Wiring Overview

This blog cover labelling wires and wiring behind the panel

Overview
Having develop wiring diagrams that use lots and lots of numbers, a method of labelling wires was required.

After reviewing Dog Aviation's method on his RV12 using the Dynamo Rhino 4200 label writer and 6 mm heat shrink to print permanent labels one was found locally at a reduced price and duly purchased.

Labeller with a sample label

As 6 mm is the smallest tube that it accepts, but these seem to work well with a wire down to 20 gauge. 

The numbering system used is in three [3] part taken from each wiring diagram.

The first group - Application or Area

The second group - Schematic drawing number

The third group - Run number

Group 1 - 2 - 3

It is necessary but appears to be flexible enough to meet the requirements at the time of installation.

Wiring behind panel
This is a task that always starts with good intentions, but somehow it gets messed up in the translation, how to achieve your dream installation is still the problem.

The factory recommends constructing a Tee shaped support with one running across the fuselage behind the panel and the other to the firewall. It was decided to start by folding a 150 x 75 x 0.5 mm C channel from 0.020'' 2024-T3 sheet. 

Next two [2] 20 x 30 angles were folded and riveted to the flange on the underside of the C channel, these have four [4] holes to accept 10 mm grommets to allow interconnecting cables to be supported when running through the bottom of the frame.

Center support

RS232 Punch

A series of holes were punched to suit 9 pin RS232 connectors on both sides to accept cables connections from the instruments.

The top of the tee is a 70 wide Z with 20 mm flanges fabricated from 0.020'' 2024-T3 and then installed at both sides. These were fixed to the C channel with M3 screws and rivet nuts then to a fabricated angle adjusted to the fuselage longeron with pop rivets.

Note: These frames would be best done before fitting the panel, but it's a journey of discovery, and it has to do as we go.

It was decided to use three [3] group buses, Essential, Avionics, Panel using 6 or 12-way terminal strips and two [2] unique buses Gear and Fuel. 

Each strip was split into a positive/negative output linked using colour coded insulated bars denoting polarity. The screws provided were long enough, so each one will take two [2] terminals. These three [3] terminals are supplied from three lever-operated circuit breakers in the breaker panel on the starboard side of the pilot's cockpit. 

The gear and fuel buses are supplied directly from the master bus to two [2] separate panels located in the lower group.

The master bus was created using a four [4] terminal strip divided into a positive and negative with two [2] terminal studs. One side was painted red to indicate positive with the only issue being that two studs may be a little tight on quantity, will just suck and see but space is the issue.

Note: The selection of materials and techniques in this area is to try and keep weight under control

Instruments
All the instruments selected had one thing in common, an RS232 plug for connection with most sourced new from UMA. In future, this should allow the removal of the main panel in one piece by disconnecting a series of plugs to improve access for future maintenance. 

All other lights and switches will be equipped with plugs to meet this design requirement as required.

RS232 Plugs

UMA photo

The 9 pin plugs supplied with the UMA instruments require the female pins to be crimped onto the wire and inserted into its correct location in the plug body. It was decided to split the power and signal into two [2] separate cables to create a tidier installation. 

During installation, a couple of the pins were inserted into the incorrect location and required extraction. UMA advised using to use a 1 mm drill bit, add it from the opposite side and with pliers it, push out. 

Holding the drill bit approx. 0.1" from the connector, so when the pin is out just 0.1" and after that just pull it out with fingers.

All other instruments used the more familiar 9 / 15 / 25 pin solder plus with plastic shells to save weight.

Comment
There will never be a perfect method, but this appears to have worked out as well as it could, and errors can be sorted when checking the wiring. 

The details here will be fleshed out in more detail in the following blog.

At the time of this post, the wiring is about 70% complete to the firewall. I will be writing notes on each circuit, but these will be an addition to the existing wiring posts in the form of letters/ images with as installed drawings.