Structural Design & Engineering

Composite Design & Engineering Services


Stress Analysis: Aero Optimal Ltd was involved in the concept configuration, optimisation & weight saving work packages of the forward and aft fuselage composite structures of the A350XWB shells.

Our internal R&D programs have resulted in the development of many software tools, notably a unique Optimisation Tool applicable to curved skin panel structures (i.e. skins, stringers & frames structures).

We use industry-standard linear and non-linear Finite Element analysis and can also offer compilation checking & approval of composite and metallic static/fatigue stress dossiers & supporting data.

Design: In support of the A350XWB metallic & composite engineering, we have provided the associated Catia 2D drawing sets with BOM's & 3D models inclusive of Fibresim content. Also, a compilation of detailed weights/inertia/CG reports per assembly for inclusion in the aircraft weights model.

Manufacturing-Support: From our experience in the development & support of A350XWB composite/metallic quality control programs, we can provide support to prove consistent manufacturing processes (Witness Specimen Program), First Article Inspections, First Part Qualification, Drawing Query Notes, Drawing Change Notes, Concessions & Generic repairs.

Structural Repair Manuals: We can provide analysis & compilation of the structural repair manual entries applicable to the primary & secondary structures to the standards demanded of EASA.

Liaison: Our extensive experience in attending multiple international program reviews will enable us to recommend improvements to the evolving design & manufacturing process whilst offering proposals & solutions to technical issues.

Structural Testing: Completing structural/certification test proposals, test rig design, forecasting strain/deflection results, FEM models & compilation of results dossiers.

Training: Based on our extensive experience and involvement with the A350XWB technical review board at the central entity, we can provide advanced, adaptable technical coaching in the design analysis and optimisation of large 'CAT- A' composite structures.

Personnel: Our technical ability has allowed us to supply stress, design, and integration teams to Airbus Americas in support of European based efforts on the A350XWB primary structures.

Pedigree: The following are programs in which Aero Optimal Ltd and its engineers have participated.
Military: - NH90, SD-330 and SD-340
Civil: A350XWB-900 & -1000, A380, A340, Avanti P180, MD11, FFA2000 and AS907/HTF7000
Space / Other: -SOHO Spacecraft / Horizontal composite wind turbine blade

Composite Structural Design, Analysis &

Recent Experience (2006 to 2017)

Our experience in the design, analysis and optimisation of lightweight structures (Composite & Metallic) such as wing, fuselage, high lift and control devices enabled us to work directly with Airbus' core engineering team in technical coaching, concept and detail design development of the A350 XWB-900 &-1000 passenger aircraft.

A350 XWB-900 Cabin Engineering Airbus  Group  Inc. USA (2015-2017)

Supporting Airbus Group Inc for the development and certification of A350XWB galleys and monuments.
Check stress analysis and validation reports (team of stress engineers at B/E Aerospace, UK)

Engineering support to Airbus America, A350XWB-1000 side shells & door surrounds (2012-2015)

Engineering support to Airbus America Engineering for developing A350XWB-1000 fwd fuselage S13/14 side shells and Pax & Cargo door surrounds structures.


  • CSPS analysis of far-field skin/stringers

  • Frames and stringers cut analysis.

  • DFEM for frames analysis

  • Stringers de-bonding and skins perforation

  • GFEM shells definition and load extraction


Design (CATIA V5)

  • LH & RH skins / stringers design principal & drawings

  • LH & RH orbital joint design principal & drawings

  • Integration activities of skins/stringers, frames, clips, and shear webs into VPM

  • Corner fittings design for the floor to side shell attachments

Engineering Support Aibus America A350XW

Definition phase (Mat A) of A350XWB-1000 aft fuselage Shells (2011 - 2012)

Configuration, pre-sizing and maturity “A” sizing of the aft fuselage Skins/stringers, frames, and clips.

Specific sizing activity of CFRP fuselage structure and variety of trade studies for the A350XWB-1000 variant.  Pre-sizing, overall optimisation and harmonisation of internal load distribution of the CFRP Aft fuselage structure. Validation of optimised sizing results of the side shells, upper and lower shells.

Skins and Stringers sizing analysis:

  • Local, General and Post buckling

  • Stringers de-bonding

  • Damage Tolerance

  • Frame-cut Large Damage capability

Frames and Clips sizing analysis:

  • Short Clips Sizing

  • Long Clips Sizing

Definition Phase (Mat A) of A350XWB-1000

Detail sizing and justification stress reports of Upper & Lower shells structures (2010-2011)

A350XWB-900 AFT fuselage, preliminary sizing & justification stress report of upper and lower shells.

Preliminary stress justification reports of status Mat 'C'

Upper shell: Skins and Stringers sizing analysis

  • ISAMI CSPS Calculations

  • General Buckling Analysis (ISAMI DFEM)

  • LDC Analysis (GFEM and ISAMI DFEM)

  • Stringers de-bonding, Rib-bay buckling and Cut-out analysis

Frames and Clips sizing

  • ISAMI Composite Frames Analysis

  • Long and Short Clips Analysis


  • Antennas Surround Structures

  • Interface Frames and Skins Analysis

  • Dorsal Fin interface Analysis & Cut-outs

Lower shell: Skins and Stringers Analysis

  • ISAMI CSPS Calculations

  • General Buckling Analysis (ISAMI DFEM)

  • LDC Analysis (GFEM and ISAMI DFEM)

  • Stringers de-bonding, Rib-bay buckling and Cut-out analysis

Frames and Clips sizing

  • ISAMI Frames Analysis

  • Clips sizing analysis (short clips and shear ties sizing)

Detail sizing justification reportinf of
A350xwb-900 LS & US.jpg

Integration support to Airbus America for A350 XWB-900 forward fuselage section side shells (2008-2014)

Engineering support to Airbus America for the development of A350XWB-900 Fwd fuselage S13/14 side shells structures.

Design and stress analysis of section 13/14 side shells excluding Pax and Cargo doors.


  • CSPS analysis of complete far-field skins/stringers

  • Frames and stringers cut analysis

  • DFEM for frames analysis

  • Stringers de-bonding and skins perforation analysis

  • GFEM definition of side shells and load extraction

Design (CATIA V5)

  • LH & RH skins/stringers design principal & drawings

  • LH & RH orbital joint design principal & drawings

  • Integration activities of skins/stringers, frames, clips, and shear webs to VPM

  • Corner fittings design for the floor to side shell attachments

Validation of CFRP door surround structures design and analysis (2010)

A350XWB-900 Aft fuselage section 16/18 PAX, BULK and CARGO doors surround structures.

Door surround skins and stringers with backup structures sizing.

  • Supporting Airbus section 16/18 side shells team in checking the supplier validation reports concerning sizing methodology.

  • Detail check stress analysis of PAX, BULK and CARGO doors surround structures DFEM (detail finite element model) and providing recommendation proposals to improve the FE models for static and buckling analysis (MSc Nastran SOL 101 & 105 analyses).

Concept & definition phase of -900 fwd & aft structures (2007-2010)

A350XWB -900 fuselage Fwd & Aft (sections16/18 & 13/14) Concept and Mat "A “.

Technical coach to the A350XWB Fwd and Aft fuselage (sections16/18 & 13/14) core engineering team and fuselage optimisation proposals.

2007-2009:  Technical coaching of both Fwd & Aft section stress team for the definition design concept, pre and target sizing of CFRP fuselage structure. Some of the main tasks are as follows:

  • Stringers pitch definition.

  • Stringers geometries definition.

  • Skins and stringers thickness & layups definition.

  • Door surrounds skins layups definition.

  • Frames layup definition

  • Longitudinal & circumferential joint layups and thickness distribution.

  • Rear pressure bulkhead intermediate and detail FEM

  • Small & large Cut out sizing

  • Window belt layups and pre-sizing definition.

  • Longitudinal and Orbital joints layups definition

2009-2010: Weight saving optimisation studies of Fwd and Aft fuselage sections shell structures (NASTRAN/PATRAN and ISAMI).
Presentation of the weight saving and optimisation design philosophy proposal of skins and stringers

Overall assessment of A350 CFRP wing & pre-sizing of CFRP upper cover (2006-2007)

A350XWB Wing Upper Cover (Wing Upper cover) Structure.

A350 wing (upper cover skins and stringers assessment, Mandatory Passage Hole)

  • Preliminary design and stress study (FE & Analytical) of the stringers mandatory fuel passage hole and its effect on the skins/stringers of the A350 CFRP wing structure.  Performed both linear and non-linear analysis of skins/stringers with different MPH shapes of various local reinforcement shapes and reported various stress concentration factors for the three types of studies resulting in significant weight saving.

  • Review the complete wing box GFEM model (MSc NASTRAN/PATRAN) and modify the upper CFRP cover's geometry, mesh, and layups/properties.

  • Sub-structure static stress analysis of the upper cover (IFEM) with detailed representation of the skins/stringers design leads to a more accurate definition of a load path and higher weight efficiency.

  • Overall static/buckling analysis of the CFRP upper cover and comparison of result to conventional boom represented FE model of the wing.

Overall assessment of A350 CFRP wing and