How Aircraft are Protected from the Damaging Effects of Lightning?
According to the Federal Aviation Administration (FAA), a commercial jet airliner is estimated to be struck by lightning once every 1,000 hours of flight. During flight, aircraft may even trigger a lightning strike by passing through an ionized cloud. Despite the commonality of aircraft lightning strikes, there has not been a commercial plane crash directly caused by lightning since 1967. The lack of accidents caused by lightning and high reliability of aircraft after strikes is due to advanced aircraft lightning protection that is implemented across various structures, including lightning arrestors and exterior metal and skins.
When lightning does strike an aircraft, the most common areas that are hit are the wings, tip, nose, or rudder and such occurrences happen most often while flying in altitudes of 5,000 to 15,000 feet. The most critical areas that are protected from lightning include the aircraft interior, electrical wires, and the flight control system. The metal exterior of a standard commercial aircraft is very thick and conductive, often already providing much protection against strikes. Nevertheless, this may not always be enough to fully protect critical areas. Thus, the aircraft lightning protection system may also include lightning arrestors, conductive meshes, and shield wiring.
Lightning arresters are devices that provide a path to divert high voltage lightning currents from important areas or equipment. To do this, lightning arresters use spark gaps or blocks that are manufactured from semiconducting materials and are connected to lines that enter volt sensitive electrical equipment. Common types of lightning arrestors include sphere gap, auto valve, oxide film, road gap, horn gap, multi gap, impulse protective, electrolytic, expulsion, valve, thyrite, and metal oxide lightning arresters.
The aircraft fuselage also has conductive, gapless skin designed to provide a conductive shield. This skin acts like a Faraday cage which distributes electrical charges so as to cancel the charge effect on the cage interior. When lightning strikes the skin of the aircraft, the voltage travels throughout the exterior and exits. A lightweight mesh or foil may also be installed within the outer skin to provide for a conductive path and fasteners around such areas are encapsulated or sealed off with a non conductive material, such as plastic, to avoid arcing of the current. As lightning can cause transient charges underneath the skin, equipment will utilize grounding, surge suppression, and shielding to remain protected. With a mesh or foil, even aircraft that have composite structures can be protected from strikes.
The fuel system of an aircraft is a critical area to protect from lightning strikes, as stray currents near fuel can be disastrous. Because of this, the skin surrounding the fuel system is engineered to be thick enough to even avoid a burnthrough caused by lightning strikes. As flight instruments are susceptible to damage from lightning, the radome that contains them is fitted with diverter strips. Diverter strips are placed around such important areas to act similarly to a building lightning rod, directing current away from the structure.
When it comes time to begin sourcing the aircraft lightning protection system parts and components that you need for your next project or operation, Aviation Parts Online has you covered with everything you are searching for. Aviation Parts Online is owned and operated by ASAP Semiconductor, and we can help you find the aviation parts and components that you are searching for, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. ASAP Semiconductor is an FAA AC 00-56B accredited and ISO 9001:2015 certified enterprise. For a quick and competitive quote, email us at sales@aviationpartsonline.com or call us at +1-720-923-2840.
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