During a lightning strike, the current pulse flowing through a building, aircraft or other structure generates fast-changing magnetic fields. These fields induce voltage and current transients in any wiring routed nearby or within that structure.

Electrical or avionic equipment needs to be protected against the transients induced in the wiring, to avoid damage, misleading information or system interrupt.

An important part of the design and qualification process is to understand the magnitude/type of transients, so that the equipment can be appropriately protected against them. There are two ways in which this can be done:

  • Perform a full vehicle test at low level (between 1kA and 10kA typically) and measure the induced transients on the wiring.
  • Perform an analysis of the installed wiring and lightning current paths in order to predict the transient levels on the wiring.


Frequently both approaches are combined.


Full Vehicle Testing

Cobham offer full vehicle tests at customer premises, in a programme of testing which could extend typically over a couple of weeks. A return conductor cage is constructed around the aircraft. This is designed to allow different lightning attachment scenarios and current paths to be simulated.

A current generator typically capable of 1kA-2kA is used, although a transportable 10kA generator is sometimes preferred.

Current pulses at this level are applied to the aircraft, whilst remote measurements are made of cable harness currents and individual wire pin voltages, concentrating especially on the more critical systems and more exposed harnesses.

We can also provide support in helping identify the most useful and effective measurements to make, and in interpreting the results.


Cobham's experience of aircraft test and measurements provides an insight into lightning induced effects and their avoidance; this experience underpins the consultancy support provided to our customers.

Our experience is supplemented by our in-house software tools, in particular the INDCAL program. This is a 2D modelling program ideally suited to solving current distribution and induced voltage problems in structures such as aircraft fuselages and wings.

INDCAL's results are used in support of design or certification by determining the transients induced in wiring, to allow them to be compared to the transient protection of the connected equipment.

The approach also helps to identify optimum and cost-effective lightning protection in the installation of electrical/avionic systems.

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