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Some early reports by witnesses to the Air Algérie Flight 5017 crash claim that lightning caused the plane to crash:

A GROUP of herders who say they saw Air Algerie flight AH5017 crash claim it went down after being struck by lightning, local officials told Reuters. Louis Berthaud, a community counsellor in Gossi near where the plane carrying 116 people went down, said: “The herders were in the bush and saw the plane fall.” He added: “It must have been a storm and it was struck by lightning. They said it was on fire as it fell, before it crashed.”

I have done a lot of research before I read this article. I know that planes are made of metals that are good conductors of electricity. From what I know, this means that the electricity will flow 'around' the outside of the plane and is essentially a Faraday cage. That means that the lightning itself won't be able affect the plane except for scorches on the outside.

Can lightning ignite a fuselage or bring down a plane?

  • Careful: the witnesses are apparently saying they saw the plane struck by lightning. They are not asserting that lightning was the cause of the crash. – Nate Eldredge Jul 29 '14 at 11:46
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    I don't know about igniting a fuselage, but it can play hell with electrical systems. I worked avionics for ten years, and after any reported lightning strike we had a lengthy checklist of problems to look for. A system failure resulting in a crash sounds very plausible, at least to me. – Is Begot Jul 29 '14 at 12:39
  • Do a google image search for "plane lightning damage" and look at the images and judge yourself if those damages provide a possiblity (not a necessity) for a plane to come down. Especially intresting is one image of a twisted tube inside the plane. – PlasmaHH Jul 31 '14 at 14:10
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It is possible, however unlikely in modern commercial aircraft.

Some of past incidents:

  • 1963 – Pan Am Flight 214, was hit by lightning igniting the fuel. Crashed killing everyone onboard (81 people).
  • 1973 – crash of an Ozark Airlines Fairchild FH227B in St. Louis, which killed 38 and injured six passengers and crew. A lightning strike on final approach was cited as a probable cause.
  • 1985 – crash of a Delta Air Lines Lockheed L-1011-385 in Dallas/Fort Worth, which killed 135 and injured 30 passengers and crew. Lighting was cited as a contributing factor.

How can it happen:

Lightning Effects

Both the occupants of an aircraft and the aircraft itself are subject to the powerful effects of a lightning strike. The inherent structural design of an aircraft provides the occupants almost complete protection despite the massive amount of current involved. This protection is based on the principle known as the Faraday cage, first devised by the physicist Michael Faraday in 1836.

A Faraday cage is a hollow enclosure made of conducting material, such as the hull of an aircraft. In the presence of a strong electric field, any electric charge will be forced to redistribute itself on the outside enclosure, but the space inside the cage remains uncharged. Thus, the metal hull of the aircraft acts as a Faraday cage, protecting the occupants from lightning.

Some aircraft are made of advanced composite materials, which — by themselves — are significantly less conductive than metal. To overcome this resulting safety problem, a layer of conductive fibers or screens is imbedded between layers of the composite material to conduct the lightning current.

Regardless of hull material, the direct effects of lightning on the exterior can also include:

  • Burning or melting at lightning strike points;
  • Increase in temperature;
  • Residual magnetism;
  • Acoustic shock effects;
  • Arcing at hinges, joints and bonding points; and,
  • Ignition of fuel vapors.

Accident data indicate that most of these effects are not serious. However, an estimated one-third to one-half of aircraft lightning strikes result in at least some minor damage. Lightning generally enters an aircraft at one location, usually an extremity, and leaves at another.

Burn marks are found at the entry and exit point(s) of the strike, although exit points are not present if the energy was dissipated via wicks or rods — static dischargers whose primary purpose is to bleed off into the surrounding air the static charge build-up that occurs during normal flight.

Because many aircraft fly a distance equivalent to several times their own lengths during a lightning discharge, the location of the entry point can change as the discharge attaches to additional points aft of the initial entry point. The location of the exit points may also change.

Therefore, for any one strike, there may be several entry or exit points.

Occasionally, in more severe strikes, electrical equipment or avionics may be affected or damaged. This potential problem is addressed in modern aircraft design by redundancy. The functions of most critical systems are duplicated, so a lightning strike is unlikely to compromise safety of flight. In most strike events, pilots report nothing more than a temporary flickering of lights or short-lived interference with instruments.

The exception is the incidence of positive lightning. Positive lightning strikes — because of their greater power — are considerably more dangerous than negative lightning strikes. Few aircraft are designed to withstand such strikes without significant damage.

source Flight Safety Foundation „When Lightning Strikes”

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