[79FT]: Building Things

In [Chickenhouse Charger] Electrical Rebuild:

Wiring Diagram, v1

...proposed


On: Aug 11, 2019
In: [Chickenhouse Charger] Electrical Rebuild
Time logged: 28.5
Tags: 6781G, MA5 Charger, electrical

So this was quite an effort - not because it was a sophisticated design, but rather because it took quite a bit of time to lay out in a reasonable fashion...

Oh, and also, somewhere in between I had a break for Oshkosh and a work trip :).

I decided to post this in a form of design notes, so that I can go around asking people what they think...

The New Wiring Diagram

I have posted it in PDF over here.

Wire length / drop / load calculations are in the Excel spreadhseet over here.

  • The design is based on Figure Z-11 from AeroElectric Connection by Bob Nuckolls, with the following tweaks:
    • I'm using the B&C LR3C Voltage Regulator, so it's wiring has been incorporated
    • I dropped the Endurance and Main Battery busses
    • I have tweaked the starting switches circuit, main buss feeder, and how ammeter is hooked up - see below for discussion
  • The diagram is laid out to generally clump the components together as they would be on the airplane. It initially might seem convoluted - but it has a certain flow to it matching the locations of components. Start in bottom right corner for battery/starter/alternator circuitry and go counter clockwise - this will effectively take you "thru the airplane" as the components will be laid out; roughly

Review Items and Commentary on Specifics

Starter Circuitry

My current take on my Starter and Mags circuitry is this:

Starting and Mags Circuit

Starting and Mags Circuit

This is a deviation from Z-11, with both switches having to be in the momentary up position for starter to engage. I like this better for two reasons:

  • It makes the act of starting the motor more explicit
  • It returns back to correct "running" position automatically

I need to test the ergonomics of pressing up a couple switches together. If I don't like it, another alternative would be to replace the "Right Mag" switch circuitry from -5 to -1: making the top position on it non-momentary (as noted on the diagram). This will reduce the "user-friendliness" but will still keep the explicitness, especially with my using pull-to-unlock switches from Honeywell.

Main Power Distribution

The Charging and Buss circuitry excerpt below:

Power Distribution

Power Distribution

Note that:

Shunt is set up to be in the "battery" lead. I like "battery lead" style ammeters, showing charge current on the 12-o-clock-plus segment, and discharge current on the 12-o-clock-minus segment.

Note that the buss feeder wire is protected by a slow-burn 35A current limiter. In Z-11, that wire is not protected at all. My reasoning for this decision is that this wire is relatively long on my plane (around 4 feet), since fuse block is near the rear cockpit. I wanted to protect it.

One area of concern here is that in the event of alternator short, the Ammeter Shunt will be a part of the alternator circuit that will see a lot of current while the 40A slow burn opens up. My gutfeel says it should be able to handle it, but I am not sure. At any rate, figure Z-11 has the same setup with shunt on the alternator's B-Lead.

Voltage Regulator Sense Wire

LR3C Voltage Regulator needs a separate "voltage sense" wire that one would normally connect to the main buss. Since the regulator in my case is closer to the firewall than to the buss (fuse) block, I am connecting it to the main battery circuitry (jumper wire between Starter and Master contactors). This is somewhat a shorter run and seems that it will be more logical to measure as close to the battery as possible (especially since I'm saving on wire lengths this way). Seems sensible to me.

The sense wire will be 20 AWG, about 3' long, and connected via 24 AWG fuselink.

Voltage Regulator Field Supply Circuit

The circuit looks like this:

Field Supply Circuit

Field Supply Circuit

I copied the AeroElectric's figure Z-11 wire gauges here. In Z-11, everything upstream of Breaker is 18 AWG, and everything downstream is 20 AWG, but it's not explained why.

Is this driven by a requirement to ensure that fuselink survives the short in the circuit in case of crowbaring, and the breaker pops first, w/o endangering the fuselink much (18 AWG allows for 22 AWG fuselink instead of 24 AWG)?

Components Location and Main Connector

Here's a relative diagram of components location, that is necessary for explaining what Main Connector is. Click it for larger version.

Key component locations

Key component locations

Note that logically, the way one would wire this airplane would be to pre-wire switches and other items that go into the pilot's (back) instrument panel with long pigtails, then install the switches, and tie down wiring behind the panel. Then, the pigtails can be connected to fuse block and loads.

Some of the load wires already exist (lighting for example), and they will have to be spliced to wires coming from switches.

I have decided instead to locate a kind of "Main Connector" right there near the Fuse Block. A wire comes off of the Fuse Block, goes to the switch on the panel, then switched power is returned to the "Main Connector". Load is on the other side of Main Connector.

This serves a couple purposes:

  • Create a logical "access point" into the main wire bundle, for reading labels, tracing wires later, and such
  • Simplify installation process
  • Connect to existing load wires that are not being replaced

For now, I am thinking about using Molex 0.093 pins in two housings (I have 13 circuits total to connect via this thing, and want to have room for further expansion). I would love suggestions here. One of the requirements is that it should be easily workable with a multimeter for tracing / testing purposes (I technically could've used D-Sub here , but am not due to this precise reason).

Separate Switch for Turn and Bank

Yes, it's weird to have that. The original electrical had it. I guess, the logic was to be able to shed half an amp of unnecessary load in the event of alternator failure, or it was just done for no good reason.

I'm keeping it :).

Front Panel Tach

It's a Westach gauge that feeds off of a magneto P-Lead. No separate power going to it.

Westach asks for a 1/4 A inline fuse. But why? Seems unnecessary (we don't need to fuse P-Leads).

Wire going to this tach in my opinion need to be shielded P-Lead wire. Not sure if I'm correct here.

I need to tie into one of the P-Leads. I have three options:

At magneto: I will effectively have two P-Leads coming off of one of them. I have Bendix mags, and connectors on those might make the whole hookup look ugly. Adds extra wire.

At mag switch in the rear panel: just adds extra ~4 feet of wire for no reason.

Y-Split the P-lead as it goes along the fuselage: this seems the most optimal wire-management wise, but I am not sure if splicing into a P-lead is kosher. I don't see any good reasons why that would be bad, but I don't know everything. This will likely be a soldered splice unless I find or someone suggests something better. This is my solution of choice at the moment.

Panel Lighting

I am on the fence on this one. On one hand, I can add a nice LED strip light and dimmer to light the panel up.

On the other hand, this is extra weight, and "this is a biplane! you won't fly it at night!" vs. "well what if you find yourself out late" keeps nagging me. Note: I do not have a landing light (though in a biplane... that's somewhat a non-necessity ;) ).

I am leaning towards doing it, because doing it now will be easy, and I will have the option to see my gauges at night, even if that Dark and Stormy Night will be a result of bad planning rather than an intentional thing.

10 AWG Feeder for Radios

Radio stack was wired via the "Radio Master" switch prior. I was initially going to run separate power feeds to each of the things in the radio stack, but to get to it, I'll need to pull the wings off (yeah...). It's in between pilot's legs attached to the bottom of the cockpit.

So, the feeder is staying. The stack has been wired by previous owner recently, and isn't wired badly - with individual fuses for each radio, and a 10 AWG feeder to it and ground "return" from it.

I'm just putting this "hose" on a 30A fuse, which is more than enough to protect the wire and support all the loads from that stack.

Strobe and Nav on the Same Circuit

I am replacing (TailNav, WingNav) + (old heavy strobe on belly) with SkyBeacon and SkySensor on wingtips and nav/strobe on the tail, but I don't have enough wiring in the fuselage and wings to have a separate circuit for strobes. I do not plan to fly IFR (biplane!) so "strobes in the clouds" is not really an issue. When I will have the rag off the airplane, I will add a separate switching circuit for just the strobes.


First, listen to the question the student asked, then listen to the question he didn't ask and then figure out the question he really meant to ask.


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In [Chickenhouse Charger] Electrical Rebuild:

Electrical Disassembly

...fun with wires


On: Jul 01, 2019
In: [Chickenhouse Charger] Electrical Rebuild
Time logged: 13.1
Tags: 6781G, MA5 Charger, electrical, soldering

Well, all the electrical on the Charger is disassembled now. I logged about 24 hours doing it.

Firewall wire harness, looking into the side conduit

Firewall wire harness, looking into the side conduit

I have started with wires on the terminal block and in the side channel, and was moving back and forth between various locations - get bored in one, move on to the next.

The disassembly has begun!

The disassembly has begun!

In the side conduit, going on the right side of the plane to the back cockpit, I was slowly removing the wires, and the oil and fuel pressure lines.

Had to be careful to mark the wires I wanted to keep - all the wires going to the lights, and some instruments in the front and back.

Wire by wire...

Wire by wire...

I would cut them off, and pull them out one by one.

Behind the panel is a rat's nest!

Behind the panel is a rat's nest!

I pulled the mechanical tach and it's cable, and the oil temp and pressure and fuel pressure gauge.

By the way, the oil temp gauge was unpowered! And still ran on a thermocouple - but it's huge, to generate enough power to move the needle.

Old school!

Old school!

Heck, I'm keeping it as my IHT Gauge!!! (Internal Hangar Temperature, that is). It just looks too cool.

Eventually, all the wires were gone from there, aside from the ones I'm keeping; and the ones I'm keeping got temporarily marked.

All done!

All done!

By the way, I found a burnt wire! Was one of the unfused wires going to the voltage regulator.

Burnt wire - can you see it?

Burnt wire - can you see it?

I cut off the burnt chunk.

Front

Front

Back

Back

See those little "boil bubbles" on the back side? Insulation was super brittle, and just a minor twist cracked it open.

Cracked

Cracked

Meanwhile, behind the panel were a couple of soldered things - with wires unsupported. One of them was the master switch, the other one was this weird resistor in the voltage regulator circuit where the low voltage alarm light was supposed to be.. go figure.

But look at the solder joints:

Master Switch

Master Switch

Resistor

Resistor

Notice, they were not done very carefully (especially the ones on the Master Switch). Flux was not cleaned. But! The joints look, and are, solid. They are almost 40 years old.

I think I am officially now in the "no soldering on airplanes is an old wife's tale" camp.

At some point, I decided to take a break, and try on the new Voltage Regulator I'm planning on installing.

....it's not up to scale, and I did not have the time to paint it...

....it's not up to scale, and I did not have the time to paint it...

FWF location

FWF location

Side Conduit location

Side Conduit location

I'm thinking I'm gonna mount it in that conduit on the side. It'll stay cooler, and generally be tidier. I'll use the space occupied by the old voltage regulator for my current limiters and the ammeter shunt, though still need to think a bit more about placement. Maybe those will go somewhere else, too.

By the way, the old voltage regulator in all it's glory:

A Mechanical Switching Voltage Regulator

A Mechanical Switching Voltage Regulator

I also completely removed the strobe - I'll be replacing nav lights with SkyBeacon/SkySensor; which will cover my blinking needs.

Wanna see a couple old electrolytic caps? The strobe power supply still worked, by the way!

The Strobe power supply and bulb

The Strobe power supply and bulb

I have disassembled the charging and starting circuits completely, too. Since I'm redoing everything anyway, adding better wires, and new terminals would not add too much expense, and be good for the system. I also want to modify how battery is grounded.

Found this next to the Master Contactor

Accidental welding on firewall

Accidental welding on firewall

Do you see it? Two spots, above the screw? Someone didn't disconnect the cable when working on her! :). (And, no, that wasn't me)

And finally, here's how almost the entirety of electrical system looks like.

Most of the electrical of a biplane

Most of the electrical of a biplane

Some swithces, some fuses, some wire, and that's it!


Flying is not Nintendo. You don't push a button and start over.


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In [Chickenhouse Charger] Electrical Rebuild:

Wire Markings, Fuselinks, Load Measurements, and Turn-and-Slip

tested fuselinks, measured loads, removed and diagnosed turn-and-slip indicator


On: Jun 18, 2019
In: [Chickenhouse Charger] Electrical Rebuild
Time logged: 6.5
Tags: 6781G, MA5 Charger, electrical, experiments, research, instruments, soldering

Finally, doing some actual work on the airplane, and having fun! And I decided to start logging time.. because, why not!

Wire Marking

I like marked wires. I used to be a networking guy, and I was very meticulous about marking every single wire in my cabinets, so that I knew exactly what was plugged in where.

It took a bit of upfront time, but saved a bunch of it later on.

So naturally, I was planning to do the same on the Charger, and, more importantly, make it look professional.

Thanks to living in this day and age, that is simple. No, I'm not gonna pay someone to laser etch my wires - that's a cop out :). It's like paying someone to paint your plane.

Instead, I have researched and found a perfect label maker - Brady BMP21 (not including a link here because it will probably go dead after some time... just search for it). This thing has 3:1 heatshrink tube cartridges.

The proverbial coupon

The proverbial coupon

Prior to shrinking

Prior to shrinking

Shrunk!

Shrunk!

Load Measurements

Prior to ripping the old wiring out, I wanted to take some real life load measurements with various things turned on, so that I don't get any nasty surprises.

But this plane has no ammeter... damn. I searched around, and found this little doodad:

Hall Effect ammeter

Hall Effect ammeter

Very nice. It basically measures current on the wire passing thru this big white ring using Hall effect. Very cool! No need to splice into the battery leads and install a temp shunt.

So, I rigged it up and took some numbers.

Rigged up

Rigged up

  • Master On: 1.5 amps
    • Includes: Master Solenoid, and a couple of gauges
  • Fuel Pump: 0.2 amps
  • "Radios" switch (turns on engine monitor, and power to radios: turning backlighting on them): 0.8 amps
  • I-Com Radio, Transmit: 2.6 amps
  • Intercom: 0.1 amps
  • Transponder: 1.1 amps
  • Smoke Oil pump: 2.2 - 2.6 amps (high on startup)

So couple interesting things here. I think the x-der number is too low, but it wasn't being interrogated, and I can't make it be interrogated without flying the plane or using a transponder tester which I don't have. Also, Master On is too high seemingly... Will need to double check later and isolate things (master solenoid, hobbs, voltmeter, voltage regulator, fuel gauge) if I care enough - I don't think I do. Also, fuel pump is too low seemingly. Need to double-check the spec.

And then, I could not turn on the Turn-Slip Indicator...

Turn-Slip Indicator

Sad, sad indicator... see, it's long. And it's wire connector is sticking out. And it's right behind the front seat's headrest, and there's just not enough room for it, and the connector.

So whomever put it in... did this:

Sad, sad wiring

Sad, sad wiring

It's hard to see; but basically, those wires are bent "down" at a very sharp 90 degrees angle. Notice how he just used pins without the actual connector. The distance between them is tiny! I am surprised they haven't shorted over all these years. I really am.

Initially, I thought the gauge didn't turn on because that wiring was all bust up, so to test it, I decided to pull it out.

On the bench

On the bench

I cut off the wires with those pins on them to hook it up to my testing battery... hmm.. but I needed some leads! Well, I was gonna make a bunch of various test leads - so this is as good a time as any! Man, I love soldering...

I long decided to make a bunch of leads with "passthru" banana plugs on one end, and something (a crocodile clamp, a battery clamp, a ring terminal) on the other. This way, I could mix and match, and plug them into my multimeter; daisy chain, and have multiples depending on what and how I needed to hook up. I had all the bits (clamps, crocodiles, banana plugs), and even got a roll of very nice super flexible silicone coated probe wire.

Components, and the battery clamp crimped on

Components, and the battery clamp crimped on

Release the Soldering Kraken!

Release the Soldering Kraken!

The banana plug pin

The banana plug pin

All hooked up

All hooked up

The gyro in the gauge didn't start. Damn.

But I had resistance between + and -. And I had voltage! Hmmm..

Second time I hooked it up, I saw a bit of a spark when I put the positive clamp to the battery, and heard something.

I spun the gyro with my finger.... it spun up!

Well, well. So that gyro "froze" in a bit... Yep, it was hard to turn over with a finger - no doubt a small motor in there had a hard time!

I probably "cleared it up" a bit when turning it over with my fingers - but that won't last long... damn.

Are we looking at the overhaul for this thing too now? Sigh.... Maybe I can find parts to do that myself, but not so sure about that.... It's not common for owners to overhaul their instruments - they're precision clockwork, after all...

Oh well.

And I will have to figure out how to solve that wiring problem with no space to hook up the right type connector. I am thinking along the lines of maybe routing a wire from inside of the gauge down thru a hole I'd drill, a grommet it it, and covering the whole business with with some sealant or something, so that the dust doesn't get in. we'll see. Need to ponder this a bit more.

PS

... and here's what happens to airplanes that aren't flown enough...

Dinner for someone...

Dinner for someone...


It at first you don't succeed, well, so much for skydiving.


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In [Chickenhouse Charger] Electrical Rebuild:

The Flying Fire Hazard

...sparks galore!


On: May 16, 2019
In: [Chickenhouse Charger] Electrical Rebuild
Tags: 6781G, MA5 Charger, Annual, electrical

This thing nagged me for a while. The Charger did not have the Field breaker. For that matter, it didn't have the Alternator master breaker, either.

It had this weird "main buss" breaker for 60 amps, but that didn't look like the Alternator breaker to me.

So in between dealing with other things after having decided to put her thru Annual in 2019 a bit early, I was running around with my multimeter, tracing wires.

Initially, I quickly discovered that some lines were definitely not fused; like Battery -> Main Buss line, and thought I'd put inline fuses into them, and be done.

She has an old charging system; a mechanical switching voltage regulator, and a Delco Remy alternator seemingly from a tractor:

The old Delco-Remy

The old Delco-Remy

Voltage regulator didn't make sense. It had 4 wires (should be 2: supply and field output, or 3: supply, sense, and field output).

Alternator didn't make sense. Instead of 1 wire for Field input, it had two wires.

Additionally, Battery Contactor didn't make sense. One terminal had a wire going to it. The other was grounded....

Interlude

Battery Contactor is an interesting point here. Normally, one terminal is connected to the "always hot" side of it (basically, directly to the battery) and the other goes to the Master Switch. Master Switch turns the Battery Contactor on by grounding that wire, providing the negative side to the circuit. It's a safety thing. If that wire breaks, it'll either turn the electrical off (open circuit), or it will keep it turned on (short to ground). That's it.

But, one of the terminals on the Battery Contactor was grounded... that means, that the other terminal (the wire coming from the Master Switch) must provide positive side??? Huh? But where does it get it's power from?

Tracing

So to tracing we went. I spend maybe 10 hours trying to find diagrams and understand that alternator and voltage regulator hookups.

And me tracing it spelled my doom.

The Diagram

Now, I didn't trace the rest of it. Just the main distribution system. That was enough.

Shall we?

The current  main power system of the Charger

The current main power system of the Charger

Yep, the diagram is missing the main power buss. It's dangling off of the same spot where everything else that's interesting is - the Battery Contactor (marked MA RELAY) <-> Starter Contactor (marked STARTER REL) link.

So let's see what we have here.

  • Lots of unfused wires. Do you see a single fuse here? Nope. That's because there aren't any. All the fuses are further downstream, off of the main buss.
  • Voltage Regulator has this extra wire running to / from cockpit that isn't really necessary and could've been kept on the hot side of the firewall (terminal 4 wire)
  • Alternator field broken at output (F->ALT) rather than at input (battery -> terminal 3)
  • And the best part? Always hot wire that you can't turn off between the battery and the Master Switch to turn the Master Solenoid on.

That last bit bugged me. I couldn't find the damn thing. Even before actually tracing it, I knew that if the Master Solenoid is switched on the "hot" side, it needs to get the power from somewhere, and that only could be battery. But I didn't see any wires on the always hot side of the Master Solenoid. Only when I traced it, I actually traced the physical wire to where it goes, and then found it. It was so tucked behind the battery -> Master Solenoid wire that it was invisible:

This little !@#!S@#....

This little !@#!S@#....

Oh; and by the way, the Master Switch is the only switch that's soldered in, and w/o any good insulation around the terminals, and over-stripped wires. So that's just waiting to short, and the magic smoke that'll be let out behind the panel when that shorts can't be stopped (always hot wire, remember?)

Master Switch

Master Switch

The Wires

So I kinda went backwards here; but I thought it'd be easier to see the diagram first.

Let's see.

Most of connections are made on this very nicely marked terminal block:

The terminal block

The terminal block

All the switched power comes out there, and every wire is marked. This actually helped a lot in tracing. This block is on the side of the plane, right next to the front hole's backrest.

You know what threw me off the most with that damned always hot wire (I ended up tracing it physically)? It's how it's hooked up.

Yep, it is hooked up to that terminal block. To the terminal... that is marked.. (drumroll).... "Master Switch".

Wait.. this actually makes sense... But where's the "return" from the switch?

Ah! It's the wire that's marked.... drumroll... "Fuel Gauge"!

So really, let's look at what's going on, shall we? Zoom in the image below, it's annotated.

Untangled

Untangled

So let's see. We've got this bundle of wires, a lot of which are not fused, and one of which is always hot.

The Main Buss wire is the thickest one (10 gauge maybe?) that's not fused between this buss bar and the source (engine compartment).

Oh, did I mention that this buss bar is on the side of the plane near the rear instrument panel (so that 10 gauge run, and the rest of the harness between firewall and the panel is about 30 inches long)?

What else do we see there? Oh! The two little 1/16inch thick aluminum lines carrying.. fuel pressure (and oil pressure).

Shall I say more?

Shall I say that there's a fuel tank in between the front hole (passenger) and the firewall?

That the wires run along between firewall and rear cockpit along that fuel pressure line (to fuel pressure gauge)?

That if one shorts to this very nearby fuel pressure line, it'll burn a hole straight thru it, and then ignite the gas that'll start coming out?

Yep.

Can I fix all of that?

Sure. But rewiring will be much much easier, because I have to touch pretty much everything. Re-running half of individual wires in a bundle is much harder than re-running them all.

So, I made a decision to rewire the plane... Sigh. Looks like I won't be flying for a looooong time.

Oh, and tell you what. Tracing wires on a biplane is dangerous. I ended up twisting my knee and pulling a muscle while trying to get behind the panel so badly that I couldn't walk (or sit) for 2.5 days :(.


Helicopters don’t fly, they just vibrate against the earth and the earth rejects them into the air.



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