Today's Message Index:
----------------------
1. 06:03 AM - ELT location (James H Nelson)
2. 08:50 AM - Re: ELT location (Ed Holyoke)
3. 10:33 AM - Re: Static wicks (Robert L. Nuckolls, III)
4. 12:11 PM - Re: Will other wiring interfere with Magnetometer? (Robert L. Nuckolls, III)
5. 01:20 PM - Re: Static wicks (BobsV35B@aol.com)
Message 1
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Hi Ed,
Signed off and flying !!!!
Jim
____________________________________________________________
Come clean with a brand new shower. Click now!
http://thirdpartyoffers.juno.com/TGL2141/fc/PnY6rw1wsgyplM6sWzTdAzPIKtAeZbj06hKJGMTU7MVQ2WL6FeifP/
Message 2
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| Subject: | Re: ELT location |
Cool!
Ed
James H Nelson wrote:
>
> Hi Ed,
> Signed off and flying !!!!
>
>
> Jim
> ____________________________________________________________
> Come clean with a brand new shower. Click now!
> http://thirdpartyoffers.juno.com/TGL2141/fc/PnY6rw1wsgyplM6sWzTdAzPIKtAeZbj06hKJGMTU7MVQ2WL6FeifP/
>
>
>
Message 3
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| Subject: | Re: Static wicks |
> 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- )
----------------------------------------
Message 4
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| Subject: | Will other wiring interfere with Magnetometer? |
At 04:46 PM 1/22/2009, you wrote:
>
>Getting ready to pull a twisted pair from panel to position lights in tips.
>I was measuring for how long to cut the wires and I had a couple of
>questions:
>
>Does the pair of wires feeding each nav light need to be twisted the entire
>length from panel to light or just some distance before and after as it
>passes the magnetometer?
I don't have first-hand experience with chasing a magnetometer
interference problem. I DID work a case where the B&C SD-20
was swinging a glareshield mounted compass several degrees.
The problem became un-observable when the compass was moved
vertically about 10" to a location on the windshield.
This example speaks to the fact that magnetic interference
coupling falls off very rapidly with increase of distance
between antagonist and victim. As long as your potential
emitters of undesirable magnetics are say 2 feet or further
away from the magnetometer, it's unlikely that you'll see
any problems.
>And since my leading edge landing/taxi lights (located several feet inboard)
>will be grounded locally can I shorten the length of the nav light ground
>wire and ground to the airframe at the same place? And then twist from
>there to the nav light?
That ought to work.
Bob . . .
Message 5
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| Subject: | Re: 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@aeroelectric.com writes:
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<nuckolls.bob@aeroelectric.com>
> 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- )
----------------------------------------
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