Wiring - The Process

I have come to realise that wiring is not as structured as the rest of the build - an aileron has defined steps. Wiring is much more organic! It seems that when i have a device which needs power, i first find a good place to mount it. I then work out a good path for the wires. This is often done in amongst other work, or in little fits-and-spurts. 

So keeping a record of my wiring is going to be a little difficult - but i will do my best to highlight the best bits! 

First up - a word on "The Process"

Wiring is tedious and detail oriented. In order to make sense of it all, i have two tools to assist me. 

The first is KiCAD - software designed to create printed curcuit boards. This has a schematic feature which allows you to make custom components (with custom pinouts), and then wire then up. So every wire is planned in this way, then added to the wiring diagram. The 'wiring diagram' is not one page - it is split up based on where the items are physically located in the aircraft. So wires will run from one page to another using 'Global Labels'. 

This is the 'root' page - with each wiring diagram page laid out roughly as per the physical locations within the aircraft. 

To illustrate this point, i will use something basic - the curcuit to run the taxi lights. We start with the 'CB' page - this is the cicruit breakers. Look for the wire highlighted in pink below:

The pink highlighted wire shown above starts at the 'Main Fuse' block. 

The main fuse block was previously installed on the left sub panel. 

This shows the wire, labelled "TAXI LT PWR SRC" coming out of slow 26 in the 'Main Bus' fuse block. It is 18 AWG and is coloured Yellow. 

Note above there is a 'Global Label' - the Arrow Box labelled "TAXI LT PWR". This allows this wire to transfer across sheets. There is a note that we should follow this wire to the "LSP" page (aka, Left Sub Panel), and in this case to the 'Taxi Lt Sw' - Taxi Light Switch.

Also note there is a little green "D" box on the wire. This translates as "Drawn" and means that this wire has been added into the 'Master Wire Book' spreadsheet. This is a single list of every wire in the aeroplane - and allows me to make sure the wire is sized appropriately, as well as provides me a tool to tally up the wire lengths i will need for ordering. Other wire status codes are "Roughed" - meaning the wire is in place but not finished, or "Pinned" - meaning both ends are where they need to be (in a connector etc). 

The highlighted wire "TAXI LT PWR SRC" is an 18 AWG, Yellow wire which runs from the CB page 'Main Bus' to the LSP (Left Sub Panel), "TAXI" Switch. It will carry a load of 2amps, and has a 5amp fuse which is on the MAIN Bus. 

Following this wire to the "LSP" (Left Sub Panel) page, we see that it goes to 'terminal 2' on the "TAXI" Light swtich. 

From here we can keep tracing the wire - there are 2 output wires for this switch. "L/R TAXI LT PWR" which are 18AWG and Red in color. The left one goes to the "FL" (Fuse Left) page, and the right one goes to the "FR" (Fuse Right) page. 

Following the left wire, we see it travels to the Left hand wing root CPC connector, in pin position 2. 

It then goes to the "WL" (Wing Left) page, and we can see that it travels to the taxi light. 

There are more complicated examples, which include shielded multi core wire, such as this Aileron Trim position sensing wire, which travels from the aileron trim motor to the GEA24 (Engine Information System) box.  

This wire is a 22AWG shielded wire labelled "ATRIM POS", which has a white jacket. The 3 wires inside are wht (white), blus (white with blue stripe), and orgs (white with orange stripe). At the Garmin Box end, the shield is grounded to the connector (the 'S' in the traiangle at the bottom of the shield symbol), while at the trim motor end the shield is trimmed off and left floating (the absence of a triangle on the shield symbol). 

The triangle with the "S" means the shield gets a wire with a solder sleeve, then this is terminated to the backshell of the connector.

The absence of a triangle, means the shield is trimmed flush with the jacket and covered in heat shrink (aka, 'left floating')

As always, the wire is included in the wire book. Note the green "D" symbols - this means this has been drawn up only, but has not been instlled in the aeroplane as yet. It is a 'Data' wire, so carried no apprecaible current. 

So that is a little overview of the process for planning out the wiring. When it comes time to physically run the wire, i use some plastic tube to work out the route and length needed, then cut a piece of wire to fit. I have a setup in the shed now so i can do all this live, using the actual software. 

It gets run along the intended route, and temporatily held in place with rubber cable ties, bread ties, or temporary (orange) cable ties. 

All wire labels shown in these diagrams and the wire book, are the actual wire label text which is applied using heat shrink tubing labels.

Here are some examples of the wiring done so far:

So moving forward, i will complete a blog entry where i do something which is worthwhile sharing with regard to wiring - I will try and show where i mount each box or piece of equipment, but won't show every wire. Don't want to bore everyone to death.