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Old 05-31-2022, 01:15 PM
  #10  
JohnBurke
Disinterested Third Party
 
Joined APC: Jun 2012
Posts: 5,926
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Arcing and discharges can certainly occur within the aircraft, as well as without. I have seen this in aircraft, and in vehicles on the ground. I was involved in recovery of an aircraft on a mountainside, offroad, with the vehicle parked nearby. With severe thunderstorm activity in the area and a lot of lightning, I decided to get off the mountain. The vehicle was full of tools, and when I entered the vehicle, large arcs were snapping between objects inside, between tools and implements; it wasn't associated with a lightning strike on the vehicle, but there was a lot of discharging going on. There was a strong smell of ozone. The arcs were bright, some made a snapping or sizzle sound, some none. I had concern about stepping into the vehicle or touching it to open a door, because of the perception of a potential path to ground through me; a door was open and I dove into it; whether a shock hazard existed or not, I can't say, but I didn't want to find out, and I didn't want to stay on the mountainside.

While that kind of arcing was bright and intense in appearance, mostly whiteish or yellow-white, the corona I've seen in and around aircraft is typically blue or green, sometimes reddish, with typical st. elmos and other such arcing is usually a yellow, white, or bluish tint. All fairly low intensity, and don't tend to disrupt night vision. Large discharges like previously described are much brighter, and can be accompanied by loud noise. When "ball lightning" is encountered in homes, in vehicles, and in aircraft, it's typically seen as a low-intensity lighting, rather than bright, usually comes with no sound or a low hiss or sizzle, and moves much more slowly than a typical lightning strike or high intensity discharge. It doesn't tend to disrupt night vision. It's isolated, meaning it has. beginning and an end, like a traveling ball of energy; more like a plasma than a beam of light. I believe such discharges or manifestations are more of a visible passing of a corona along a path to ground, between wingtips, down the aisle, etc.

If one has flown behind propellers in the right conditions at night, one has probably seen the prop tips, and the arc, blow green or blue, along with wingtips, radomes, antennas, wipers, and so on. We've probably all seen st. elmo's.

An aircraft structure, because of bonding and an electrical ground path almost almost everywhere on the aircraft, is a big faraday cage, of sorts, largely transporting large electrical paths through the structure, rather than the interior; any passage of electricity through the interior would have to be a very intensive discharge and path, with a bright flash, and rapid movement; such a path would appear instantaneous, no indication of travel in one direction or the other, would be loud, and heat the air around it, and cause damage. Lower intensity discharges that have visible, defined movement, color, and don't bear the characteristics of a lightning bolt are usually the result of static buildup on the exterior, moving between points of polarity on the structure, along a path that might be anything with a lower resistance than the surrounding air.

When flying in significant electrical activity, I've often wondered about the potential to be a path to ground through the flight controls while holding a yoke or stick. Zap.
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