More Avionics Wiring

Today I spent a solid chunk of time routing wires. Making wiring harnesses has been one of my the more satisfying parts of the project so far.

Firewall forward

I started by organizing the firewall forward sensor wires. This bundle contains everything from engine temps, to oil and fuel pressure and the ignition harnesses. These are now secured to the engine mount and won’t be able to move.

On the other side of the firewall I’ve secured everything and routed a portion of the harness down the left side of the fuselage in order to route the wires to proper area.

Center tunnel main harness bundle

This is the center section between the pilot and passenger seats. The main harness here is routed up to the vertical power above for all the power distribution. Other parts of this include all the serial connections, and the electric pitch and roll trim motors.

Here’s another look at all the wires and how they’re routed (Ignore the tie wraps and scraps). The harness splits to allow for the left and right lighting wires to route to the correct wing. I’ve isolated all power wires from my radio wires so that there will be no interference.

Serial Hub

This is my serial hub, it had ports for the primary and multifunction flight displays (empty slots) and the five serial avionics. The ADSB, transponder, Vertical Power, GPS and ELT (black box) all communicate via serial. This hub allows all the components to connect to the two main flight displays in parallel for each of the five serial ports. Once I’m down with all the routing of the wires this will be mounted to the sub-panel permanently.

Fuel pump and selector valve

Once I finished with the wiring I wanted to test fit my fuel pump and selector valve. I have custom fuel hoses from TS Flightlines, so I had to modify the brackets to allow the hoses to fit (you can see the cut bracket on the left below the wires). Once I mount the wings, the two fuel hoses will attach to the fuel tanks.

More Avionics Wiring

Ignition Harnesses

Tonight I spent a few hours making my ignition harnesses. My engine uses twin P-Mag ignitions, so I had to make two identical harness.

I started by removing the connectors on the ignitions so I can attach the wires. The connectors use a screw-clamp style connection.

Right ignition

Here you can see the connector attached to the ignition with the wires attached. This is a six pin connector with Ground, ignition kill, power, and RPM out. There are two additional pins that can be shorted in order to change the default timing of the ignition.

Left ignition

The left ignition connector is on the bottom of the ignition and is a bit more challenging to get to, but I managed.

Completed harnesses

Here are the bundles completed. Looking forward to the day I get to start it up!

Ignition Harnesses

Engine Controls Bracket

Yesterday I spent a few hours making the engine controls bracket. The bracket that comes in the kit is flimsy 0.032 aluminum sheet that is bent so it can attach to the bottom of the panel. I knew I wanted to use something different than the stock bracket, so I made one.

Here you can see the completed bracket. It’s made from 1/4” aluminum angle. It’s very hefty. The three holes are for the throttle, prop and mixture control. The two larger holes have relief cuts made on the back of the angle to allow for the nuts to hold the controls onto the bracket.

I then lined the bracket up with the control panel, and drilled matching mounting holes. I then added some nut plates to the panel so that this can easily be mounted flush to the bottom of the panel. Now it just needs some priming and painting and the bracket is done.

Engine Controls Bracket

EMS wiring

This weekend I spent time working on the main EMS wiring harness. It includes everything for engine monitoring including oil pressure, temperature, fuel flow, fuel pressure, manifold pressure, rpm, etc. It’s quiet extensive.

I started by reviewing my wiring diagram that I made, and reviewed the pin out of the EMS D37 connector.

EMS box and connectors

I then opened up the main harness that is included in the skyview EMS in order to identify every pin.

Top half of the connector

I used my multimeter to check each wire and then I used that to label each one according to the function.

EMS temporarily installed

Here’s the EMS and the main harness (silver) plugged in. As you can see in this picture, the wires are labeled and then separated out into the appropriate pairings (e.g. oil pressure power, ground and signal). Then I began to wire the engine sensors and measure the wiring runs.

Firewall pass-through for main harness

Here you can see the main EMS harness come through for all the firewall forward components. Mounted to the top of the firewall is the sensor manifold, which includes oil pressure, fuel pressure, and manifold pressure.

Sensor manifold closeup

Here’s the oil and fuel pressure sensors mounted to the firewall. These are wired into the main harness and share their 5v source on the same pin (pin18) of the EMS. It’s a common source for low power components and is shared between several other sensors.

Oil temperature sensor

Here’s a close up of the oil temp sensor wired to the harness.

Manifold pressure sensor

Here’s the manifold pressure sensor. It has a tube that’s connected to a T in order to share a manifold pressure source with the ignition system. E-Mag ignitions also need to know the pressure of the intake in order to adjust timing of the spark.

Continuing the work is a bit slow, but it’s getting there. Lots left to do.

EMS wiring

Fuselage gussets

Today I spent a couple hours putting the forward fuselage gussets in place. They are unique to the -7 vs the -7A. The tri-gear plane rear landing gear are mounted just forward of the center section. Since the -7 is a tail trager, there is a gap here that need to be reinforced using these gussets. They are attached to the sides of the fuselage with 5 bolts that need to be match drilled. The gussets also line up with the bottom wing attach bolts.

I lined everything up and then drilled the holes to #40 and then enlarged for the AN3 bolts. I prepped and primed these and then attached them to the fuselage. The whole interior will be painted with my interior paint, but it’s good to prime all the parts especially mating surfaces.

I also sent a bit of time working on the panel attachment brackets. Since I’m using twin Skyview HDC screens, I need to move the Vans panel supports inboard. This requires making some custom brackets to attach the panel to the sub panel. I received a shipment of L stock from vans that worked perfectly for this.

I decided to wrap up the center section bolts that are used for the tricycle gear. In the tail dragged version the bolts need to be put into the center section.

The bottom bolts were difficult to reach but everything is now in place and torqued.

I also placed the remaining two cover supports on the sides of the fuselage, forward of the center section.

Next up is to wrap up the exhaust hangar modification. And to drill the wing fuel attachment bracket to the sides of the fuselage.

Fuselage gussets

Heat Muff, Exhaust, and Fuel Tubes

Today I spent a few hours working on the exhaust hangars, heater and the fuel lines.

It’s been on my to-do list for a long long time, but I finally marked and drilled the hole in the firewall for the fuel line.

I then test fitted the fuel line between the pump and firewall fitting. I had to fabricate a new tube in order to fit the position I drilled the hole. In hindsight I should have drilled it about one inch to the left of this, in order to provide more room for the heater scat tubing on the other side, however it should be fine.

The forward tunnel cover will go over this portion of the tubing as well as the wiring harness.

I then worked on the hangars for the exhaust as well as heat muff.

Here you can see the hangars before I installed the heat muff. The left hangar here will need to be modified to account for it.

I didn’t get any pictures during the install, but here is the heater installed with the tubing. I will need to add some support to prevent chaffing of the tubes on the engine mount.

I will also need to add some support for the fuel tubing here to prevent rubbing on the tube. It shouldn’t be too difficult to keep these two separated.

I will need to fabricate a support bar to extend the exhaust mount a bit wider in order to attach the hangar in order to avoid the scat tube.

Heat Muff, Exhaust, and Fuel Tubes

Engine work

Today I spent a few hours cleaning the shop and installing some fittings on the engine. My goal is to hang the engine next weekend. 

I started by rotating the prop governor and installed the cable bracket. 

I cut the safety wire on the six screws holding the governor so that I could rotate the lever arm. I then installed the cable bracket in white and reinstalled the screws and re-safety wired them. 

I needed to install the oil cooler fittings, but that requires removing the right p-mag. Once off I could easily screw the fitting in. 

This is the fitting installed and with tape over it to keep moisture out. You can see how tight it is to get a wrench on there. 

The other oil fitting is much easier. 

The fitting (with tape over it) is right above the left p-mag and just under the oil breather tube (with the red cap). 

I also installed the fuel pump outlet and fitting for the fuel pressure. 

Fuel will come out the bottom port and go to the fuel servo near the front of the engine. 

I also installed the oil pressure fitting


And the manifold pressure fitting from the number 3 cylinder. 

You can see it here wrapped in tape just above the oil return line. 

I finally installed the fuel overflow fitting to the fuel pump. 

There are a few more things to install, but that can be done after the engine is hung. There are a few more holes I need to drill in the firewall for cables and wires, but that’s no more than an hour of work, and I’m hoping to get it done some time this week. 

Engine work