A static wick

[BOOTY MONSTER]

i found an interesting article on the WWW and thought id post it here just for conversation and opinions if others find it interesting .

How is a plane protected from Lightning strikes?

heres the part that made me go hmmmmm......

"The way an aircraft tries to dissipate these step leaders is through the use of something called a "static wick". A static wick is a piece of metal connected electrically to the frame of the aircraft, with one or two spikes or needles on the end. It is housed in a fiberglass rod to insulate it from the airplane. Because the spikes concentrate the electric charge around them, and they are connected to the airframe, they allow the airplane to dissipate any static electricity it may build up out into the air. Also - if lightning DOES strike the plane, the chances are that the electricity will go through the dissipator and not through the airplane."

ive seen post suggesting the fiberglass enclosed antennas pick up less static and are less prone to lightning strikes , seems they are perfect lightning rods for airplanes except they arnt stiff enough .

 

[packrat]

There is little chance of static build up / discharge in an airplane because it is not grounded. I am not sure what the idea is if the static is still discharged into the airframe anyway.??? The "static wick" thing is like the devices used on sailboat masts to discharge static buildup to prevent lightening strikes, but they are grounded to the water. Corona ball?

 

[GLR]

There is little chance of static build up / discharge in an airplane because it is not grounded. I am not sure what the idea is if the static is still discharged into the airframe anyway.????

My understanding is that the wicks don't allow the current to discharge into the airframe rather dissipate through the wicks into the surrounding air and are generally on the elevator in a light airplane. IFR flight doesn't interest me much though, life is simpler slow and low.

 

[Captain Kilowatt]

ive seen post suggesting the fiberglass enclosed antennas pick up less static and are less prone to lightning strikes , seems they are perfect lightning rods for airplanes except they arnt stiff enough .

Static wicks are basically the same thing as lightning rods. The purpose of a lightning rod is not to attract lightning but rather to dissipate the buildup of static before it can arc over.

As for posts suggesting that fiberglass enclosed antennas pick up less static and are less prone to lightning strike, they will suffer less from precipitation static because the electrically charges rain or snow does not contact the grounded metal antenna and therefore cannot discharge upon contact and produce static in the receiver when doing so. As for less likely to be hit by lightning I have to disagree. I have use commercial antennas housed in fiberglass radomes before and the only purpose of the radomes was to prevent the buildup of ice and snow which would cause detuning and a high SWR. As for lightning, I had a four bay twelve panel FM broadcast antenna that was struck by lightning. The end result was that five radomes were blown apart and four antennas had holes burned in them. It was probably struck several times in the same storm. The radomes did NOTHING to prevent being hit.

 

[Captain Kilowatt]

There is little chance of static build up / discharge in an airplane because it is not grounded. I am not sure what the idea is if the static is still discharged into the airframe anyway.??? The "static wick" thing is like the devices used on sailboat masts to discharge static buildup to prevent lightening strikes, but they are grounded to the water. Corona ball?

An airplane certainly can and does build up a huge static charge while flying through dry cold air. The fact that they are not grounded means that they need a way to dissipate that static back into the air safely and that is what the static wicks do. They do in fact operate the same way the devices on sailboat masts do. A static charge will tend to accumulate around a pointed object much more densely than a smooth object and will therefore build up to the point of arcing over much more easily,in fact so easy they bleed the static off before it can build up enough to flash over.

Ever notice that when a small plane is refueled the first thing the pilot does is connect a ground lead to the airframe before refueling? That is to make sure the static that was built up while it was sitting there does not cause a spark while fueling. Ungrounded objects can create HUGE static charges. I am reminded of the time I was knocked to my knees while installing a new 160 foot AM tower. It was in a large open field and was sitting on it's huge base insulator floating above ground. (electrically speaking) It was in the first week of December when the air is getting quite dry here and there was a brisk wind. I was installing the ground radials at the time and had forgotten to install the lead going to the static drain choke. I stood up to give my back a break and leaned against the tower. After I picked myself up off the ground I grabbed the jumper cables from the back of the truck and clamped them between the tower and the ground screen for extra insurance against that happening again until the system was finished.