Franck Flourens

From a single approach for A380 transfer functions determination to in-flight lightning measurements

This document presents the test method settled and applied for A380 lightning and low frequency HIRF transfer functions determination, deals with method evolutions necessary for composite aircrafts and is completed by in-flight lightning measurements system now available thanks to ILDAS project and its future application to A380.

In-strike dynamical measurements of contact resistances

Assemblies representative of aircraft junctions made of two materials and a fastener have been subjected to lightning current waveforms in laboratory. Current distributions on the different parts of the assemblies have been measured. An electrical equivalent circuit of the assemblies has been built. An inverse method has been designed to extract the dynamical in-strike electrical parameters (resistances, inductances, generators) of the circuit from the measured current distributions. It is shown in particular that the in-strike contact resistances between the different parts are systematically very small, even when the pre- or post-strike values are large. This effect is related to the appearance of internal discharges in the gaps of the assembly.

Modeling strategy for functional current return in large CFRP structures for aircraft applications

The strong increase of utilization of CFRP materials in industry has deeply modified the methods of analysis and challenged the numerical tools. In electromagnetism, many issues arise from the replacement of metallic elements by CFRP ones, the main being the protection against direct and indirect effects of lightning. An other important issue is the sizing and optimization of functional current return path on a large structure as an aircraft fuselage. The object of this paper is to present an original approach for studying the current return in a partially metallic fuselage structure covered with CFRP panels in a frequency range comprised between the continuous current up to few tens of kHz.

A unified approach for lightning and low frequencies HIRF transfer functions measurements on A380

In this paper the studies conducted at AIRBUS with the aim of using a unified method to assess the internal induced threats on aircraft in case of lightning and low frequencies High Intensity Radiated Fields (HIRF) are presented. The approach is presented as well as some results obtained during A380 certification.

Modeling of lightning indirect effects in CFRP Aircraft

This paper presents design principles to ensure lightning indirect effect protection for new generation of Aircraft based on an intensive use of CFRP (composite fiber reinforced plastic). Metal foil efficiency embedded into structural panel is demonstrated and different harnesses protection means are compared. Moreover, modeling results are validated with measurements on a specific demonstrator.

Numeric lightning protection prediction for wires in an aircraft wing raceway

Measurement or numeric simulation are well known means in the EMC business. Both can give an early idea of the electromagnetic protective performance of a particular design that should be optimized for example to provide for lightning protection. Measurements require hardware; models need to be well understood. This contribution deals with the application of tools for assessing the lightning protection performance during the design phase of an aircraft. The subject of investigation is the protection performance of so-called raceways which are installed inside an aircraft wing. The raceways are extruded aluminum profiles with bays in which the wire bundles are routed. The wire bundles are protected against the lightning impact by the depth of the raceway bays, their minimized exposure along raceway interruptions and the filling level of the bays. All this protection is given by the presence of the conductive aluminum material. On the other hand an optimum design from a weight or mechanic perspective may be achieved with minimal use of material. In order to optimize all design aspects measurements can help but require effort in organization and prototype availability. Full-scale models of an aircraft can be exhaustive but cumbersome when optimizing small scale details. This paper outlines a methodology which avoids these drawbacks by a simplified network model.

In‐Flight Observation of Positron Annihilation by ILDAS

Abstract We report a 511‐keV photon flux enhancement that was observed inside a thundercloud and is a result of positron annihilation. The observation was made with the In‐flight Lightning Damage Assessment System (ILDAS) on board of an A340 test aircraft. The aircraft was intentionally flying through a thunderstorm at 12‐km altitude over Northern Australia in January 2016. Two gamma ray detectors showed a significant count rate increase synchronously with fast electromagnetic field variations registered by an on‐board antenna. A sequence of 10 gamma ray enhancements was detected, each lasted for about 1 s. Their spectrum mainly consists of 511‐keV photons and their Compton component. The local electric activity during the emission was identified as a series of static discharges of the aircraft. A full‐scale Geant4 model of the aircraft was created to estimate the emission area. Monte Carlo simulation indicated that the positrons annihilated in direct vicinity or in the aircraft body.

In‐Flight Observation of Gamma Ray Glows by ILDAS

Abstract An Airbus A340 aircraft flew over Northern Australia with the In‐Flight Lightning Damage Assessment System (ILDAS) installed onboard. A long‐duration gamma ray emission was detected. The most intense emission was observed at 12 km altitude and lasted for 20 s. Its intensity was 20 times the background counts, and it was abruptly terminated by a distant lightning flash. In this work we reconstruct the aircraft path and event timeline. The glow‐terminating flash triggered a discharge from the aircraft wing that was recorded by a video camera operating onboard. Another count rate increase was observed 6 min later and lasted for 30 s. The lightning activity as reported by ground networks in this region was analyzed. The measured spectra characteristics of the emission were estimated.

Edge glow: A combined voltage/power controlled mechanism?

The improvement of CFRP mechanical properties has led to the development of new materials in aeronautic industry. In the frame of engineering experiments for developing lightning strike protections, a phenomenon has been observed on edges of aircraft composite substructures, consisting in a bright glow combined with strong ejections. Uncertainties in the nature and the severity of this threat, so-called “edge glow”, make necessary to consider it as a potential fuel ignition source and to implement appropriate lines of defense. Behind the most intense event that seems controlled by the voltage drop across plies, a second edge glow regime seems related to a thermal mechanism at pre-existing contacts on the composite edge. The context of this work is the mitigation of edge glow phenomena with appropriate protection designs and installation principles. This paper presents experimental investigations on generic test coupons that aimed at understanding how current distributes into a local assembly governed by non-linear contacts and how far it impacts edge glow occurrence and intensity.

Simulation test bench for LIE and HIRF on a communication bus

This paper deals with the building of a theoretical simulation test bench for LIE and HIRF on a communication bus. For that purpose, we propose a description of the methodology used to predict the induced levels on the BUS for typical scenario derived from aircraft topology. Models needed to perform such a simulation are coupler model, transformer model, cable model, injection model. To validate the simulation chain before the exploitation, we perform two kind of validations i.e. simulations / measurement comparisons: one at component level and the other one on a setup representative of aircraft. The predicting tool used in this study is Aseris NET. It solves network equations in the frequency domain with multiconductor transmission lines method.