1. A Moving-Aperture (E-Field Topology Driven) Method for Laboratory Simulation of Swept-Stroke Lightning Attachment
Shahriar Khosravani
A novel laboratory method is presented for simulating swept-stroke lightning attachment on aircraft outer skins using a stationary high-voltage (HV) electrode and a dynamically moving dielectric aperture. The system consists of two concentric dielectric cylinders incorporating narrow helical slots of opposite chirality. Counter-rotation of the cylinders produces a translating diamond-shaped aperture that moves linearly along the substrate (Al, CFRP) panel under test (SUT), while the HV electrode remains fixed along the system axis. Electrical discharge is initiated at the point of minimum breakdown distance defined by the aperture geometry. As the aperture translates, the established plasma channel is continuously dragged along the SUT, reproducing the swept-stroke phenomenon observed during aircraft motion through an established lightning attachment. Unlike traditional methods that rely on mechanical electrode translation or airflow-assisted arc deflection, this approach leverages the intrinsic tendency of lightning to follow evolving electric-field minima. A critical feature of the method is the controlled interaction between the plasma channel and the rotating dielectric tube surfaces. The no-slip boundary condition induces a Coandă-type effect, stretching and stabilizing the plasma column beyond static Paschen breakdown limits. This enables extended arc lengths at constant applied voltage, closely mimicking real swept-stroke behavior. The method offers high repeatability, precise control of effective stroke velocity, and scalability without increasing HV source energy. It provides a practical, non-destructive, and reliable physics-consistent alternative to existing swept-stroke simulation techniques for lightning direct-effects testing of aircraft structures.
2. A Current Rise Rate Dependent Nonlinear Electrical Conductivity Model of Carbon Fiber Reinforced Polymer for Lightning Strike Simulation: Development and Validation
Pei Xiao, Bin Yang, Jiang Xie, Zhenyu Feng
The evolution of electrical conductivity in carbon fiber reinforced polymer (CFRP) under lightning strike is a critical issue that requires accurate characterization and modeling for reliable simulation. Due to the combined effects of dielectric breakdown and inductance, the through-thickness electrical conductivity-potential gradient relationship of the material exhibits a pronounced rate effect. This study establishes a power-law model that accounts for the current rise rate to describe the nonlinear relationship. The results demonstrate that the proposed power-law model achieves high fitting accuracy within a current range of 200 A to 6000 A. At peak currents of 259.3 A and 1697.2 A, the simulated voltages based on the power-law model show good agreement with experimental data (peak errors of −3.4% and +1.2%, respectively), significantly outperforming the linear model that ignores rate effects (errors of +28.2% and +5.1%, respectively). During the application of electrical current, the electrical conductivity of the material increases significantly, yet the temperature change remains minimal. This observation indicates that conductivity models based on temperature or degree of pyrolysis are not applicable under these conditions. Deviations observed in simulations under high-current impact, and analysis indicates that the peak electrical conductivity in the tests continued to increase with rising potential gradient and did not reach a stable state. This study provides an important analytical tool for the high-precision prediction of lightning strike damage in CFRP.
3. Personal Protective Lightning Equipment: A Wearable Garment to Reduce Lightning Induced Death and Morbidity
Dan Schlager, Harvey W. Meislin
Currently, no human personal protection equipment (PPE) exists that can be worn by individuals during a lightning storm with the capability to diminish the risk of sudden death and other lightning induced morbidity. Utilizing a uniquely developed technology that incorporates strategically oriented conductive strips into wearable garments, we have developed wearable Personal Protective Lightning Equipment (PPLE), designed to protect individuals from lightning-induced injuries, including sudden death. This study analyzes the ability of our PPLE technology to divert lightning level current away from the anatomic areas of the heart and brain stem, as current injury to these areas may result in sudden death. In controlled testing on a PPLE garmented mannequin subjected to lightning level charges, this study positively demonstrated the effectiveness of the PPLE garment and its ability to redirect potentially lethal currents away from anatomically sensitive areas. Various conductive garment configurations and garments themselves (shirt, jacket, pants, hood) were evaluated, including a garment with no direct grounding. The PPLE garments demonstrated the ability to both attract the lightning level charge and divert its path This ability to effectively divert current, thus protecting the human wearer, represents a significant advancement in direct human lightning protection. This concept is a groundbreaking approach to safeguarding humans against lightning induced sudden death and has significant potential to mitigate non-fatal lightning-related injuries. While promising, further research and refinement are needed to ensure the safety and applicability of PPLE.
4. Inside Draft IEEE Standard 2838 Aerospace Components Direct Effects Lightning Qualification Standard
Frederick Heather
The IEEE Working Group 2838 is sharing the new Draft IEEE Standard 2838 Aerospace Components Direct Effects Lightning Qualification Standard that has been under development for the past couple of years and is planned to be published by the end of 2026. The initial target audience for this standard was civil and military aircraft with lightning requirements. However, the increased commercial involvement in spacecraft expanded the standard to cover spacecraft with lightning requirements, ergo the use of ‘Aerospace” in the title. The new standard is built on the wealth of knowledge on aerospace component direct effect lightning testing from lightning experts and various lightning publications and recommended practices. We will show how the standard fills the void in lightning standards and can be used to by the aerospace industry to achieve standardized lightning direct effect component qualification. The presentation (and paper) will describe in detail the approach to lightning direct effects certification levels, standardize lightning direct effects component test methods, and tailoring options for unique components.
5. Evaluation of Triggered-Lightning Safe Distance of a UAM Vehicle Based on Simplified Electrostatic Models
José Antônio S. Mariano, Rodrigo Cabaleiro Cortizo Freire, Ricardo Rezende Schoenacher, José Pissolato Filho
This paper presents an engineering assessment of the minimum separation distance that a notional Urban Air Mobility (UAM) vehicle should maintain from thunderstorm clouds to reduce the risk of aircraft-initiated lightning under quasi-static electric fields conditions. The study combines simplified electrostatic models of the atmospheric electric environment and numerical simulations of interaction between the vehicle with this environment. Two screening metrics are evaluated: a local amplification factor criterion and a heuristic leader-inception criterion based on a combined field-and-charge requirement. The resulting triggering distances are compared for representative lumped and distributed cloud-charge models.
6. A220 LIGHTNING IN SERVICE EXPERIENCE VS LIGHTNING ZONING
M Jalali, K Baalbaki, L Leblanc, L Jia
Narrow-body Airbus A220 got the initial type certification by Transport Canada on 18 December 2015 and entered in-service on 15 July 2016 with Swiss Global Air Lines. The lightning zoning of the A220 including aircraft surfaces, or zones, where lightning strike attachment to the aircraft is probable and the portions of the airframe through which lightning currents must flow between attachment points was defined as per SAE ARP 5414A. Based on the subsequent in-service experience of various airframe manufacturers, updated SAE guidance material was published in ARP 5414-B (Aircraft Lightning Zoning). This paper presents the in-service experience of the A220 fleet in accordance with the updated ARP 5414-B framework. The main topic that has been addressed: In-service experience of the A220 shows that there is a low probability of lightning attachment to the wing surfaces aft of power plant mounted under the wings of narrow-body aircraft. Most of recorded attachment are on center fuselage, cockpit and empennage. Majority of recorded cases of attachment on wing are on winglet(s). Removal of lightning Zone 2A/2B from the area behind the powerplant installation such that most of the wing skin comprising the upper and lower boundaries of the fuel tank is located in within a Zone 3 lightning strike region. Still, there is a Zone 2A lightning attachment region at the inboard end of the fuel tank, root joint area. It should be noted that the current lightning zoning at the wing tips will remain unchanged as the lightning zone 1A/1B already extend inboard to the extent defined in SAE ARP 5414-B and the Zone 2A/2B is conservatively left unaffected even though they have been removed from ARP 5414-B for the wing tip area. Conclusions from our in-service data are therefore supporting the recommendation of ARP 5414-B.
10. Qualifying an Advanced Lightning Protection Laminate for Wind Turbine Blades
Aaron Jones, Harlan Sharpe
Lightning strikes remain a significant reliability concern for wind turbine blades, particularly in severe environments. Despite advancements in lightning protection systems and retrofit solutions, failures in effective lightning current transfer continue to result in blade and component damage, causing operational losses until repairs are completed to the wind turbine. ShockTape™ is a patented multilayer conductive laminate developed to enhance existing blade lightning protection systems by providing a controlled surface current path that transfers lightning current to the blade receptor while protecting the underlying composite structure. Previous ICOLSE publications introduced the original concept, documented laboratory proof-of-concept testing, and presented early field deployments. Since those publications, the technology has undergone substantial refinement through material optimization, environmental durability improvements, independent qualification testing, and continued operational service.
This paper presents the latest stage of the laminate development through high-current qualification testing performed in accordance with the principles of IEC 61400-24, environmental durability evaluations including accelerated salt fog exposure, and continued field validation on utility-scale wind turbines operating in high-lightning regions. Laboratory testing evaluated repeated lightning attachment, current transfer capability, laminate durability, and protection of representative composite substrates. Environmental testing assessed long-term durability of the laminate construction under conditions representative of service environments, while field inspections provided validation under natural lightning exposure.
The combined laboratory and operational results demonstrate that laminate effectively transfers repeated high-current lightning discharges while protecting the underlying blade structure and maintaining environmental durability. These results support the use of laminate as a practical retrofit enhancement for existing wind turbine blade lightning protection systems while providing a foundation for integration into future blade designs.
11. A Bayesian Approach for Uncertainty Quantification and Parameter Calibration: A Study on Lightning Multiphysics Model at Fastener Data
Stefani Mokalled, Louisa Michael, Derek Tuck
Computational models, such as finite element or finite volume models, are often used as a cheaper and more time-efficient method to represent physical processes compared to experiments. This results in two sources of information: simulated and experimental data that span the same (for validation purposes) or a complementary (for application) parameter space. However, discrepancies between computational models and true physical processes are to be expected, due to many aspects, including measurement errors, noise in test data that cannot be explained and input parameter uncertainties. The latter refers to parameters that are required as input to run the computational models, but whose exact values are either unknown or are associated with a large uncertainty. We propose a Bayesian approach of combining these two sources of data to a) improve prediction error by accounting for some of these sources of uncertainty, b) generate practical analytic models to be used in place of computational models and c) predict unknown input parameters for numerical simulations. We demonstrate the performance of this methodology on a lightning multiphysics model at fastener application for lightning direct effects ignition sources. The parameter prediction methodology is applied to physics prediction models of structure subjected to lightning strike generating potential ignition sources.
12. Spatiotemporal Characteristics of Lightning Activity in a High-Convection Tropical Region: Multi-Year Analysis over Western Java, Indonesia
Daniel Pardede, Fauzik Darmawan
Western Java, including West Java Province, Jakarta, and Banten, represents one of Indonesia’s most lightning-active regions due to persistent tropical convection and complex terrain influences. Reliable cloud-to-ground (CG) lightning detection in this environment is essential for operational weather monitoring and severe storm warning. This study evaluates the performance characteristics of a ground-based Lightning Detection Network (LDN) operated by BMKG using CG stroke-level data from 2022 to 2025 derived from operational lightning mapping and real-time monitoring systems. Spatial analysis reveals that several localized hotspots experience peak annual CG stroke densities ranging from 12 to 37 strokes km⁻² year⁻¹ (with cumulative 4-year densities reaching up to 75 strokes km⁻² in localized hotspots). Grid-based density mapping was applied to identify persistent lightning hotspots across urban lowlands and mountainous regions. Seasonal and diurnal variability, peak current distribution, and temporal detection stability were statistically examined under varying monsoonal regimes. Results indicate consistent seasonal and diurnal signatures characteristic of tropical convection, with peak activity occurring during the rainy season and late afternoon hours. The upgraded network, leveraging modernized Boltek LRX-1 receivers with high-precision RS485 GPS synchronization, demonstrates stable temporal performance and robust validation against historical localized networks. This operational assessment supports continued enhancement of lightning-based early warning capability in densely populated tropical environments.
13. Equivalent Material for Paint Layer Replacement in Lightning Strike Damage Test in Composite
Audrey Bigand, Naresh Kumar Krishnamurthy
Paint thickness is a key driver for the damage on composite structures. This is attributed to the constriction effect of the paint on the arc root and confinement of lightning strike explosion with the lightning current flow. Aircraft certification requires lightning testing with the worst-case paint thickness. Manual paint application done during the samples manufacturing frequently results in non-homogenous thickness and deviations from specifications. These inconsistencies often lead to variable and potentially inconclusive test results. Furthermore, manual paint application could lead to delay due to the difficulty with paint shop availability or repainting needs. To address these challenges, this paper proposes replacing paint with an equivalent constant-thickness dielectric film. Five different dielectric films – selected for their mechanical similarity to the reference paint – were screened during a first test campaign. Within this selection, two integration processes were studied: adhesive bonding and co-curing. These candidates were evaluated by comparing their damage signatures against a painted reference. A second phase validated the down-selected candidate by assessing its performance across different key parameters of damage generation in composite structures, including dielectric thicknesses, Lightning Strike Protection (LSP) type, current threat levels, and composite substrate variations. Results confirm that the co-cured dielectric film replicates the electrical and mechanical confinement effects of the aeronautical paint with reproducible results. Consequently, it is considered as a reliable paint surrogate for composite damage assessment during both engineering and certification lightning tests.
14. Ignition Potential of Edge Glow Based on Signature of Detected Light
Giorgia Bartolucci, Sophie Parker, Simon Evans, Audrey Bigand, Irene Borillo-Llorca
Edge glow, a known lightning direct effect in the aerospace industry, manifests as electrical breakdowns or hotspots at cut edges of Carbon Fibre Reinforced Polymer and is a potential ignition source within the fuel tank. Fuel vapour ignitions must be prevented according to CS25.954. As per EUROCAE ED-105B, ignition sources can be identified via the optical method, which is cost-effective but conservatively demands zero-light emission. The alternative is the ignitable mixture test method, which is complex and expensive to implement. Building on the edge-glow-performance screening methods presented at ICOLSE 2022, this paper investigates a criteria based on the visual signature of edge glow that is necessary to ignite a calibrated gas. The approach combined data from simultaneous optical and ignitable mixture testing for several materials to identify edge glow capable of ignition. Analysis showed significant variation in edge glow spatial distribution and intensity, depending on the material architecture and current level. It was determined that a threshold exists, below which edge glow cannot trigger ignition. Consequently, this paper presents an approach to identify non-igniting edge glow via an optical method. A conservative edge glow threshold based on visual signature could enable the identification of intrinsically safe materials that cannot create edge glow capable of causing ignition. The approach could also streamline certification activities by replacing the complexity, lead time, and cost of the ignitable mixture test using an optical method.
15. An Improved Method to Identify Lightning Strikes to Tall Objects Using a Novel Autoencoder-based Signal Modeling
Siyuan Pan, Yuanhan Chen, Ziqin Ding, Hanbo Yang, Si Chen, Vladimir A. Rakov, Kang Yang, Joel B. Harley, Yanan Zhu
Tall objects, such as communication towers, wind turbines, and lightning protection towers, are favored by cloud-to-ground lightning strikes as they strongly enhance the ambient electric field. Previous work shows that it is feasible to identify lightning strikes to tall objects through using their characteristic far electric field waveforms. In this paper, we present an improved method to identify lightning strikes to tall objects (≥200 m). We developed a semi-supervised learning framework that equips an autoencoder to learn the complex microsecond-scale pulse patterns of the lightning electric field. Compared to the previous study, this method requires no labeling to the data. Further, we found that this framework can accurately reconstruct the electric field waveform of the lightning strikes to tall objects based on very limited positive samples. This is a great improvement since the positive samples determine the identification efficiency due to its imbalanced presence in the previous training dataset. This suggests that one does not have to rely on large dataset to automatically identify lightning strikes to tall objects using machine learning approach.
17. Lightning strike damage in AA 6061-T6: two distinct mechanisms across aircraft lightning zones
Johanna Nino-Uribe, Alban Douyere-Dumesnil, Yann Lefaux
SAFRAN Nacelles, an aeronautical systems manufacturer, evaluates the behavior of aluminum components subjected to lightning strikes through standardized tests. This study analyzes the damage mechanisms and structural modifications in these waveforms after controlled discharges. This research was conducted on aluminum alloy samples, characterized nondestructively using 3D profilometry to quantify the extent of surface damage caused by the lightning strike. The samples underwent metallographic preparation and transverse analysis and microhardness measurements. This made it possible to evaluate the damage morphology of the impacted zones and the induced microstructural modifications. In addition, electron backscatter diffraction (EBSD) analyses were performed in the transition zones between the impacted regions and the surrounding material to characterize crystallographic and microstructural changes associated with the thermal and mechanical gradients generated by the discharge. The tests included the IA and 2A certification zones, combining aluminum and paint thicknesses. Characteristic lightning strike damage was observed, such as localized melting, porosity, microcracking, and microstructural alterations. The analysis revealed that the tests in Zone 2A (peak current of 100 kA) caused more extensive damage than those in Zone IA (peak current of 200 kA). In Zone 2A, the lower current intensity favored energy dispersion in the material, increasing the affected surface area and the depth of absorption. By contrast, in Zone IA, the higher current caused more localized damage and concentrated material loss, with less extent. The EBSD analysis complemented the optical microscopy observations, revealing changes in the crystalline microstructure and the distribution of crystallographic orientations associated with different impact conditions.
18. Linking Contact Resistance Variability to Sensitivity in Lightning Performance Prediction
Nitish Chandra, Brian Egenriether, Benjamin Westin, Derek Tuck, Andrew Choi
Prediction and simulation of lightning current conduction through fastened assemblies to estimate damage and sparking performance thresholds for safety critical systems allows for early design optimization, focused test matrices, and traceable certification processes. The quality of simulation and uncertainty in prediction depends on extracting physical parameters from Multiphysics testing and mapping test article data onto complex structures in simulations. Electrical contact resistance underpins the physical interactions at the fastener-structure interface. The contact resistance measurement exhibits large variability as it depends on fastener-fit, material properties, coatings, injected energy, and parasitic interactions. We present the test method to precisely characterize contact resistance as a function of contact pressure and current at metal-composite interface. Small composite samples and polished metallic electrodes made of fastener materials represent a simplified interface in the structure. The voltage is measured at each interface and across the composite as the pressure and current are varied to characterize the changes in contact resistance and bulk conductivity. The extracted circuit parameters are then included at each fastener interface in a finite-difference time-domain (FDTD) model. A sensitivity study is performed to study the influence of variability of contact resistance and representation of bulk materials on system level performance. Linking physical drivers of coupon-level contact resistance variation to system-level FDTD studies enhances confidence in understanding how design parameters and defects influence lightning performance in structures. The method presented provides a path for standardizing test methodology to estimate contact resistance and application to lightning direct effects simulation paves a path towards simulation-based certification.
21. Lightning Environment Reassessment for eVTOLs
Gabriel Martins Vulcani, Sidney Osses Nunes, Eduardo Henrique Correa Ferreira, Diego Faria Amaral
Current certification standards for lightning protection are based on standardized waveforms defined in ARP5412, including the 200 kA Component A peak amplitude. These standards assume an external lightning environment of 95%, derived from ground-based measurements. However, the emerging class of electric vertical takeoff and landing (eVTOL) aircraft, flying under unique operational conditions with a very light vehicle, urges for a definition of a lightning certification environment which is safe and suitable for this new category. Operating primarily under visual flight rules (VFR) with lower altitude ceiling, eVTOLs exposure to lightning incidence is significantly reduced. This paper presents a quantitative assessment proposing a reduced lightning environment in which eVTOLs will be exposed and that is still sufficient to assure safe operation of the fleet. Building on industry, a risk-based methodology is proposed to demonstrate that a lower lightning threat level maintains an equivalent level of safety provided by 200 kA lightning level requirements for conventional aircraft. The approach aims to balance realistic lightning risk with an appropriate lightning peak level for compliance demonstration with lightning requirements, contributing with additional material to support the scalability and safety of the Advanced Air Mobility ecosystem.
22. Investigation of Lightning Indirect Effects on a Composite Aircraft Fuselage Segment
Renan H. de Moraes Callegari, Ricardo Rezende Schoenacher, José Antônio S. Mariano, Rodrigo Cabaleiro Cortizo Freire, Sidney Osses Nunes, José Pissolato Filho
This paper investigates indirect effects of lightning on a carbon fiber composite structure designed to represent a small segment of an aircraft fuselage. An electromagnetic model developed using commercial simulation software is employed to determine the induced voltages and currents resulting from current impulses applied to the structure, using standardized electrical current waveforms simulating lightning attachment points on an aircraft. The outcomes of this study were compared with measurements obtained from laboratory tests. The test specimen was constructed using multiple layers of carbon fiber composite without any metallic mesh or foil integrated into the laminate. It was equipped with a limited set of wires and harnesses solely for the purpose of evaluating induced voltages and currents. The outcomes of this study will be compared with analyses previously performed on similar configurations. Finally, the paper presents the combined results and discusses the conclusions drawn from this work.
23. Machine Learning Models for Lightning Analysis of A Wing Box with an Aperture
Flavis Awungabeh, Kyu-Pyung Hwang, Terry Vogler, Benjamin Westin
Electromagnetic analysis of a conducting enclosure with an aperture or opening is a classic engineering problem with much relevance to practical aircraft electromagnetic effects analysis. This paper proposes Artificial Intelligence-Machine Learning (AI-ML) techniques to predict voltage signals inside a wing box under lightning attachment. Wing box models are analyzed using 3-D Electromagnetic (EM) solvers with a finite set of variations in aperture position, size, and orientation, and wing box volume for ML model training. Electric field integration lines inside the wing box capture the induced voltage signals as system responses. These input variables and responses are fed into ML models with different algorithms for training. Both open aperture and closed aperture cases are considered in the analysis and ML training/test. For the closed aperture case, an explicit 3-D representation of the access door seam is first modelled in EM solvers, and its equivalent implicit seam model is attempted using a transfer impedance representation of the seam. The trained ML models successfully predict peak values of voltage signals from the given test set of geometric input variables without invoking computationally expensive 3-D EM computations.
24. Lightning Environment for Operation of eVTOLs Vehicles
Diego Faria Amaral, José Antônio de Souza Mariano, Lollan Naru Nonaka, Gabriel Martins Vulcani, Sidney Osses Nunes, José Pissolato Filho
The increasing adoption of electric Vertical Takeoff and Landing (eVTOL) aircraft introduces new challenges in lightning protection due to the extensive use of composite materials, reduced structural weight, and low-altitude urban operations. This article investigates the interaction between atmospheric electrical phenomena and VTOL vehicles, aiming to propose requirements for an improved lightning prediction and avoidance tool to support future certification in both VMC and IMC conditions. The work begins with a literature review on lightning incidence in aviation and includes operational analysis of eVTOL flight envelopes, as well as experimental testing performed at the High Voltage Laboratory of University of Campinas (UNICAMP). Conceptual experiments were conducted using Field Mill sensors, scaled environments, and test samples representing scaled models to measure electric field intensities and determine dielectric breakdown distances under controlled high-voltage conditions. The results will be used to investigate how vehicle models modify discharge occurrence in the environment and how this may influence the intensity and frequency of lightning strike rates in actual air vehicles. Operational data will also be reviewed to assess whether eVTOL vehicles, constrained to low-altitude operations, are inherently less exposed to lightning events compared to commercial aviation. Finally, requirements for providing real-time quantitative atmospheric electric field data integrating ground-based Field Mills, satellite observations and datalink transmission will be discussed to enhance operational safety, reduce maintenance costs, and support potential changes in certification levels for lightning protection. Main goals of this study are to establish technical foundations and requirements for a lightning environment monitoring system.
28. DIELECTRIC BREAKDOWN RISK ASSESSMENT FROM SWEPT LEADER ATTACHMENT SIMULATION
Sara Francis, Megan Maguire, Brock Milford, Cody Weber, Justin McKennon
Predicting dielectric breakdown risk to dielectric structures such as windshields or radomes from the lightning swept channel environment and the initial leader attachment environment can be performed in a computational electromagnetic (CEM) solver such as EMC Plus. Dielectric breakdown of radomes is driven by the electric field enhancement created by the conductors underneath the radome. This field enhancement is driven by the geometry and the material properties of the conductor and the dielectrics. These factors are easily represented in simulation with a reasonable mesh size. The actual dielectric breakdown is driven by much more complicated phenomena such as material imperfections and uniformity which are not easily captured or predicted within the model. By directly importing detailed CAD geometry, users can assign material properties and physical parameters that accurately represent the pertinent physics of the test article. Within the solver, customized sources can be defined to represent the high voltage initial leader attachment environment or the swept channel attachment environment based on the lightning zoning of the design. The relative electric field enhancement across the dielectric can be determined by comparing the measured field values against the background field. The field enhancement can be compared to the expected breakdown strength of the air and the dielectrics between the source and the underlying conductor to determine the risk of puncture. The risk assessment may be used to define the testing necessary to ensure the design is protected from hazards relating to lightning attachment. This type of analysis shouldn’t be relied upon as full replacement to the necessary verification tests, but can help build confidence, or reduce risk as part of engineering design activities or test preparation.
30. Numerical Modeling of Induced Transients on Aircraft Wiring with a Hybrid FDTD/MTLN Approach: Application to Falcon Full-Scale Aircraft
Thomas Strub, Fabien Terrade, Christophe Guiffaut, Christophe Girard, Fabrice Tristant, Alain Reineix
Full 3D electromagnetic simulation, and especially FDTD (Finite Difference – Time Domain) is widely used by aeronautics industry for HIRF (High Intensity Radiated Fields) and LIE (Lightning Indirect Effects) substantiation. While the oblique thin wire formalism in FDTD solvers has successfully reproduced bundle currents, further integration into design and certification processes requires advanced hybrid modeling. This paper presents the theoretical approach and implementation of a bidirectional coupling between two independent time-domain solvers: the FDTD solver TEMSI-FD and the Multi-conductor Transmission Line Network (MTLN) solver MILO. The robustness, accuracy, and computational efficiency of this hybrid approach are demonstrated through a large-scale application on a complete Falcon aircraft featuring its full wiring network. Finally, the methodology is validated by comparing numerical results against both full-FDTD simulations and experimental data collected during HIRF and lightning measurement campaigns.
31. Considerations for Peak Rate of Change using Waveform Norm Reduction from SAE ARP5415B
Brock Milford, JT Millar
The Waveform Norm reduction method was introduced into SAE ARP5415 Revision B. This method allows for all aircraft response waveforms to be reduced to four waveform norms that can be used to select standard test waveforms. Use of this method can greatly reduce the processing time for waveform reduction via automated processing methods. Revision B was issued in 2020. This paper provides feedback on the waveform norms method, and discusses some of the authors’ experiences with nuances surrounding peak rate of change calculations. The paper will also present alternative methods for calculating peak rate of change and provide a procedure for relating peak rate of change to specific standard test waveforms.
32. Three-Dimensional Reconstruction and BOS Characterization of Long Arcs in Swept Stroke Phase
Fayleon Lin, Vincent Andraud, Joan Montanya, Rafael Sousa Martins, Carmen Guerra-Garcia
The interaction between lightning arcs and aerodynamic flow plays a critical role in aircraft lightning-attachment processes, including the swept-stroke phase and lightning zoning assessment. Despite its importance for lightning protection design, quantitative experimental data on long-arc behavior in crossflow remain limited, particularly in conditions representative of aircraft in flight. Thus, a comprehensive collaborative experimental effort is currently underway, systematically scaling up the testing parameters while also employing state-of-the-art fluid and arc visualization techniques alongside electrical diagnostics. The resulting dataset will provide a mechanistic, quantitative characterization of the long-arc behavior in aerodynamic crossflow and will support the validation of high-fidelity simulations and reduced-order models of arc-flow interaction. Previously, high-speed imaging was combined with Particle Image Velocimetry (PIV) to simultaneously resolve the arc-column morphology, arc-root motion, and the surrounding flow field. Custom image-processing algorithms were also developed to automatically track the root position, the column trajectory, and the characteristic temporal and spatial scales of the arc motion from high-speed recordings. These measurements were synchronized with electrical diagnostics to estimate the arc’s internal electric field behavior. More recently, two new diagnostics were incorporated and tested to tackle previously observed shortcomings. Background Oriented Schlieren (BOS) enables visualization of fluid flow near the arc, where the PIV fails. At the same time, multi-view 3D reconstruction of the arc column provides a clearer picture of the arc column mechanics and morphology while providing a better estimate for the arc column length, and, by extension, a better electric field estimate. This paper will detail the implementation process and discuss the merits of these methods and current shortcomings.
33. GUIDE FOR CERTIFICATION OF AIRCRAFT ELECTRICAL/ELECTRONIC SYSTEMS FOR THE EFFECTS OF LIGHTNING – SAE ARP5415C CHANGES AND MAP TO AC 20-136C
Joshua D. Bakk
SAE International Aerospace Recommended Practice ARP5415 Revision C provides valuable improvements to the Guide for Certification of Aircraft Electrical/Electronic Systems for the Effects of Lightning. The purpose of this paper is to provide experience practitioners of lightning protection regulations compliance activities with a useful reference to facilitate interpretation and utilization of ARP5415C, which has an expected issue date in the first half of 2027. This paper identifies the most significant clarifications and changes since ARP5415B, provides a map from each AC 20-136C section to the most applicable ARP5415C material, along with some of the key concepts covered, and goes deeper to discuss a number of major changes. Major changes discussed include margin selection, variability of aircraft responses and uncertainty considerations for verification methods, lightning safety assessment, selection of series resistance that may be added during pin injection tests, systems lightning immunity testing of externally mounted equipment, model validation process, estimation of Component H response transients from Component A response transients, general guidelines for use of simplified circuits as interface loading, and waveform set selection.
34. A Robust Simulation Methodology for the Lightning Zoning Assessment of Protrusions on Rotorcraft
MEYER Marc, REVEL Ivan
Recent updates in ED-91A/ARP5414B have expanded rotorcraft Lightning Zone 3 to include the nose, lower fuselage and tail, requiring large protrusions to be evaluated for Zone 1B inclusion. As part of the mandatory Lightning Hazards Analysis (ED-113/ARP5577), this paper proposes an electrostatic methodology to assess attachment risks on external installations. A robust validation process required for certification compliance is detailed, alongside a discussion on modeling limitations and uncertainties, provided that such an approach supports the certification process. Notably, this methodology has been selected as a simulation use case for the upcoming EUROCAE DP-022 document entitled “Guidance for the use of simulation for aircraft certification of lightning and other EM Hazards”.
35. Collaborative Lightning Research: The Role of Pre-Test Simulation Results in Validation Activities Associated with a CFRP Aircraft Wing Environment Definition
Megan Maguire, Ted Angleton, Ian Delk, Alyssa Gonzalez, Cody Weber, Nick Conquest
According to AC25.954, applicants must establish the airplane lightning environment when certifying transport category aircraft for fuel systems lightning protection, starting with the idealized waveforms for direct attachment zones 1, 2, and 3 provided by ARP5412B. However, a complex network of aircraft structures and systems can create conducted current distributions away from the strike point that have many paths and dependencies, which the applicant may characterize through test, analysis, or similarity. A validated simulation model can offer the most comprehensive method for characterizing this fuel systems coupling response. This paper covers testing, simulation, and validation activities relevant to a fuel systems lightning certification program.
A finite difference time domain (FDTD) numerical model was created to compare with lightning tests performed on a wing made of CFRP skins, donated to the National Institute for Aviation Research (NIAR) as part of a KART research program, having originally been built as a structural test article. Testing, performed by NIAR at their ETL facility in Wichita, KS, measured bulk currents on structural components and internal wires, magnetic fields characterizing surface currents, and voltages developed between internal wiring and ribs. Current was injected at a defined location on the wing and returned through an RCS, designed and built by NIAR to negate facility effects and emulate the test article’s natural lightning response.
The numerical model was constructed to match the test configuration in significant detail. While numerical models can be calibrated with substantial fidelity to match test results after the fact, significant trust in a simulation model and its results can instead be built by generating predictions before testing and showing that those predictions agree well with what testing later reveals. Highlighting this value of pre-test simulation, as a means of building confidence in the modeling approach, is a primary goal of this paper. There are critical parameters and configuration of an aircraft, that if captured in the model, can give high fidelity results that can guide design decisions, without being initially validated against a large test specimen.
In this work, we present comparisons between numerical simulation and test results for three attachment and detachment configurations, along with descriptions of the modeling approach, including the representation of rib, skin, and spar joints, and of the experimental set-up used.
37. Model Validation for Aircraft Lightning Indirect Effects through Element-Level Testing
Shintaro Kamiyama, Hisashi Shimizu, Kenji Asakawa, Yoshiyasu Hirano, Makoto Goto
Currently, the certification of aircraft systems against the indirect effects of lightning relies heavily on empirical data derived from full-scale aircraft testing. While effective, this approach presents significant logistical and financial challenges, including substantial costs and extended development timelines. Consequently, there is an increasing industry-wide demand for “Simulation for Certification” (Sim4Cert), a framework that integrates high-fidelity simulations into the formal certification process. This shift is currently being formalized through the development of international standards by organizations such as SAE AE-2 and EUROCAE WG-31. A key technical challenge in implementing Sim4Cert lies in developing simulation models capable of accurately representing complex electromagnetic environments and their interactions. To address this, the present study investigates fundamental coupling mechanisms through controlled element-level evaluations. This paper presents results from simplified element-level experiments and their corresponding numerical simulations. The study demonstrates good agreement between the element-level experimental results and corresponding numerical analyses, providing evidence of the model’s predictive capability for the investigated configurations. These results establish a technical basis for extending the validation approach to substructure- and full-aircraft-level models.
38. Zoning Test for Manned Drones and Lightning Protection Regulations
Haruka Horiba, Kazuo Yamamoto, Takuto Matsui, Shinji Shiraishi
In recent years, global warming has emerged as a critical issue around the world. The cause of global warming is the continuous emission of greenhouse gases. Carbon dioxide accounts for over 80% of such emissions. Emissions from transportation account for approximately 20% of total emissions in Japan. Therefore, achieving decarbonization in the transportation sector is a critical challenge, and the shift from internal combustion to electric vehicles is increasing. As part of this effort, electric vehicles are gaining popularity. They are expected to serve as a means of transportation that promotes the use of sustainable energy. Against this backdrop, flying vehicles or manned drones are gaining attention as next-generation transportation, with development progressing in many countries. Manned drones are expected to be used in various fields such as logistics and private use, as their electrification makes them environmentally friendly and a faster means of transportation than conventional automobiles. However, manned drones present unique technical challenges. One of which is the risk of damage caused by lightning. Conventional aircraft can avoid thunderclouds by flying at high altitudes, but manned drones are structurally incapable of flying at such altitudes. Due to its electric power, the aircraft must be lightweight, making it difficult to implement robust lightning protection used in conventional aircraft. Therefore, to ensure the safe operation of manned drones, it is necessary to devise appropriate protective measures against lightning strikes. This study conducted high-voltage zoning tests to clarify lightning strike patterns and investigated the zones where manned drones are susceptible to lightning.
39. An End-to-End Simulation-Based Workflow for Lightning Zoning
Nathanael Jenkins, Louisa Michael, Benjamin Westin, Carmen Guerra-Garcia
There is a present need for quantifiable and physics-based zoning methods. Standard methods (ARP5414B and ED-91A) are not applicable to unconventional aircraft as they use empirical models from in-service experience on conventional aircraft. The standards are also qualitative, so the zoning risk tolerance could be inconsistent between different aircraft. Several physics-based models have been proposed for initial attachment or the swept stroke that produce probabilistic results rather than a map of discrete zones, compatible with current standards. This work presents an end-to-end simulation-based workflow for zoning, including an original mapping technique (physical quantities to standard zones 1, 2, 3) and comparison of the results to state-of-the-art zoning.
The workflow uses finite-element simulations for aircraft electrostatics and inviscid fluid dynamics. These global models, at the aircraft scale, are combined to reduced-physics models for initial attachment and long arc sweeping. Simulation of thousands of lightning strikes produce probabilistic results which are mapped into aircraft lightning zones based on thresholds for failure probability. Results of the zoning analysis on conventional transport aircraft and an unconventional blended-wing body are presented. The conventional aircraft is compared to in-service experience and standard zoning diagrams to demonstrate consistency with the state-of-the-art, as a first attempt to contribute towards validation efforts.
The results of this physics-based zoning workflow are found to be consistent with standard practices, and can provide more information through quantitative estimates of the failure probability for each zone. Leveraging modern computing hardware, zoning can be completed in hours. The next revisions of zoning standards, ARP 5414-C and ED 91-B, will incorporate simulation-based methods. This work contributes towards discussions about how to conduct zoning by simulation, and how to address validation. Future work will extend the workflow from fixed-wing aircraft to rotorcraft, including VTOL vehicles.
42. Study on the Lightning Attachments for Large-scale Floating Vertical Axis Wind Turbines Based on Initial Leader Attached Test
Kazuki Motoda, Kazuo Yamamoto, Takuto Matsui, Hiroyuki Ohira, Hitomi Nagase
In Japan, efforts are underway to expand the use of renewable energy in order to realize a decarbonized society, it has recently been developing a floating axis wind turbine (FAWT) as a new offshore wind power generation technology. As Japan has many deep-water areas, this technology is attracting attention. FAWT can be installed in locations where attracting attention. FAWT can be installed in locations where conventional bottom-fixed wind power generation is difficult. However, tall structures in such offshore areas have a high risk of being struck by lightning and causing damage. Furthermore, as offshore wind power generation facilities continue to grow in size, the importance of lightning protection is increasing. Currently, existing lightning protection methods have usually been developed for horizontal-axis wind turbines. Therefore, lightning protection systems for FAWT are needed. This paper summarizes the behavior of lightning attachments on FAWT. This data is crucial for designing lightning protection systems. A test circuit that simulates positive and negative lightning has been built, as well as upward and downward lightning. Then, impulse voltages were applied to a reduced scale of FAWT model. As a result, the location of lightning strikes on the FAWT was confirmed. This clarifies the areas where lightning protection is required. Test results indicate that lightning strikes concentrated on the top and sides of the arm section, as well as on the tip and outer surface of the blade. Therefore, these locations should be considered in the design of lightning protection systems.
44. Conductivity-Based Analytical Method for Lightning Direct Effects Test Article Design to Characterize Finite Width Effects
Harris Goetz, Jared Cohen, Derek Tuck
Lightning poses various threats to aircraft systems and structures. Instead of directly testing aircraft level behavior, small surrogate parts are chosen to represent larger structures. The ability of carbon fiber reinforced polymers (CFRP) test coupons to represent larger aircraft structures is limited by their anisotropic material properties. Anisotropic conductivity results in localized current density within lighting test articles which vary with size. As lightning test article length decreases, the total resistance of fibers bridging the electrodes decreases, reducing orthogonal current flow into surrounding fibers, potentially altering test results. Anisotropic conductivity is an inherent electrical property of CFRP, leaving lightning test article size as the primary controllable variable. We propose an analytical method for guiding lightning test article dimensions that avoids unintended finite width-effects by relating the ratio of current along the fibers bridging electrodes to the total current. This method converges to a constant value as lightning test article size approaches infinity. This analytical method enables test engineers to choose test article dimensions that best represents aircraft scale current distribution.
45. Wind Turbines Electric Field Modeling for Lightning Attachment Study
Jeb Rong, Andy Plumer
Lightning attachment represents a major reliability challenge for modern wind turbine generators (WTGs), particularly as turbine dimensions continue to increase and installations expand into lightning-prone offshore and mountainous regions. This paper presents the development of a three-dimensional electrostatic finite-element model of a generic utility-scale WTG using COMSOL Multiphysics. The model was created to investigate electric-field distributions and to identify likely lightning attachment locations under varying geometric and environmental conditions. A parameterized model architecture allows systematic evaluation of turbine dimensions, blade orientation, dielectric properties, lightning leader position, and corona space-charge effects. Simulation results demonstrate that turbine dimensions and blade orientation strongly influence electric-field enhancement at receptors, down conductors, and carbon fiber composite spar caps, whereas blade shell dielectric constant exhibits relatively minor effects. The analysis also highlights the importance of conductive internal components in determining lightning attachment locations. The developed methodology provides a practical tool for evaluating lightning attachment behavior and supporting lightning protection system design for future large-scale wind turbines.
46. Lightning Current Parameters of Subsequent Return Strokes Measured with the Lightning Key Data Systems in Wind Turbines
Lisa Carloni, Kristoffer Reinholt Thomsen, Mahmoud Ahmed, Stephan Vogel
While accurate characterization of lightning current parameters is essential for the design and validation of lightning protection systems for wind turbines, comprehensive measurement data from operational turbines remain scarce. This paper presents a statistical analysis of subsequent return stroke parameters measured using the Polytech Lightning Key Data System (LKDS). The data were recorded in operational wind turbines via Rogowski coils installed in each blade root. The comprehensive dataset comprises 3066 lightning events, including both upward and downward strikes, captured between 2019 and 2023 in the North Sea and in the Mediterranean area. These 3066 events contained 2267 upward and 496 downward lightning strikes. The downward lightning strikes contained a total of 981 subsequent return strokes that were used for the detailed analysis.
The focus of this work is placed on current steepness, a critical factor for wind turbine blade design. The investigation specifically analyses the current steepness calculated from the 30% to 90% rise time as well as the maximum instantaneous steepness of the current waveform. Current steepness is a determining factor for induced potential differences between parallel conductive paths within a blade, making its precise characterization vital for ensuring structural integrity during a lightning event.
The results of this extensive measurement campaign are presented and compared with the Lightning Protection Level 1 (LPL 1) requirements stipulated in the IEC 61400-24 Ed2 standard and the CIGRE’ data it is based upon. This work provides an updated and robust dataset that offers valuable insights for engineers, standard committees, and researchers involved in the optimization of wind turbine blade design and the enhancement of lightning protection reliability.
47. Construction of a lightning failure diagnosis flow for automobiles
Yua Matsui, Kazuo Yamamoto, Akihiro Doi, Takayuki Hirano
In the global promotion of a sustainable society, the automotive industry has undergone a rapid transition toward electrification and functional enhancement, such as advanced driver assistance systems. This evolution has increased the density and complexity of onboard electronics, making vehicles more vulnerable to electromagnetic disturbances like lightning surges. An analysis of 382 automobile lightning accidents revealed that electrical and electronic failures accounted for the largest proportion of the reported damage. When conducting lightning failure investigations, it is essential to distinguish whether a failure resulted from external factors such as lightning strikes or internal factors such as maintenance issues and aging. However, the lack of an established diagnostic methodology makes it difficult for insurance companies to process claims appropriately. This study aims to establish a practical lightning failure diagnosis method through experiments with a hybrid electric vehicle. First, a small-current injection test (approx. 265 A peak) was conducted to clarify the current distribution characteristics within the internal wire harnesses. Subsequently, failure mode tests were performed by increasing the impulse current in 1 kA increments. At a peak current of 3 kA, a hybrid system failure occurred, rendering the vehicle inoperable. Investigation identified specific burnout on a printed circuit board (PCB) inside the inverter; replacing the damaged PCB restored the vehicle to an operable state. The reproducibility of this failure mode was confirmed through repeated testing. This paper presents a framework for the construction of a “lightning failure diagnosis flow” to enable accurate damage assessment of lightning-related failures in automobiles.
48. Optical Analysis of Edge Glow Discharge Emission in CFRP Aircraft Structures
Takayuki Nishi, Shintaro Kamiyama, Yoshiyasu Hirano, Sou Furubayashi, Jimpei Furuta, Shinya Ohtsuka
Lightning remains a significant risk for CFRP (Carbon Fiber Reinforced Plastics) aircraft structures, affecting both operational safety and manufacturing costs. Preventing internal discharges during lightning strikes is a key challenge, as such discharges can lead to fuel ignition and damage to aircraft systems. Therefore, the presence of internal discharges is carefully inspected during lightning testing. However, a phenomenon known as “edge glow,” in which a faint glow appears at the edge of a CFRP panel, can complicate the assessment of discharge hazards. The mechanism responsible for edge glow has not yet been fully understood. In this study, a microscale investigation of edge glow emission was conducted to elucidate its underlying mechanism. CFRP laminates were subjected to current injection tests using the SAE ARP 5412 current waveform, and the location and morphology of edge damage associated with edge glow were evaluated. The evolution of the edge glow morphology was captured using a high-speed camera, while damage to the CFRP layers before and after current injection was examined using optical microscopy. Furthermore, edge-element specimens were fabricated for experimental validation, and the relationship between the applied voltage and the light emission was investigated. Observation of edge glow revealed characteristic localized structural damage within the ±45° fiber layers on the cathode side, whereas extensive surface degradation was observed on the anode side. These findings suggest that “Electrical Sparks” is the primary mechanism responsible for the initiation of edge glow.
49. Mechanical damage to metallic panels under strong impulse current
Zaepffel Clement, Lalande Philippe, Sousa Martins Rafael, Thomas Kilian
Mechanical plastic deformation of metallic panels is sometimes observed when thin panels are subjected to a lightning strike, with extreme cases resulting in puncture, as reported by NIAR. The stresses induced by the electric arc on the panel are sufficient to mechanically tear the material, producing a larger hole in the structure compared to the size observed with only melting effects on thicker panels. NIAR observed this behaviour on thin metallic plates subjected to a current component A. With the increase in flight traffic in the coming decades, extreme lightning strikes will occur more frequently, and the probability of such tearing may increase. Moreover, a model is under development at ONERA based on the use of a multiphase Eulerian MHD solver (APE3X), in which phase change physics and solid mechanics have been incorporated, and experimental validation is needed. Puncturing CFRP panels is one of the main objectives of this model, but it is a significant step; therefore, starting with metal panels is preferred. For these two reasons – increased risk probability and the need for model validation – we investigated aluminum and titanium panels covered by a dielectric layer simulating paint. These were tested against a current component A following SAE recommendations. The current is injected using a new ONERA generator, and high-speed imaging and deflection measurements are performed. Several dielectric and panel thicknesses are tested to acquire imaging data and determine a threshold for the transition between mainly thermal damage and the tearing phenomenon observed in thin panels.
50. Modernizing Lightning Qualification Through an AI-Enabled Digital Thread
Benjamin Shea, Sofia Graham, Philipp Boettcher, Jared Cohen
Maintaining a clear digital thread from lightning regulations and guidance to final safety artifacts presents many opportunities for aerospace organizations. This paper presents a practical, scalable approach that uses open-source tooling and Artificial Intelligence (AI) within a docs-as-code workflow to manage and share lightning compliance, standards, and safety knowledge aligned with model-based systems engineering (MBSE) principles. The approach supports traceability across the lightning qualification lifecycle by linking regulations and requirements to defined means of compliance and associated analysis and test artifacts. This traceability enables the transition creates durable, reusable, auditable engineering knowledge, and alignment with system models and virtual twin environments.
54. Exploding-Wire Screening of Polysulfide Fuel-Tank Sealants After Prolonged Soak in Sustainable Aviation Fuel
Emily Schaefer, Phillipp Boettcher, Jacob Lee, Barton Stevens, Rachel Short, Brian Egenreither, Caroline Nemire, Vicktoria Gonzalez, Eva Nee, Stefani Mokalled, Jessica Boze, Melinda Miller, Brendan Finn, Jason Damazo
Boeing Product Development is evaluating how the compositional range of today’s jet turbine fuels (including Jet A/A-1) and potential non-drop-in Sustainable Aviation Fuels (SAF) affects electromagnetic-effects (EME) protection materials, with a focus on lightning direct effects (LDE). Polysulfide sealants in fuel tanks are critical for containing LDE‑related ignition hazards—plasma arcs, ejected hot particles, and ejected hot gas—without fracturing. This work presents an exploding‑wire de‑risking test that applies localized, high strain‑rate energy to sealant specimens after prolonged soaks in conventional Jet A-1 and SAF representative fuels. The study includes detailed fuel‑type data and compares A‑to‑B performance between Jet A-1 and SAF soaks to identify any differences in sealant containment under LDE‑like conditions. Results provide a rapid, low‑cost A/B screening metric to inform SAF compatibility with LDE protection systems and to prioritize follow‑on qualification testing. This method is not a certification pass/fail test but a screening tool to guide material selection and further investigation.
56. Lightning Components A/D vs Components B/C/C* as Design Drivers in Typical Fastener Interfaces in Metallic Fuel Tank Structure
Richard Olson
SAE ARP6205 [1] Transport Airplane Fuel System Lightning Protection gives guidance on the process for showing no ignition sources result from a lightning attachment, under the requirements of 14 CFR 25.954 Amdt 146 [2]. The applicant must determine the expected fuel system lightning environment and compare it to the non-sparking thresholds of all components, including structural fastener interfaces, within the fuel system. This comparison involves evaluation of critical waveform parameters, including peak amplitude, action integral, charge transfer, and rate of rise. Separate scaling factors are defined for peak amplitude and action integral of components A/D, based on the portion of the external lightning environment associated with the applicable installation. While the distribution of lightning currents for different waveforms with different durations will vary, the scaling factor of the charge transfer associated with components B/C/C* is based on the most severe scaling factor from components A/D peak amplitude and action integral. Installations located internal to the fuel tank, and dominated by redistributed lightning currents, may experience higher portions of components B/C/C* than components A/D. However, the approach in SAE ARP6205 [1] was chosen due to (1) historical industry focus on components A/D in lightning transient analysis testing and simulation and (2) components B/C/C* posing a lower risk to creating ignition sources from conducted lightning currents. This paper will present test data, performed per SAE ARP5416A [4], showing charge transfer from components B/C/C* is not a design driver for typical fastener interfaces in metallic structure.
57. Evaluating Leader Progression Model Performance Across Multiple Transmission Networks Under Incomplete Observation of Lightning Attachments
Jan Mikeš, Ivan Soukup, Ondřej Hanuš, Marcela Efmertová
Validation of lightning attachment models under field conditions is fundamentally constrained by the fact that only a fraction of actual lightning strikes to transmission lines are detected and recorded – typically only those causing operational faults. This observational incompleteness introduces systematic bias into conventional performance metrics such as sensitivity and specificity. In this study, we apply the Sima-Rakov Leader Progression Model (LPM) to a large-scale dataset comprising 54 high-voltage transmission lines operated in the Czech Republic, spanning diverse topographical conditions and tower configurations. Using 15 years of EUCLID lightning location system data and corresponding confirmed fault records, we evaluate LPM prediction performance across networks and examine how model accuracy metrics vary under different assumptions about the true detection probability of lightning attachments. We complement this analysis with a quantification of how measurement uncertainties inherent to the EUCLID system – particularly stroke location error and peak current estimation – affect LPM output through the model’s physically-based calculations. The multi-network scope of this study enables, for the first time, a network-scale statistical assessment of LPM reliability that accounts for both input data uncertainty and incomplete observational ground truth.
59. Simulation-Based Optimization of Material Use and Personnel Safety in LPS Design
Eduard Shulzhenko, Kamila Costa, Michael Rock
External lightning protection systems (LPS) are commonly dimensioned according to standard-based rules that ensure robust protection, but do not quantify the trade-offs between interception, personnel safety, magnetic-field penetration, grounding performance, and material demand. This paper presents a consistent 3D simulation workflow for initial evaluating these aspects. A total of 720 mesh-cage configurations are investigated for three buildings of increasing size, covering lightning protection levels (LPLs) I–IV, one to three ring earth electrodes, five specific soil resistivities, and four frequencies representing different lightning current rise times. In addition, 60 single air-termination rod configurations (hereafter denoted as single-rod configurations) at LPL II, generated using a rolling-sphere algorithm and verified by a numerical protection envelope, are analyzed for comparison. The assessed quantities include grounding impedance, prospective touch and step voltages, magnetic-field penetration, conductor length, normalized material intensity, and a first-order estimate of embodied CO2. Normalized material demand decreases with building size and from LPL I to LPL IV, while additional ring electrodes reduce grounding impedance with diminishing returns. For the same earth-termination system (ETS), the single-rod concept requires approximately 30–40% less conductor than the mesh cage while providing equivalent rolling-sphere interception and comparable grounding performance. Prospective touch and step voltages are comparable for both concepts and are governed mainly by specific soil resistivity and building size. The single-rod concept generally produces higher magnetic-field magnitudes along the investigated injection-to-center path than the mesh cage, particularly at higher frequencies. These results indicate a trade-off between material reduction and magnetic-field penetration, while the implications for the EMC of installed equipment require further investigation.
61. In-flight Characterization of Aircraft P-static Charging
Ivan Revel, Dominique Lemaire, Frédéric Therond, Adil Soubki, Audrey Bigand, Philippe Lalande, Aurélie Bouchard, Magalie Buguet, Rafael Sousa Martins, Patrice Blanchet, Vincent Gaudineau
While the fundamental physics of triboelectric charging and corona discharge are well-understood, the real-time evaluation of an aircraft potential in complex weather conditions due to P-static charging remains a technical hurdle. This paper presents the methodology and the results of a dedicated flight test campaign aimed at consolidating the understanding of aircraft electrostatic behavior and developing a simplified monitoring solution to assess P-static charging conditions severity.
62. GPU-Accelerated Multiphysics Modeling of Electrical Arc Dynamics
Timothy J. McDonald, Bryon Neuf, Jacob Johnson
Predicting electrical discharges in air requires simultaneous treatment of electromagnetic fields, charged particles, collisions, gas species, and chemical reactions over disparate temporal and spatial scales. This paper presents a GPU accelerated numerical framework in EMA Charge Plus that couples a time domain finite element electromagnetic solution with particle in cell transport, Monte Carlo collisions, fluid species, and gas phase reactions. The formulation follows discharge inception, avalanche growth, and gap breakdown without prescribing an arc path or a fitted breakdown voltage. The principal validation reproduces a published nanosecond breakdown experiment in pressurized synthetic air using a one millimeter gap at 1.5 bar. A nitrogen reaction set with 72 elastic, ionization, dissociation, recombination, and excitation processes predicts breakdown at 9.22 kilovolts, about 3 percent below the approximately 9.5 kilovolts measured experimentally and within the reported experimental uncertainty. The computed electron density also falls within the range reported for comparable atmospheric pressure nanosecond discharges. GPU execution makes the tightly coupled field, particle, and reaction updates practical on engineering meshes, including fully three dimensional geometries that are uncommon for reaction resolved discharge modeling. The same framework provides a foundation for lightning attachment studies and for coupling plasma energy deposition to heating and material ablation.
63. RF Protection of Transport Category Airplane Fuel Tanks
Nick Conquest, Ted Angleton, Johan Kohler, Richard Olson
For decades, the broader aerospace industry has considered the potential for RF (Radio Frequency) energy to create ignition sources in aircraft fuel tanks. Specifically for transport category airplanes, 14 CFR 25.981(a)(3) requires fault tolerant fuel tank ignition source prevention. AC 25.981-1D discusses different environmental considerations, including HIRF (High Intensity Radiated Fields) and other sources of RF energy, however little guidance on methods of compliance is provided. At the present time, the most direct reference to specific commercial guidance on fuel ignition prevention from RF energy is given in SAE ARP5583B that refers to PD CLC/TR 50427 for general test safety guidelines and does not address compliance. This British standard is written for industrial plants with flammable vapors; however some applicants apply the guidance to transport category airplane fuel tanks in absence of specific compliance guidance in commercial standards. While military aircraft use MIL-STD-464D and/or NAVSEA OP 3565/NAVAIR 16-1-529 for HERF (Hazards of Electromagnetic Radiation to Fuel) compliance, the aerospace industry needs a commercial standard method that specifically applies to aircraft and addresses the fault tolerant requirements of 14 CFR 25.981(a)(3) and AC 25.981-1D. This paper summarizes the methods described in the previously mentioned standards and describes difficulties with applying those methods to commercial airplane fuel tanks. Additionally, results from recent testing related to RF and fuel tank ignition sources are introduced to characterize the potential risk of RF caused fuel tank ignition sources. Lastly, this paper proposes a simple compliance approach for commercial transport category airplanes that could be developed into a future SAE and EUROCAE document, building on existing fuel tank lightning and electrostatics protection design features and requirements.
64. Experimental Investigation of Spark Discharges in Aircraft-Relevant Configurations
Samuel Austin, Louisa Michael, Jaime Peraire, Carmen Guerra-Garcia
Understanding the physics of spark formation and ignition pathways in combustible environments is crucial to assessing the risk of ignition in aircraft fuel tanks subjected to a lightning strike. However, current certification approaches are not ready to address the needs of next-generation aircraft, which may use novel fuels such as hydrogen and non-drop in Sustainable Aviation Fuel (SAF), and lead to sparking in ways we did not anticipate with existing configurations. Direct application of the current standards by adjusting the relevant thresholds from old configurations or fuels would be difficult to perform. The community makes use of the Minimum Ignition Energy (MIE) metric to enable tractable engineering analyses of spark ignition for aircraft certification. However, the MIE does not account for the rate of energy delivery, electrode geometry, spark-gap size, gas composition, or the role of localized energy delivery. In this work we present experimental efforts to understand the physics of spark discharges which have applications in improving upon the MIE metric, allowing the sparking assessment of broader geometrical configurations, validating multiphysics numerical models, and constructing reduced physics models of electrical breakdown in small gaps. Capacitive discharges are used to initiate sparks in non-flammable gases with a variety of gap sizes and background pressures. Electrical measurements, direct optical imaging, and Schlieren imaging are implemented to understand the electrical and gas dynamic response.
65. Modeling of Lightning Indirect Effects on Aircraft Empennage and Impact Analysis of Contact Resistance Variability
Hisashi Shimizu, Koki Fukuda, Yoichi Nakai, Hideo Yamakoshi, Tomonori Okumura, Shintaro Kamiyama
Simulation has been utilized to assess harness lightning actual transient levels (ATLs) on an aircraft empennage region. The simulation results are compared against experimental ATL measurements as part of a validation effort. Empennage elevator actuators are typically safety critical systems for aircraft and aircraft OEM should measure the associated ATLs. These systems are typically in highly exposed areas, and high transients can develop because of their location. There are numerous current paths connected to the control surface and actuators that impact cable transients including hinges, actuator arm, actuator hydraulics tubes, bond straps and cables. Using sensitivity studies and parameter sweeps, the simulation model can show how the different resistance values impact the current distributions in that region. OEMs do not control the resistance across hinges or actuator arms. There is likely to be variance across aircraft for these unknown parameters. This paper demonstrates the impact of these parameters on ATLs to better understand current distributions in this aircraft region and highlights the ability of simulation to explore parameter variability.
67. Experimental Study on Aircraft Lightning Zoning under Extremely High Voltage
Zemin Duan, Wei Yan, Xiaoliang Si, Zhibao Li, Zhiyong Geng, Liyun Gu
Aircraft lightning zoning is an important part of aircraft lightning protection design and development. SAE ARP 5416 requires the aircraft to be 50 m from the high-voltage electrode; however, limited by high-voltage generation capability, 50 m air breakdown cannot yet be achieved in the laboratory. Therefore, reduced-scale aircraft model tests at voltages around 5 MV have traditionally been used for lightning zoning tests. However, reduced-scale testing has inherent problems: the dielectric properties of air cannot be scaled, and scaling the model changes curvature, thereby affecting the electric field distribution and causing strong nonlinear effects. Based on such test conditions, the international community considers reduced-scale testing unsuitable for scale models smaller than 1/30, but this view lacks adequate theoretical and experimental support. To address these issues, this paper carried out long-gap discharge tests with synchronous observation and aircraft lightning zoning tests at different scale ratios using a 16.8 MV ultra-high-voltage lightning generator, together with corresponding simulations. The results show that when the scale ratio decreases from 1/10 to 1/40, the lightning attachment locations and probabilities on the aircraft at extremely high voltage change significantly. As the scaled model becomes larger, the probability of lightning attachment to the upper fuselage and wing tips gradually increases, while the attachment probability to the nose and vertical tail decreases. In addition, increasing the scale ratio makes protruding structures such as fuselage antennas impossible to ignore, thereby increasing the probability of lightning attachment to the upper fuselage.
68. Experimental Study on Protection Range of Lightning Rods with Long Gap Discharge
Ze-Min Duan, Xiao-Liang Si, Lei Li, Kang-Long Yao, Zhong-Xiang Wang, Zhi-Bao Li, Shan-Liang Qiu
Lightning rods are crucial devices for protecting ground structures from lightning strikes. However, previous research on the actual protection range of different lightning rods under long gaps was insufficient globally due to the lack of ultra-high voltage lightning generators capable of breaking down long gaps. Hangtai Institute of Electrophysics (HTIEP) has now built an ultra-high voltage lightning generator with a voltage level of 16 MV, capable of breaking down air gaps of over 15 m while meeting the voltage waveform specified in the SAE ARP 5412 standard. Based on this ultra-high voltage lightning generator, this study investigates the electric field distribution characteristics and lightning interception characteristics of lightning rods under different lightning rod heights and different numbers of ends by experiments and electrostatic field simulations. This study, for the first time based on a 15-meter long gap discharge conditions, experimentally studies the influence of the geometric parameters of lightning rods on protection performance, providing a new reference for the optimized design of lightning protection engineering and the revision of standards.
69. Study on lightning strike damage mechanisms of thermoplastic carbon fiber composites
Mingquan Zhu, Shijun Wang, Xiaoer Li, Hongli Tan, Zhiyong Geng, Bo Zhang, Xuelong Yang, Hu Ge, Zhibao Li, Xiaoliang Si, Zemin Duan
Thermoplastic matrices are attracting increasing interest in aerospace applications owing to their recyclability, impact resistance and fatigue durability. PEEK‑based carbon fiber reinforced polymers (CFRPs) are already employed in components such as wing trailing edges and cabin interiors and are therefore exposed to lightning strike environments. Most existing studies, however, focus on single‑component lightning waveforms, and there is still no systematic investigation of the failure behavior of PEEK‑based CFRPs under combined‑wave (Zone 1A, Zone 2A) lightning. The associated failure mechanisms under such complex loading conditions remain insufficiently understood. we comparatively evaluate the lightning strike performance and failure mechanisms of PEEK‑based and epoxy‑based CFRPs. Under lightning strike, epoxy‑based CFRP shows extensive ablation and deep delamination, whereas PEEK‑based CFRP exhibits only slight surface damage. For epoxy‑based CFRP, matrix decomposition and carbonization accompanied by intense interlaminar gas expansion drive severe ablation and deep delamination. In contrast, the PEEK matrix softens, melts and flows, forming local melt craters and re‑solidified structures that localize damage and provide a degree of thermal self‑healing. An electro‑thermal model, established on the basis of these observations, captures the distinct damage evolution in the two systems. Mechanical tests further show that, after Zone 2A lightning, the residual bending strength of PEEK‑based CFRP decreases by only ~10% compared with ~36% for epoxy‑based CFRP, and after Zone 1A by ~36% and ~83%, respectively. These findings reveal a fundamental difference in failure modes between thermoplastic and thermoset CFRPs and underscore the substantial potential of high‑performance thermoplastic composites for lightning strike protection. In particular, under Zone 2A conditions, PEEK‑based CFRP shows promise for meeting load‑bearing requirements with significantly reduced, or even without, conventional metallic lightning strike protection layers.
70. Three-dimensional multi-physics simulations of direct lightning damage to anisotropic composites
Jakob Julian Schoser, Stephen Millmore, Nikolaos Nikiforakis, Louisa Michael
Emerging aircraft configurations utilising carbon fibre reinforced polymers (CFRP) require a re-evaluation of lightning strike protection due to complex, three-dimensional internal damage mechanisms. While numerical modelling can accelerate design evaluation, accurately capturing the multi-physics coupling between the lightning plasma arc and anisotropic composites remains a significant challenge. This paper presents a novel computational multi-physics framework that simulates lightning strikes to anisotropic substrates. Based on a unified system of partial differential equations, the framework couples resistive magnetohydrodynamics with elastoplastic equations on a single computational mesh. The governing equations are solved using a finite volume method with adaptive mesh refinement and distributed parallelisation to handle fully three-dimensional interactions. The model captures two-way coupling between the plasma arc and the substrate, incorporating a 19-species plasma equation of state (EoS) and an anisotropic EoS for CFRP. The framework is validated against experimental measurements of arc radii and rear surface deflection.
71. Hybrid time-domain solver for evaluation of transient noise level induced on light train harness
Antea Perrotta, Giancarlo Guida
Light railway systems are safety-critical infrastructures that must operate reliably under all electromagnetic conditions. Non-compliance with EMI/EMC standards can lead to system failures, endangering human lives and infrastructure integrity. This work presents a simulation approach to modeling railway systems, ensuring electromagnetic safety and performance according with EN 50121-3-1 and IEC 62305-4 standards. The study addresses key challenges such as crosstalk between cables, electromagnetic field propagation, and direct/indirect lightning effects, including overvoltage, electromagnetic interference, flashover phenomena and damage to sensitive electronics. A validated workflow to simulate lightning effects, identify vulnerabilities and mitigate EMC risks has been developed to reduce failure probabilities and improve safety. The solution introduces LPZ-based simulation for railways, combining system-level modeling of chassis, cables and active components. Novel contributions include mesh optimization for close cables to avoid overlapping areas and improve accuracy, as well as accurate modeling of electrical systems (inverters and motors) in Ansys EMC Plus. Results demonstrate the effectiveness of the simulation framework, with high-resolution meshing and precise threat modeling (e.g., lightning current sources). The approach bridges EM simulation with certification, offering early EMI prediction, reduced testing and improved reliability.
72. Field Test Results of a Coating That Reduces Lightning Damage on Wind Turbine Blades
Neal Fine, Christopher Szlatenyi, Adam Janik, Andy Plumer
A previous ICOLSE paper [1] described the development and laboratory validation of a non-sacrificial wind turbine blade coating (ALP20) that reduces lightning damage by enhancing existing receptor-based lightning protection systems. Small discrete conductive elements in the coating locally enhance the electric field above the blade surface, promoting earlier surface flashover and enabling leaders emanating from the receptors to travel faster and farther across the blade, intercepting downward stepped leaders before competing internal streamers can puncture the blade skin. Laboratory testing showed an average 76% reduction in flashover time relative to a baseline topcoat and no coating damage at currents up to 200 kA. In IEC-standard initial-leader-attachment tests on 5-m GE 1.5sle blade tips (161 strike events), the coated configuration sustained punctures at 6.7% per strike versus 20.8% for the baseline — a statistically significant 68% reduction (p = 0.006), including zero punctures in 66 strikes at the blade angles that account for 98% of observed field attachments — corresponding to a predicted 73% reduction in field puncture rate. This paper revisits the coating’s concept of operations and summarizes the laboratory evidence, then presents results from operational field deployments that began in 2022 at three wind farms — two in the United States (New Jersey and Illinois) and one in the Asia-Pacific region (APAC). The APAC deployment is the most rigorous field test to date: at a 123-turbine site, 15 turbines received the ALP20 coating, 17 received segmented diverter strips, and the remaining 91 carried no additional lightning protection; the fleet was monitored through an exceptionally active lightning season (306 sensor-recorded strike events), followed by a fleet-wide drone inspection campaign. The ALP20-coated turbines absorbed 35 lightning flashes with zero confirmed new lightning damage, while comparably exposed unprotected turbines sustained repair-level damage at 6.6 findings per 100 flashes; segmented-diverter turbines showed no detectable benefit relative to unprotected machines. Strike incidence on coated turbines was statistically indistinguishable from unprotected turbines, supporting the assertion that the coating manages attachment rather than altering strike frequency. The combined laboratory and multi-year, multi-site field evidence is consistent with the laboratory-derived damage-reduction prediction and informs recommended practices for application to existing and new blades.
73. Space Weather Risk Assessment and Threat Reduction Techniques
John Lackey (Jeff)
Space weather is a major concern as we seek a permanent presence beyond Earth’s protection. Solar Flares, Coronal Mass Ejections, Radiation Belts, and interplanetary charging threats are a serious concern as missions grow in length and complexity. Knowing how to select surface materials and shield electronics in space environments has become critical for the future of mankind in Space. The Artemis program has made significant progress in defining these environments over the last decade. This paper provides an introductory example of basic technologies, techniques, and tool kits for assessing environmental charging profiles for new materials, and the ability to assess their impact on thermal protection systems, avionics boxes, sensors, and RF communications.
74. External Lightning Environment Considerations for eVTOL Aircraft
Murray Marple, Cody Weber
This study reviews the foundational aircraft lightning environment and evaluates potential amendments applicable to eVTOL aircraft. SAE ARP5412 specifies the external lightning environment for aircraft certification, establishing a 200 kA Component A test waveform and other characteristics derived from ground-based tower strike data. While this standard successfully maintains aviation safety, probability statistics regarding aircraft dimensions, flight profiles, and Advanced Air Mobility (AAM) avoidance measures suggest its requirements may be overly conservative for eVTOLs. Furthermore, this paper examines the correlation between smaller vehicle size and reduced strike frequency—a relationship already leveraged in FAA Policy Statement ACE-23-10 to simplify lightning compliance for the type certification of Part 23 aircraft. Given that over 90% of strikes are aircraft-triggered rather than naturally intercepted, this research explores the primary factors influencing the rate and amplitude of these lightning events, identifying areas where further investigation is needed to accurately quantify strike severity. Finally, it reviews the potential to significantly reduce or even eliminate strikes through active lightning avoidance in AAM airspace. By synthesizing the variables that dictate lightning encounters for small, low-flying eVTOLs, this research aims to improve hazard management and overall safety. Ultimately, if these factors can be comprehensively understood, optimally managed, and corroborated by field data, a strong case can be made for defining a reduced-severity lightning environment and adopting a simplified compliance approach for eVTOL aircraft.
75. Guidance for Powered-Lift Electric Propulsion System Lightning Hazard Assessments
Faisal Ahmad, Murray Marple
The rapid development of powered-lift aircraft introduces novel electric propulsion systems lacking established service histories in lightning environments. To ensure flight safety applicants will show compliance with the airworthiness criteria outlined in FAA AC 21.17-4 (Type Certification Powered-Lift). This will ensure that these aircraft are safeguarded against catastrophic vehicle-level effects as well as hazardous or major propeller-level effects resulting from lightning strikes. This paper provides comprehensive guidance for conducting a Lightning Hazard Assessment (LHA) explicitly tailored to powered-lift electric propulsion systems. Applying the methodology outlined in SAE ARP5577 (Aircraft Lightning Direct Effects Certification), this assessment evaluates the direct effects of lightning attachment and current transfer on the structural and mechanical elements of the propulsion unit. By defining a simplified propulsion unit architecture, this paper traces expected current conduction paths from the propulsor blades through the hub, motor shaft, bearings, and motor controller down to the airframe. Furthermore, it details potential failure mechanisms for critical components, including resistive heating and acoustic shock damage in composite blades, arcing and pitting at metallic bearing interfaces, dielectric breakdown of internal motor insulation, and injected transients affecting sensitive power electronics. The assessment also accounts for novel operational scenarios inherent to these vehicles, such as distributed electric propulsion and vectored thrust tilt mechanisms. Ultimately, this paper highlights critical verification strategies—primarily laboratory testing—and continuing airworthiness considerations, such as post-strike inspections, essential for ensuring the long-term safety and reliability of powered-lift electric propulsion systems.
76. Flight Test Instrumentation and Data Analysis for Separating Triboelectric and Exogenous Charging in Severe Precipitation Static Environments
Derek Tuck, Joe Heeter, Brian Egenriether
For certification, large transport aircraft must be tested in adverse weather conditions where precipitation impacts the forward surfaces, potentially generating electrostatic discharges that can interfere with communication and navigation systems. Flight testing within the defined “severe” precipitation environment often requires multiple flights without a comprehensive understanding and interpretation of the resulting flight test data. This paper provides new insights into the airplane charging environment by distinguishing between triboelectric charging and exogenous airplane-level charging conditions using data from onboard instrumentation. These insights can be used classify flight test data as gathered during “severe” charging conditions during system functionality verification. The authors aim to complement the verification methods for p-static protection effectiveness described in ARP5672.
