Case Study: Load Analysis of a New Commercial Jet using AeroSimulations

In aerospace engineering, the structural integrity of a commercial jet depends on a thorough understanding of the loads it will experience throughout its service life. From the steady forces of level flight to the transient shocks of turbulence or hard landings, every component must be designed to withstand a spectrum of mechanical and thermal stresses. This case study presents how AeroSimulations, a state-of-the-art multiphysics simulation platform, was employed to perform a comprehensive load analysis of a newly designed 180‑passenger narrow‑body commercial jet. The study focuses on the methodology, key findings, and design improvements that resulted from the simulation campaign.

Background: The Importance of Load Analysis in Aircraft Design

Load analysis is not merely a regulatory checkbox; it is the foundation upon which safe, efficient, and durable aircraft are built. During the design phase, engineers must estimate the external aerodynamic loads (lift, drag, side forces), inertial loads (mass properties, accelerations), and internal structural loads (bending moments, shear forces, torsion). These loads vary with flight condition, weight distribution, and control surface deflections. Traditional methods rely on semi‑empirical formulas and wind‑tunnel tests, but modern computational tools like AeroSimulations allow for high‑fidelity, coupled simulations that capture complex fluid‑structure interactions.

The subject of this study is a next‑generation commercial jet designed for fuel efficiency and passenger comfort. Its aerodynamic configuration features a high‑aspect‑ratio supercritical wing, a swept tail, and engine nacelles mounted under the wings. To certify the airframe for an expected service life of 30 years, the design team needed to quantify loads across all critical flight conditions, including gust encounters, manoeuvring limits, and emergency descent scenarios.

Introduction to AeroSimulations

AeroSimulations is a comprehensive simulation environment that integrates computational fluid dynamics (CFD) for aerodynamic loads with finite element analysis (FEA) for structural response. It offers a unified workflow for modelling complex geometries, applying boundary conditions, and solving coupled physics problems. Key capabilities relevant to this study include:

  • Unstructured mesh generation for arbitrary aircraft shapes
  • Reynolds‑averaged Navier‑Stokes (RANS) and detached‑eddy simulation (DES) solvers
  • Fluid‑structure interaction (FSI) coupling via iterative exchange of loads and displacements
  • Automated post‑processing tools for load extraction and stress mapping

AeroSimulations has been validated against experimental data from wind‑tunnel tests and flight‑test campaigns, giving engineers confidence in its predictive accuracy for both steady and unsteady load cases.

Methodology of the Load Analysis

2.1 Digital Model Preparation

The first step involved creating a detailed three‑dimensional model of the entire aircraft. The geometry was imported from the CAD system used by the design team and then cleaned to remove surface imperfections. Critical features such as slats, flaps, ailerons, and wing‑body fairings were retained, while small holes and fasteners were suppressed to simplify meshing. The final model consisted of approximately 12 million surface elements.

2.2 Simulation Setup and Boundary Conditions

Engineers defined a matrix of 50 flight conditions representing the certification envelope specified by aviation authorities (EASA CS‑25 / FAA Part 25). These conditions included:

  • Steady symmetric flight: cruise, loiter, and maximum‑range configurations
  • Manoeuvre loads: pull‑up, push‑over, roll, and yaw manoeuvres at limit load factors
  • Gust loads: discrete “1‑minus‑cosine” gusts of varying length and orientation
  • Ground loads: landing impact, braking, and taxiing

For each condition, the CFD solver used a RANS turbulence model (Spalart‑Allmaras) with appropriate inlet and outlet boundary conditions. The structural finite element model, which included the wing box, fuselage frames, and tail empennage, was meshed with 3.5 million nodes and 2.8 million reduced‑integration hexahedral elements. Material properties were assigned based on aluminium‑lithium alloys for the wing and carbon‑fibre composites for the fuselage skin.

2.3 Coupled Fluid‑Structure Simulation

To capture the interaction between aerodynamic loads and structural deformation, the team performed two‑way coupled FSI simulations for the most critical load cases (e.g., maximum positive manoeuvre load factor). In each coupling step, the CFD solver computed the pressure and shear stress distribution on the wing surface. These loads were mapped onto the structural mesh using a conservative interpolation scheme. The FEA solver then computed the resulting displacement field, which was passed back to the CFD solver to update the fluid mesh. This iterative loop continued until convergence (residuals below 1×10⁻⁴ for force and displacement).

2.4 Data Extraction and Post‑Processing

After each simulation, engineers extracted the following load quantities:

  • Spanwise lift and bending moment for the wing
  • Pitch, roll, and yaw moments about the centre of gravity
  • Reaction loads at attachment points (wing‑body joint, engine pylon)
  • Stress and strain in critical structural components

Results were consolidated into a load envelope database that served as the basis for static and fatigue strength assessments.

Results and Findings

3.1 Wing Load Distribution

The simulation results confirmed that the wing design meets all limit and ultimate load requirements. The maximum positive bending moment at the wing root occurred during a 2.5‑g symmetric pull‑up at dive speed (VD/MD). The value was 1.85×10⁶ N·m, which is 12% below the ultimate design limit of 2.1×10⁶ N·m. The margin is acceptable but left room for further optimization.

Notably, the spanwise load distribution showed a slight outboard shift compared to the initial aerodynamic predictions. This shift, caused by aeroelastic wash‑out effects under load, increased the bending moment at the wing‑body junction by 5%. The design team was able to accommodate this by adding a local reinforcement patch in the lower wing skin.

3.2 Fuselage and Empennage Loads

Fuselage loads were dominated by pressurisation and landing impact. The maximum hoop stress in the fuselage barrel occurred during the 1‑cosine gust condition at 1.5 times the maximum operating altitude. The stress (205 MPa) remained within the allowable for the composite material (ultimate strength 380 MPa with a safety factor of 1.5 on limit load). The horizontal tail experienced its highest downward bending moment during a rapid push‑over manoeuvre, which was well below the ultimate strength of the spar.

3.3 Critical Insights and Design Changes

Three findings led to tangible design modifications:

  1. Wing‑root reinforcement: As noted, the aeroelastic redistribution required additional skin thickness near the root. By redesigning the local laminate layup, the team increased strength while adding only 8 kg per wing.
  2. Engine pylon load alleviation: The coupled simulations revealed an interaction between the wing bending and the pylon bracket loads during a sideslip condition. A revised bracket geometry reduced peak stresses by 30%.
  3. Landing gear attachment: The ground‑load analysis showed that the original trunnion bearing design could experience galling under combined vertical and drag loads. A material change to a high‑strength stainless steel was implemented.

These changes were re‑simulated and validated, confirming that all margins met or exceeded requirements.

Discussion: The Value of Coupled Load Analysis

This case study illustrates the limitations of treating aerodynamics and structures as separate domains. The outboard load shift that appeared only in the coupled FSI simulations would have been missed by a conventional “rigid‑body” load analysis. By using AeroSimulations, the engineering team gained early visibility into aeroelastic effects that could otherwise have led to weight‑adding oversizing or, worse, in‑service failures.

Furthermore, the ability to run high‑fidelity simulations across the full flight envelope significantly reduced the number of expensive physical tests required. For example, the gust‑load database was generated entirely from simulation, with only a few confirmatory wind‑tunnel runs for calibration. According to the project’s cost estimation, this approach saved approximately 18 months of development time compared to a traditional test‑heavy programme.

External Resources for Further Reading

For readers who wish to explore load analysis in greater depth, the following resources offer authoritative guidance:

Conclusion

The load analysis of this new commercial jet using AeroSimulations demonstrates how modern multiphysics simulation can provide a detailed, validated picture of the structural loads an aircraft will encounter in service. By integrating CFD, FEA, and fluid‑structure interaction within a single workflow, the design team was able to identify critical load paths, optimize structural mass, and ensure compliance with certification requirements. The resulting aircraft is both lighter and stronger than a design that would have relied on traditional, decoupled methods. As simulation technology continues to advance, such integrated load analysis will become the standard for all new aircraft programmes, enabling safer and more efficient flight.