Commercial aircraft are struck by lightning far more often than nervous flyers realize. On average, every airliner in service is hit at least once a year. In the golden age of aviation, when planes were riveted tubes of gleaming aluminum, this was rarely a dramatic event.
Aluminum is an exceptional conductor of electricity. When a bolt of lightning—carrying up to 200,000 amps and 30,000 degrees of heat—struck the nose of a Boeing 747, the aircraft acted as a perfect Faraday cage. The electricity flowed harmlessly across the metal skin, skipped over the rivets, and exited off the tail, leaving the passengers inside unaware and the structure largely untouched.
But the golden age of aluminum is ending. Modern aircraft, like the Boeing 787 and the Airbus A350, are black planes painted white. They are made primarily of carbon fiber reinforced polymer (CFRP). While these materials are lighter and stronger than metal, they possess a potentially fatal flaw in a thunderstorm: they are electrical insulators.
The Resistance Problem
Carbon fiber itself is somewhat conductive, but not nearly enough to handle a lightning strike. Worse, the fibers are embedded in epoxy resin, which is basically plastic. Plastic stops electricity.
If a lightning bolt hits a piece of raw composite, the current cannot flow smoothly across the surface. Instead, it fights to get through. This resistance generates massive, instantaneous heat. Without protection, a lightning strike on a composite wing wouldn’t just scorch the paint; it could delaminate the layers, blow structural holes in the fuselage, or in the worst-case scenario, spark an explosion in the fuel tanks located inside the wings.
So, how do engineers make a plastic plane act like a metal one? They have to dress it in armor.
The Copper Sweater
The solution is a critical, often invisible step in the production process known as Lightning Strike Protection (LSP).
Before the paint goes on, manufacturers embed a conductive layer into the top surface of the composite skin. The most common material is “Expanded Copper Foil” (ECF).
Imagine a roll of kitchen foil that has been slit and stretched into a diamond-patterned mesh, looking somewhat like a microscopic chain-link fence. This mesh is incredibly light, but it provides a continuous superhighway for electrons.
When lightning strikes a modern aircraft, the current grabs onto this copper mesh. The mesh spreads the energy out over a large surface area, preventing it from digging down into the structural carbon fiber below. It guides the electricity safely to the discharge wicks at the trailing edges of the wings and tail.
The Manufacturing Headache
While the concept is simple, the execution is a nightmare for manufacturers. You cannot just glue copper to carbon and hope for the best.
Carbon and copper are enemies on the galvanic chart. If they touch in the presence of moisture, they create a battery, and the aluminum or copper will corrode rapidly. To prevent this, a thin layer of fiberglass isolation ply is often placed between the structural carbon and the protective copper mesh.
Furthermore, this mesh must be applied perfectly smooth. Any wrinkles or gaps creates a point of high resistance where heat can build up. In the cleanrooms where these wings are laid up, automated tape-laying machines must position the LSP layer with sub-millimeter precision, often over complex curves like the nose cone or the wing-to-body fairing.
The Weight Penalty
The irony of this technology is that it fights against the very purpose of using composites. Engineers switch to carbon fiber to save weight. But then, to make it safe, they have to add hundreds of pounds of copper mesh, isolation glass, and surfacing film back onto the aircraft.
This “parasitic weight” is a constant battle in Aerospace Composite Manufacturing. Every ounce of copper added for safety is an ounce of fuel efficiency lost.
The Future: Nano-Conductivity
Because of this weight penalty, the industry is currently racing to delete the mesh entirely. The next frontier is “Conductive Resins.”
Researchers are experimenting with mixing carbon nanotubes or graphene directly into the epoxy resin. The goal is to make the glue itself conductive. If the resin can carry the current, the entire skin of the plane becomes a Faraday cage without needing a separate layer of metal foil.
Until that technology matures, however, we remain in a hybrid era. We fly in plastic planes wrapped in copper sweaters, a hidden layer of metal ensuring that when the sky lights up, the only thing that breaks is the silence, not the wing.