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Static wicks

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jessejenks(at)hotmail.com
Guest

Posted: Mon Jan 19, 2009 6:50 am Post subject: Static wicks

I have always wondered why (most) certified airplanes have static wicks C but not homebuilts? This makes me want to know what their actual function is? I was always taught "they dissipate static electricity". Is static really that big of an issue C and if so C do wicks actually make a difference? I'm building an all metal airplane C and so far have not given any thought to control surface bonding C or static wicks.

Thanks. 

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harley(at)AgelessWings.co
Guest

Posted: Mon Jan 19, 2009 7:31 am Post subject: Static wicks

They can work to dissipate static if they are attached to a conducting surface.  That way, they can bypass whatever is creating the static and insulating the object from a normal ground (like the plastic or rubber tires on a fork lift). 

 

 But on many homebuilts, the plane is made of non conducting materials (wood and fabric or fiberglass and/or epoxy), and a static wick will only discharge the point that it is attached. A couple of inches away from that point, the charge remains as strong as ever. 

 

 I had many a discussion with fork lift drivers at Pennwalt when they would attach a static wick to the plastic part of the frame on the truck (it was easier to drill a hole into), and then complain that they still got zapped when they stepped off the truck. For those that really thought they needed it, we would attach the wicks to the metal frame under the truck. But, that often didn't help either, because the wick was often dragging on a non conducting surface (epoxy sealed floors). 

 Also, the line operators used vacuum cleaners to pick up the spilled foot powder...even though they used a so-called static proof hose (it had a grounded wire spiraling along the length of it) they would still get zapped when they put the hose down.  The charge was decreased, because of the presence of the wire, but still built up on the hose between the wire coil wraps. 

 

 In short, you need a continuous conductive path to discharge a static charge.  From every area where the charge can build. 

 

 Harley 

   

 

 Jesse Jenks wrote: [quote]    .hmmessage P { margin:0px; padding:0px } body.hmmessage { font-size: 10pt; font-family:Verdana }   I have always wondered why (most) certified airplanes have static wicks, but not homebuilts? This makes me want to know what their actual function is? I was always taught "they dissipate static electricity". Is static really that big of an issue, and if so, do wicks actually make a difference? I'm building an all metal airplane, and so far have not given any thought to control surface bonding, or static wicks.

 Thanks. 

   

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BobsV35B(at)aol.com
Guest

Posted: Mon Jan 19, 2009 9:23 am Post subject: Static wicks

Good Morning Jesse,

  

 I have almost no experience in homebuilt aircraft, but I do have several  thousand hours in aircraft that were equipped with static wicks and several  thousand hours in aircraft with no static wicks applied.

  

 My suggestion would be to thoroughly bond all control surfaces, flaps  included, but not bother with static wicks unless you note a problem.

  

 The static problem was greater in the days of low frequency radio. It was  not at all uncommon to lose all communication capability when we were using the  HF transmitters and receiving on low frequency. I have encountered precipitation  static strong enough to knock out VHF communications for just a very few  minutes, but that has never lasted more than four or five minutes.

  

 I have also experienced static discharges, but that has always been on  aircraft that were equipped with static wicks. There is no doubt that I have  flown in much heavier precipitation in static wick equipped airplanes than I  have in airplanes that are not so equipped, but I have flown both in some rather  severe situations. 

  

 Wait and see if you have a problem. 

  

 If you lose VHF navigation capability in a heavy thunderstorm, you may want  to add static wicks or you may just decide to stay out of such conditions!

  

 In any case, I have never seen a GPS signal affected by any static build  up.

  

 The only time I would suggest using static wicks is if your only means of  navigation is a LORAN. Even then, you don't need it if you stay out of  precipitation.

  

 Summary? Bonding YES, Static Wicks? NO

  

 Happy  Skies



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West 86th  Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22   

  In a message dated 1/19/2009 8:52:32 A.M. Central Standard Time,  jessejenks(at)hotmail.com writes:

  	  Quote: 	
		  I have    always wondered why (most) certified airplanes have static wicks, but not    homebuilts? This makes me want to know what their actual function is? I was    always taught "they dissipate static electricity". Is static really that big    of an issue, and if so, do wicks actually make a difference? I'm building an    all metal airplane, and so far have not given any thought to control surface    bonding, or static wicks.

Thanks.  

	






A Good Credit Score is 700 or Above.  See yours in just 2 easy steps!

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jan 21, 2009 9:58 pm Post subject: Static wicks

At 08:48 AM 1/19/2009, you wrote:

 	  Quote: 	
		  I have always wondered why (most) certified airplanes have static 

wicks, but not homebuilts? This makes me want to know what their 

actual function is? I was always taught "they dissipate static 

electricity". Is static really that big of an issue, and if so, do 

wicks actually make a difference? I'm building an all metal 

airplane, and so far have not given any thought to control surface 

bonding, or static wicks.

Thanks.


	


   When two dissimilar materials slide past each other

   rapidly, there is a tendency for electrons to be transferred

   from one material to the other . . . usually from

   the lesser conductor to the greater conductor.



   Shuffle your feet on the carpet and you can get a

   pretty good zap touching a doorknob. Slide out of

   your car on a cold dry day and it's not uncommon to

   find your body charged with a noteworthy packet of

   energy that wakes up your nervous system where the

   sparks jump from your bod.



   Airplanes flying in snow, ice particles or even rain

   can accumulate a surface charge of excess electrons.

   The faster airspeeds and higher particle density

   makes the build up stronger.



   If the quantity of excess charge is great enough

   AND there's some handy point or edges where the

   charges tend to collect, you can SEE the effects

   in the form of a luminous hazy discharge along

   the edge or at the point.



   On some models of King Airs we used to get reports

   of luminous glow around the window frames of glass

   fitted with internal de-icing heaters. While the

   airplane is shedding excess charge from trailing

   edges, antennas, window frames, propeller tips, etc

   the phenomenon creates a broadband radio noise that

   HAS been strong enough to disable ADF, LORAN, Omega

   nav, HF communications and in severe cases, gets the

   VHF comm and nav receivers too.



http://en.wikipedia.org/wiki/St._Elmo%27s_fire



http://science.howstuffworks.com/st-elmo-fire1.htm



   The big problem we were having with discharges

   around the window frames is that it was etching

   the glass and in some cases, killing the de-ice

   heat sensors. VERY expensive.



   The radio noise comes from the disordered, high density

   discharge of an un-treated structure. The cure is

   to provide devices that have a propensity for dropping

   electrons off into the slip stream. These can be

   "wicks" . . . a thing that looks like a fine brush

   of copper cat-hairs . . .



http://www.aircraftspruce.com/catalog/elpages/staticdischrgr.php



  Or an array of tiny points like these:



http://www.b737.org.uk/wingtips.htm



http://www.aircraftspruce.com/catalog/elpages/nullfieldtip.php



   This effect is not limited to airplanes. It can

   be a significant noise problem on stationary radio

   installations when there is blowing snow, dust, rain

   or significant convective activity as far away as

   20 miles.



   If you have a sensitive enough ammeter, you can probe

   and actually measure this current as cited in

   this article.



http://www.repeater-builder.com/pdf/staticbusterarticlecomplete.pdf



   A number of years ago, Beech did some extensive

   testing on the discharge characteristics of various brands

   and styles of wicks in the lab. There was a huge difference

   in performance of products then offered. I think folks making

   these things now are much better at it.



   Doing a GOOD discharger is not a trivial task although

   many folks have attempted it. Check out some of the

   techniques suggested here:



http://www.aeroelectric.com/Reference_Docs/Patents/Static_Dissipation/



   There have been a number of articles and postings to

   various forums about how to build your own. I've never

   seen an article that actually tested the handy work

   on the bench. Given what I witnessed at Beech many moons

   ago, I'm convinced that performance of DIY static

   wicks is a dart throw without quantified bench marks.



   The same process used to test wicks is use to test the

   airplanes probable discharge locations. The airplane is

   set up on plastic blocks. A long wand with a spherical

   end on it and a pico-ammeter in series is raised up to

   about 100,000 volts dc. You can run the wand along the

   trailing edges of possible concentration points and

   see the ammeter go up when the wand is closest to

   a location that would benefit from an effective

   discharge wick.



   Wicks are useful only on metal airplanes and then

   finding the optimum wick and placement is difficult.

   The occurrence of p-static is pretty rare for us

   guys who don't fly for a living.



   It won't hurt to have a half dozen wicks on your airplane

   but it may not be all that helpful. Wicks have

   nothing to do with lightning protection. Bonding

   the hinges on an airplane has nothing to do with

   mitigation of p-static effects. The idea here is

   to avoid welding the hinge rigid in case a lightning

   strike attaches to the control surface.



   Here's an short article I did on static-wicks for

   an EAA chapter newsletter some years back.



http://www.eaa326.org/Newsletters/eaa326-3-2005.pdf



   Bob . . .

rv8builder

Joined: 02 Jan 2009
Posts: 56

Posted: Thu Jan 22, 2009 6:27 am Post subject: Static wicks

I flew DeHavilland Dash-8's for nearly 20 years and despite lots and lots of static dissipation & airframe bonding efforts through out (to include lots of static wicks) you could still see St. Elmo's Fire from the prop tips.  It took moderate to heavy precipitation for the St. Elmo's Fire to be visible.  And then only visible at night.  It was neat to see from front end.  The passengers seldom saw it because the cabin lights were too bright!!

--

_________________
Dale

mlas(at)cox.net
Guest

Posted: Thu Jan 22, 2009 7:50 am Post subject: Static wicks

On Airbus jets with all the static wicks they have we still suffer  

from reduced VHF radio performance in hi P-static environments.  On  

the Lancair airplanes many builders have installed wicks with limited  

to no improvement to radio performance during high P-static events.   

Many over time have then removed the wicks.



Mike



On Jan 22, 2009, at 7:24 AM, Dale Ellis wrote:



[quote] 

 >



 I flew DeHavilland Dash-8's for nearly 20 years and despite lots and  

 lots of static dissipation & airframe bonding efforts through out  

 (to include lots of static wicks) you could still see St. Elmo's  

 Fire from the prop tips.  It took moderate to heavy precipitation  

 for the St. Elmo's Fire to be visible.  And then only visible at  

 night.  It was neat to see from front end.  The passengers seldom  

 saw it because the cabin lights were too bright!!

 --

walter.fellows(at)gmail.c
Guest

Posted: Thu Jan 22, 2009 1:10 pm Post subject: Static wicks

On a plastic airplane, if the composite parts are made with a specialized copper or aluminum mesh in the first layer of the mold, the parts of the airplane can be bonded together and static wicks added to give the same p-static bleed as an aluminum airplane (this the major part - without the wicks - of a program to provide lightning protection in composite aircraft). However there are weather conditions that will overwhelm the system even in an aluminum airplane, I had my HSI spinning and a loss of VHF reception (while retaining VHF transmission ability) over Lake Michigan at night in a Cessna 210 due to p-static apparently caused by almost invisible ice crystals in the air. I was IFR at the time and inadvertently stepping on center trying to restablish communcation much to their annoyance.

 

On Thu, Jan 22, 2009 at 7:44 AM, MICHAEL LARKIN <mlas(at)cox.net (mlas(at)cox.net)> wrote:

[quote] --> AeroElectric-List message posted by: MICHAEL LARKIN <mlas(at)cox.net (mlas(at)cox.net)>

 

 

 

 On Airbus jets with all the static wicks they have we still suffer from reduced VHF radio performance in hi P-static environments.  On the Lancair airplanes many builders have installed wicks with limited to no improvement to radio performance during high P-static events.  Many over time have then removed the wicks.

  

 Mike



 

 

 

 On Jan 22, 2009, at 7:24 AM, Dale Ellis wrote:

 

 [quote] --> AeroElectric-List message posted by: Dale Ellis <rv8builder(at)earthlink.net (rv8builder(at)earthlink.net)>

 

 I flew DeHavilland Dash-8's for nearly 20 years and despite lots and lots of static dissipation & airframe bonding efforts through out (to include lots of static wicks) you could still see St. Elmo's Fire from the prop tips.  It took moderate to heavy precipitation for the St. Elmo's Fire to be visible.  And then only visible at night.  It was neat to see from front end.  The passengers seldom saw it because the cabin lights were too bright!!

  

 

 --

mprather(at)spro.net
Guest

Posted: Thu Jan 22, 2009 3:18 pm Post subject: Static wicks

An aside:



Bob Buck, author of "Weather Flying" flew many research missions during

and after WWII with the specific purpose of understanding P-static and

testing equipment designed to alleviate its effects on aircraft systems. 

His discussion of this in his autobiography ("North Star Over My

Shoulder") is quite interesting.



There is also anecdotal information that suggests that electrical bonding

of control surfaces to the airframe can alleviate certain p-static

effects.  Apparently the charge that builds up on the body of the airframe

doesn't always readily pass through the hinges and control mechanisms to

control surfaces.  A small charge builds up between the control surface

and what it's mounted to, and then bleeds off in small discharges.  Each

discharge radiates a small amount of electrical noise which can apparently

interfere with the function of some equipment.  The story about this that

I read was one about a shipboard tactical Navy aircraft which suffered

poor nav system performance without the control surface bonding.  Again,

this is anecdotal..

Regards,



Matt-



[quote] On a plastic airplane, if the composite parts are made with a specialized

 copper or aluminum mesh in the first layer of the mold, the parts of the

 airplane can be bonded together and static wicks added to give the same

 p-static bleed as an aluminum airplane (this the major part - without the

 wicks - of a program to provide lightning protection in composite

 aircraft).

 However there are weather conditions that will overwhelm the system even

 in

 an aluminum airplane, I had my HSI spinning and a loss of VHF reception

 (while retaining VHF transmission ability) over Lake Michigan at night in

 a

 Cessna 210 due to p-static apparently caused by almost invisible ice

 crystals in the air. I was IFR at the time and inadvertently stepping on

 center trying to restablish communcation much to their annoyance.



 On Thu, Jan 22, 2009 at 7:44 AM, MICHAEL LARKIN <mlas(at)cox.net> wrote:



> 

>

> On Airbus jets with all the static wicks they have we still suffer from

> reduced VHF radio performance in hi P-static environments.  On the

> Lancair

> airplanes many builders have installed wicks with limited to no

> improvement

> to radio performance during high P-static events.  Many over time have

> then

> removed the wicks.

>

> Mike

>

>

> On Jan 22, 2009, at 7:24 AM, Dale Ellis wrote:

>

>  

>> rv8builder(at)earthlink.net>

>>

>> I flew DeHavilland Dash-8's for nearly 20 years and despite lots and

>> lots

>> of static dissipation & airframe bonding efforts through out (to

>> include

>> lots of static wicks) you could still see St. Elmo's Fire from the prop

>> tips.  It took moderate to heavy precipitation for the St. Elmo's Fire

>> to be

>> visible.  And then only visible at night.  It was neat to see from

>> front

>> end.  The passengers seldom saw it because the cabin lights were too

>> bright!!

>>

>>

>> --

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jan 23, 2009 10:33 am Post subject: Static wicks

 	  Quote: 	
		    Apparently the charge that builds up on the body of the airframe

doesn't always readily pass through the hinges and control mechanisms to

control surfaces.  A small charge builds up between the control surface

and what it's mounted to, and then bleeds off in small discharges.  Each

discharge radiates a small amount of electrical noise which can apparently

interfere with the function of some equipment.


	


   I've heard this on numerous occasions and listened/participated

   in a number of discussions about the physics of how this might

   happen.



   P-static currents are measured in micro-amps. The energies

   that might be released as electromagnetic radiation in hinge

   gaps is pretty small. The gap is measured in thousandths of

   an inch and the arc-over voltage for this is low assuming

   a perfectly spaced gap and high resistance. A hinge will never

   go open circuit . . . it's more appropriately described as

   a dynamic resistance on the order of hundreds of milliohms.

   Static wicks have HUGE resistors built in (many tens of

   megohms) for the purpose of killing the ability of the

   wick to resonate and to convert energy to heat (like the

   resistor wires on spark plugs).



   We could see how a hinge in motion might generate moderate

   CONDUCTED noise into an electrical system if say a landing

   light were grounded to a gear door and the hinge resistance

   was wobbly as the door moved.



   But the idea that dynamic resistance characteristics of

   hinges at p-static currents produces detectable noise

   in the RF spectrum was pretty far fetched. I'd like to

   read an explanation of the simple-ideas that support the

   notion of bonding hinges for the purpose of reducing

   deleterious effects of p-static.



   Now, there could be OTHER radio frequency issues that

   are addressed by bonding. I think I described a case

   where the unintended consequences of going from a

   voltage fed wire HF antenna to a current fed loop

   on the vertical fin turned the whole empennage of

   the airplane into a high energy RF test chamber. The

   unintended consequences of which showed how many

   pieces of 1980's technology would scream for mercy

   as the transmitter was keyed.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

BobsV35B(at)aol.com
Guest

Posted: Fri Jan 23, 2009 1:20 pm Post subject: Static wicks

Good Afternoon Lectric Bob,

  

 I have no doubt that what you have told us is good information and that it  was derived from careful observation. Nevertheless, when Loran was all the rage,  we found that adding bonding straps to every possible control surface or gear  door made a huge difference in the reception of adequate Loran signals. Adding  static wicks added a bit more, but the cost of installing and maintaining the  static wicks was quite high and the bonding costs were next to nothing. It may  not do much good, but I still vote for bonding and only going to static wicks as  a last desperation "throw money at the problem" solution.

  

 This time I vote for the OWT!  

  

 'Course, you may not need anything at all!

  

 Happy  Skies



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West 86th  Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22   

  In a message dated 1/23/2009 12:35:22 P.M. Central Standard Time,  nuckolls.bob(at)aeroelectric.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "Robert L. Nuckolls, III"    <nuckolls.bob(at)aeroelectric.com>

 	  Quote: 	
		    Apparently the    charge that builds up on the body of the airframe

doesn't always    readily pass through the hinges and control mechanisms to

control    surfaces.  A small charge builds up between the control    surface

and what it's mounted to, and then bleeds off in small    discharges.  Each

discharge radiates a small amount of electrical    noise which can apparently

interfere with the function of some    equipment.


	


   I've heard this on numerous occasions and    listened/participated

   in a number of discussions about the    physics of how this might

   happen.



   P-static    currents are measured in micro-amps. The energies

   that might    be released as electromagnetic radiation in hinge

   gaps is    pretty small. The gap is measured in thousandths of

   an inch    and the arc-over voltage for this is low assuming

   a perfectly    spaced gap and high resistance. A hinge will never

   go open    circuit . . . it's more appropriately described as

   a dynamic    resistance on the order of hundreds of milliohms.

   Static wicks    have HUGE resistors built in (many tens of

   megohms) for the    purpose of killing the ability of the

   wick to resonate and to    convert energy to heat (like the

   resistor wires on spark    plugs).



   We could see how a hinge in motion might generate    moderate

   CONDUCTED noise into an electrical system if say a    landing

   light were grounded to a gear door and the hinge    resistance

   was wobbly as the door moved.



      But the idea that dynamic resistance characteristics of

   hinges    at p-static currents produces detectable noise

   in the RF    spectrum was pretty far fetched. I'd like to

   read an    explanation of the simple-ideas that support the

   notion of    bonding hinges for the purpose of reducing

   deleterious effects    of p-static.



   Now, there could be OTHER radio frequency    issues that

   are addressed by bonding. I think I described a    case

   where the unintended consequences of going from    a

   voltage fed wire HF antenna to a current fed    loop

   on the vertical fin turned the whole empennage    of

   the airplane into a high energy RF test chamber.    The

   unintended consequences of which showed how    many

   pieces of 1980's technology would scream for    mercy

   as the transmitter was keyed.

           Bob . . .



           ----------------------------------------)

        ( . .    .  a long habit of not thinking   )

           ( a thing wrong, gives it a superficial )

           ( appearance of being right . . .       )

           (                                             )

        (                     -Thomas Paine 1776-  )

            = Use  lities  y                 - MATRONICS WEB FORUMS  =========================<             - List Contribution Web Site  ;                             =========================



	




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