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2010
Industrial Attachment Report
Submitted by: Tham Jia Yin, Sarah
Supervised by: Mr. Eric Tan (SAESL)
Professor Zhou Wei (NTU)
Industrial Attachment Report
i
Abstract:
As part of her Aerospace Engineering undergraduate studies, the author served as an
intern at Singapore Aero Engines Services Limited (SAESL) from the 11th of January to
the 11th of June 2010. The author was attached to the department of repair development.
Being a Rolls-Royce jet engine Maintenance, Repair and Overhaul (MRO) workshop,
the role of the aforementioned department was to increase and improve the repair
capabilities of the company through the introducing and assimilating of new
technologies into the company’s daily functions.
This report documents the author’s 22 weeks spent as a trainee engineer under the
guidance of her supervisor and mentors. The report first presents the corporate profile of
SAESL as Rolls Royce’s Centre of Excellence, before introducing the working
principles and different sections of a commercial jet engine. Following that, the report
chronicles the major projects undertaken by the author during her period of employment,
the most significant being the assisting in the setting up of a new repair cell, the Front
Combustion Liner cell.
Through the various tasks, the author was exposed to the many levels of work that take
place in such an engineering company, from the menial, to the mundane, to the formal.
After her 5-month stint in SAESL, the author has had her technical knowledge solidly
reinforced, and has drastically widened her perspective on the industry. Now equipped
with a wealth of new hands-on experience and workplace skills, the author is much
better prepared for the working life that lies ahead.
Industrial Attachment Report
ii
Acknowledgements:
The author would like to extend her sincerest gratitude to the following personnel for
their invaluable assistance and guidance rendered throughout her attachment:
• Mr Chan Swee Heng, Manager, Engineering Department
• Mr Eric Tan, Head, Repair Development, and supervisor to the author
• Mr Koh Li Teck, Principal Technologist
• Mr Adrian Chia, Engineer, Repair Development, and mentor to the author
• Mr Alex Ong, Engineer, Repair Development
• Miss Khoo Yi Wen, Engineer, Engineering Department
• Mr Chua Koon Tiong, Inspector, Machining Cell
• All technicians in the various repair cells at SAESL
The author would also like to thank all her colleagues, of whom there are too many to
name, for their tolerance shown toward her inexperience, and their guidance in her
everyday tasks. Special thanks also go out to SAESL for the wonderful opportunity
presented to the author to pursue her Industrial Attachment at such an established
company placed at the forefront of the MRO industry. Last but not least, the author
would like to thank her tutor, Dr. Zhou Wei, and the NTU Career and Attachment
Office, for making such a life changing experience available for her.
Industrial Attachment Report
iii
Table of Contents
1. Introduction to Industrial attachment................................................................................... 1
1.1. Objective: ....................................................................................................................... 1
1.2. Scope: ............................................................................................................................ 2
1.3. Company Profile ............................................................................................................ 3
1.4. Repair Development Department ................................................................................. 5
2. The Jet Engine ........................................................................................................................ 6
2.1. Fan ................................................................................................................................. 6
2.2. Compressor .................................................................................................................... 7
2.3. Combustor ..................................................................................................................... 8
2.4. Turbine ........................................................................................................................... 9
3. Orientation – Induction to the shop floor ........................................................................... 11
3.1. Fan blade cell ............................................................................................................... 11
3.2. Fitting cell .................................................................................................................... 13
3.3. Shot peening cell ......................................................................................................... 15
3.4. Machining .................................................................................................................... 17
4. Repair scheme reviews ........................................................................................................ 20
4.1. Standard Equipment .................................................................................................... 21
4.2. Consumable Materials ................................................................................................. 22
4.3. Equipment capabilities ................................................................................................ 22
5. The Front Combustion Liner cell .......................................................................................... 25
5.1. The Front Combustion Liner ........................................................................................ 25
5.2. GOM machine – Optical measuring technique ........................................................... 27
5.3. DMG – Automated Machining ..................................................................................... 29
5.4. Planning the repair matrix ........................................................................................... 31
Industrial Attachment Report
iv
6. Personal Reflections and Conclusion ................................................................................... 33
6.1. Personal Reflections .................................................................................................... 33
6.2. Conclusion ................................................................................................................... 36
References
Appendix A – Organizational Chart of SAESL
Appendix B – Full Repair Scheme K004
Appendix C – Repair Capability Form
Appendix D – SolidWorks Model of the Trent 500 Front Combustion Liner
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Industrial Attachment Report
v
Table of Figures
Figure 1 – Birds-eye view of the SAESL facility .............................................................................. 3
Figure 2 – SAESL’s in-line engine gantry (left) and cleaning line (right) ....................................... 4
Figure 3 – Cutaway of a classic jet engine ..................................................................................... 6
Figure 4 – Cutaway of a jet engine compressor ............................................................................ 7
Figure 5 – A jet engine combustion chamber ............................................................................... 8
Figure 6 - pictorial of airflow in a jet engine turbine ..................................................................... 9
Figure 7 – Workflow of a typical fan blade repair ....................................................................... 12
Figure 8 – Different surfaces of the fan blade after various processes ...................................... 13
Figure 9 – the workflow for the repair of a composite fairing .................................................... 14
Figure 10 – fundamentals of shot-peening ................................................................................. 15
Figure 11– Types of machining: a) Turning; b) Milling; c) Drilling; d) Grinding ........................... 18
Figure 12 - Clocking the reference datum before drilling ........................................................... 19
Figure 13 – Flowchart for the scheme review database ............................................................. 20
Figure 14 – The combustion rear inner case ............................................................................... 21
Figure 15 – Flowchart of the scheme review process ................................................................. 23
Figure 16 – Cross section of a combustion chamber ................................................................... 25
Figure 17 – Close-up of the FCL: a) Cooling holes b) Liner tiles ................................................... 26
Figure 18 – The GOM scanning unit and the triangulation principle .......................................... 27
Figure 19 – The Front Combustion Liner in scan (left) and in 3-D model (right) ......................... 28
Figure 20 – Inspection data of the FCL ........................................................................................ 28
Figure 21 – The probe of the adaptive machine ......................................................................... 29
Figure 22 – Probing an uneven surface before machining .......................................................... 30
Figure 23 – A sample repair matrix ............................................................................................. 31
Chapter One – Introduction to Industrial Attachment
1
1. Introduction to Industrial attachment
1.1. Objective: As part of the curriculum for students pursuing a degree in Aerospace Engineering at
Nanyang Technological University, Industrial Attachment is a compulsory 22-week
programme conducted for students in a relevant engineering company. The objective of
this attachment is to reinforce the university’s technical and theoretical teachings by
providing an opportunity for the students to apply it on valuable hands-on opportunities,
preparing them for their professional future as engineers.
The attachment program should enable the students to:
• Apply their technical knowledge
• Gain hands-on experience
• Acquire the necessary skills all good engineers should be equipped
with, such as manpower management, attention to detail, creativity and
flexibility in application of technical know-how, etc.
• Strengthen their work integrity and values through their time spent in a
professional capacity at the company and
• Pick up vital inter-personal skills that will help to the student build a
cohesive working environment for him/her with his/her colleagues.
Chapter One – Introduction to Industrial Attachment
2
1.2. Scope: The scope of this Industrial Attachment was for the author to fully assume the role of a
Development Engineer. A Development Engineer oversees the repair capabilities of
SAESL, and is in charge of introducing and setting up new technologies that will
expand and improve the company’s present capabilities.
During her attachment, the author was required to familiarize herself with the various
repair operations being carried out in SAESL. Having done so, she was then put in
charge of SAESL’s scheme review process. This process entailed reviewing the various
repair schemes provided by Rolls-Royce, and then deciding and declaring if it was
within SAESL’s capacity to carry out the respective repairs. Knowledge of the shop
floor was essential for this task, as the author needed to know exactly which types of
repairs could be carried out, and which types could not and hence needed to be
outsourced.
The bulk of the author’s time at SAESL was dedicated to her largest project, the setting
up of the new Front Combustion Liner (FCL) cell. Incorporating cutting edge
technologies like optical measuring scans and adaptive machining, this cell will serve a
niche market around the world for FCLs. The cell was developed from scratch;
machines had to be imported, its software had to be set up, and all the necessary
paperwork from Rolls-Royce had to be processed.
This report will document these tasks undertaken by the author during her employment
in SAESL.
Chapter One – Introduction to Industrial Attachment
3
1.3. Company Profile Singapore Aero Engine Services Private Limited (SAESL) was established in 1999 as a
S$185 million tripartite joint venture between SIA Engineering Company (50%), Rolls-
Royce (30%) and Hong Kong Aero Engine Services Limited HAESL (20%). It is part
of Rolls-Royce’s Aero Repair and Overhaul Committee (AROC) network of Rolls
Royce engine Maintenance, Repair and Overhaul (MRO) repair facilities around the
world. As part of AROC’s network, SAESL operates as the MRO centre of Rolls-Royce
Trent engines within the Far East, the Middle East, Australasia and the Pacific Rim.
Figure 1 – Birds-eye view of the SAESL facility[1]
SAESL is a Rolls-Royce authorized MRO shop, and is the only shop in the world
capable of servicing the complete line of Trent Family engines as listed below:
• Trent 500 Series Engines
• Trent 700 Series Engines
• Trent 800 Series Engines
• Trent 900 Series Engines
SAESL is also the first MRO facility in the world to service the new Trent 900 engine
that powers the famous Airbus A380.
Chapter One – Introduction to Industrial Attachment
4
Covering an expanse of 30,000 square metres, SAESL's facility is designed to repair up
to 250 Trent engines a year. The building houses state-of-the-art aero engine MRO
systems, including the in-line gantry system for engine strip and assembly, as well as
the world’s first fully automated chemical cleaning line.
Figure 2 – SAESL’s in-line engine gantry (left) and cleaning line (right) [1]
In 2007, SAESL’s Compressor Blade Cell was awarded the coveted Rolls-Royce Centre
of Excellence – Gold award. This $13 million repair facility was the first in the world to
employ robots as part of their processes, and the employment of such a technology
helped to reduce required man-hours, lower repair costs, and hasten the cycle time for
each repair.
Presently, SAESL’s clientele includes Singapore Airlines, Virgin Atlantic Airlines,
Emirates, Thai Airways, Qatar Airways, Air New Zealand, and many more. With such a
sound customer base and a growing list of impressive accolades bearing testament to the
first-class repair services offered by SAESL, it comes as no surprise that SAESL is
known around the world as a Trent Centre of Excellence.
Chapter One – Introduction to Industrial Attachment
5
1.4. Repair Development Department The repair development department in SAESL is a branch of the Engineering
department, and is responsible for introducing new technologies into SAESL’s
production line. The development engineers constantly study emerging technologies
and identify relevant ones. They then undertake the project of importing the
technologies into SAESL, and ensuring its full functionality in terms of hardware,
software, and skilled manpower. This department is vital in ensuring that SAESL
remains at the forefront of the MRO industry with the employment of cutting edge
technology, and provided an excellent learning ground for the author.
Chapter Two – The Jet Engine
6
2. The Jet Engine
Figure 3 – Cutaway of a classic jet engine [2]
The figure above shows a cutaway of a classic jet engine. Comprising a fan, a
compressor, a combustor, a turbine and an exhaust nozzle, it relies mainly on Newton’s
Third Law of motion to deliver the thrust required to power a plane. In the subsequent
paragraphs, the mechanics of a jet engine will be detailed according to its individual
modules.
2.1. Fan The fan is the primary producer of thrust in a jet engine. Functioning as a low pressure
compressor, the air that passes through the fan is compressed to almost twice its original
pressure. Approximately 10 to 20% of the compressed air then enters the engine core.
The remaining 80% of the air is immediately expanded through the constricted exhaust
of the fan case. The expanded air accelerates, and it is this accelerated air that, in
Chapter Two – The Jet Engine
7
accordance with Newton’s Third Law of reactive forces, provides the engine with
approximately 75% of its overall thrust delivered [2].
2.2. Compressor
Figure 4 – Cutaway of a jet engine compressor[2]
A single stage compressor is made up of an adjacent row of rotor and stator blades. The
rotor blades are mounted onto a bearing drum connected via a shaft to the turbine at the
rear of the engine which rotates the rotor at a high speed. When the air passes through
the rotor, some kinetic energy from the rotor is transferred to the air, causing a pressure
rise. The stator located downstream (seen as Variable Stator Vanes (VSVs) above), then
removes the swirl in the air caused by the rotating motion of the rotor, preparing it for
the next stage of the compressor.
The fan, as mentioned, functions as a low pressure compressor (LPC), which is
followed by the Intermediate Pressure Compressor (IPC). The figure above shows
labels such as IP1 and IP8. IP1 stands for Intermediate Pressure Compressor Stage 1
and IP8 for stage 8. Several stages are required in a compressor, as a single stage is not
able to accomplish the necessary pressure rise. However, it is important to note that the
rotors are connected to a single bearing, and hence rotate at the same speed.
Chapter Two – The Jet Engine
8
The final module of the compressor is known as the High Pressure Compressor (HPC).
The HPC operates at a higher rotational speed than the IPC due to the decreased
compressibility of the pressurized air, hence the need for higher energy transfers. By
separating the HPC from the IPC, the two modules are connected to different sections of
the turbine that will allow the two compressors to rotate at different speeds. This split
compressor technology is a Rolls-Royce trademark, and is one of the major contributing
factors for the superior efficiency of Rolls-Royce’s Trent engines.
2.3. Combustor
Figure 5 – A jet engine combustion chamber[2]
The combustor handles the task of burning the large volumes of compressed air exiting
the compressor. The air exiting the compressor is drastically decelerated, and enters the
main component of the combustion chamber, the Front Combustion Liner (FCL). A fuel
injector sprays fuel into the incoming air, creating a highly combustible air/fuel mix. A
spark plug then ignites the mixture that will burn in a self-subsisting flame for the entire
flight cycle. The combustion process dramatically raises the temperature of the
Chapter Two – The Jet Engine
9
incoming air. According to the laws of thermodynamics, the pressure drop in the hot air
as it expands through and turns the turbine is less than its initial pressure rise caused by
the compressor. The excess pressure then becomes available as engine thrust when it is
exhausted from the nozzle.
2.4. Turbine
Figure 6 - pictorial of airflow in a jet engine turbine[2]
Like the compressor, the turbine is made up of rows of stators and rotors. However, in
the turbine, the stator is placed before the rotor. Following the combustion process, the
high temperature-and-pressure gas is forced into the High Pressure Turbine (HPT). The
nozzle guide vanes swirl the air in the direction of the turbine blades’ rotation. Energy is
then extracted from the tailored flow that creates a torque on the turbine, causing the
turbine disc to rotate, and in turn drive the compressor at the front of the engine.
After passing through the entire core of the engine, the air is exhausted to the
atmosphere in a constricted exhaust, just like that of the fan. The exhaust, being a high
velocity and high pressure gas stream, acts as a reactive force on the rear of the engine,
Turbine
Nozzle Guide Vanes (stator)
Chapter Two – The Jet Engine
10
contributing to the other 25% of the jet engine’s overall thrust. With that, this chapter
concludes the introduction to the working principles of the jet engine.
Chapter Three – Orientation on the Shop Floor
11
3. Orientation – Induction to the shop floor Repair jobs come from airlines all over to world to SAESL in three forms – as a whole
engine, as individual modules (for example: a high pressure compressor), or as a single
component. The engines and modules are stripped to their individual parts before being
sent for cleaning, and subsequently, inspection. Parts found to be damaged beyond
repair are discarded, and replaced with new parts. Parts found to be damaged but still
repairable are then sent to the shop for repairs according to standard repair procedures
set out by Rolls-Royce.
In her first month at SAESL, the author was attached to various repair cells for short
periods of time. The purpose of this was to introduce the author to the different types of
repair carried out in SAESL, to prepare her for her subsequent tasks in the company.
3.1. Fan blade cell The first cell that the author was attached to was the fan blade cell (FBC). Unlike other
cells, the FBC was different in that it was a component cell. A component cell is a
stand-alone, capable of existing on its own without support from other cells. The FBC
repairs only fan blades, and is able to independently carry out most repairs that a fan
blade might require.
There are two standard repairs that all fan blades sent for overhaul will undergo.
Assuming no abnormal damages such nicks or dents on the blades, each blade will have
its leading edge profile and aerofoil surface restored during overhaul. Throughout the
author’s two-day attachment, she assisted the technicians in the cell in carrying out the
above two repairs on a set of Trent 800 engine fan blades.
Chapter Three – Orientation on the Shop Floor
12
Figure 7 – Workflow of a typical fan blade repair
Each engine consists 26 fan blades. The figure above demonstrates the procedure of a
typical fan blade repair. After being stripped from the engine and cleaned, the set of
blades were sent to the FBC. The author inspected the blades visually and with
ultrasound to check for surface damage or interior cracks. None were present. The
blades then had their leading edge profile checked against a standard mould provided by
Rolls-Royce. After several cycles of engine run, the blades which were initially
designed aerodynamically for drag reduction purposes had experienced erosion of their
leading edge. The author used a hand-held grinding machine to file the leading edges of
the blades back to their original profile, and polished them with an abrasive stone to
smoothen the edge.
Chapter Three – Orientation on the Shop Floor
13
Figure 8 – Different surfaces of the fan blade after various processes
Following that, the blades were loaded into the glass peening booth, for the surface of
the blade to be blasted with glass beads. Glass peening is similar to shot peening (to be
discussed later), and is used to improve the surface strength of the titanium fan blades.
This will prevent cracks from forming. This step was particularly time-consuming as the
machine was only able to process one blade at a time with a cycle time of 20 minutes
per blade. After this step, the author brought the blades to the final station – the vibro-
polish station. The blades were loaded onto the polishing machine and submerged into a
tank of pink aluminium oxide media. The machine vibrated the blade, causing the
Aluminium Oxide to rub against and polish the surface. After the blades had been
polished, the author’s last task was to measure the surface roughness of the blades, to
ensure that they were compliant to Rolls-Royce standards. Once all 26 blades had
passed the checks, her assignment in the fan blade cell was considered complete.
3.2. Fitting cell The next cell that the author was attached to was one of the most important cells in
SAESL – the fitting cell. Unlike the fan blade cell, all subsequent cells that the author
was attached to were process cells that specialized in processes, not components.
Repairs in this cell are carried out manually by technicians, using simple hand tools like
drills, grinders and even penknives. As a result, this cell covers a very wide range of
Surface of Engine-run blade Surface of glass-peened blade Surface of vibro-polished blade
Chapter Three – Orientation on the Shop Floor
14
repairs in SAESL, because the repairs are not limited by the capabilities of the machines
employed in other cells.
Figure 9 – the workflow for the repair of a composite fairing
The author spent a week at the fitting cell, repairing composite fairings. A fairing is a
light-weight structure used to cover oddly-shaped protrusions on the aircraft, making it
more streamlined and hence reducing drag. It is made of a carbon fibre sandwich, with a
honeycomb core in the middle, making it extremely lightweight. In the component sent
for repair, the carbon fibre had become delaminated from the honeycomb, and work was
required to bind it back. The author first drilled 1mm holes all over the carbon fibre in
the area that had become delaminated. These holes were used for forcing adhesive into
the sandwich, and the sandwich was then clamped together to allow the adhesive to cure.
After curing, as an additional measure, blank metal plates were screwed together on
both sides of the sandwich. The fairing was then considered successfully repaired.
Chapter Three – Orientation on the Shop Floor
15
Although this was a complex process that took almost a day for each single fairing, the
author was able learn a lot, from wielding the tools, to making the metal blanks and
mixing the necessary products to make the adhesive. Through the process, the author
also learned about safety standards in the work place, as well as other aerospace
standard practices like tool box organization – tools are placed in toolboxes in
customized grooves, known as shadow boxes, which make accounting for the tools easy
after each repair, ensuring that no tools have been accidentally left on the component. In
her attachment to this cell, the author was able to understand and appreciate the menial
jobs that the technicians were required to carry out, and which helped her understand
the shop floor operations much better.
3.3. Shot peening cell The shot peening cell is new in SAESL, only set up in September 2009 by the repair
development department. Shot peening is a process used on metals that will increase
surface hardness. Countless small spherical particles (known as shots) are thrown at the
metal surface at a very high speed, deforming the molecules and creating residual
compressive stress on the surface. This internal stress will act against external tensile
forces to increase the strength of the metal, and will prevent crack propagation, as seen
in figure 10 below.
Figure 10 – fundamentals of shot-peening
Deformed molecules Crack being pushed together
Chapter Three – Orientation on the Shop Floor
16
Rolls-Royce has stipulated the use of the shot peening treatment on many metal parts
deemed to undergo a lot of stress during engine run. Because shot peening is a very
complicated technology due to the randomness in the firing of the shots, it is a very
carefully controlled process by Rolls-Royce. The approval to carry out this process is
granted only to a select few companies worldwide, including SAESL, who have
demonstrated their shot-peening capability to Rolls-Royce.
In SAESL, shot-peening is a fully automatic process. A nozzle is affixed to the head of
a 6-axis robot, and the shots are fired from the nozzle. The speed and volume of the
shots being fired per second is controlled by the shot peening machine. The component
to be peened first has to be masked – using rubber plugs to cover and protect the areas
of the component not meant not be peened. Then, the part is mounted on to a rotating
turntable in the booth. For each type of repair of each part, a computer program has
been written for it, directing the movement of the nozzle (i.e. robot arm), the intensity
and volume of the shots being fired, and the rotation of the turntable. Once the part is
loaded into the machine, the doors are closed, and the machine is set to run
automatically.
The attachment to the cell for the author was relatively simple, as the process was
completely automated. However, through the attachment, the author learnt about the
properties of the different metals in a jet engine and the fundamental theory of shot
peening. Also, through maintaining the shot peening machine, the author learnt about
the mechanics of the machine, and how the shots are processed, both before, and after
being fired.
Chapter Three – Orientation on the Shop Floor
17
3.4. Machining Machining is an age-old process used since the 18th century, and involves using a cutter
to remove material from a component to achieve a desired geometry. It is one of the
most important processes in any production or repair factory, and likewise in SAESL.
Like the shot peening cell, the cutting tool on the machine is also attached to a robot.
However, the machining robots only move in 3-axes (up, down, left, right, front and
back), and are manually operated.
Machining can be broadly divided into 4 categories:
• Turning: is where the cutting tool is stationary, and the work piece rotates.
• Milling: is where the work piece remains stationary and the cutter is a rotating,
multi-tooth cutter. The axis of rotation of the cutter is often perpendicular to the
work piece.
• Drilling: the creation of cylindrical holes using twist drill on a stationary work
piece.
• Grinding: a process used mainly for finishing touches on surfaces, removing
very small amounts of material.
Chapter Three – Orientation on the Shop Floor
18
Figure 11– Types of machining: a) Turning; b) Milling; c) Drilling; d) Grinding
One of the most important steps in machining is the clocking of the reference datum.
Because the cutter only has 4 axes of motion, the position of the repair component is
very important. In drilling, it is important that the surface to be drilled is set
perpendicular to the cutting tool. Likewise, in turning, the component to be machined
must be placed directly at its centre of rotation. If it is slightly off-centre, the machine
will wind up cutting too deep into one side of surfaces, and not cutting the opposite side
at all. The clocking process is carried out using a pressure dial attached to the robot in
place of the cutting tool. When clocking the reference datum, the dial should read a
constant pressure from the spindle for the entire surface. If there are abnormalities in the
a) b)
c) d)
Chapter Three – Orientation on the Shop Floor
19
readings, the repair part will then have to be re-positioned. After the part has been
positioned, the cutting tool is attached to the robot, and the operator will begin
machining it. The parameters to be controlled are the speed of rotation of the component
(for turning), the speed of rotation of the cutting tool (for drilling and milling), and the
position and movement of the cutting tool. After machining, the operator has to finish
off the machined surface by hand, using sandpaper to even out the texture of the metal.
Figure 12 - Clocking the reference datum before drilling
This attachment was particularly interesting for the author, as machining is a
fundamental industrial process. The author was able to identify the various cutting tools,
as well as recognize the purposes and surface finish created by each tool. The author
was also able to learn from the experienced technicians and operators the speed at which
the tool/work piece should be rotated to achieve a clean surface finish. The author now
understands the machining process much better, which is knowledge that will come in
useful both in the production and the overhaul industry.
Chapter Four – Repair Scheme Reviews
20
4. Repair scheme reviews The author’s orientation to the shop floor was aimed to prepare her for her next task –
taking charge of SAESL’s scheme review system. SAESL is a Rolls-Royce MRO shop,
servicing only Rolls-Royce engines and parts. As such, all repairs carried out by SAESL
are governed by repair schemes planned by Rolls-Royce, known as Full Repair
Schemes (FRSs). FRSs are designed by Rolls-Royce engineers to dictate all repair
procedures, and are meant to cover any form of defect or damage that may occur to any
component of the engine when in use. Any damages not identified by the FRSs will be
considered irreparable, and the part will be scrapped. Being in charge of reviewing the
FRSs, the author’s responsibility was to constantly update SAESL’s own repair
capability database according to each FRS in the Rolls-Royce database. Rolls-Royce
constantly updates and creates new FRSs, and the author was required to ensure that
SAESL’s own database accurately reflected the company’s ability to carry out each
repair. The technicians at the Inspection Cell will then refer to the database to determine
if a certain repair can be carried out within the SAESL facility, or if it is necessary to
send the part to a sub-contractor who is able to carry out the repair. To document the
process, the author will use a case study of FRS K004 as attached in Appendix B, which
is a repair scheme for repairing cracks at the front flange bolt holes of the Combustion
Rear Inner Case (CRIC). In the subsequent paragraphs, the author will explain the
procedure of reviewing an FRS.
Figure 13 – Flowchart for the scheme review database
Rolls Royce
Full Repair Scheme
• Technicians in the inspection cell
• SAESL engineers
SAESL database
Author
Provides:
Reviewed by: Input to:
Accessed by:
Chapter Four – Repair Scheme Reviews
21
Figure 14 – The combustion rear inner case
FRSK004 dictates the repair of a CRIC, as shown in the figure above, whose bolt holes
have cracked during engine run. First, the cracks are dressed, i.e. enlarged, to create a
suitable profile for subsequent welding. This is to ensure that the weld filler is able to
enter the space of the small crack. After dressing, the crack is then filled with filler from
argon arc welding. Following the welding, the CRIC is sent for heat treatment to relieve
it of the thermal stresses occurred during welding, before being machined to the final
required dimension. To conduct a proper scheme review, there are several areas that
require attention.
4.1. Standard Equipment As found in section 2 of FRSK004, and in all FRSs, there exists a list of standard
equipment required to conduct the repair. This repair calls for argon arc welding
equipment, copper chills, degreasing equipment, drill bits, hand tools, heat treatment
equipment, inspection equipment, machining equipment, penetrant crack test equipment,
swab etch equipment, vapour blasting equipment, and finally vibration peen equipment.
It was the author’s responsibility to ensure that all equipments were available and
functional in SAESL, before carrying on with the repair. If there were to be certain
Chapter Four – Repair Scheme Reviews
22
equipment that were not available in-house, the author was then required to identify the
unavailable procedures, and make arrangements for the procedures to be sub-contracted
to a third party vendor to complete the repair. In order to carry out this step, it was
necessary for the author to have a firm knowledge of all equipments available in
SAESL, which took a few weeks, and many trips to each individual cells, to acquire.
4.2. Consumable Materials Consumable materials, otherwise known as OMat, are the substances and products used
up in the process of the repair. It is, although smaller in scale, as important as the repair
equipment, as a repair cannot be carried out without either. The author was required to
ensure that SAESL constantly maintained a stock of all OMats required for each repair.
If there were OMats which SAESL did not maintain a stock of, the author had to ensure
that there were either other equivalent OMats available, or bring the matter to the
attention of the Materials Planning department, who would then stock the missing OMat.
4.3. Equipment capabilities In the most important step of reviewing a repair scheme, the author had to assess the
capabilities and limitations of the equipment, and if it were capable of carrying out the
task. In the FRSK004 example, dressing and welding were manual repairs carried out
by technicians, and usually face no capability problems. However, repairs using
machines and other complex equipments face more constraints. In heat treatment, it is
important to note if SAESL’s furnace is large enough, and if it is able to reach the
specified temperatures. In machining, because most machines only move along 4-axes,
it is important to note if the surface areas that require machining are accessible by the
cutting tools on the machines. This is the most complex step of the review, and the
Chapter Four – Repair Scheme Reviews
23
author had to learn the capability of each individual machine, or seek the opinion of an
operator with such knowledge. It was through this exercise that the author was able to
learn much more about the functions and mechanic principles of the various machines.
After confirming all above criterion, the author was required to fill in necessary
paperwork in the SAESL database. The standard forms, filled out to FRSK004, are
attached in Appendix C. After filling out the forms and updating it into the SAESL
database, the review would be considered complete. Hence, in the future, if the
inspection technicians were to notice a defect on the CRIC that required a FRSK004
repair, they would be able to see, through the database, if SAESL was able to handle
this repair, or if it had to be sent to a sub-contractor. A summary of the scheme review
process is shown in the diagram.
Figure 15 – Flowchart of the scheme review process
Full Repair Scheme
Equipment
Yes
No Outhouse
Consumables
Yes
No Request to purchase
Equipment capability No Outhouse
Yes Develop solution to overcome equipment limits
D
A
T
A
B
A
S
E
Chapter Four – Repair Scheme Reviews
24
Through her task of reviewing and updating more than two hundred FRSs, the author
had become more familiar with the administration style of Rolls-Royce. She also gained
much more knowledge about all shop floor operations in SAESL, as well as established
a strong rapport with the technicians, known commonly as “the hands on the ground”. It
was a meaningful task for the author, as she was not only able to contribute to the
company by updating its database, but also benefitted from the learning experience of
this task.
Chapter Five – The Front Combustion Liner Cell
25
5. The Front Combustion Liner cell No attachment to the Repair Development department would be complete without
taking up a development project. During the author’s attachment to the department, she
joined a team of two other colleagues, in the process of building a new repair cell, the
Front Combustion Liner (FCL) cell. The first in Singapore and second worldwide to
service Rolls-Royce FCLs, the new cell incorporates cutting edge technologies which
will be explained in subsequent sections. As the project is still under development,
much of the information is confidential, and cannot be discussed in detail.
5.1. The Front Combustion Liner An FCL is commonly known as a combustion chamber, and is the component in which
the combustion in a jet engine takes place. A cross section of the FCL is shown in the
figure below; while the combustor assembly is shown in figure 5 of section 2.3. The
FCL is a fairly complex component due to the extremely high temperatures and
velocities of the airflow involved, in excess of 2100˚C and 150m/s respectively.
Figure 16 – Cross section of a combustion chamber
Chapter Five – The Front Combustion Liner Cell
26
As can be seen from the figure 16, only a small portion of the airflow enters the FCL
directly. The rounded section at the front of the FCL, known as a Head, acts as a
diffuser to slow down the airflow coming into the FCL. The remaining air either enters
the airflow through several holes all around the FCL, or only rejoins the air at the end of
the combustion process, to cool the airflow before it enters the turbine. Fuel is sprayed
through nozzles in the head to create a combustible air/fuel mix, before being ignited.
The lowered-velocity airflow, coupled with the recirculation of the air caused by the air
entering the FCL through holes in the wall, is then able to sustain a steady flame.
The walls of the FCL are lined with ceramic-coated tiles, known as liner tiles. These
tiles are designed to contain the heat of the flame, and its cooling technique is shown in
the figure below. Infinitely many cooling holes are drilled into the walls of the FCL, as
seen in Figure 17a). These holes allow the cool air running outside the FCL to transpire
into it. Then, as seen in b), the cool air impinges on the tile, before moving through the
gap between the tile and the wall, cooling it through convection. These tiles are
removable for easy maintenance and replacement. In carrying out repairs on the FCL,
the tiles are always removed before any work is to be done on it.
Figure 17 – Close-up of the FCL: a) Cooling holes b) Liner tiles
a) b)
Chapter Five – The Front Combustion Liner Cell
27
5.2. GOM machine – Optical measuring technique In attempting to automate all processes in the FCL cell, SAESL imported a relatively
new technology of 3D optical measuring from German company GOM – their
Advanced Topometric Sensor (ATOS) system for the purpose of inspection. The central
projector on the ATOS unit projects a unique fringe pattern on the FCL, and the two
cameras mounted on either side of the projector is able to measure the 3-D coordinates
of the fringe pattern based on the triangulation principle as illustrated in the figure
below.
Figure 18 – The GOM scanning unit and the triangulation principle
Through measuring the coordinates of the fringe patterns projected onto the FCL
surface, ATOS generates a cloud of 3D coordinates that map out its surface. The GOM
software on the computer then transforms the coordinates into an editable mesh. After
making necessary adjustments to the mesh (removing anomalous points and redefining
complex edges), the solid surface of the FCL is then generated. A semi-generated
Projector
Cameras
α β l
d?
Chapter Five – The Front Combustion Liner Cell
28
(software is not completely set up) FCL is shown in the figure below, and in Appendix
D.
Figure 19 – The Front Combustion Liner in scan (left) and in 3-D model (right)
As mentioned previously, the GOM ATOS system is used for inspection. Inspection is
done by comparing the solid surface of the live FCL to pre-existing Computer-Aided
Design (CAD) data, created by the author on the SolidWorks program. The Solidworks
model, shown above and in Appendix D, is created from technical drawings from Rolls
Royce, and represents the ideal shape and geometry of the FCL. The GOM software is
then able to calculate and display the surface deviation between both models (example
shown on following page), and hence highlight the areas of deformation on the live FCL.
Figure 20 – Inspection data of the FCL
Chapter Five – The Front Combustion Liner Cell
29
Although the setup of the GOM inspection is still a work in progress, the advantages are
clear. By automating the process, not only does it save time, inspection is also less
subject to human error and oversight – one of the largest problems with visual
inspection.
5.3. DMG – Automated Machining The other new technology employed in the FCL cell is the DMG (Deckel Maho
Glidemeister, a German machining company) machine, used to carry out adaptive
machining. Adaptive machining is an up-and-coming technology in the aerospace
industry[3], and SAESL is one of the first MRO firms in Singapore to employ it in its
operations. In the subsequent paragraphs, the author will explain the principle of
adaptive machining. As it is still under development, information regarding its purpose
in the FCL cell is confidential to SAESL and will not be discussed in detail.
The adaptive DMG machine begins by probing the surface of the component, in this
case, the FCL. This is to determine the exact position of the FCL, and hence set the
reference datum of the cutting tool. This saves time as there is no need to clock and
adjust the position of the as opposed to conventional machining (section 3.4).
Figure 21 – The probe of the adaptive machine
Chapter Five – The Front Combustion Liner Cell
30
The DMG machine then uses the same probing tool to probe the surface that requires
machining, for example, a welded area that needs to have its geometry and dimensions
restored. As welded surfaces are often uneven, the probe traces the surface of the weld,
and is able to effectively communicate the path that the cutting tool should take when
machining the weld. This helps to avoid over/under-machining, which is a common
problem for conventional machining when faced with uneven surfaces. With intelligent
adaptive machining, the cutting tool knows the exact topography of the surface, and is
able to adjust accordingly to give an even thickness on the finished product.
Figure 22 – Probing an uneven surface before machining [3]
Another application of the adaptive DMG machine that is particularly relevant to the
aerospace industry is its ability to machine components that have been distorted out of
their original shape. As jet engines run at extremely high temperatures, many
components, especially the FCL, that come in for repair are seldom still in their original
shape due to heat distortion. In such cases, the GOM technology will be able to detect
the deviation of the part’s geometry, and coupled with the surface probing by the
adaptive machine, a customized toolpath can be generated for the machining of the
distorted part that would otherwise have been a slow and manual process.
Chapter Five – The Front Combustion Liner Cell
31
In helping to set up the two state-of-the-art machines in the FCL cell, the author has
gained much knowledge. Not only did the task provide her with a glimpse into the
future of the MRO industry in optical scans and adaptive machining, it also taught her
the fundamentals of what it meant to be an engineer – to identify new technologies,
recognize their potential to suit your needs and adapt it accordingly, while keeping an
agile mind to deal with all the problems that crop up along the way.
5.4. Planning the repair matrix The author’s other task with the FCL cell was more administrative – planning what is
known as a repair matrix. There are several repair schemes that govern the repairs of an
FCL, and any FCL that comes into SAESL would possibly require none, one, more, or
all of the repairs. The repair matrix, as attached and shown in Appendix E, combines all
the repair schemes of the FCL, or any other component in question, and groups similar
processes, such as cleaning, or machining together. The order of the individual repair
schemes cannot be jumbled (i.e. if the repair scheme calls for welding before machining,
the FCL must first be welded before being machines). Care must also be taken when
fitting the repairs together, as certain repair processes may interfere with each other, and
cannot be simply combined. A simple example is shown below:
Component X Repair 123 Repair 456 Cleaning x x Inspection x x Water jet stripping x Plasma coating x Welding x Machining x x
Figure 23 – A sample repair matrix
Chapter Five – The Front Combustion Liner Cell
32
By planning such a matrix, it ensures that all FCL components that arrive in SAESL for
repair is able to have any combination of repairs carried out on it in a very efficient
manner, as the repairs are able to run side-by-side, instead of first completing repair 123,
before starting on repair 456. Such efficient systems allow SAESL’s manufacturing
processes to be leaner, hence contributing to SAESL’s overall productivity, and market
competitiveness.
Chapter Six – Personal Reflections and Conclusion
33
6. Personal Reflections and Conclusion
6.1. Personal Reflections The 22 weeks I spent at SAESL has been an incredible learning journey, and will
certainly be one that I carry with me through my working life. It has provided me with a
wonderful introduction not only to the career and daily life of a professional aerospace
engineer, but also to the fundamental operations of any engineering firm.
When my mentor, Adrian, arranged for me to be attached to the various repair cells, his
purpose was for me to not only gain hands-on experience with the engine components,
but also to have a greater understanding of the technicians and the work that they do. He
believes that in order to know a process, person or machine well, one has to get his hands
dirty, to know their problems, to respect, eat and sweat with them. This understanding is
important for an engineer, as engineers are the “brains” in the office, planning the repairs
and procedures for the technicians, commonly known as the “hands”, to follow. Without
a good understanding of the technicians’ capabilities, engineers will face problems in
their planning processes. Through my attachment at the repair cells, firstly, I was grateful
for the opportunity to see and handle the engine components that I had previously only
read about and seen pictures of in textbooks. This greatly enhanced my understanding of
the jet engine, through my understanding of its individual components. However, more
importantly, I was able to build up a good rapport with the technicians in the various
cells, as they imparted their years of experience and wisdom to me. In helping to carry
out repairs, I was also able to fulfill Adrian’s target for me – to know the capabilities and
the limitations of the technicians and the tools they access, so as to enhance my own
Chapter Six – Personal Reflections and Conclusion
34
understanding of the shop floor, and hence improve my planning capabilities as an
engineer.
In my second task at SAESL, taking charge of the scheme review database, although
seen as a mundane task, was actually very interesting for the author. Having made friends
with the technicians, this task became relatively simple, as I was able to seek their
opinions on SAESL’s or even their own repair cell’s capability on the various repairs.
This task exposed me to many engine parts that I did not have a chance to handle while I
was in the repair cells, as I had only worked on a few components. In addition, I was also
introduced to other repair and process cells outside of the four cells I was attached to.
These included the cleaning line, the plasma cell, and several other cells that I was
formerly unfamiliar with. This enabled me to learn more about the various cells not just
in SAESL, but in any standard jet engine Maintenance, Repair and Overhaul shop. All in
all, I felt that this task really familiarized me with the standard operations of an MRO, as
most jet engine companies, such as General Electric and Pratt and Whitney, adopt similar
working styles, building their MROs around repair schemes dictated by the engine
makers.
Of course, the most enriching learning experience was my most important, and indeed,
most interesting task – the setting up of the FCL cell. Setting up this cell was quite a
roller coaster, and I regret that it was not able to be completed before the end of my
attachment. This task taught me several key skills of becoming an engineer. The main
machines, the GOM and the DMG, as explained in Chapter 5, were the brainchild of my
colleague, Alex, who noticed these up-and-coming technologies, and saw their potential
to meet his needs in the FCL cell. However, the setting up of these machines proved to
Chapter Six – Personal Reflections and Conclusion
35
be no simple task. A new problem arose from the machines almost every day in the
starting stages, and through learning to identify and overcome these problems on a daily
basis, I learnt the importance of being a quick and critical thinker as an engineer.
Machines, no matter how developed they become, will never be perfect substitutes for
human labour. However, in this day and age, machines are extremely vital in any
engineering process and hence, all good engineers must learn to work with machines, and
be able to deal with any problems that the machines may throw at you. The second thing
that I learnt was the ability and willingness to pick up any new skills that may be
required of you in your workplace. When I first entered SAESL, I had little knowledge
about Solidworks, or any Computer Aided Design software for that matter. However,
when CAD models were required for the GOM machine in the FCL cell, I had to learn it
quickly to meet this need. I borrowed books from libraries, sought help from online
forums, and was able to pick up the skill in time to draw the rather complicated FCL
model, as is shown in Appendix D. I learnt that we may not always have the necessary
skills, but it is important to be willing to learn in order to maximize your own
productivity for the company. Another learning journey was the background work that
went on for the setting up of the FCL cell. As engineers, it is easy to assume that our
responsibilities are mainly to handle the machines. However, that is not true. An engineer
that handles a project will have to liaise closely with the management for their support,
with financial managers to ensure that the project is operating within budget, with safety
officers to ensure that safety standards are being met, etc. A project is never a one man
show, and engineers must also display communication prowess in seeing a project to its
successful completion. This task has equipped me with many critical professional skills
that can be applied to my career, not only in engineering, but in other industries as well.
Chapter Six – Personal Reflections and Conclusion
36
Along the way, I have also taken up several small projects, of which there are too many
to document in this report. For example, I have written computer programs to automate
the processing and updating of information for databases in SAESL. These programs will
greatly simplify processing the database for my colleagues in the future. Most
importantly, I have learnt that a willing attitude is very important in the workplace. One
must never be too calculative about his/her own workload, must be willing to learn the
things he/she does not know, and must always help your colleagues when possible.
6.2. Conclusion In conclusion, I would like to thank all my colleagues in the Engineering Department,
who went out of their way to assist me in my inexperience, and who made my initiation
to the working life very enjoyable. Their warm-heartedness was very much appreciated
to a fresh student who had not worked in the capacity of an engineer before, and I
sincerely hope to have the chance to be their colleague once again.
I hope that I have been of good service to SAESL, and that the projects and tasks that I
have undertaken will be useful to their operations. SAESL is indeed a company at the
forefront of the MRO industry, and I am honoured to have completed my Industrial
Attachment here.
The lessons and skills that I have picked up in SAESL will accompany me no matter
where I go, and I now await my return to school in September 2010, where I am sure my
increased knowledge of the jet engine, and the aerospace industry, will be very useful to
my academic pursuit.
Chapter Seven - References
References
[1] Singapore Aero Engine Services Limited. (n.d.) Our Facility Retrieved 21 May 2010, from http://www.saesl.com.sg/index.html
[2] Rolls Royce. (2005). The Jet Engine. United Kingdom: St Ives Westerham Ltd.
[3] Peter Dickin, November 2008. The Adaptive Approach. Control Engineering Asia
Appendix
Appendix A – Organizational Chart of SAESL
CEO
Gary Nutter
Manager Finance & AdminWoo Lai Kuen
ManagerEngineering, HS&EChan Swee Heng
Manager Quality & C I
Tay Hang Chua
ManagerProduction
Leck Tea Kiang
Manager Cust Business Lawton Green
Snr Mgt Asst - Elsie Chan Mgt Asst - Stephanie Sim
Senior Mgt AccAudrey Pang
Head Fin A/gNicholas Cheong
Head Engrg(Overhaul Support) Gan Chin Yee
Head HS&EJohnny Cheng
Head Gen Repairs IYap Joo Ann
Head B3Yeo LP, Choy WP,
Leonard
Head B0Hamzah, Greg,
Chang
HeadTham JL
Manager Component Repair & Material
Tan Wai Meng
HeadLog & Warehousing
Jeffrey Ng
Head Material PlanningRavind
Finance Exec Finance Asst
Accountant A/C ExecsA/C Assts
HR Execs Snr/Tech Svc EngrsAsst Tech Svc Engrs
Procurement Execs
Material PlannersKitting Assts
Inspectors, Trainers,Technicians &Trainees
Inspectors, Trainers, Technicians,
Operators & Trainees
Cust Biz Exec (Head) David Su
Cust Biz Execs
Facilities Maint
� Finance & A/Cs Function� Business Plan deviation
monitoring� Liason with auditors� Prepare Company Finance
Manual� Provide Financial
performance� Company Secretary� Cash Management� Asset� Cashier� Credit Control� Legals� Facilities Maintenance
� Product Engineering� Workscope Requirement� SB Control / AD� Technical Library � Process Sheets� Safety� Workscope � T.V. Evaluations � HS&E
� Engine Receipt, Strip, Build,Prepare for Test, DespatchPrep & mvmt
� Module; Strip & Build,
� Clean, NDT,� Maintenance of Equipment
� Material Planning� Procurement� Control of Vendors� Shipping and receipt of
Goods� Warehousing� Kitting
� Head of Biz Process� Marketing� Sales� Bio Evaluation� Customer Comm & Sppt� Margin Protection� Contract Maintenance� HAESL, Head of Marketing
Liason� Credit Control
SAESL STRUCTURE - Key Roles / Responsibilties
ManagerPlanning & IT
Khoo Kee Swee
4 Layers StructureTo Man an Integrated Business and Production Processes
ManagerHuman ResourcesChristina Lee
Cust Biz Coordinators
Head HRMLynn Lim
Head, CompressorBlade
Sean Ho
Head Engrg(Repair & Support)
Chris Chu
Engineering SpecialistsSnr/Tech Svc EngrsAsst Tech Svc EngrsTechnical Coordinator
Head ProcurementAndy Goh
Material PlannersKitting Assts
Head Material Planning II Gary Goh
Head Plasma CoatingNg Boon Wee
HS&E Exec
Head Planning & IT Iris Tan
Prod Planners
IT Executives
� ContractManagement for IToutsourcing
� Master Planner� Production Planning� Production Status
� Staff Recruitment� Compensation & Benefits Mgt, Payroll� Learning & Devmt� Employee Relations� Grievance Procedure
� Direct access forQuality relatedmatters
� ISO 9000/ 14000� QA Admin & Audit� Technical Records� FAA, CAAS, JAA
Liason� Continuous
Improvement� Process Compliance
� General Repairs� Plasma Spray� Fan Blade Cell� Compressor Blade Cell� Lab Dev� Process Improvements
Black Belt CatherineAdrian
Trainee Black Belt Siew Tin Head NDT/ Cleaning
Oh Inn Chiam
Component Exec
PrincipalTechnologistKoh Li Teck
Updated as at 19 May 2009
Inspectors, Trainers,Technicians &Trainees
Inspectors, Trainers,Technicians,
Operators & Trainees
Equip Maint Tech
Head Sentencing Ng Kwee Liang
Inspectors, Trainers,Technicians &Trainees
Head Gen Repairs IIRandy Yap
Inspectors, Trainers,Technicians,
Operators & Trainees
Inspectors, Trainers,Technicians,
Operators & Trainees
Head QualityGanesh
Quality Engineer Training & Dev Engineer
Head Quality Ku Eng Chuan
Snr/Quality Engineers Asst Quality EngineerTech Rec Officers
Head BET1 (Test Cell & E&I) Sean BooInspectors, Trainers,
Technicians &Trainees
Head Gen Repairs III Lewis Foo
Inspectors, Trainers,Technicians,
Operators & Trainees
LabTechnicians &Operators
HR Exec
Head HRD Ferry Falco
Head NDT(Standards)Hendrich Lim
Compressor BladeInspectors, Trainers,
Technicians,Operators & Trainees
Fan BladeInspectors, Trainers,
Operators & TraineesTechnicians,
Log Execs & Log AsstsLogistics
Store InspectorsWarehouse Assts
Warehousing
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix B – Full Repair Scheme K004
Appendix
Appendix C – Repair Capability Form
Appendix
Appendix C – Repair Capability Form
Appendix
Appendix D – SolidWorks Model of the Trent 500 Front Combustion Liner
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell
Appendix
Appendix E – Scheme Matrix for the Front Combustion Liner Cell