22. HYDROSTATIC TEST:
A hydrostatic test is performed to determine the integrity and soundness of pressure vessels and
piping joints. A decrease in the applied pressure or leakage through the products or joints or plastic
deformation or distortion or bulging in the product is indication of inadequate quality of the product
under test. This test method is also termed as Leak testing (based on
the principles of leakage during pressurized condition) and Pressure
Drop Test (based on the principles of decrease in pressure during test
due to unacceptable discontinuities). It is also the most common
method often employed and it is the one of the most reliable test
methods when determining the integrity and soundness of the vessel
This test is preferred over pneumatic test due to safety reasons .This
test is applied on new parts and also on repairs.

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OUR EXPERIENCE AT PIA
At the start of our internship at PIA, we had made our minds to seek maximum knowledge to our
respective engineering field, but PIA not only provided us with maximum knowledge to our respective
engineering field also provided us with the awareness of different engineering aspects followed in PIA.
The kind of difficult situation PIA is facing right now, because of different political issues, we had in
mind that there is less to learn and explore, but credit and sincere thanks to the management that they tried
to help us in every aspect and gave us the maximum knowledge they had, and not only they provided the
theoretical aspect but also gave help practically.
Being as metallurgical engineers, the technologies that attracted most of our attention were,
electroplating, plasma, thermal spray, hardness testers, profilometers, NDT, cleaning, heat treatment,
welding, vacuum furnace etc. we would like to share our detailed experience in:
NDT: As NDT has a great importance in the metallurgical engineer’s knowledge, at PIA we performed it
practically which give us maximum idea of NDT, before the internship we just knew it theoretically.
VACUUM FURNACE: As we all know that it is a rare furnace, we are deeply thankful to the staff
responsible for this furnace that they provided us with maximum information regarding this furnace.
PLASMA AND THEMAL SPRAY COATING: Before coming to PIA we were not aware that such
coating also exists, now we have gained good amount of knowledge about these types of coatings.;
ELECTROPLATING: PIA has provided us with practical explanation of electroplating, before this we
had knowledge about it theoretically, now we know the proper steps followed in electroplating.
CNC MACHINING: We are really thankful to the people of PIA that they gave us a chance to see the
CNC boring machine, lathe machine and milling machine. We were really surprised to see the huge
amount of modern machinery specially that milling machine that works on AUTOCAD .
CONCLUDING REMARKS:
We really like to give our sincere thanks to all the people associated with our internship, to all who
have provided us with accessories and helped us in meeting our needs .We tried to remain disciplined in
this internship period, but if have committed something wrong that affects the management or any person
associated with PIA we would be sorry to the respective person.