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Aerospacelab

Space Launching Site Protection against Lightning Hazards

Auteurs: 

F. Issac, E. Bachelier, D. Prost (Onera), V. Enjalbert (DGA), L. Mohedano (APAVE)

A launching pad, because of its activity, is particularly sensitive to the risk of lightning. The use of Standard IEC62305 "Protection against lightning" establishes the general framework for the Lightning Protection System (LPS). However, the specific activity of a launching pad requires special analysis on specific points of the LPS. Indeed, it is necessary to take into account the lightning conductor system particularity on the one hand, and the launcher electromagnetic susceptibility on the other hand.

The Interaction of Lightning with Aircraft and the Challenges of Lightning Testing

Auteurs: 

D. Morgan, C. J. Hardwick, S. J. Haigh and A. J. Meakins (Cobham)

Aircraft are struck by lightning in flight with some regularity and are required to have demonstrated protection against this threat; much of this demonstration is provided by simulating in test the effects of lightning on aircraft structures, components and systems. Clearly these tests need to be carried out in a representative manner and guidance on how to do this is provided in the Aerospace lightning standards and guidance materials produced by the SAE/EUROCAE committees.

Indirect Effects of Lightning on Aircraft and Rotorcraft

Auteurs: 

J.-P. Parmantier, F. Issac, V. Gobin (Onera)

This article discusses issues related to indirect lightning effects on aircraft/rotorcraft. The standard waveforms used for qualifying the vulnerability of a system are introduced, with their frequency spectrum. The identification of the elementary EM coupling phenomenon allows the understanding of the key drivers of the current distribution and field scattering on a complex structure.

Videos: 

a) Configuration "Engine to tail"

b) Configuration "Engine to Wing"

c) Configuration "Wing to Tail"

a) Configuration "AASM – AASM" in free flight

b) Configuration "AASM – wing"

c) Configuration "AASM – AASM"

Standard lightning waveforms and general lightning current
sequence

Direct Effects of Lightning on Aircraft Structure: Analysis of the Thermal, Electrical and Mechanical Constraints

Auteurs: 

L. Chemartin, P. Lalande, B. Peyrou, A. Chazottes, P.Q. Elias (Onera),
C. Delalondre (EDF), B.G. Cheron (Cnrs), F. Lago (DGA)

This paper deals with the direct effects of lightning strike on aircraft structures. In a first part, the phenomenology of lightning arc attachment on aircraft is introduced. Some specific features of lightning arcs observed in flight or created in the laboratory are presented. Some recent developments and results from numerical simulations are shown. The shapes, the behaviors and other specific points are compared with experiments, in order to bring to light some explanations on the complex features of lightning arcs.

Numerical Methods for Zoning Computation

Auteurs: 

P. Lalande, A. Delannoy † (Onera)

Zoning consists in establishing lightning strike zones to locate and classify surfaces on an aircraft which are exposed to a part of the lightning current components. The current standard used to certify aircraft is empirical and qualitative, and fails to predict certain features, such as lightning attachment on the middle of the wing. Furthermore, the standard will be difficult to apply to the next generation of aircraft having geometry, engines and fuselage material that will be very different from current designs.

A Physical Model of Branching in Upward Leaders

Auteurs: 

P. Lalande (Onera), V. Mazur (National Severe Storms Laboratory)

The physical processes leading to branching and physical factors affecting branching features are poorly understood. We are applying the tested physical model of axisymmetrical leader development following the streamer-leader transition to a 3-dimensional propagation of the leader with branching. The propagation of the leader is driven by the potential drop at the leader tip. The branching occurs when the drop potential at the leader tip reaches a threshold.

Experimental Studies of Lightning Strikes to Aircraft

Auteurs: 

P. Laroche, P. Blanchet, A. Delannoy †, F. Issac (Onera)

Civil aviation transportation has been growing since the early forties and has become today a massive and unique transport system for people across continents and large countries. First age propeller airliners flew at low altitude and were often subjected to dangerous atmospheric and cloud hazards. Low visibility, heavy precipitation, severe turbulence, wind shear, icing and lightning are common weather hazards that are a challenge for flight safety. Among those weather hazards, lightning was the most unrecognized and misunderstood.

Triggering Lightning Experiments: an Effective Approach to the Research of Lightning Physics

Auteurs: 

X. Qie, R. Jiang (LAGEO), P. Laroche (Onera)

Artificial triggering lightning experiments by launching a small rocket trailing a thin wire toward a charged cloud overhead have been conducted since the 1960s. After decades of development, this has become an important means for investigating lightning physics and validating lightning protection and location techniques. Observations of the triggered lightning have provided considerable new insights into different aspects of lightning discharges.

Polarity Asymmetry in Lightning Leaders: the Evolution of Ideas on Lightning Behavior from Strikes to Aircraft

Auteurs: 

E. Williams (MIT), S. Heckman (Earth Networks)

This study is concerned with outstanding questions on the mechanism of lightning and its theoretical treatment as a bidirectional leader. Previous studies of lightning strikes to aircraft are reviewed to highlight the key physical phenomena: the simultaneous action of both positive and negative leaders, the frequent tendency for electrical current in certain channels to cut-off abruptly, and the subsequent tendency for recoil leaders to initiate in these previously cut-off channels to establish a new stroke in the flash.

Review of the Location of VHF Pulses Associated with Lightning Discharge

Auteurs: 

Z. Kawasaki (E-JUST and Osaka University)

This article gives a brief summary on VHF pulse radiation associated with lightning discharges and its location. There are two independent techniques: Time of Arrival and Interferometry. VHF pulses are believed to be emitted during all of the processes of a lightning discharge. Thus, the mapping of VHF pulses associated with lightning yields information not only on lightning channel, but also on the charge distribution.

Videos: 

Positive cloud-to-ground flash

Negative cloud-to-ground flash