Groundbreaking lightning strike simulation project

Lightning strike tests of a helicopter at Eurocopter's Donauwörth facility, in Germany, has verified the accuracy of finite element analysis techniques for characterising the electromagnetic behaviour of complete and custom-cabled modern aircraft structures constructed using advanced composite materials.

The exercise was performed using the Opera electromagnetic design software from Cobham Technical Services, as a final element of the company's work for the ILDAS (In-flight Lightning Strike Damage Assessment System) project.

Simulation of the ILDAS tests highlight how finite element techniques can easily generate accurate models of complex assembled airframes, and simulate the effects of lightning strikes rapidly - in around a day on a standard office PC - to help developers evaluate and optimise lightning protection measures during the design cycle.

John Simkin of Cobham Technical Services said: "These real-life tests of ILDAS's embedded monitoring system concept illustrate how airframe-specific lightning protection can now be accurately evaluated and optimised during the design cycle."

Commercial passenger aircraft are struck by lightning once a year on average. Powerful strikes can result in costly delays for inspection and repair. The industry's current certification against lightning is based on threat levels derived from measurements of cloud-to-ground strikes.

While this approach has served well for traditional airframes with good metallic conduction, modern aircraft are incorporating increasing amounts of lightweight composite materials. This makes them more susceptible to direct damage at lightning entry and exit points, and potentially to indirect energy coupling effects into the electrical systems as current flows through the aircraft.

The ILDAS project was conceived to develop an in-flight embedded system for measuring actual lightning strikes. This will help to better understand the threat, aid the design of lightning protection measures, and streamline post-strike inspections and maintenance by capturing and communicating actual data on occurrences, intensity, and strike points.

John Hardwick of Cobham Technical Services says: "Airframe structures making extensive use of composite materials have less natural protection against lightning. As lightning protection measures such as conductive coatings or strips add weight it's important to optimise the design and simulation provides an effective means of achieving this."

Author
Justin Cunningham

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