Wiring Panel

This blog covers the wiring behind the panel

Overview
The work to convert all the wiring schematics into the physical world has now to be undertaken. Without detailed design work and drawings a lot has to be left to the imagination, while living in the hope of finishing with a product that appears to have a small amount of intelligence applied.

The primary goals set for the installation : -

1 - The panel must be removable by disconnecting plugs. 

2 - Weight to be kept to a minimum.

3 - Wiring to be in a orderly  and logical 

The channel was secured at the firewall and the lower panel using four [4] M3 rivet nuts at both ends. The lower rail that the panel is mounted on had a series of holes drilled to align with the front mounting screws of the channel.

The side Z panels for mounting other hardware were now installed and secured with self tapping screws. These should have been installed much earlier as access for the fixings was a real issue requiring the removal of the mounting angles for the panel cover.

T panel installed - undercarriage terminal strips on left with
first of the AMP plugs installed for the intercom. Additional plugs will be
installed to connect to the breaker / switch panel 

RS 232 connectors mounted in channel for tacho,manifold pressures and AOA [LHS]
Cables for engine instruments shown on RHS connected to power bus

Note: The mounting panels are screwed only to allow removal / replacement in the event of a major change at some future date. The T mounting was necessary to provide adequate mounting points for the electrical hardware

Component assembly center support
Master terminal strip would have been better at six studs
with the shunt relocated

RS232 Connections
While the UMA instruments selected had a RS232 plug, a number of other instruments did not namely the AOA indicator, trim indicators and assorted lights.

Punch openings and RS232 connectors
Note the flattening of the ferals after installation

As supplied - LHS

Center support punched to allow the mounting of the RS232 connector with incorporated terminal strip. Each wire was fitted with a ferrule to protect the wire when clamped into the strips. The hex mounting nuts supplied with the terminals were removed and replaced with longer one to allow fixing onto the center channel.

The LED indicators has a RS232 socket soldered onto the factory wires and supported with a 0.040'' 2024-T3 brackets fixed to the panel using 3M automotive trim tape.

RS232 plugs LED / AOA indicator

These brackets carry the load and provide strain relief for the solder connections with a short cable connecting the instrument to the channel connectors as outline above.

Firewall Penetrations

IP68 Glands

Many of the cables from the engine instruments are required to penetrate the firewall. Though there are many systems around these are large, expensive and not available in Australia. With our main enemy being fumes, brass IP68 glands were sourced from JayCar and then installed with the seals located on the inside face placing the open base at the firewall side. The glands are tightened around the cable with the open face to be sealed with high temperature red silicone. 

Each cable is tagged with its cable ID at the exit. This is to assist troubleshooting and locating to correct cable to hook to the sensors.

Firewall penetrations IP68 glands
All labels printed with the Dymo printer on heat shrink tube

Note: The pitch chosen was a little tight and this builder would recommend spacing to suit your ring spanners. 

Starter Solenoid
The starter solenoid was mounted adjacent to the master positive stud located in the firewall and connected with a brass bus. This will have a insulated coating applied at final installation with a insulated coating applied to the brass bus.

Starter solenoid connected to positive battery stud
connected with 20 x 1.5 mm brass bus

Comment
Kaos appearing to ease as each wire is terminated with the largest issue just converting the schematics into real world wire and seeing how to have them interact with each other.

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.

Intercooler - Part 2

This blog covers the selection of an intercooler solution

Overview

An intercooler was always to be a part of this installation based on reasoning outlined in a previous blog on intercooling.

Many hours were spent on a design and through practical, the lowest weight achieved was slightly over 2 kg and with the weight sensitivity of my aircraft it was placed on a backburner to be examined later once a more accurate overall weight distribution could be determined.

A few weeks ago FlyGas sent an email announcing their new intercooler with an installed weight of 1.3 kg that would be debuted at the Paris Air Show in June. 

It was a clever use of space by replacing the 400 gram manifold at the carburetor inlet with a core directly connected to the supercharger outlet, creating a total weight penalty of 900 grams - SOLD!

Flygas Flyer

The company was contacted and indicated they were available for shipping and an order was placed to suit the Flygas Supercharger installed on the Tucano.

Trial fit - all OK

The final issue will be the air inlets and outlets that will have to be addressed once the cowls are installed.

Comment
A problem solved  - next.

Map Pocket

This blog covers the finishing of the map pocket

Overview
Any aircraft needs a place to store the mandatory paperwork that must be available to those who rule on any flight.

Installation
The map pocket was outlined in a previous blog.

The installation of the throttle cables needed the bowden cable connecting the rear throttle to cross the backing for the map pocket. This meant that the plastic frame could no longer bear on the skin and a packing of about 6 mm was required to clear the cable. 

Not being overwhelmed by the idea of fabricating a backing it was remembered that a second net was purchased and as luck would have it it was just the right thickness and of course matched its cousin.

There is a local saying in Rylstone "better looking at it than for it" and that was the case here.

The cord was cut and threaded from the frame and then it was placed over the cable using the mounting holes as a reference, the location of the cable was marked and the 6 mm chain file use to shape a slot at the marked location.

Spacer frame

All rivet nuts were chased with a M4 tap and longer M4 cap head screws were sourced and the new frame fitted and the elastic cover overlay-ed and secured with five screws. The covering plugs for the holes were not installed as they look good but make maintenance very messy.

Map pocket installed

Comment
Problem solved - next job

Co-Pilots Foot Rest

With the co-pilots rudder and cables installed it was time to reinstall the foot rest at the mounting points fitted earlier

Overview
The factory foot rest is secured using a pair of M4 screws fitted into rivet nuts installed in the floor plates with the rear unsecured which could be caught by a person positioning their feet in that confined area.

It was decided that Velcro strips would be the best method to secure the rear tab. This would allow the removal of the plate for access to the rudder cables. 

Installation
A trial fit showed that the foot rest cleared the seat and belts so a pair of complete Velcro attachments were installed under the rear tab [black/yellow area].

The attachment face for the spar had the protective coating remove and replaced with a scrap piece of plastic bag for removal at installation. The footrest was fixed in position using two [2] cap head screws and spring washers, finally the plastic covering was removed and the pads fixed to the top side of the spar.

Co-Pilots rest including cable guard
Velcro located under yellow/black cover

A passenger on a flight decided that the underside of the rudder pedals would be a good place to place his shoes - do not laugh, it actually happened at the club that I fly from and that gap looks inviting. The pilot landed but needed the seat cushion prized from between his butt cheeks.

The guards were fabricated from 0.030'' 2024-T3 sheet, folded, punched and painted and then fixed to the side of the foot rests on both sides using eight [8] 3 mm od pop rivets each.

Cover ready to install

Installed cover showing rudder cable

Comment
Worked as described - next job.