Electrickery

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DonutHole
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Re: Electrickery

#76 Post by DonutHole » Tue Feb 09, 2016 8:26 pm

NeverBlue wrote:
By omission it states that the GPS install isn't a major modification.

What's "it"?

You need to read the TCCA policy letter re gps installation approval.

What the FAA considers minor is not necessarily what TCCA does......
What's "it" ?

Holy shit. Whatever man, you're right, the rest of us are wrong. You need it more than we do.
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Re: Electrickery

#77 Post by PilotDAR » Tue Feb 09, 2016 8:44 pm

AC500-002 offers a definition:
Electromagnetic Interference (EMI) means the phenomenon occurring when electromagnetic energy present in the intended operational environment interacts with the electrical or electronic equipment causing unacceptable or undesirable responses, malfunctions, interruptions, or degradations in its performance.
'Doesn't mention RF. I entirely agree that RF interference would be classified as "EMI", but obviously TC considers "EMI" to be more broad than simply RF. I'm a little surprised that the AC does not also state "compass" as a victim, but practically a compass must be considered a possible EMI victim, because TC requires an EMI test to include a check for posible affects upon the compass - and I have found them during EMI tests.

If you were to present a mod to TC for an EMI test for design compliance, that test would be incomplete without a compass swing too.
EMI is RF..
Not according to TC's AC, though the reverse is true.
A magnetic field is not an RF field.
Agreed, though it can still be a source of "EMI" (which could result in a failed EMI test.
An electromagnet does not use induction.
Agreed, but it can still be a source of EMI!
Well YOU are totally wrong.
'You know... I have never been told that before! TC has accepted my EMI test plans, delegated me to witness EMI testing, make a finding of compliance for 2X.1301 and 1309, and issue an STC, so they don't think I'm wrong. My clients keep hiring me back, so they don't think I'm wrong... Yet one grumpy, anonymous guy on the internet, whom my peers don't seem to respect, wants me to think I'm wrong? I am unconcerned....
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Re: Electrickery

#78 Post by DonutHole » Tue Feb 09, 2016 9:16 pm

It's like he has half a clue.

That policy letter he was referencing says in pretty explicit terms that the type of GPS mod we are talking about is a minor modification.

Props for knowing it existed.
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Re: Electrickery

#79 Post by NeverBlue » Tue Feb 09, 2016 9:36 pm

It does not say that donuthole...not at all.

Read the Required Data section at the end.


HOLY COW DAR! You're confused.

EMI is RF..............

And electromagnetic wave is a radio wave...they are one in the same.
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Re: Electrickery

#80 Post by NeverBlue » Tue Feb 09, 2016 10:02 pm

And please....

A magnetic field and an EM field are not the same thing at all....and they don't act the same at all.

EMI moves...propagates...

A magnetic field doesn't move...it exists...the lines of flux move but only between magnetic poles of the field.....they do not propagate.

A magnetic field will induce electricity in another conductor but only if the field expands and collapses continually (AC frequency)

That's why we hear inverters all the time in headsets....
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Re: Electrickery

#81 Post by DonutHole » Tue Feb 09, 2016 10:08 pm

read the damn thing.

you have specified data and accepted data coming out the ass.
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Re: Electrickery

#82 Post by NeverBlue » Tue Feb 09, 2016 10:30 pm

4.8 Data Requirements

Documentation and approval requirements for GPS equipment are as identified in section 4.1 of this document.

The GPS installation shall be performed in accordance with either approved or specified data.
...better yet you read it...
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Re: Electrickery

#83 Post by DonutHole » Tue Feb 09, 2016 10:47 pm

better yet... *you* read it.

I read it and geez, wouldn't you know. specified data
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Re: Electrickery

#84 Post by PilotDAR » Wed Feb 10, 2016 5:03 am

In the global perspective, in Canada, we are very lucky to have the freedom to fly, own aircraft, and further, to modify them, compared to most other nations one earth. I won't go so far as to say that we can take flying as a right here, but we are a heck of a lot closer to that than most other nations! We enjoy this, because we have an aviation industry which is (for the most part) mature. Transport Canada, who itself has excellent world wide respect, demonstrates confidence in its industry, and provides paths to accomplish what the industry itself knows it needs - modified aircraft, for the purpose of this discussion. This path is an awesome economic benefit to operators, if followed well.

The path which TC places before industry to accomplish objectives, is regulated and usually very informative (lots of references, and guidance material). Sure, that path has requirements, but in nearly all cases, meeting those requirements is just good safety, and good business. Transport Canada depends upon we in industry to work as a team to execute the most safe aviation (in this case, modifications) we know to do, for its own sake. TC certainly does not have the resources to check everything, and if we place them in that position, we'll be mired to a standstill.

So we, industry, for our own sake, have to act as a cohesive team all the time. This goes right down to mods on aircraft. We all have a role, right down to the pilots I instruct, as to what they are going to fly for me during an EMI test flight. We can all be a team, and get the job done, safely, and to the satisfaction of the possible oversight of TC, or we can fail to do that, and competence is questioned, not to mention retesting and economic disadvantage to the aircraft operator.

So, when work with a team to accomplish an approval, we will work together, harmoniously toward a common goal, or I will pause the process to review the objectives. We will not work toward a goal, which is different from, or incomplete, in consideration of the TC requirements (unless we're aiming for restricted category, or an exemption - a whole different discussion). Sometimes a team member brings attention to something else to be considered, and that will be discussed. If the team cannot reconcile it them, it will go back to TC for consideration = delay and cost (so we do that judiciously)

So, for me, when a member of the team apparently view their own importance, or sense of being right during a project as to over rule the interests (or performance expectations) of the other team members during an approval process, that really slows things down = cost the aircraft owner money. Was it worth it? Rarely.

When am invited to a project to witness an EMI test, I come with the TC requirements for demonstration of compliance pretty well established. I did not create those requirements, they are a tool provided to me by TC to get the job done for the client. If another person involved with that project objects to my using that certification tool as I have been instructed by TC, and we do not come to agreement, one of us will be taking a step back. I am aware that aircraft owners have asked a person, who could not bring themselves to agree with the program, to step back.

S Neverblue, as I said much earlier, you work in your world, and I'll work in mine, After a hundred or so witnessed EMI test, on behalf of TC, I know what they expect of me, and that's what I'll be doing, whether you agree or not. If you are signing out modified aircraft with authority, continue along doing your job. In the mean time, I'll continue doing mine, as specified by TC, using "data" correctly, and doing thorough EMI testing, whether you like it or not!
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Re: Electrickery

#85 Post by NeverBlue » Wed Feb 10, 2016 6:08 am

I read it and geez, wouldn't you know. specified data
no...it clearly says "approved or specified data"...and the specified data must be specific if you read.

Which...if you look at the requirements for a major mod in Canada...not the US...are EXACTLY THE SAME!

Approved or Specified Data.

I may be wrong...but show me a minor mod in Canada that requires approved or specified data.
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Re: Electrickery

#86 Post by NeverBlue » Wed Feb 10, 2016 6:25 am

If you are signing out modified aircraft with authority, continue along doing your job. In the mean time, I'll continue doing mine, as specified by TC, using "data" correctly, and doing thorough EMI testing, whether you like it or not!
I don't know what you are talking about...I've never commented on your doing those tests. They are absolutely essential. I've never said they weren't.
I never said that you didn't know what you were doing during those tests...I'm sure you follow very specific instructions with very sophisticated test equipment right??????

I said you don't know what EMI is...or how it gets into the systems...that's all

Here you are arguing for the EMI test and I would be willing to bet that Hoptwoit never even thought of doing one for his installation.
So what are we talking about here?

You claim to be a DAR...You can't tell me whether the feed-line movement is a major mod or not...but you seem to be stuck on your point that EMI testing is a very important test in a minor mod or any mod for that matter...that doesn't require approved data...


I'd also be willing to bet that the Hoptwoit installation probably included a fuse rather than a breaker...the fuse is probably installed in a commercial grade in-line fuse holder that has PVC insulated leads and a flammable plastic housing for the glass fuse...totally against AC43.13....and the fuse is probably not very easily accessible by the pilot during flight for replacement...also against AC 43.13.

...just guessing of course...
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Re: Electrickery

#87 Post by CID » Wed Feb 10, 2016 8:58 am

Neverblue, I'm concerned that you're coming across as an authority on the subject matter you're commenting on but many of your comments are incorrect. I hope the less experienced in the group are checking these things out for themselves.

It's odd that you accuse PilotDAR of not being able to determine if a mod is major or not. Although DARs are a good source to help make the assessment, the decision remains in the maintenance realm. That's why all of regulations regarding this decision is in 571. DARs work mainly in the realm of 505 and 521 and of course the deign standards in 523/525/527/529/551. A DAR can certainly offer an opinion but the decision is the AME's.

With respect to RFI and EMI, the guidance I pointed out does the job of defining EMI. RFI is a type of EMI that includes frequencies in the radio frequency bandwidth which is generally accepted to be in the 3KHz to 300GHz band. Electromagnetic waves in this region of the spectrum can more easily propagate where as lower frequencies tend to be induced or conducted as a source of interference. So it's generally accepted that RFI is a type of EMI.

You are VERY wrong in how you characterize DC feeders. DC generators and alternators are very noisy devices electrically speaking. For starters, Regulation uses a abrupt switching method which basically applies and removes fixed voltages at various rates. Generator field wires are incredibly noisy because of this. Add brush noise and the constantly changing current and you have an electromagnetic nightmare. There are no pure DC voltages on the generator/alternator distribution buses on ANY running airplane. The current is constantly changing at various frequencies and amplitudes depending on the loads applied. If you don't believe me, use a capacitor to couple a headset to a DC generator line and have a listen. This is why Cessnas have that big capacitor bolted to the alternator.
That's why we hear inverters all the time in headsets....
That's interesting. Inverters in the headset is almost always due to poor shielding techniques in audio wires. Audio systems should always have a single point ground and the shields should not be grounded at both ends. I'm sure that your mind is going to explode now as I explain that continuously changing currents flow in wires that are connected to ground at both ends. The farther the connections, the larger the current. If the wire is a shield, the current is carries will be induced into the wire it's trying to shield. Furthermore, it's not the radiated AC that doing it, it's the current in the return path which is basically the aluminum fuselage.

This is a very common mistake made by "experienced avionics techs".

Face it Neverblue, you have a LOT of studying to do before you claim to be an authority on EMI and I'm really doubting your basic avionics skills if you come up with all this misinformed rubbish.

For (another) example. Electromagnetic waves are very real. Did you know that light is made of electromagnetic waves? And I'm pretty sure an electromagnet won't work with light. Electromagnetic waves have both a magnetic and electrical field. The fields are on planes separated by 90 degrees which is why ADF antennas are in a different plane than a VHF COM. Of course VHF NAV antenna are on their side but only because the signal is polarized differently. Pure DC currents have no electric field and are therefore purely magnetic and the field is constant or at least proportional to the current.

So yes, generator feeds have very large electromagnetic fields around them.
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Re: Electrickery

#88 Post by Posthumane » Wed Feb 10, 2016 10:40 am

Neverblue, I'm not sure where you got the idea that EMI only referes to RF interference. RFI is a subset of of EMI when it occurs within the radio frequency range of the spectrum, but electromagnetic interference can occur anywhere within the EM spectrum. It is generally defined as any disturbance that occurs as a result of electromagnetic induction, electrostatic/magnetostatic coupling, conduction, etc. IEEE identifies some coupling mechanisms that can cause EMI, including:
-Electric field coupling – caused by voltage difference between conductors.
-Magnetic field coupling – caused by current flow in conductors.
-Conductive coupling – noise coupled between components through interconnecting wires, e.g. through power supply and ground wires.
-Common impedance coupling – caused two or more currents flowing in the same impedance, e.g. in power supply and ground wires.
Static electric and magnetic fields can cause EMI. When you have a voltage difference between two conductive surfaces you end up with capacitance, which can happen throughout the spectrum (including DC) and cause issues for some electonics. A DC current flowing through a conductor causes a static magnetic field, which can interfere with systems that are sensitive to magnetic fields (PilotDAR's example of a compass is a good one, but there are others). Ground loops are an example of conductive coupling, which is considered a source of EMI.

Anyway, others have already pointed out some of the errors of your assumptions. You've claimed they don't know what they're talking about regarind EMI. Are you going to claim that IEEE also has no clue about electromagnetics, EMI, EMC, etc.?
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Re: Electrickery

#89 Post by DonutHole » Wed Feb 10, 2016 11:32 am

NeverBlue wrote:
I read it and geez, wouldn't you know. specified data
no...it clearly says "approved or specified data"...and the specified data must be specific if you read.

Which...if you look at the requirements for a major mod in Canada...not the US...are EXACTLY THE SAME!

Approved or Specified Data.

I may be wrong...but show me a minor mod in Canada that requires approved or specified data.
If you read the entire thing it tells you exactly which specified data to use.
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Re: Electrickery

#90 Post by CID » Wed Feb 10, 2016 11:43 am

I may be wrong...but show me a minor mod in Canada that requires approved or specified data.
Technically, in Canada there is no such thing as a "minor" mod. So show me what the definition of a minor mod is. Having said it, your question is nonsensical. It's like saying show me an apple that isn't a fruit.

By definition, a major mod requires approved or specified data. If a mod isn't major, it may use acceptable data but approved or specified data can certainly be used for no other reason (for example) than to prevent rejection of the paperwork when you sell the airplane.
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Re: Electrickery

#91 Post by NeverBlue » Wed Feb 10, 2016 3:00 pm

It's like talking to a wall...

CID... :lol: I know what RF is... :lol: ...I've been trying to tell you all thread.... :lol:

Posthumane...I know what coupling is..... :lol: ....standard practices, deal with coupling problems.....any avionics tech knows that and how to deal with it.


"There are no pure DC voltages on the generator/alternator distribution buses on ANY running airplane."

WRONG!

"Pure DC currents have no electric field and are therefore purely magnetic and the field is constant or at least proportional to the current.

So yes, generator feeds have very large electromagnetic fields around them."

...and I contradict myself?

If the alternator is working correctly, the rectifier/filter is working correctly and you have a good battery...it's pure DC.
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Re: Electrickery

#92 Post by NeverBlue » Wed Feb 10, 2016 3:11 pm

Technically, in Canada there is no such thing as a "minor" mod
Whatever.....that's what you've picked out of all this?
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Re: Electrickery

#93 Post by CID » Wed Feb 10, 2016 3:25 pm

Dear avionics manufacturers. You've all been wasting your time designing complex power supplies with filtering. The DC buses on aircraft are "pure". Neverblue figured it out! Generators and alternators are perfect little constant current supplies no matter how the load changes. No ripple, no brush noise and regulator induced buzz. Just pure clean constant current power.

No besides the obvious sarcasm above...there is no contradiction. Pure DC currents have no electrical field. DC generators in aircraft regardless if they are generators or alternators are not providing "pure" constant current DC so the feed cables have electromagnetic fields that have the potential to induce noise in wiring.
I know what RF is...
That really isn't apparent by what you write.
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Re: Electrickery

#94 Post by NeverBlue » Wed Feb 10, 2016 3:37 pm

You nailed it...the generator and alternator and avionics manufacturers deal with the noisy DC.

I never ever said that DC wasn't noisy...just not in every live aircraft as you put it...and it's still DC.

And you need to explain how every current carrying wire in an aircraft is all of a sudden a radio transmitter.
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Re: Electrickery

#95 Post by photofly » Wed Feb 10, 2016 3:45 pm

If you've invented a wire that conducts but doesn't radiate, I'd keep quiet about it until the patent application is through, ol' chap. And I don't think you're going to have to worry about installing GPS units for long, afterwards.
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Re: Electrickery

#96 Post by Posthumane » Wed Feb 10, 2016 4:16 pm

Neverblue, you may know what coupling is, but just a few posts prior you said that EMI is strictly caused by RF. That is demonstrably not true. There is a reason that EMI/EMC standards specify multiple interference modes to be tested, do to well below radio frequencies. While I don't work in aviation, most of the EMC work I've done is in line with MIL-STD-461 which specifies testing down to 30 Hz. I can assure you that the interference mode in that range is not RF propagation. Some other standards specify testing down to static fields, and some equipment is sensitive to those fields. If every avionics tech knew how to eliminate all coupling methods then there would be no need for all the modelling and testing currently done in product development - the engineers would simply ask them how to do it. You would be rich.

By the way, what do you define as "noisy" DC? Most engineers and technicians would define it as a signal which should, in theory, be DC but in reality has some AC components in it as well (i.e. ripple). An adequately clean DC supply produces power with the AC components sufficiently small that you generally don't have to worry about them, but that doesn't mean they don't exist. Even a purely DC carrying conductor could induce currents in adjacent conducting objects in a non-static environment. Physical movement of various parts is a consideration in EMC testing and design as well.
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Re: Electrickery

#97 Post by NeverBlue » Wed Feb 10, 2016 4:40 pm

I'm sorry but a single conductor carrying DC current ( noisy or not) does not radiate EM waves.

Please patent that if you can...
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Re: Electrickery

#98 Post by NeverBlue » Wed Feb 10, 2016 4:49 pm

Noisy DC does not have AC components to it.

DC is either positive or negative...it DOES NOT ALTERNATE.
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Re: Electrickery

#99 Post by NotDirty! » Wed Feb 10, 2016 5:14 pm

NeverBlue wrote:I'm sorry but a single conductor carrying DC current ( noisy or not) does not radiate EM waves.

Please patent that if you can...
Some light reading for you.
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Re: Electrickery

#100 Post by Posthumane » Wed Feb 10, 2016 6:12 pm

NeverBlue wrote:Noisy DC does not have AC components to it.

DC is either positive or negative...it DOES NOT ALTERNATE.
Noise on a DC line is by definition anything on that line that is not DC. It can be random (as in the case of thermal or atmospheric noise) or it can be periodic (as is usually seen when AC is converted to DC, as the conversion is never perfect). Both can be represented by a sum of AC signals at various amplitudes and frequencies (see https://en.wikipedia.org/wiki/Fourier_analysis for some more light reading). These AC signals are usually unintentional and can be reduced by having and AC coupling to the ground reference (which is what DC filters do), but they can sometimes be useful (such as in DC powerline communication, or for detecting the RPM of your engine from the cigarette lighter plug).

You did have one thing right though. This is very much like talking to a wall.
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