Lightning strikes are an everyday occurrence on planet Earth: on average, lightning strikes occur 100 times every second throughout the whole world.Boeing 787s, for instance, are impacted up to 4 times by lightning strikes every year. However, due to the Boeing 787 lightning protection, most of the strikes do little-to-no-damage, and most of the time, passengers do not even notice when the aircraft is struck.
Boeing 787, like the other aircraft types, possesses protection from lightning strikes. First, most of the external parts are metal composed, with sufficient thickness to resist lightning strikes. This ‘metal skin’ offers the aircraft its basic protection, while also controlling the entrance of electromagnetic energy into the electrical wires of the airplane, keeping it at a sustained level without damaging the aircraft.Second, the ‘skin’ around the cabin and interior compartments are designed with a metal mesh that goes all the way through to provide an additional layer of protection. This conducts the electricity through the outside of the vessel, protecting the crew, passengers, and electronics inside from any voltage. It works as a Faraday cage, blocking the interior of the aircraft from electromagnetic fields.Moreover, some areas that are more lightning-strike prone may incorporate wire bundle shields, ground straps, or some types of composite parts, such as expanded foils, wire mesh, aluminum flam spray coating, embedded metallic wire, metallic picture frames, diverter strips, etc.
Contrary to the other aircraft types, the Boeing 787 contains more composite materials such as carbon fibers, that are less conductive than aluminum. To create a conductive path to exit a lightning strike from the aircraft, a lightweight mesh of foil is embedded in the surface film of the aircraft’s outer skin. This path is placed in contact with metal bonding strips that connect to the outer surface to a metallic-ground plane, such as an engine or metal conduit in the fuselage. Thus, due to a higher proportion of composite materials contained by the Boeing 787, there are a lot of conductive paths.
In 2019, Boeing introduced changes to the lightning strike protection on the 787. As mentioned above, the Boeing 787 lightning protection consists mostly of carbon composites. In order to protect the wing fuel tank, Boeing implemented special measures while developing the Dreamliner. As a result, a metal fastener has been sealed into the wing, complete with an insulating cap, and copper foil has been added in strips across the skin of the wing to disperse the electrical current from a lightning strike.Having first stopped adding the insulation fastener caps, Boeing decided to stop adding the copper foil as a cost-cutting measure. Therefore, the entire wing surface of any jet delivered in the last years lacks both protections.
On February 22, 2019, the Federal Aviation Administration (FAA) initially rejected the removal of the foil from the wing, when its certification office ruled that Boeing had not shown the fuel tank would not ignite.Following Boeing’s appeal, the FAA managers reconsidered and reversed the ruling a week later, allowing the aircraft with the implemented changes to fly.According to Boeing, the 787 has “several other layers of protection from lightning strikes”. In addition, each design change “was properly considered and addressed by Boeing, thoroughly reviewed with and approved by the FAA.”However, in the wake of the two Boeing 737 MAX crashes, the lightning protection changes to the 787 delivered between 2019 and 2020 are now being discussed.