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Question

If lightning strikes an airborne aircraft, are the occupants affected? Why or why not?
Asked by: Arjang Hourtash

Answer

This is, by all accounts, a fairly common occurrence. Clearly the aircraft shell can build up static from it's flight through the air. This is why the wheels on an aircraft have a conducting compound in order to dissipate ('earth') the charge build-up and prevent fatalities through electric shock.

There have been documented cases where staff have been electrocuted because new wheels were not tested adequately.

The principle is the same in this situation and the one your question addresses. Why is the presence of this charge not felt within the aircraft? We can consider the aircraft as a metallic shell which is charged after the event of being struck by lightning or spending hours flying through clouds.

Electrostatics theory tells us that there is no electric field inside a charged shell. Since it is the electric field which causes the motion of charged particles, there can be no current inside the shell either. The current is only experienced as you pass through the shell. This is why, although the aircraft is very highly charged, you are in no danger of being electrocuted unless you touch the outer surface (as the unfortunate hostess did).

A practical example of this, and a much safer example, I may add, can be experimented with as you get out of a car after a long drive. The body of the car has become charged and if you earth the car after you have exited the shell, you get a shock. Try holding on to the frame as you get out of the car. No shock, no problem.

Oh, and check those aircraft tires before you fly.
Answered by: Neil Robertson, M.S., Computer Vision Researcher, Oxford, UK


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