Best Practices for High-Fidelity Modeling of Lightning Indirect Effects on Aircraft

Lightning indirect effects modeling is a cornerstone of modern aerospace electromagnetic compatibility (EMC) engineering. As aircraft become increasingly electrically complex, with distributed electronics, advanced composites, and dense wiring networks, the ability to simulate lightning‑induced transients accurately and repeatably is essential.

Electro Magnetic Applications, Inc. (EMA) has decades of experience performing indirect effects of lightning simulations. This article shares best practices for developing high-fidelity, configuration-controlled lightning models using Ansys EMC Plus. It covers:  

• Modeling workflow
• Parameter selection
• Geometry simplification
• Material assumptions
• Probing strategies
• Data traceability

This workflow supports the creation of accurate, maintainable models that meet certification-grade analysis requirements.

Establish Rigorous Configuration Control Early

High‑fidelity, full-aircraft models are large, complex, and frequently worked on by multiple engineers. Ensuring traceability throughout the modeling process is essential for maintaining consistency, reliability, and long‑term usability. An effective configuration control document keeps assumptions clear, prevents model drift, and supports seamless collaboration across teams.

A configuration control document should include all model inputs, including:

• Structural simplifications and included/excluded features
• Material assignments and conductivity values
• Joint and seam representations
• Cable and harness definitions
• Boundary conditions
• Mesh and lattice parameters
• Solver settings and time-stepping methods
• Probe placements and measurement definitions

In addition, assumptions should be recorded in real time. Capturing decisions as they occur prevents loss of detail and avoids the inaccuracies that arise from retroactive documentation. Figure 1 provides an example configuration control document for structures.

Indirect vs. Direct Lightning Effects

Lightning effects fall into two categories:

• Direct effects: Physical damage to structure at the attachment point
• Indirect effects: Induced electrical transients that couple onto cables, electronics, and structures throughout the aircraft

Indirect effects drive the bulk of full‑platform simulation work because they influence system‑level EMC performance, equipment qualification, and safety margins. Resulting transients are analyzed at the pin, connector, and bundle levels to evaluate worst‑case stress on avionics modules and wiring.

Use Standardized Electrical Metrics: VOC and IOC

Lightning indirect effects simulations typically focus on two fundamental electrical metrics that quantify how energy from a lightning strike couples into aircraft wiring systems:

• Open‑Circuit Voltage (VOC): Worst‑case induced voltage on a pin
• Short‑Circuit Current (IOC): Worst‑case induced current path

These standardized electrical metrics form the foundation of aircraft transient levels (ATL) specifications and system‑level immunity assessments. VOC and IOC define the electrical environment that aircraft systems must withstand and directly influence the qualification levels applied during certification programs.  

Additionally, VOC and IOC results guide waveform selection, current and voltage injection levels, and test configurations for follow-on hardware evaluations. Anchoring simulations to these standardized electrical metrics ensures consistent interpretation of results across modeling, testing, and certification activities, creating a unified framework from analysis to verification. Figure 2 illustrates elevator actuator pin evaluations, showing cable-bundle excitations locations and the resulting short-circuit current and open-circuit voltage responses.  

Apply Smart Probe Placement Strategies

Accurate probing is essential for producing valid transient predictions in lightning indirect effects simulations. Probe data forms the foundation for interpreting how currents and voltages propagate through aircraft structures and wiring networks, making probe placement one of the most influential factors in overall model fidelity. Poorly placed probes can obscure critical coupling paths, distort measured transients, or lead to costly reruns of computationally intensive full-platform simulations.  

Effective probing practices ensure that measured waveforms reflect the true electromagnetic behavior of the system and allow the model to be reused confidently for related analyses and certification workflows.

Best practices for probe placement:

• Collect bundle currents at every connector, ideally on both sides of bulkhead interfaces, to understand current flow between structure and harnesses
• Place pin probes at connectors or approximately 50 mm (2 inches) from connectors to align with industry measurement conventions
• Probe long cable runs at multiple axial locations whenever feasible to capture spatial variations in coupling

High-quality probe data improves traceability, supports more accurate transient-level assessments, and enhances overall simulation credibility. Suggested parameters for cable harnesses and probes are shown in Table 1.

Optimize Simulation Efficiency with Purposeful Model Reduction

Full per‑pin, per‑waveform, per‑attachment simulations can be computationally prohibitive.

Strategies to reduce runtime include:

• Combining VOC and current-based analyses when conservatism allows
• Using half‑LLC approaches when a less conservative but faster model is acceptable
• Prioritizing high‑value cables (e.g., safety‑critical or flight‑essential systems)

Reductions must be recorded in configuration control to preserve transparency of assumptions.

Build and Manage an Effective Electromagnetic Domain

A well-defined modeling domain is essential for achieving both numerical stability and physical accuracy. The domain determines how electromagnetic fields propagate, reflect, and decay around the aircraft. Improper sizing, meshing, or boundary selection can introduce artifacts such as artificial reflections or unstable field behavior. A properly constructed domain provides sufficient spatial buffer, appropriate boundary conditions, and a mesh resolution suited to the frequencies of interest, ensuring that simulated transient arise from true physical coupling rather than numerical error.

Domain setup guidelines:

• Use adequate buffer space between the aircraft geometry and the simulation boundary (e.g., ≥ 150 mesh cells for a regional jet)
• Select boundary conditions matched to the problem:
  • Absorbing (H‑field = 1) for open‑air problems
  • Periodic/PML for specialized configurations
• Define lattice/mesh size based on aircraft scale:
  • ~50 mm cell size for large vehicles
  • ~25 mm for small aircraft

Time-stepping recommendations:

• Constant time step for most cases
• Magnetostatic incremental scaling for cases dominated by low‑frequency behavior (lightning indirect effects)

These parameters directly influence numerical stability and runtime. Table 2 shows suggested domain parameters.

Use Material Properties Thoughtfully, Especially for Composites

Aircraft increasingly rely on composite structures. However, composites complicate modeling because:

• They are anisotropic, causing electrical and structural properties to vary by direction
• The simulations in contrast often require isotropic equivalents to maintain numerical stability
• Physical thickness of composite layups rarely matches mesh cell thickness, requiring conductivity scaling to preserve correct electromagnetic behavior

Best practices for materials:

• Compute effective isotropic conductivity by averaging directional resistances
• Scale conductivity so electrical resistance matches reality despite mesh thickness
• Use authoritative values for common materials (e.g., CFSP, ECF, aluminum)
• Round thicknesses to practical engineering values (e.g., 1.73 mm → 2 mm) to reduce unnecessary variation

Effective material modeling ensures that composite heavy aircraft designs exhibit realistic electromagnetic behavior without compromising numerical stability or fidelity.

Model Seams, Fasteners, and Joints as Key EMC Features

Structural discontinuities play a critical role in how lightning currents propagate through an airframe, making accurate representation of seams, joints, and fasteners essential for high-fidelity electromagnetic modeling. These features may appear small in the CAD model, but they can dominate current division, alter coupling behavior, and introduce localized impedance variations that significantly affect transient responses. Their impact is especially pronounced in composite aircraft, where conductivity is nonuniform and return paths are more sensitive to structural interfaces.

Recommended approach:

• Use equivalent RLC seam models layered on existing materials
• Choose between:
  • Absolute impedance (Ω, H, F)
  • Density-based impedance (per‑unit‑length)
• Assign values based on expected bond quality (good, moderate, poor)
• Model fasteners as parallel networks; for example, 100 fasteners at 5 Ω each produce a 0.05 Ω equivalent

Modeling seams is a major contributor to fidelity, but also increases runtime, requiring engineers to balance detail and computational cost thoughtfully. Figure 3 shows how seams are shown in Ansys EMC Plus.

Treat Harness and Cable Modeling as a First-Class Citizen

Cable systems are often the dominant coupling paths for lightning because their extended lengths, routing through multiple electromagnetic environments, and proximity to structural features makes them highly susceptible to induced transients. Even when structural conductivity is well-represented, cables can capture and channel significant portions of the lightning-induced energy directly into avionics and subsystem interfaces. As a result, understanding cable coupling is essential for predicting worst-case system responses and ensuring that downstream equipment meets required immunity levels.

Cable modeling best practices:

• Use MHARNESS®, a transmission-line solver, integrated with the EM solver for realistic cable physics
• Assign accurate definitions for:
  • Shield geometry and braid coverage
  • Wire gauge
  • Insulation thickness
  • Pigtail lengths
  • Termination resistances
• Represent routing as connected segments with consistent metadata
• For low‑frequency lightning behavior, enable low‑frequency approximation, since composite shields can appear semi‑transparent

Wiring metadata should be recorded in configuration tables including pinouts, LRU connections, and cable type identifiers.

Maintain a Clean, Hierarchical Model Structure

Large aircraft models become unwieldy without structure, especially as geometric detail, material definitions, and simulation settings increase in complexity. Without a consistent organizational framework, even small updates can become error-prone or time-consuming. A structured model hierarchy keeps data accessible, reduces redundancy, and supports reliable collaboration across engineering teams.

Recommendations:

• Use component trees to organize skins, substructures, and LRUs
• Preserve original CAD naming whenever possible
• Maintain a mapping table linking:
  • Original part names
  • Simplified surface names
  • Material assignments
  • Thickness assumptions

This improves clarity, minimizes duplication, and makes troubleshooting dramatically easier.

Ensuring Accuracy and Efficiency

High‑fidelity modeling of lightning indirect effects requires a balance of physics accuracy, computational efficiency, and rigorous documentation. By following these engineering best practices, including strong configuration control, disciplined domain and mesh design, thoughtful material modeling, and careful signal probing, you create models that are both technically robust and operationally maintainable.

EMA specializes in delivering high-fidelity lightning indirect effects simulations for aircraft of all sizes, combining decades of engineering experience with advanced simulation with Ansys EMC Plus. EMA scientists manage the full workflow, from geometry preparation and configuration control through material modeling, seam characterization, and cable harness simulation, to produce certification ready transient predictions with confidence and traceability. EMA’s proven methodologies reduce risk, accelerate development, and ensure compliance with industry standards.

To learn how EMA can support your program or to start a lightning indirect effects study, contact EMA now.

Learn more in the EMA Expo 2026 session “Generating High Fidelity Models for Indirect Effects of Lightning Simulation.” Watch now by clicking here.