I've been reading some stuff on this.
It turns out to be quite a complicated topic.
Even though most light-GA wicks are just a piece of stranded wire, some wicks (those on jets especially) contain a resistor.
The reasoning for the resistor is that the RF energy produced by the discharge is not conducted back into the airframe.
There is an amazingly detailed US military study here (9MB PDF). It studies how static accumulates during flight, etc. A more basic wiki article is here.
Local copy of above: http://peter-ftp.co.uk/aviation/misc-euroga/2017-static-wicks-AD0261029.pdf
The wicks are critical for radio comms and radio nav. After one Annual, my elevator bearings got greased rather too well and no longer provided a path for the airframe static. The result was that the static was arcing across the bearings, resulting in a total loss of COM2 which was the antenna nearest the bearings. So I got a couple of braided straps riveted in there so one is not relying on the bearings to conduct - hard to see how Socata managed to get away with that all those years. They do have a strap from the rudder to the airframe, but not from the elevator to the airframe.
I am wondering whether resistive wicks are not worth experimenting with, with the squelch turned off so one can see the improvement more clearly.
I totaly agree with this issue and one of my annual concerns is to replace all those broken wicks and check those linking straps. Another ULTRA serious (but unknown) issue is the good "RF ground" needed for our L/4 antennas to remain efficient and transmit the most RF far away instead of warming up and eventualy "bake" the Comms. The flat seat of these antennas should allways face a fresh uncorroded aluminium part of the airframe.The Aluminium oxide that eventualy develops should be lightly sanded and covered with Alodine. So,whenever you seem to pick up statics instead of wanted radio signals,it's time to remove your antennas and treat.Much cheaper than replacing good radios for no reason.
73 de SV5AZR
There are also these static wicks which are a plastic straw with some slightly conductive paint (black) on it. These are quite frequently used in GA, and are easily damaged. When measuring them I often find more than one failing. When the black is gone and only the white / clear straw is visible it will need to be replaced, but also small cracks in the paint can prevent it from doing it’s job good.
I personally think they often fail because people walk against them in crowded hangars, and some people seem to want to play with it, and thick on the end part of the static wick, destroying it by doing that.
Static wicks are often overlooked in maintenance, or found ok as long as they haven’t broken off, without looking into there functioning.
So any suggestions for a source for replacements and if replacing (as I need to) which to use?
Thanks
Replace it with either resistive wire, of those with regular wire and a resistor. The resistor is often found under the base. Make sure to check if that is allowed for your aircraft.
Do not use the ones that use a coating.
Replace it according to the aircraft IPC. Many diamond aircraft (composite) tend to have lots of defective wicks…
/Sam
Cirrus – no static wicks?
Someone mentioned this recently, so I did a quick google and found this
I used to work in high voltage engineering, and I can’t see how you can get rid of the charge (which is inevitably picked up if flying in IMC) unless
Point 1 doesn’t mean “plastic planes” can’t fly in IMC but it does mean they will probably lose VHF and UHF comms and navigation, in IMC – unless some precautions are taken. IMHO they will require the panels to be – at least – sprayed with a conductive paint on the inside, and these areas of paint will need to be wired together. The absence of such protection will also carry the risk of a flashover from a plastic panel to any nearby wiring, which will prob99 crash the avionics. However, paint is not going to protect from a lightning strike unless it is really thick and very conductive.
But an SR20/22 is already bonded – it could not be certified otherwise because it would be extremely vulnerable to a lightning strike fusing the control linkages.
Did the early SR20/22s have wicks, and Cirrus have found they are not needed?
The SR22 has a copper mesh inside the composite structure of the fuselage, otherwise it would not have gotten IFR certification.
The SR22 has a copper mesh inside the composite structure of the fuselage, otherwise it would not have gotten IFR certification.
Yes, but even all-metal aircraft require static wicks. Otherwise the electrons will take the next easiest route towards freedom which are the antennae.
The SR22 has a copper mesh inside the composite structure of the fuselage
Of course, otherwise it could not be bonded. You can’t bond one plastic panel to another…
Does anyone have any info on the absence of static wicks?
