1. I
TEAM AER4855 INTEGRATION PROJECT 4
ÉCOLE POLYTECHNIQUE DE MONTRÉAL |
PRESENTED TO : ABDELKADER KHERRAT
PROJECT AFT FUSELAGE
2016
2.
3. I
Team Members
Integration
Member Role
Genevieve Archer Vézina Project lead; ergonomics
Rose Beaulieu Mass manager
Julie Tran Main integrating resource; ergonomics
Frédéric Laham Ergonomics
Primary Structure Team
Member Role
Thomas Derenne Lead primary Structure; stress design
Mohammad El Bsat Design GFEM
Ali Kmeyha Design GFEM
Mohammed Mahdi Tika Design CATIA
Laura Sab Leblanc Stress design
Salah Wali Eddine Design CATIA
Secondary Structure Team
Member Role
Émile Cossette Lead secondary structure; systems positioning;
rack design
Augustin Eyebe Researcher
Gabriel Fortin Systems positioning; rack design
David Joseph Rack design (stress)
Jean-Philippe Roy CATIA design
Philippe Savard Rack design (stress)
Alexandre Scott Rack design (stress)
Mina Soleiman System positioning
Manufacturing Team
Member Role
Ulrick Gagné Lead manufacturing; cost estimation
Alexander Lesiak Material process; floor plan layout
Brigitte Robichaud Task cards; floor plan layout; ergonomics
4.
5. II
Abstract
The Aft Fuselage of the airframe structure is one of the key elements to complete the preliminary design
of the aircraft. This design must overcome multiple challenges through the requirements from different
departments and certification standards to ensure a rational and meaningful design.
The main topic of this project is to demystify the requirements of each section then to propose a process
that covers the different aspects of the product. This project covers the integration of the product between
primary and secondary structure, the incorporation and positioning of systems, the development of a
manufacturing procedure and assembly plant, and finally an ergonomics study on the whole.
The primary and secondary structures will both present the final results of the looping between the CAD
and the GFEM models, and the general methodology pursued in the elaboration of the different aspects
of the design. This part of the project will also include the dimensioning of the final parts, the tools created
in order to synchronise the model, and the final positioning for all the systems will be presented to
complete the general requirements of the two departments.
The ergonomics’ part in the project covers the methodology used in order to define and classify the critical
systems, adjustments to their positioning or installation, and certification standards. In addition, it will
provide a global design analysis from the point of view of the ergonomics department.
Finally, the project will present the new feature that includes the cascade of the manufacturing process.
This section covers the floor plan design, the analysis and the selection of the different materials, and the
overall cost of manufacturing. To conclude, the assembly process with all the worksheets for most of the
parts that are developed will also be presented.
6.
7. III
ACRONYMS
Assy Assembly
CG Center of Gravity
FEM Finite Element Model
Fuse Fuselage
GFEM General Finite Element Model
IML Inner Mold Line
NTEW Not to Exceed Weight
OML Outer Mold Line
PS Primary Structure
SS Secondary Structure
RBE Rigid Body Entity
MPC MultiplePoint Constraint
SPC Static Point Constraint
8.
9. IV
Table of Content
Team Members..................................................................................................................................... I
Integration........................................................................................................................................ I
Primary Structure Team .................................................................................................................... I
Secondary Structure Team ................................................................................................................ I
Manufacturing Team......................................................................................................................... I
Abstract................................................................................................................................................... II
ACRONYMS............................................................................................................................................. III
List of tables .......................................................................................................................................... VII
List of figures ........................................................................................................................................ VIII
REQUIREMENTS AND OBJECTIVES............................................................................................................ 1
1. Requirements............................................................................................................................... 1
2. Given Information........................................................................................................................ 1
3. Objectives .................................................................................................................................... 2
General............................................................................................................................................ 2
Primary Structure............................................................................................................................. 2
Systems............................................................................................................................................ 2
Secondary Structure......................................................................................................................... 2
Manufacturing ................................................................................................................................. 2
PRODUCT................................................................................................................................................. 3
General Overview ................................................................................................................................ 3
1. Integration ................................................................................................................................... 4
1.1 Mass and CG......................................................................................................................... 4
1.2 Final Cost.............................................................................................................................. 9
1.3 Nomenclature..................................................................................................................... 10
2. Primary Structure....................................................................................................................... 14
2.1 Final Design and Results...................................................................................................... 14
2.2 Methodology and Hypotheses ............................................................................................ 24
2.3 Design Tool......................................................................................................................... 28
2.4 Modeling (GFEM)................................................................................................................ 30
2.5 CATIA Model....................................................................................................................... 32
2.6 Detailed Design................................................................................................................... 39
3. Systems...................................................................................................................................... 46
10. V
3.1 Final Positioning ................................................................................................................. 46
3.2 Positioning Tool.................................................................................................................. 51
4. Secondary Structure................................................................................................................... 52
4.1 Final Design ........................................................................................................................ 52
4.2 Methodology and Hypotheses ............................................................................................ 56
4.3 Design Development........................................................................................................... 58
4.4 Design Analysis Results....................................................................................................... 62
4.5 Detailed Design of Rack 7.................................................................................................... 63
5. Ergonomics ................................................................................................................................ 69
5.1 Methodology and Hypotheses ............................................................................................ 69
5.2 Critical Systems and Evaluation........................................................................................... 70
5.3 Primary Structure Maintenance and Manufacturing Considerations ................................... 73
6. Manufacturing ........................................................................................................................... 74
6.1 Materials & Processes......................................................................................................... 74
6.2 Floor Plan ........................................................................................................................... 77
6.3 Assembly Steps................................................................................................................... 83
6.4 Total Cost of Production ..................................................................................................... 89
CONCLUSION....................................................................................................................................... 103
RECOMMENDATIONS .......................................................................................................................... 104
Mass................................................................................................................................................ 104
Primary Structure............................................................................................................................. 104
Manufacturing ................................................................................................................................. 104
Secondary Structure and Systems .................................................................................................... 105
APPENDICES.............................................................................................................................................. i
APPENDIX 1: PROJECT TIME LINE..........................................................................................................ii
APPENDIX 2: SYSTEMS LIST, COMPLIANCE MATRIX, SYSTEMS POSITIONS.............................................vi
APPENDIX 3: FEM RESULTS....................................................................................................................x
APPENDIX 4: ERGONOMICS................................................................................................................xiv
APPENDIX 5: TASK CARDS................................................................................................................. xxxi
11. VII
List of tables
Table 1: Weight Distribution for the Final Product.................................................................................... 4
Table 2: Detailed Weight Distribution and Weight Origins........................................................................ 5
Table 3: CG coordinates in CATIA ............................................................................................................. 7
Table 4: Nomenclature for parts in CATIA .............................................................................................. 11
Table 5: Nomenclature for sub-assemblies in CATIA............................................................................... 11
Table 6: Nomenclature for parts for Racks FEM...................................................................................... 12
Table 7: Materials used.......................................................................................................................... 14
Table 8: Stringers sections ..................................................................................................................... 20
Table 9: Dimensions of the frames......................................................................................................... 23
Table 10: Floor beam's dimensions ........................................................................................................ 23
Table 11 : Materials used for the Avionic Racks...................................................................................... 52
Table 12: types of sections..................................................................................................................... 53
Table 13 : Static Margins for Rack 7........................................................................................................ 62
Table 14 : Dynamic Analysis for Rack 7................................................................................................... 62
Table 15: Critical systems....................................................................................................................... 70
Table 16: Excel document “Manufacturing Costs Estimation.xlsx” organisation summary ...................... 74
Table 17: General processes selection for primary structure components. ............................................. 76
Table 18: General processes selection for secondary structure components. ......................................... 76
Table 19: Types of task cards (assembly and sub-assembly) for structure component ............................ 83
Table 20: Types of task cards for systems............................................................................................... 84
Table 21: Summary of the production and acquisition costs of the aft fuselage components. ................ 92
Table 22: Summary of the production and acquisition costs of the aft fuselage components. ................ 97
Table 23: Summary of the total production costs of the aft fuselage. ................................................... 102
Table 24 : Static Margin for Rack 1 & 3......................................................................................................x
Table 25 : Static Margin for Rack 2 & 4......................................................................................................x
Table 26 : Static Margin for Rack 5 ............................................................................................................x
Table 27 : Static Margin for Rack 6 ...........................................................................................................xi
Table 28 : Static Margins for Rack 8..........................................................................................................xi
Table 29 : Dynamic Analysis for Rack 1 & 3..............................................................................................xii
Table 30 : Dynamic Analysis for Rack 2 & 4..............................................................................................xii
Table 31 : Dynamic Analysis for Rack 5....................................................................................................xii
Table 32 : Dynamic Analysis for Rack 6...................................................................................................xiii
Table 33 : Dynamic Analysis for Rack 8...................................................................................................xiii
Table 34:Systems criticality evaluation....................................................................................................xv
Table 35: Systems criticality evaluation..................................................................................................xvi
12.
13. VIII
List of figures
Figure 1: CATIA Model of the Aft Fuselage ............................................................................................... 3
Figure 2. Distribution of fuselage weight.................................................................................................. 4
Figure 3. Aft-fuse CG as seen from the front ............................................................................................ 6
Figure 4. Aft-fuse CG as seen from the left............................................................................................... 7
Figure 5. Mass timeline............................................................................................................................ 8
Figure 6: total production costs for one aft fuselage ................................................................................ 9
Figure 7: Nomenclature table for racks .................................................................................................. 10
Figure 8: Nomenclature for systems....................................................................................................... 10
Figure 9: Product tree ............................................................................................................................ 12
Figure 10: stringers separation............................................................................................................... 13
Figure 11: Skin splicing........................................................................................................................... 15
Figure 12: Mapping of the skins ............................................................................................................. 16
Figure 13: Security margin for the skins.................................................................................................. 17
Figure 14: Unrolling of the skin into splices ............................................................................................ 18
Figure 15: Minimal dimensions of the stringers...................................................................................... 19
Figure 16: Stringer distribution (1) ......................................................................................................... 20
Figure 17: Stringer repartition (2)........................................................................................................... 21
Figure 18: Minimal light frame dimensions ............................................................................................ 22
Figure 19: Dimensions of the flange for a light frame ............................................................................. 22
Figure 20: Minimal heavy frame dimensions.......................................................................................... 22
Figure 21: primary structure design process........................................................................................... 24
Figure 22: Minimal dimensions of the stringers...................................................................................... 25
Figure 23: Dimensions of the flange for a light frame ............................................................................. 26
Figure 24: Minimal light frame dimensions ............................................................................................ 26
Figure 25: Minimal heavy frame dimensions.......................................................................................... 27
Figure 26: Representation of a typical “Z” shaped stringer in the GFEM ................................................. 30
Figure 27: Representation of a heavy stringer in the GFEM .................................................................... 30
Figure 28: Representation of a light frame in the GFEM ......................................................................... 31
Figure 29: Integrated floor in the GFEM ................................................................................................. 31
Figure 30: Solid model of the fuselage section ....................................................................................... 33
Figure 31: CATIA solid frames................................................................................................................. 34
Figure 32: CATIA solid stringers.............................................................................................................. 35
Figure 33: CATIA solid skins.................................................................................................................... 36
Figure 34: CATIA solid skin splicing......................................................................................................... 37
Figure 35: The actual design Process...................................................................................................... 38
Figure 36: Primary Structure .................................................................................................................. 38
Figure 37: CATIA solid floor.................................................................................................................... 39
Figure 38: Detailed floor section ............................................................................................................ 39
Figure 39: Floor and frame assembly...................................................................................................... 40
14. IX
Figure 40: Door contour......................................................................................................................... 41
Figure 41: Mouse holes in the light frame .............................................................................................. 41
Figure 42: Solid Brackets to assemble the frames sections ..................................................................... 42
Figure 43: Sheet metal bracket .............................................................................................................. 43
Figure 44: The bracket for the J stringer................................................................................................. 44
Figure 45: Bracket of the Z stringer ........................................................................................................ 45
Figure 46: System positioning, right side................................................................................................ 47
Figure 47: System positioning, left side .................................................................................................. 48
Figure 48: Cylinders mounted under the floor........................................................................................ 49
Figure 49: Large diameter tray ............................................................................................................... 49
Figure 50: Small diameter trays.............................................................................................................. 49
Figure 51: Example of tray mounts......................................................................................................... 50
Figure 52: Hold down mechanisms and guiding pins .............................................................................. 50
Figure 53: Derogation for systems 14 and 15 ......................................................................................... 51
Figure 54: L shaped beam (left); rectangular shaped beam (center); circular rod (right) ......................... 52
Figure 55: Omega beam section............................................................................................................. 52
Figure 56 : Punched sheet metal for sides.............................................................................................. 53
Figure 57 : Racks and their connectors (right side) ................................................................................. 54
Figure 58 : Rack 1 & 3 and their connectors ........................................................................................... 54
Figure 59 : Rack 5 and its connectors ..................................................................................................... 55
Figure 60 : Racks 7 and its connectors.................................................................................................... 55
Figure 61: RBE3 to simulate system’s fixation with racks........................................................................ 56
Figure 62: SPC between the rack and the floor....................................................................................... 56
Figure 63: SPC between the fuselage and the rack ................................................................................. 57
Figure 64: RBE2 between two beams ..................................................................................................... 57
Figure 65 : FEM model of Rack 1 & 3...................................................................................................... 58
Figure 66 : FEM model of Rack 2 & 4...................................................................................................... 59
Figure 67 : FEM model of Rack 5 (left) & FEM model of Rack 6 (right)..................................................... 60
Figure 68 : FEM model of Rack 7(left) & FEM model of Rack 8(right) ...................................................... 61
Figure 69: S-10007-R00 Render Structure (Left) and CATIA model with systems (Right).......................... 63
Figure 70: Rack 7 position (1) ................................................................................................................. 64
Figure 71: Rack 7 position (2) ................................................................................................................. 64
Figure 72: Render of a generic clevis ..................................................................................................... 65
Figure 73: Swage tubes example (left) and axis (right)............................................................................ 65
Figure 74: Shelf side pannel Assy section................................................................................................ 66
Figure 75: Al Alloy Side panel ................................................................................................................. 66
Figure 76: unfold side ............................................................................................................................ 67
Figure 77: Shelf P-60005-R00 fold .......................................................................................................... 67
Figure 78: Shelf P-60005-R00 unfold ...................................................................................................... 67
Figure 79: Omega Beam......................................................................................................................... 68
Figure 80: Nut plate ............................................................................................................................... 68
Figure 81: maximum weight and height ................................................................................................. 69
15. X
Figure 82: example of special equipment (U14)...................................................................................... 71
Figure 83: example of visibility check (U14)............................................................................................ 71
Figure 84: example of removal/installation check .................................................................................. 72
Figure 85: example of maintenance under the floor............................................................................... 72
Figure 86: maintenance of the primary structure ................................................................................... 73
Figure 87: manufacturing processes selection’s Excel sheet ................................................................... 75
Figure 88: Floor plan overview............................................................................................................... 78
Figure 89: Receiving, shipping and quality control.................................................................................. 78
Figure 90: Workshop.............................................................................................................................. 79
Figure 91: Chemical and treatment zone................................................................................................ 80
Figure 92: Assembly department ........................................................................................................... 80
Figure 93: PS Assembly .......................................................................................................................... 81
Figure 94: Rack sub-assembly area......................................................................................................... 82
Figure 95: Last installations and final steps............................................................................................. 82
Figure 96: detail of the first step ............................................................................................................ 84
Figure 97: detail for the second step ...................................................................................................... 85
Figure 98: Assembly of 4 skins and front heavy frame ............................................................................ 86
Figure 99: Installation of rear heavy frame............................................................................................. 86
Figure 100: Floor sub-assembly (step 3) ................................................................................................. 87
Figure 101: Floor installation.................................................................................................................. 87
Figure 102: closing of the aft fuselage.................................................................................................... 88
Figure 103: components costs for primary structure’s Excel sheet ......................................................... 90
Figure 104: primary structure's components manufacturing costs estimation’s Excel sheet ................... 90
Figure 105: secondary structure's components manufacturing costs estimation’s Excel sheet................ 91
Figure 106: material costs summary’s Excel sheet.................................................................................. 92
Figure 107: finished parts costs distribution for one aft fuselage............................................................ 93
Figure 108: components costs for primary structure’s Excel sheet ......................................................... 94
Figure 109: primary structure's components manufacturing costs estimation’s Excel sheet ................... 94
Figure 110: secondary structure's components manufacturing costs estimation’s Excel sheet................ 96
Figure 111: material costs summary’s Excel sheet.................................................................................. 97
Figure 112: finished parts costs distribution for one aft fuselage............................................................ 98
Figure 113: capital costs estimation’s Excel sheet................................................................................... 98
Figure 114: labour & administration costs estimation’s Excel sheet...................................................... 100
Figure 115: total production costs for one aft fuselage......................................................................... 102
16.
17. 1
REQUIREMENTS AND OBJECTIVES
1. Requirements
Bombardier Aerospace has a project to increase their business jet family with a new version of the
Challenger aircraft. This aircraft is a small business jet based on the customer's comfort. Bombardier has
to present an innovative design at low cost, insuring performance and reliability all while respect the mass
criteria to woo potential clients. As such, the company is looking at different providers to design parts of
the new aircraft.
Team PI4-B was assigned the following mandate: design the new Challenger's aft fuselage. This section of
the fuselage is composed of the primary structure, systems, and racks which are driven by manufacturing
and ergonomics considerations.
The team had four month to comply with the requirements and hand in their results. The project starts on
January 8th
, 2016 and ends on April 14th
, 2016 when they have to present the final product review. The
team, composed of undergrad students in mechanical and aerospace engineering had to meet all the given
requirements for the aft fuselage within the designated time.
2. Given Information
In order to comply with Bombardier’s methodology and for them to be able to integrate the aft fuselage
to the rest of the aircraft, basic input files were available to the team:
1) GFEM and load cases with dummy properties for the primary structure
2) CATIA model with reference lines for the primary structure
3) List of the systems to be integrated
4) Limitations to respect in the installation of the systems
5) Static and Dynamic criteria to respect
6) Bombardier references for ergonomics
7) Bombardier bill of materials (BOM)
18. 2
3. Objectives
Team PI4 elaborated the following objectives to be able to comply with Bombardier’s requirements. The
project is divided into 5 main sections, as described below.
General
1) Establish processes;
2) Establish nomenclature for all components;
3) Ensure the mass does not exceed the Not To Exceed Weight;
4) Ensure the integration of all sub-parts.
Primary Structure
1) Design of stringers, frames and skin for the aft-fuse;
2) Material choices;
3) Create a Finite Element Model;
4) Create a CATIA model;
5) Design a detailed light frame and a detailed section of a heavy frame.
Systems
1) Place all systems while respecting all restrictions and ergonomic considerations;
2) Create a compatibility matrix for the systems.
Secondary Structure
1) Design avionic racks that will hold the systems and are attached to the primary structure;
2) Design the racks in order to comply with static and dynamic criteria;
3) Material choices;
4) Create a Finite Element Model;
5) Create a CATIA model for a detailed rack;
Manufacturing
1) Define assembly sequences for the aft fuselage;
2) Create a floor plan model;
3) Define material processes for in-house transformations;
4) Define components that will require suppliers;
5) Define the total cost of production.
This document will follow the same structure as presented above.
19. 3
PRODUCT
General Overview
The aft fuselage is divided into 3 parts: Primary Structure, Secondary Structure and Systems. For each
team, manufacturing and ergonomic considerations were taken and will be explained in sections 5 and 6.
The figure below shows the final product in CATIA.
The product is a semi-monocoque aft fuselage composed of 8 skins. On the aircraft, it is the non-
pressurized section between the bulkhead and the tail cone. There is a cut out in the primary structure
and floor to have allow a quick access for the maintenance crew to access the systems.
The aft fuselage will receive a total of 70 systems, divided into 5 types: avionic, electrical, and mechanical
boxes, as well as hydraulic and oxygen tanks. There are 8 racks between which all the systems are divided
are attached to the primary structure.
Most assembly parts are extrusions (stringers, floor beams, etc.). The frames, however, are machined, and
the skin requires forming and chemical milling. For the racks, they consist of sheet metal and beams. All
production, parts, processes, assemblies, and man hours costs are included in the final cost of the product.
All the attachment points from the racks are integrated in the existing GFEM of the primary structure.
Where possible, links were created between the new nodes and the primary structure’s existing nodes. All
the effort from the racks are applied to those nodes and are transferred to the primary structure.
Figure 1: CATIA Model of the Aft Fuselage
20. 4
1. Integration
1.1 Mass and CG
All weight aspects are discussed in this section. First, the aft fuselage total mass and its distribution are
presented. Secondly, the center of gravity position is studied. Finally, the mass follow-up through the
project duration is shown and commented.
The aft fuselage’s total mass which includes the primary and secondary structures and systems is 1482 lbs.
This mass remains below the Not to Exceed Weight (NTEW) given as a project requirement: 1487 lbs. The
suggested and actual weight segregation are presented in the table below. The Secondary Structure is
roughly 9 lbs over the target weight and the Primary Structure roughly 15 lbs under.
Table 1: Weight Distribution for the Final Product
NTEW Distribution (lbs) Actual Weight Distribution (lbs)
Systems and cables 666,8 666,8
Secondary Structure 230 239,4
Primary Structure 590 575,4
Total 1487 1482
1.1.1 Mass distribution
The detailed weight distribution and the extraction origins are shown in the graph below. Moreover, all
considered mass are listed in the table below. The gray categories in the table were grouped under P.S.-
Other and S.S-Other in the figure due to their particularly small weight, lower than 1% of the total weight.
The heavier parts of the aft fuselage are, in order, the systems, the skin and the racks; together they make
up 69 % of the total weight.
Figure 2. Distribution of fuselage weight
System-System
43%
System-Cables
2%
P.S.-Skins
16%
P.S.-Stringers
7%
P.S.-Heavy
frames
7%
P.S.-Light frames
5%
P.S.-Floor beams
2%
P.S.-Other
2%
S.S.-Racks
10%
S.S.-Tray mounts
4%
S.S.-Hold down
mechanisim
1%
S.S.-Other
1%
S.S.-Other includes:
- Rivets
- Guiding pins
- Bolts
- P.S. & S.S.
P.S.-Other includes:
- Primer
- Cladding
- Rivets
- Assy set (Bolt,
washer, nuts)
- Assy-Plates
21. 5
The systems' group includes the systems themselves and their connection which represent 5% of their
weight. The Primary Structure includes the structural parts, the assembly parts, the primer and the
cladding. The Secondary Structure includes the structural parts, the assembly parts, the tray mounts and
the guiding pins. The attachment category refers to the attachment parts linking the Secondary Structure
to the Primary Structure.
Table 2: Detailed Weight Distribution and Weight Origins
Group Sub-group Category Extracted from Types (lbs)
System System System Given 635
Cables Cables Given 31,75
Primary Structure Structural parts Skins Excel Design Tool 243,04
Stringers 105,89
Heavy frames 98,24
Light frames 67,3
Floor beams 32,69
Primer Primer Estimated 4,04
Cladding Cladding Estimated 0,04
Assembly parts Rivets Estimated 5,91
Assy set1
Estimated 4,20
Assy plate Estimated from CATIA 14,05
Secondary Structure Structural parts Racks Patran 154,5
Tray mounted Tray mounted Estimated 51,8
Hold down
mechanism2
Hold down
mechanism
Estimated 19,14
Assembly parts Rivets Estimated 0,9
Guiding pins3
Estimated 0,339
Bolts4
Estimated 4,78
Secondary and
Primary Structure
Attachments
Attachments Estimated from CATIA 7,96
TOTAL 1482
1
Assembly set includes: bolts, washer and screw.
2
Hold dodwn mechanisim are used to stabilized the systems one installed.
3
Guided pins are used to assemble some avionics systems.
4
Bolts set used for the racks assembly: bolt, washer, screw.
22. 6
As for the total mass value:
1) Includes an estimation of light frames' reduced weight due to the mouse holes. The percentage of
mass reduction due to the mouse holes was calculated from ¼ of a light frame. This ratio was then
applied on the total light frame weight;
2) Includes a skin cladding of 0,002’’ applied on the whole fuselage's outer surface;
3) Includes assembly parts such as rivets, bolts, and assembly plates;
Includes only the exceeding weight of the rivet, not the part filling the hole since the hole
was not considered in the weight calculation;
4) Includes an estimation of primer inside and outside the fuselage based on the fuselage surface
area;
5) Does not include the system handles, since it was assumed included in the systems' weight as
received;
6) Does not include the paint, since it depends on the airliner.
1.1.2 Center of gravity
The center of gravity is presented on Figure 3 and Figure 4. The figures corresponds to 100 points from a
Monte Carlo study. The center of gravity was estimated with the mass and positions extracted from the
CATIA model of the primary and secondary structure based on the weight and positions of:
- Systems;
- Structural parts of the racks;
- Structural parts of the primary structure.
It neglects:
- Assembly parts as rivets, guiding pins, assembly plates, bolts, attachments etc;
- Skin cladding, the paint, the primer.
Figure 3. Aft-fuse CG as seen from the front
23. 7
Figure 4. Aft-fuse CG as seen from the left
Table 3: CG coordinates in CATIA
X (in) Y (in) Z (in)
723,5 -0,1 109,5
Based on the tolerance values supplied by the various manufacturing processes and assembly
misalignment, a Monte Carlo study was conducted on the CG position. The results of this study show a
convergence at the red cross indicated on the Figure 4 and whose coordinates are shown in Table 3Table
1. Hence one can conclude that the center of gravity is quite certain according to the study. However, this
study neglects all sub-assembly misalignment. A misalignment of a sub-assembly would invalidate the
normal distribution assumptions for the Monte Carlo study, since this implies independent behaviors.
1.1.3 Mass follow-up through the project
The Figure 5 shows the mass estimation through time. From the first design review, the design was
advanced enough to estimate the first primary structure's weight. The secondary structure, however, was
estimated from the second design review. The systems weight is set since the beginning of the project.
One may notice that the first mass estimation for each structure (2016-02-12 for primary structure and
review 2 for secondary structure) was overweight, but was later smoothed. The secondary structure
loading, including the systems, were incorporated into the primary structure by 2016-04-08. Even though
24. 8
all stringers' and frames' margins were left at 20 % as a buffer prior to the secondary structure and systems
incorporation, the primary structure gained approximately 52 lbs in the period following.
Figure 5. Mass timeline
The racks design was only finalised in the last week. Thus, significant safety factors were applied on the
racks’ estimated weights before the last review. The actual final mass for the racks is lower than the one
estimated with safety factors.
Moreover, the primary structure's mouse holes were only included during the last week with a reduced
mass estimated from the CATIA model. Furthermore, the assembly parts' weight estimation was refined
in the course of the last week due to the accomplishment of these parts’ modeling in CATIA. For the
reasons stated above, the total weight fluctuated a little in the final week.
One may notice that the weight variation in the last weeks is hard to read. At the end of the project, the
weight tend to stabilized which could give one a certain confidence that it should not significantly change
in the future. The weight oscillates around the NTEW.
0
500
1000
1500
2000
2500
Mass(lbs)
Time Primary Structure
Secondary Structure
Systems and cables
Set
Target
Target
Legend
Target: given objectives
Excel : Estimated mostly with Excel
Patran: Estimated mostly with Patran
Excel
Excel
NTEW
Patran
NTEW =15001448
Final weight
= 1482
25. 9
1.2 Final Cost
After calculating the production costs of the components for the full structure (fuselage and racks), the
capital costs for the factory (including machines, the building itself and various other equipment) as well
as the labour and administrative costs (salary of the employee’s including assembly and production
workers, maintenance and more), the final price of production of the aft fuselage is estimated at
203,735.96 USD without engineering development costs. The following graph (Figure 6) shows the cost
distribution:
Figure 6: total production costs for one aft fuselage
Cost calculation is detailed in section 6 of this report.
P.S. - Components
Costs
36%
(72,210.35 USD)
S.S. - Components
Costs
16%
(32,986.23 USD)
Capital Costs
22%
(45,680.40 USD)
Labour &
Administrative Costs
26%
(52,858.97 USD)
TOTAL PRODUCTION COSTS DITRIBUTION FOR ONE AFT FUSELAGE
26. 10
1.3 Nomenclature
Nomenclature is central to the historical retracing of parts in a logical manner. For the design of the
Challenger 300’s aft-fuse, several nomenclature procedures have been established for the various design
supports. The development of each nomenclature had their own requirements and the Integrations
worked closely with each of the teams to develop a system that would answer their needs. The present
section details the rules guiding nomenclature for the various elements in the CATIA and MSC Nastran
models for a better understanding of our model parts. It also includes nomenclature for the manufacturing
part.
The tracking of the various parts are done through a Google Sheet which the entire team has access to,
and which eliminates the risk of overwrites. Team members can reserve part numbers on this spreadsheet
with a brief description and the part’s author. A preliminary mass estimation is also done on this
document, as the mass needs to be entered for each part. The reason behind this is to verify if a part has
been updated in the CATIA but not in the description when we see that the mass is not the same in both
documents and to make sure we didn’t forget any parts in the assembly descriptions.
Figure 7: Nomenclature table for racks
Figure 8: Nomenclature for systems
27. 11
CATIA Nomenclature
CATIA part products and named following this form: P - XZZZZ - Y(s) - R00
Table 4: Nomenclature for parts in CATIA
P Indicates it is a Part
X 1- Frame
2- Skin
3- Access/Opening
4- Beam
5- Attachments
6- Panels
7- Systems
9- Other
ZZZZ Number generated on Google Sheets (first come, first served basis)
Y Indicates the part was originally created to be installed on the ___ side of the fuselage
1- Top
2- Bottom
3- Left
4- Right
s Indicative of a symmetry born from pre-existing part
Ex :
P-100212-4-R00 is the original part created for the right side of the fuselage
P-100212-4s-R00 is the mirror piece that goes on the left side of the fuselage, generated
by a symmetry
R00 Review number, applicable when a released part undergoes modifications under a
request for change (RFC)
Assemblies and sub-assemblies in CATIA have their own form of nomenclature to allow small part
groupings: S-ZZZZZ-R00
Table 5: Nomenclature for sub-assemblies in CATIA
S S for Sub-assembly
ZZZZZ Number generated on Google Sheets (first come, first served)
R00 Review number, applicable when a released part undergoes modifications under a
request for change (RFC).
Assemblies are the regrouping of all the modeling done by a team. The assembly A1 groups everything
belonging to Primary Structure in the CATIA model, and A2 groups all the racks and avionic boxes made by
the Systems’ team. Furthermore, all the avionic racks are grouped as a sub-assembly to be able to
manipulate each rack independently.
28. 12
Figure 9: Product tree
When it comes to the final assembly, our integral CATIA model is named AER4855_H2016.CATProduct.
FEM Nomenclature for Racks
Nomenclature in Nastran only allows for 8 bits, so we are limited as well when it comes to the Patran
model, seeing as we want to import and export data between the two programs. In collaboration with the
Secondary Structure team, here is the nomenclature developed for finite elements’ analysis: QWZ-YT- ZZZ.
Table 6: Nomenclature for parts for Racks FEM
Q Rack number
W Type of element :
1- Bar
2- Rod
3- Quad
X Orientation :
1- Horizontal
2- Vertical
3- Cross-sectional
Y Shelf level :
Start at 1 for lowest level and work up to 9 and 0 is the tenth level
Racks will not have more than 10 shelves
T Beam positioning :
1- Inboard forward (vertical element)
2- Inboard aft (vertical element)
ZZZ Number generated on Google Sheets (first come, first served basis)
29. 13
Installation Manuals
For the installation manual, the manual itself will be named C300 for Challenger 300, followed by the
applicable ATA number, and a four digit generic number generated once again by Google Sheets on a first
come first served basis (C300-ATA-ZZZZ). Assembly manuals will be named after their assembly name as
seen in CATIA: S-ZZZZZ. For simplifications, stringers that are separated in 3 sections are names as: P-XXXX-
A, P-XXXX-B and P-XXXX-C.
Figure 10: stringers separation
A
B
C
30. 14
2. Primary Structure
2.1 Final Design and Results
Part of the structure including the outer mold line, the quantity and positioning of the stringers and a finite
element model was given as an input in the project. Beside the dimensions’ optimization, design decisions
were made on the materials, the splicing of the skin, the shape and sizes of the stringers and frames and
the detailed design of a heavy and a light frame. The final design is introduced below.
Materials
Every element type of the primary structure with identical loading characteristics was associated with a
material and are introduced in the table below:
Table 7: Materials used
Skins
Clad Aluminium 024-T3 AMS-QQ-A-205/5
The supplier provides this material as plate metal which will be formed internally as
follow to obtain the parts destined for assembly: drilling of holes, curve forming
and chemical milling to obtain various thicknesses.
Heavy frames
Aluminium 7050 T7451-AMS 4050
The supplier provides this as a semi-finished part. Various precision drillings and
surface finish will be done internally.
Light frames
Aluminium 7050 T4751 AMS 4050
The supplied part is an extrusion of the desired "C" cross-sectional light frames. The
extrusion will be hot rolled by the supplier and drilled internally to obtain its final
form with holes.
Stringers
Aluminium 2024 T3511
The supplier provides the thermally treated stringers as extrusions which will be cut
and machined internally if necessary.
Floor beams
Aluminium 2024 T3511
Like the stringers, the floor beams are supplied as thermally treated extrusions
which will be cut, machined and drilled internally.
Skin Splicing
Multiple factors influenced the positioning and amount of splicing:
The size of the chemical baths;
The manufacturing ergonomic factors;
The access door which should be part of a single skin;
The requirement to align the skin splicing at frames and stringers locations.
As a result, the aft fuselage is made out of eight skins, cut at the red section as seen in Figure 11. The axial
splicing is located at the front of the heavy frame for a manufacturing reason. Indeed, it is preferable that
31. 15
the skin splicing is close to the access door. As for the longitudinal splicing, symmetrical solutions were
favored on the grounds of loading and inertia considerations. An easy access during manufacturing and
assembly was taken into account in the splicing choice. This splicing also permits the skins to fit in the
chemical baths.
Figure 11: Skin splicing
34. 18
As for the skin mapping, there are only five different thicknesses per splice, including the pad-up, due to
the high manufacturing costs. The different splices are delimited by the bold lines in the Figure 12 and the
Figure 13. The skins are opened from the top and unrolled to have a better visual presentation. However,
it is important to highlight the fact that the top splices are divided. The splices are the addition of the top
and the bottom of the previous tables as demonstrated in the sketch below.
Figure 14: Unrolling of the skin into splices
35. 19
Every skin panel is bordered by two frames and two stringers and each of them is linked to an optimized
skin thickness.
The security margin table is a summary of the minimum margin for every skin panel considering every load
case. It is possible to note that the margins are high. Those value are due to the smoothing of the skin.
Since many panels had to be over thickened, the margins are higher than what is necessary, in order to
respect the maximum of five different thicknesses per splice. However, it would be possible to lower the
margins by selecting other thicknesses for the smoothing.
Stringers Design
The stringers mostly have a “Z” shape. This shape allows a bigger inertia due to its shape factor, which
reduce the area and the weight of the section necessary to sustain the applied load. Some stringers, at the
splicing position, have a “J” shape. This allows the two skins to be riveted to the stringer without
overlapping the skins. The Figure 15 represents the minimal dimensions of the stringers.
Figure 15: Minimal dimensions of the stringers
The next table shows the various dimensions of the stringers in the aft fuselage. There are four section
types in order to make a compromise between the manufacturing cost and the mass saving without
compromising the structural integrity.
0.4”
0.8”
0.06”
36. 20
Table 8: Stringers sections
The two following figures allow a better visualisation of the distribution of the various types of stringers
all around the rear fuselage. It is important to highlight the fact that the bigger stringers are, for the most
part, at the front section and in the lower half of the fuselage.
Figure 16: Stringer distribution (1)
Section type 1 2 3 4
thickness (t) (in) 0,06 0,07 0,09 0,11
width (h) (in) : 0,8 0,9 1 1,2
flange length (b) (in) : 0,8 0,8 0,8 0,8
free flange length (in) 0,4 0,4 0,4 0,4
Color Blue Yellow Orange Red
38. 22
Frames Design
There are two types of frame in the aft fuselage design. There are five light frames and two heavy ones.
The light frames have a “C” shaped cross-section. This allows a bigger inertia and a lower area and mass
for this section. Plus, the C shape can be manufactured around the diameter of the fuselage.
Figure 18: Minimal light frame dimensions
The frames are symmetrical for loading and inertia considerations. The inner and outer flanges are
identical for both heavy and light frames.
Figure 19: Dimensions of the flange for a light frame
The heavy frames are “I” shaped for the same reasons as the light frames, but they need to sustain more
loads than those so they are attributed a larger section.
Figure 20: Minimal heavy frame dimensions
39. 23
The next table details all the dimensions of the frames. It is important to note that both heavy frames take
more effort and thus, are way bigger than the other frames.
Table 9: Dimensions of the frames
Frame # 1 2 3 4 5 6 7
Type Light Light Heavy Light Light Heavy Light
tcap (in) 0,22 0,13 0,15 0,095 0,095 0,15 0,105
bcap (in) 2,18 1 1,6 0,8 0,095 1,6 0,8
tweb (in) 0,138 0,06 0,15 0,06 0,065 0,15 0,082
h (in) 3 3 variable 3 3 variable 3
Floor Design
The floor beams have a I section as for the heavy frames in order to maximise the critical buckling load.
The Table 10 represents the dimensions of all the beams of the floor since there is only one section of
beam. It is important to highpoint the fact that the floor is a part of the fuselage that have a major influence
on the stress distribution and those stresses are accounted for in the design of the said floor.
Table 10: Floor beam's dimensions
Floor Beam Dimension (in)
tcap 0,1
tweb 0,08
hf 1,1
bcap 0,5
40. 24
2.2 Methodology and Hypotheses
Optimization Loop
The Primary structure design process is driven by an optimizationloop shown in the Figure 21. The strength
of this optimization loop is its ability to effectively import data and export results to and from multiple
programs, as MSC Patran/Nastran.
First, the initial EndLoads (pressures supported by the structure) and Elfos (loadings between two nodes)
from the initial GFEM are imported into the Excel Design Tool (A). The Excel tool was developed to take
into account the external loading sustained by the design with respect to the aerospace security criteria
(B) and to optimize the weight accordingly.
The Excel Design tool aims to validate the structural integrity of the primary structure, as well as to
minimize the dimension, and thus the weight, of the elements. All materials and dimensions are stocked
in the Excel worksheet which can be exported in a bdf file (C). This bdf file is then executed with Nastran
(D). The most complex aspect of this loop is to affect the material properties to each GFEM element
according to its type. The Nastran output file f06 is converted to Endloads and ElementForces with the
conversion tool developed by the supplier Xpost (E). These ElementsForces can then be implemented in
the Excel Design Tool with a macro. The margin calculation will be automatically updated with the new
loads and the dimensions may then be optimised. Afterwards, the optimization loop will be run again.
Finally, when the dimensions, weight and margins respect all the imposed criteria and are optimized, the
dimensions are extracted manually from the Excel Design Tool and applied to the CATIA model. This last
step concludes the optimization loop.
It is important to notice that, the dimensions implemented in the CATIA model correspond to the
penultimate iteration of the optimization loop due to the extensive time required for the CATIA updates.
In other words, after the dimensions were extracted from the Excel Design Tool to be implemented in the
CATIA, another optimization loop ran.
When values
are set CATIA
Figure 21: primary structure design process
41. 25
The last dimensions optimized in the Excel Design tool and validated by the GFEM take into account the
attachments to the secondary structure and the systems loading. Due to the short duration of the project,
the racks were finalized far in the project. Thus, most iterations of the optimization loop did not include
the Secondary Structure and the systems loading. Only the two last iteration loops optimized the design
with the actual secondary loads. Extra security margins were applied on the stringers and the frames for
all iterations where the secondary loading was not yet implemented. These margins will be detailed further
below.
Design Assumptions
The following assumptions were implemented in the Excel Design Tool:
1. Conservative material properties were considered for the calculation of the allowable loads. Thus,
the properties in the worst mechanical direction for a given material were implemented in the
calculation regardless of the actual grain direction of the part.
2. For faster and versatile optimization, the stringers’ thickness was set as a constant through its
whole cross-section. In other words, the stringer free flange, web and fixed flange have the same
thickness which can later be optimized.
3. The free flange dimension of the stringers is set to 0.4”, an industry standard. By setting this
dimension, the number of optimization parameters is reduced. Thus, the dimensions’ optimization
and smoothing of the stringers’ dimensions can be done faster. Consequently, the optimization
parameters for the stringers are its height and thickness because they have a bigger impact on the
buckling margins due to their significant influence on the secondary moment of inertia.
4. The stringers are represented by CRODs in the GFEM. Two loads may be considered for the
calculation of the applied load on each element: the loads from node 1 to node 2 or the loads from
node 2 to node 1 (the two are not equivalent). The average of both loads was implemented as the
actual load in the applied load calculation.
5. The Gerard method was used to calculate the critical buckling load. The third hypothesis made this
method available.
6. The stringers have a “Z” shape with the following limited minimum dimensions:
a. Height: 0.800”
b. Fixed flange length: 0.800”
c. Thickness: 0.060”
Figure 22: Minimal dimensions of the stringers
42. 26
7. To ensure the structural integrity of the heavy frames, the stringers do not pass through them as
they do for the light frames. Thus, the mouse holes can only be seen on the light frames. This way,
a cut in the stringers will be required at each heavy frame. This implies that the stringers are split
into 3 distinct sections.
8. The frames are symmetrical for loading and inertia considerations. The inner and outer flanges are
identical for both heavy and light frames.
9. The light frames have an “L” shaped cross-section. The fixed flange of the “L” is twice as long as
the section in contact with the web.
Figure 23: Dimensions of the flange for a light frame
10. 5/32” rivets are used for attaching the skin to the stringers and the frames. They are largely used
in the aerospace industry and are available in multiple lengths which allows a certain freedom in
the choice of skin thicknesses. Small rivets also allow an economy in weight which is one of the
main objectives. Thus, they were chosen for this application. On the other hand, the attachment
of the skin to the heavy frames requires bigger rivets due to higher loadings passing through them.
For this application, 6/32” rivets were chosen.
All rivets are counter sunk due to the free flow.
11. The light frames have a “C” shape with the following limited minimum dimensions:
a. Height: 3”
b. Length: 0.8”
c. Thickness: 0.060”
Figure 24: Minimal light frame dimensions
43. 27
12. The heavy frames are “I” shaped with the following limited minimum dimensions:
a. Height: a project input extracted from the initial CATIA
b. Length: 1.6”
c. Thickness: 0.150”
Figure 25: Minimal heavy frame dimensions
13. Dimensions of each light frame are constant throughout the circumference of the fuselage.
14. The skin has an important influence on the critical buckling of the stringers’ and frames’ fixed
flanges. The skin effective width increases the structural resistance of the previously named
components. This dimension is calculated as 30 times the skin's average thickness.
15. The minimal skin thickness is set to 0,050”.
16. “J” shaped stringers are used at the skin splicing, where two skins meet. It allows the assembly of
the two skins by riveting them to the stringer outer caps, without overlapping the skins.
17. For the riveted sections, the fixity coefficient c=1 is used for the calculation of the inter-rivet
buckling. The coefficient is determined by the rivet types which are counter sink rivets.
18. “I” shaped floor beams were chosen to minimize the buckling.
19. All skin pad-ups required for its fixation to the stringers and frames have the same thickness. This
thickness is defined by the thickest pad-up at zero margin.
44. 28
2.3 Design Tool
A few design decisions were introduced in the assumptions' section. In this section, the structure of the
design tool used is introduced. However, before obtaining the complete design, a few steps remain to be
completed. First we will be discussing the developed Excel tool structure, followed by the chosen minimal
margin by element, the optimization methodology for obtaining the final dimensions, and finally, the
dimensions smoothing. All these considerations are implemented in the Design Tool developed on
Microsoft Excel.
Excel Tool Structure
The main advantage of Excel is its computing power. The tool structure was built to be user-friendly, not
only to rapidly find the interesting results, but also to easily optimize the dimensions. The tool was divided
into multiple worksheets following this structure:
Logbook: This sheet allows the team to keep track of all modifications of the document. The
changes’ follow-up requires the following information: the team member who did the
modification, the date and the duration of the task.
Legend: In this sheet are stated the terms and symbols used throughout the whole Excel
document.
Assumptions: All the assumptions used during the design and influencing the calculations are
stated in this sheet.
ENDL and ELFO: These sheets contain all the loads carried by the primary structure elements.
These sheets and their values are directly imported from the GFEM files using a macro.
Materials: All relevant material properties are stocked in this sheet. Each structural element is
linked to its material. These properties are used through the whole document for allowable load
calculations.
Plastic correction: Certain applications require a correction when the strain approaches the plastic
deformation region. The material properties decrease when the loads approaches the plastic
region, and it is taken into account in the calculation.
Margin and weights: This sheet is the center of the Excel Design Tool. The user can optimize all
the dimensions here. Each element is represented in the worksheet: skin, stringer, frame, and
floor beams. Each element is associated with its minimum security margin and one or more
dimensions that may be optimized. It is possible to change the load case to ensure the structural
integrity of all elements for all load cases. Consequently, the mass evolution can be followed
efficiently in this sheet.
Stringer: The buckling security margins of the stringers at yield and at tensile failure are executed
in this sheet with all the needed intermediate calculations.
Frame: The buckling security margins of the frames at yield and at tensile failure are executed in
this sheet with all the needed intermediate calculations.
Skin: All skin security margins are calculated in this sheet: the plastic strain margin, the failure
margin and the crippling margin with all the needed intermediate calculations.
Floor: All security margins of the floor beams are calculated in this sheet: the plastic strain margin,
the failure margin and the buckling margin with all the needed intermediate calculations.
45. 29
BDF: The goal of the Excel tool is to efficiently modify the dimensions and to insert these
dimensions in the GFEM to validate the design. All dimensions or material modifications made in
the other Excel sheets are automatically implemented in the BDF sheet to be imported to PATRAN
using a macro.
Minimal Margins
The optimization aimed to attain minimal margins above 0% providing for the assumption that the primary
structure sustains additional loads from the racks and the avionic systems. Without this additional loading
incorporated in the applied loading calculation, higher margins were targeted to resist the additional
expected loading. Since the frames and the stringers will carry most of the racks loadings, the first
optimization aims to reach:
Skin margins between 0% to 5% and
Stringer and frame margins of 20% or more in prevision of the additional loading.
Once the additional loading was introduced in the applied loading calculation, all margins were optimized
to fall between 0% and 5%.
Optimization Methodology
First of all, the minimal allowable dimensions determined by the manufacturing limitations were applied
to the elements. Furthermore, each load case was studied to ensure that all elements respected the
minimal margin stated above. When it wasn’t the case, the dimensions were increased as follow to reach
the targeted margins:
For the skin, the thickness is changeable.
For the stringers, the height and the thickness are changeable.
For the light frames, the thickness, the width and the height are changeable.
For the heavy frames, the thickness is changeable.
The choice of the modifiable parameters per element depends on two considerations. On one hand, by
studying the failure modes, the inertia increases mostly by modifying the height and the thickness of the
beams. On the other hand, the limitation of the parameters facilitates the optimization.
Smoothing of the Dimensions
Finally, when the skins, the stringers and the frames are optimized, they have various dimensions along
their length. The next step is to smooth the dimensions. According to manufacturing requirements:
Only 3 to 4 stringer cross-sections should be used. This decision was driven by the manufacturing
and assembly cost linked to the number of stringers. Thus, only 3 to 4 stringer types will be bought.
For the skins, only 5 processes in the chemical baths are permitted. This limit is linked to the time
required by each process. The number of chemical milling per skin is thus limited to 5, including
the pad-ups.
As previously stated, the light frames have constant cross-section.
The heavy frames may have variables dimensions since they are machined from brute material.
46. 30
2.4 Modeling (GFEM)
The fuselage was modeled in finite elements with PATRAN and in 3D with CATIA. Both models will be
discussed below.
GFEM: Global Finite Element Model
The GFEM without the floor was given as a project input. Each physical element of the CATIA model was
represented in the given GFEM. The accuracy between the GFEM and the physical components are treated
in this section. The modeling of the floor is also addressed.
Most stringers are represented by a CROD as shown on the Figure 26. Even though the figure shows the
finite element representation of a “Z” shaped stringer, the “J” shaped stringers located at the skin splicing
will also be represented by a CROD.
Figure 26: Representation of a typical “Z” shaped stringer in the GFEM
A few rare stringers are represented by 2 CRODs and a CQUAD due to their significant inertia. They are
called heavy stringers and their representation in the GFEM is shown in the Figure 27.
Figure 27: Representation of a heavy stringer in the GFEM
As for the skins, they are all modeled using CQUAD and CTRIA. The load calculation neglects the CTRIAs
due to their calculation instability. The skins’ physical properties are represented in the CQUAD using one
parameter: their thickness.
47. 31
The heavy frames are roughly “I” shaped beams. Each of the “I” sections are represented with a CQUAD.
The Excel Tool only modifies the thickness of this section. The light frames have “C” sections and are
represented by CRODs and CQUADs as shown on the Figure 28.
Figure 28: Representation of a light frame in the GFEM
For the floor's modeling, the floor beams are attached to the frames’ inner mold line (IML) and are linked
to the frames' nodes. The floor nodes correspond to the floor' upper surface as a reference.
Figure 29: Integrated floor in the GFEM
48. 32
Once the floor beams are integrated to the GFEM, the GFEM is run again to ensure the structural integrity
with the floor. Moreover, the dimensions of the floor beams were determined by a no buckling criterion
subjected to the following loading: the weight of a technician added to 1/6 of the systems' weight
multiplied by 1,5 to simulate the racks' weight. Considering that the systems' mass will be taken by 8
frames, it is conservative to apply 1/6 of the total systems' weight to a floor beam.
As for the simulations on Nastran, the big data file was divided into smaller ones for easy tracking, and the
chosen materials were properly incorporated. After this step, a loop between Nastran and the Excel tool
was created by developing a Visual Basic code for the optimization. In addition, three new subcases were
created to identify the best and worst scenarios. Regarding their integration, numerous attachment points
were shipped by the Secondary Structure team with their applied forces and moments. Ideally, a RBE3 link
between the attachment points and the structure's nodes were needed to simulate Nastran with the new
subcases, but an easier way was found. Some of the attachment points were too close to some existing
nodes, so they were replaced. As a result, forty-eight load cases were extracted and used to optimize the
dimensions of the primary structure.
2.5 CATIA Model
CATIA
The CATIA model is presented in three steps. First, the development steps are explained. Then, the solid
CATIA model is presented. Finally, the few elements or element sections were modeled in detail.
Three models were developed in steps: the wire frame model, the skeletal model and finally the part body
(solid model). The wireframe model was given as an input for the project. It gives the stringers' and frames'
positions. No shape was incorporated in this wireframe model. The skeletal model includes all element
shapes even though it is only a surface modeling and also includes the skin pad-ups. In this model, multiple
parameters are created to easily control the geometrical elements of the aft fuselage. The skin is spliced
in this model according to previous splicing explanations. Finally, the last model is the solid CATIA model
which is the most detailed and accurate. It includes the modeled solid elements as well as some more
detailed parts.
49. 33
Detailed Sections of the Aft Fuselage
In this section, all the details that have been implemented in the CATIA model will be presented and
explained.
Figure 30: Solid model of the fuselage section
The Figure 30 is the solid representation of all the work that has been done. It is possible to see all the
skins, the stringers, the frames and the floor implemented in the CATIA model. In the following figure,
every type of element is presented.
50. 34
Figure 31: CATIA solid frames
As can be seen, the mouse holes have be carved into all the light frames. A door contour has also be
outlined and will be detailed further in the report.
52. 36
Figure 33: CATIA solid skins
In the previous Figure 32 and Figure 33, the pockets of each skin has been represented and linked to the
various thicknesses defined previously in the Design section.
53. 37
Figure 34: CATIA solid skin splicing
In the previous figure, it is possible to see all the different splices as it is defined in the previous design
section. As was described in the Design section, Figure 34 shows a more detailed splicing of the fuselage
skin.
54. 38
The CAD Methodology
Figure 35: The actual design Process
The design process shown in the Figure 35 is the process that has been implemented in the project. The
first step was to classify the different parameters of the preliminary design of the aft fuse to maintain a
good continuity in the process and also to permit a large amount of changes. The second step was to create
a first skeleton that determines the master geometry and limits the design group within the OML IML
surfaces. This step enables the team to start the creation of surfaces of the different master geometries
to be included in the design (frames, skin mapping and stringers).
After the surfaces creation, the design team began the real product structure by creating solids from the
master geometry. Finally, in order to finalise the design process, the details are incorporated before
releasing the cad files.
Figure 36: Primary Structure
The Figure 36 represents the PS team's product structure for modeling the aft fuselage. Notice that the
main assembly contains 5 sub-assemblies, these sub-assemblies then regroup all the other section parts.
Parametric
Classification
Skeleton
Design
Surface
Design
Solid
Creation
Detailed
Structure
PrimaryStructure
Frames Sub_Assy
P-10000-1-R00
...
Skin Sub_Assy
P-20000-1-R00
...
Stringers
Sub_Assy
P-40000-1(A)-R00
...
Floor Sub_Assy
P-40000-1-R00
...
Master Geometry
P-90000-0-R00
...
55. 39
2.6 Detailed Design
This section will show some of the detailed that were made in the CATIA model for Primary Structure.
Figure 37: CATIA solid floor
The floor is held up by I beams fixed to the fuselage frames. The large cut-out is where the maintenance
access door will be.
Figure 38: Detailed floor section
56. 40
The floor beams have been detailed; all the radiuses have been updated in the model. From Figure 38 and
Figure 39, the bracket are visible: it is how the structure is strengthened when incorporating the floor
Figure 39: Floor and frame assembly
In the figure above, the interaction between the frames and the floor is detailed. As can be observed, the
attachment between the two structures is done by a bracket fixed to the floor beam’s web and the frame’s
cap.
The door contour has been designed to withstand the load concentration around the access trap. To do
so, an over thickened skin has been fixed around the door and a vertical section supported by stiffeners
(circled in the Figure 40) has been designed. The dimensions of those elements were not a part of the
optimisation process, however. For now, those dimensions are set to be coherent with the rest of the
structure but should be the subject of further studies and optimisation.
58. 42
The stringers have to pass through the light frame to ensure a structural continuity. To do so, holes have
to be drilled in the light frames, known as mouse holes. These mouse holes are detailed in the Figure 41.
Figure 42: Solid Brackets to assemble the frames sections
Figure 42 represents the type of brackets to be used to assemble the sections of the light frames when
placed in each splice. It is important to note that, by a manufacturing choice, the sections do not coincide
with the skin splicing
59. 43
Figure 43: Sheet metal bracket
Figure 43 presents a bracket used to assemble the stringer to the light frame by the mouse hole. This part
will fix the stringer to the light frame.
60. 44
Figure 44: The bracket for the J stringer
The bracket shown in the Figure 44 is used to assemble the stringer section to the heavy frame by a
sheet metal. It will be fixed to both sides of the stringer's skin flange.
61. 45
Figure 45: Bracket of the Z stringer
The bracket shown in the Figure 45 is a simple bracket used to fix the ‘Z’ stringers to the heavy frames. It
will be fixed in both the stringer's web and skin flange.
62. 46
3. Systems
3.1 Final Positioning
Restrictions and compliance matrix
The first step towards designing the avionic racks is the positioning of all the systems inside the fuselage
section. In total, 70 systems of varying sizes and dimensions were given to the team, of which 64 box-
shaped and 6 cylindrical pressure vessels. The list of those systems is shown in APPENDIX 2: SYSTEMS LIST,
COMPLIANCE MATRIX, SYSTEMS POSITIONS and includes the systems’ specifications:
System type and number
Dimensions
Weight
Placement and dimensions of the connection zone
Faces that must remain visible
Access time
Incompatibilities and minimal distances requirements
In order to verify that all the incompatibility requirements are met, a compliance matrix was built. This
matrix shown in APPENDIX 2: SYSTEMS LIST, COMPLIANCE MATRIX, SYSTEMS POSITIONS indicates if two
system cannot be adjacent to each other, or if a minimum distance has to be respected in order to prevent
electromagnetic interference and other issues.
Some “no-go” zones in the fuselage also have to be respected. No systems can be placed astern of the
access door or over a height of 57.64 in.
The final positioning passes all these requirements.
Final positioning
The available space in the fuselage is divided by the structural frames and the center line, resulting in 8
zones. As shown in Figure 46 and Figure 47, the larger electrical systems (elec 14 and 15) cannot be placed
between two frames. To accommodate these larger systems, the two most forward racks (presented in
red) are extended towards the back, and the second row of racks (presented in blue) are narrowed. The
final system positions are shown in the figures below.
The types of systems are mostly grouped together to simplify maintenance.
The types of systems are color-coded as follows:
Yellow: electrical
Pink: mechanical
Green: avionic
Blue: hydraulic
Purple: oxygen
63. 47
Figure 46: System positioning, right side
The system positioning is clearly mapped in APPENDIX 2: SYSTEMS LIST, COMPLIANCE MATRIX, SYSTEMS
POSITIONS. The rack numbering goes from 1 to 8 starting from the front (even numbers on the left,
uneven on the right).
64. 48
Figure 47: System positioning, left side
This layout leaves enough space to allow for future systems to be added. Some new shelves can be
installed in three locations (racks 4 and 7). Some systems can also be added under the floor. In addition,
several systems are installed with ample room to help easily remove them. This space can be reduced in
order to fit more systems per level if the ergonomic factor is reassessed.
Most systems are placed over the floor, with the exception of two cylinders mounted under the floor
beams, as shown in Figure 48.
65. 49
Figure 48: Cylinders mounted under the floor
The cylinders are secured to the racks and floor using specially designed trays. One type is made for the
bigger cylinder on the left side (Figure 49) and one for the smaller diameter cylinders (Figure 50).
Figure 49: Large diameter tray
Figure 50: Small diameter trays
66. 50
Systems with a short access time or with limited space are also installed on regular tray mounts (Figure
51). Out of the 70 systems, 30 are installed this way. Systems that are not mounted on trays will use guiding
pins and hold down mechanisms (Figure 52) installed directly on the rack shelves.
This aspect will be further discussed in the ergonomics section.
Figure 51: Example of tray mounts
Figure 52: Hold down mechanisms and guiding pins
67. 51
3.2 Positioning Tool
A script was created using MATLAB in order to position the systems as efficiently as possible while meeting
all of the requirements. The goal of this script is to minimise the loss of space by selecting the best systems'
arrangement for a given volume.
3D matrices, including every possible combination of 3 systems are created. Those matrices of dimensional
values are then compared to the available space in order to eliminate combinations that do not fit, and to
select the solution that optimises the use of space on a shelf.
Along with the dimensions, requirements such as weight, incompatibilities, visible face and hand clearance
are also taken into account in the selection.
Once a combination is selected, those systems are removed from the combination matrices and the
process repeats itself for the next shelf, from the bottom up and rack by rack.
This process is limited since a system that is placed in the beginning cannot be reused, an absolute solution
isn’t possible. This limitation is overcome by experimenting with the order in which the racks are
processed, comparing results and selecting the best one.
First, systems that can’t be easily placed are addressed. The two most problematic ones are electrical
systems 14 and 15. Their dimensions are very large compared to the rest of the systems. Their positions
are decided prior to starting the script since they are limited by compatibility and ergonomic limitations.
The position of one of those systems is shown in Figure 53, along with the exemption permitted in order
to make it fit. The cylinders are also placed manually.
Figure 53: Derogation for systems 14 and 15
68. 52
4. Secondary Structure
4.1 Final Design
Material
The racks are made out of aluminium 2024 because of its light weight, good structural resistance, and its
good resistance to fatigue when the load is applied along the grain direction.
Table 11 : Materials used for the Avionic Racks
Parts Shape Material
Side Sheet AL 2024-T42
Shelves Sheet AL 2024-T42
Cross-beams Extrusions AL 2024-T3511
Rods Extrusions AL 2024-T3511
Shape
The shape used for the elements in the FEM, as part of the hypotheses presented in the Methodology and
Hypotheses of Secondary Structure, are represented by either an “L” shaped beam, Omega beam,
rectangular beam or circular rod. Table 12 shows the measurements of the sections presented in Figure
54 and Figure 55.
Figure 54: L shaped beam (left); rectangular shaped beam (center); circular rod (right)
Figure 55: Omega beam section
H
W
Thickness
W
H
Thickness
D
H
W1
Thickness
W2
69. 53
Table 12: types of sections
Section Thickness (in) H (in) W1 (in) W2 (in) D(in)
Sheet 0.080 - - - -
Sheet 0.100 - - - -
Sheet 0.125 - - - -
Rectangular 0.080 0.75 - - -
Rectangular 0.100 0.75 - - -
Rectangular 0.125 0.75 - - -
L 0.08 0.75 0.75 - -
L 0.100 0.75 0.75 - -
L 0.125 0.75 0.75 - -
Omega 0.080 0.705 0.50 1.00 -
Rod - - - - 0.50
Process
The racks are mainly made out of multiple punched and folded sheet metals. As you can see in Figure 56,
the side of the racks and their shelves are solely made out of AL2024-T42 sheet metal. This will make their
assembly a lot easier and make the racks more affordable. There is even some cross-line between shelves
that are left on the sheet metal to help stiffen the rack and, in some case, allow the application of a
stiffener to add to the rigidity of the rack. For the heavier cross-beams and the bars that hold the systems,
extrusions were used. This method gave freedom to the designer who could add “L” shaped stiffeners
fixed with rivets to the side of the racks to help with the rigidity.
Figure 56 : Punched sheet metal for sides
Because of the shape of certain racks, some special rods were required to stiffen them. They have a circular
cross-section and end with either a plate or a joint to help link surfaces on different planes.
70. 54
Fasteners
Most parts of the racks are held together with solid rivets, while the floor connections are made with “Hi-
Lock”. The connections of the racks to the frames of the fuselage will be made with a Clevis on the rack
and a swivel joint held to a stringer and a frame by solid rivets. The elements connecting the racks to the
primary structure are showed in the following figures.
Figure 58 : Rack 1 & 3 and their connectors
Figure 57 : Racks and their connectors (right side)
71. 55
Figure 59 : Rack 5 and its connectors
Figure 60 : Racks 7 and its connectors
72. 56
4.2 Methodology and Hypotheses
To obtain racks that meet the established criteria, a strict methodology was required.
1) The first step was to use the STEP files (wire model) containing points obtained from CATIA to
create a geometry that would help mesh the racks in FEM.
2) Once the basic 1D elements were meshed, the elements were refined to obtain a convergence.
3) Then the racks were adjusted to sustain the static load cases.
4) Finally the racks were modified by adding stiffeners to meet the dynamic analysis criteria.
To simplify the FEM process, multiple hypotheses were applied:
1) “L” beams were used to mesh the side of the racks instead of QUAD4, because the gain in time
was significant while the difference of results was insignificant.
2) The systems connection to the rack is represented by RBE3s that transfers the 6 degrees of
freedom from the system to the 4 corners of the connection zone of each system.
Figure 61: RBE3 to simulate system’s fixation with racks
3) The weight and center of gravity of the cables were meshed to the center of gravity of the systems
as the difference this causes is less than 0.5%.
4) The racks' connection to the floor is represented by SPCs with its 6 degrees of freedom fixed as it
holds with “Hi-Lock”.
Figure 62: SPC between the rack and the floor
5) The rack’s connection to the frames and stringers is represented by SPCs locking the first three
degrees of freedom to simulate the ball-joint.
73. 57
Figure 63: SPC between the fuselage and the rack
6) Some cross-beams that cross multiple shelves are locked by RBE2s to the horizontal plates to
simulate rivets.
Figure 64: RBE2 between two beams
74. 58
4.3 Design Development
Figure 65 to Figure 68 show the racks' FEM models. These racks meet the design criteria, and their results
in static and dynamic analyses can be seen in Design Analysis Results and FEM results (avionic racks).
Figure 65 : FEM model of Rack 1 & 3
76. 60
Figure 67 : FEM model of Rack 5 (left) & FEM model of Rack 6 (right)
77. 61
Figure 68 : FEM model of Rack 7(left) & FEM model of Rack 8(right)
78. 62
4.4 Design Analysis Results
Static Analysis
The following table will present the lowest security margins for rack 7, for every Load Case. The first 3 Load
Cases (backwards 1.5g, upwards 3g and sideways 3g) are limit cases and require a minimum security
margin of 50%. The last 2 Load Cases are considered extreme and require a minimum security margin of
0%. The other racks have the same table presented in Secondary Structure's APPENDIX 3: FEM RESULTS.
All Racks meet the established criteria.
Table 13 : Static Margins for Rack 7
Load case Type of Elements Crippling Buckling
Backward 1.5g Beams 1302% 2120%
Rods - 1864%
Upward 3g Beams 2727% 4376%
Rods - 6174%
Sideway 3g Beams 4323% 6902%
Rods - 393%
Downward 6g Beams 367% 639%
Rods - 800%
Forward 9g Beams 134% 271%
Rods - 224%
Dynamics Analysis
The following table shows the first 10 oscillation modes for rack 7. The frequencies had to be over 25 Hz
for the modes with over 10% Effective Mass, and over 50 Hz for the modes under 10% Effective Mass. The
other racks have similar tables in the Secondary Structure's APPENDIX 3: FEM RESULTS.
Table 14 : Dynamic Analysis for Rack 7
Mode Effective Mass (%) Fréquence (Hz) Criteria (Hz) Pass/Fail
1 0.411 34.55 25 Pass
2 0.229 43.89 25 Pass
3 0.215 45.70 25 Pass
4 0.126 51.28 25 Pass
5 0.200 60.81 25 Pass
6 0.125 64.81 25 Pass
7 0.309 65.60 25 Pass
8 0.060 70.38 50 Pass
9 0.023 72.11 50 Pass
10 0.120 75.48 25 Pass
79. 63
4.5 Detailed Design of Rack 7
Following the results obtained in the FEM analysis of the wireframe rack, it is important to translate the
results and assumptions into a physical model so that it meets the required load cases. This section will
focus on the choice of design that led to the resulting detailed rack No7 (S-10007-R00) located on the right
side of the rear fuselage section near the access door. It is important to keep in mind that all along the
design process reducing weight and manufacturing costs were majors concerns.
Figure 69: S-10007-R00 Render Structure (Left) and CATIA model with systems (Right)
80. 64
Figure 70: Rack 7 position (1)
Figure 71: Rack 7 position (2)
First, the topic of the attachment points for the racks to the primary structure will be addressed, as well
as the mechanical links which contain the loads. Then will be presented the structure for rack No7 (S-
10007-R00) and the choices related to its manufacturing processes. Finally a brief look at how the avionic
boxes are fixed to the structure and tray mounted designs used in the design will be addressed.
81. 65
Attachment Point and Mechanical Links
1. Clevis
The results obtained in the design for the fixation to the primary structure is a simple machined clevis
produced on a milling machines. The pilot holes are drilled at the base to facilitate assembly to the primary
structure on the production line. Though each clevis will be machined while trying to keep the same design
ideology, each clevis will be customized to reduce weight and optimize the axis through which the load is
applied. A simple design was favored so that production is possible by 3-axis machine to reduce costs.
Figure 72: Render of a generic clevis
The subsequent steps will be a FEM analysis of the clevis to optimize its weight, the loading axis and the
selection of types of rivets used as mechanical links (ex: Hi-Lok vs. MS rivets, etc).
2. Swage Tubes
The transmission of the load from the secondary structure to the clevis of the primary structure will be
made via a swage tube. The low weight, price and flexibility of assembly for this design allows us to absorb
the constraints linked to the positioning of the clevis to the primary structure at low cost.
Figure 73: Swage tubes example (left) and axis (right)
82. 66
Rack Structure
Again, for cost and weight considerations, the entirety of the rack structure is made from extruded rods
and sheet metal. To get as close as possible to the FEM model, assembly sections are riveted and the
minimum thickness of the L sections will be respected in the thickness of sheet metal as shown in the
following figure.
Figure 74: Shelf side pannel Assy section
1. Side Panel
The side panel for the rack will be cut on a 3 axis router, then bent on a press. Here, the sheet metal
thickness is .080 inch and the bend radius on O temper will be .125 inch as shown on Figure 75. The choice
of the pocket radius is driven by the choice of router end mill and is now set to .250 inch.
Figure 75: Al Alloy Side panel
83. 67
As shown on the unfolded view of the side panel, corner reliefs have been used to allow flange bending
and to reduce unwanted stress in these corners.
Figure 76: unfold side
2. Shelf
The shelf will be machined on a 3 axis router and then bent on a hydraulic press using a form bloc. Again,
the shelf will be made of .080 inch thickness AL alloy sheet O temper.
Figure 77: Shelf P-60005-R00 fold
Figure 78: Shelf P-60005-R00 unfold
84. 68
3. Systems Holder
The boxes will be held using tray mounts if necessary and this device will be fixed to the rack by rivets on
the omega beam, shown on Figure 79. The purple line show the rivet locations. Otherwise the boxes will
be fixed on the omega beam by nut plates like the ones shown in Figure 80.
Figure 79: Omega Beam
Figure 80: Nut plate
85. 69
5. Ergonomics
Throughout the duration of the project, in every phase of the design, ergonomics was a key consideration,
especially when it came to the positioning of the systems. Ergonomic analyses had to be conducted for
manufacturing and maintenance objectives.
5.1 Methodology and Hypotheses
For the installation, removal and maintenance considerations concerning the systems, a table was created
in order to define which systems were more critical. Various weighting factors are summed depending on
the severity of the aspect on a scale of 1 to 3, 3 being the gravest appraisal. The critical factors the team
decided to study and their boolean assessment are:
Time allotted for maintenance: includes the removal, the verification and the installation of a component.
Here, a Line Replacement Unit (LRU) is a system that is allowed 15 minutes for maintenance and is
considered critical. The weight attributed for a LRU is 3. LRU are usually installed in tray-mounted, in order
to simplify maintenance.
Critical dimensions: this criteria is to evaluate if at least one out of three dimension is bigger than the
available walk-in space in the Aft Fuse section. The weighting attribute is then determined by the number
of dimensions (out of 3) that exceed the hallway width.
Visible face: depending on the orientation of the system in the rack, visibility had to be considered. It is
considered critical if the visible face is on the right, left or top of the system, when positioned. The
weighting attribute for this criteria is 1 for these arrangements.
Height and mass: The height positioning of a system contributes to the criticality assessment in the matrix.
This assessment is coupled with a mass criteria. The weighting attribute for the height and weight creteria
is 2 (see Figure 81 for details). The result is also linked to the maintenance action. Based on the systems
we had to position, none of the boxes weighed over 45 pounds and the maximum height is 4,7'.
Figure 81: maximum weight and height
