Most of my time recently has been getting all the wiring for the Firewall forward needs out through my firewall passthroughs and in a position to hook up.
This has largely been things coming from the Garmin GEA-24 and the SDS EFII ECUs.
On the co-pilots side, the main bus feed was brought from the primary alternator through a 60A ANL to the fuse blocks on the right side of the subpanel.
The left (pilots) side is mostly the GEA-24 (on the left) which has wires for cylinder head temps, exhaust gas temps, and various fuel, oil, and manifold pressure sensors.
Along with the SDS ECU box which has connections to the manifold pressure sensors, Cylinder head temps, airflow temps, wideband O2 sensor for air fuel ratio measurements, and injector power and ground wiring.
Also Coil pack wiring. This thing needs a lot of connections.
And finally, an overview picture of the panel so far.
I decided to send my Mountain High bottle back to take the regulator off of the bottle (shown on the bottle below) so I could remote mount the regulator. That will give me the option to take the tank out and get it filled at a shop somewhere. I chose to copy Joe Keys’ installation and mount the bottle to the right side behind the baggage bulkhead. I used an ELT mount along with some angle and flat 1/8″ stock aluminum bar. The angles were mounted to the J stiffeners and I used one hole of the ELT mount for attaching the mounting brackets. It’s hard to see in the pictures, but I used 1/8″ flat aluminum bar between the bottle mounting bracket and the angle/ELT mount to Secure to extend as far as I needed to and attach to the structure.
In somewhat of a paranoid redundancy of my engine bus move, I decided to modify the fuse block to add a 2nd stud. The unit has a spot (both a hole and an indent in the plastic) for a 2nd stud.. it’s just not exposed. Below is a picture of the fuse block as it came to me.
I popped the top open and inserted a second stud and then drilled the plastic to expose the stud and be able to tighten down the nut. This will allow me to have the 2 separate feeds of the engine bus connect to different locations protecting against a nut coming loose or something breaking from removing power from the fuse block.
I then moved on to more AC work. I got the skinnier return ducts from Bill and installed them. This moves the whole evaporator forward to give more clearance to the J stiffeners on the top.
With those installed, I positioned the evaporator, and fabricated new forward brackets with an angle and some scrap metal, seeing it sat much higher than the bracket provided to me and they didn’t reach the shelf. This was a suggestion from Bill.
I spent some additional time routing the hoses to the evaporator unit with the service ports easily accessible by taking the lower baggage bulkhead off.
Then it was on to antennas.. More in the category of finishing electrical runs out to the tailcone. One of the things I had yet to finish was mounting the NAV antenna on top of the Vertical Stabilizer. I fabricated a doubler plate and drilled holes in the skins at an angle to accept the cat whiskers.
I sanded down a long wooden dowel to a point in order to insert nutplates up into the VS to hold the antenna puck in place. I’ve also seen people use a rod threaded for the 10-32 nutplate as well, but this worked okay too.
ELT antenna was next. A lot of builders try to mount this inside under the fiberglass. Some DAR’s, including the one I’m using, want to see this external to the airplane.. so I decided to just bite the bullet and put it just forward of the Vertical Stabilizer. I fabricated a doubler, riveted it to the skin, and mounted the antenna in place.
I also utilized another ELT mount on the left side to mount the diode with it’s heatsink and the Battery Bus relay. Shown just below and aft of the ELT.
Then it was lots of panel wiring. I first got the remote transponder mounted on the left side with some angles added front to back.
I mounted all the needed components not already on the avionics shelves to the sub panel shown below.
I then put the metal panel frame and outer panel back in place and got the wiring harness re-attached to all the switches etc..
A bunch of time was spent locating the fuse blocks and getting the basic power connections hooked up. Still lots to do, but this is a snapshot of where I am today. Left side, right side, and center of the panel.
Now that the center support bar is in, it was time to finish the front of the cabin top to glass it in. I started by taking some scrap fiberglass pieces from the Aerosport headliner carrier material and drilling a couple of holes to hold things down with clecos. I then mixed up some epoxy and thickened it with Cabo so it wouldn’t run all over the place. This was left overnight to cure.
Once cured, a quick sand and then application of micro. Again wait overnight to cure.
Then began the sanding process to get it to be as flat as possible and also blend into the surrounding surfaces that I had already finished.
Once I was satisfied, I filled in a couple of divots with glazing compound, sanded, and applied a skim coat of epoxy with a squeegee and foam roller. That was left overnight, lightly sanded and then painting started. I followed the same process as the cabin top where I sprayed black DPLF primer, cleaned the gun, then shot K36 high-build primer. Just one coat was needed. After that dried, I sanded with 400 grit and cleaned prepping for topcoat paint.
Then it was time to apply the omni sealer, top coat (Oxford White), finsishing with a matte clear coat. I donned my fresh air breathing hood and matching bunny suit due to the toxic nature of these paints. I applied the omni sealer, waited the time required to dry, followed by 4 coats of paint. Once dried, I applied the clear coat and let it cure overnight.
Lower door frames are not as perfect as the rest of the cabin top, but also there will be the McMaster door seal sitting here too, so not as much surface area will be exposed.
I had previously mentioned that I needed to modify my engine mount to accommodate the Barrett Cold Air Induction. I sought out a local welder and dropped it off for him to cut the existing bar out and replace with this curved one proving more clearance. I was never able to get an exact number on how much clearance was needed. I was mostly directed to leave about 1″ from the existing weld on each side and cut the new bar provided down to meet up and weld together. My welder was able to leave a little less than an inch from the weld on each side, which left approx. an inch of clearance, which should be more than enough. Now to prime/paint the exposed steel.
Initially, I had crimped some of my battery wires with a hex die hydraulic crimping tool. I was told by the supplier through ACS that that is not correct method for the terminals I had bought. I then decided to buy the crimping tool that Stein sells along with the terminals they sell as well to re-do everything I had already done. I don’t want any flakiness in the battery connections, so re-doing was simply the correct thing to do.
A side view of the plane as it stands. I’m just now starting to work on window installation using Silpruf. More details to come on that method.
I’ve been knocking off lots of tasks here there and everywhere lately. I got the defrost fans and their plates installed. Below are views from the top and bottom side.
While waiting for some additional firewall items to arrive, I started pulling some #2 fat wire, 1 for each battery from the tailcone to the firewall. I fished the wire through the previously installed conduit
A bunch of work getting Adel clamps, drilling holes for bushings and routing the wires down the left side of the plane.
I added some Adel clamps around the 2 larger lighting holes with some caterpillar grommet around the holes for extra protection. The wires end up away from the edges of the holes, but I want to be sure these runs are solid.
I also took the time to install the spring and collars on the brake cylinders. I’ve heard that if the rudder assembly isn’t 100% square, that some binding can take place and cause the brakes to stay slightly engaged. These will help ensure that they always return all the way out ones your feet are off the brakes.
I then got to modifying the stock battery box. It needed some slight modifications to support two batteries. I decided to see if I could bend the sides downward to gain more space left and right. It seemed to work, and was a pretty close fit in the end. I’m glad I went this route, rather than cutting the sides off.
I then used some angle stock to retain the battery on the left and right. I also added an angle on the forward side to eat up an approx 1/4″ gap. Another angle was used on the left side below the whole assembly to house the battery contactors. You can see the holes for AN4 nut plates ready to go.
I then installed a ELT/Strobe bracket between the J-channels of the tailcone that I had on hand from Van’s to house a couple of fuse blocks. These will be the main and aux battery bus hubs for all things related to my EFII installation.
Then it was time to go back and work on mounting the firewall related items. I’m doing all of this prior to installing insulation of the engine side of the firewall. I want to have as many of the passthroughs and holes/nutplates setup as possible before I do this. I mounted the cross-feed contactor in the stock location for the starter solenoid, and mounted the starter solenoid just above and to the right of it.
I also go the ground block (forrest of tabs) installed. This is a kit that has 24 grounds on the engine side and 48 grounds on the cabin side of the firewall. This will be the central point of all grounds.
I’m now working on Installing a couple of ANL bases between the alternators and the main/aux busses on the firewall. I’ve also ordered the AntiSplat aero Air/Oil separator and will be locating that on the firewall too. My air conditioning unit should be shipping soon so I’ll likely hold off a bit longer to drill holes for the 2 hoses that have to pass through the firewall too. Once I get to a point where I’m mostly comfortable with the firewall the path forward will be as follows:
Install upper forward fuse permanently.
Finish installing what I can of the Skybolt flanges.
Install firewall insulation.
Install support bar in center of windscreen area.
Finish fiberglass area around support bar.
Paint remaining areas of fiberglass around support bar and lower door area.
Plane up on gear!!!
I hope to have all of this done before I have my engine in April/May timeframe.
While waiting for epoxy to cure.. I spent some time on my overhead lighting plan. I am essentially copying what Ed Krantz came up with for an overhead lighting control circuit. It is car-like in operation. I plan for overhead white lights above the front and rear seats as well as in the baggage compartment. These overhead lights will be on a dimmer. I’ll have red map lights also dimmable. I plan to install footwell lights as well as panel/avionics lights also on dimmers. The door pins have magnets in them and I plan to use 4 proximity sensors (1 for each door pin; 2 per door). Not only will these be used to ensure that all 4 door pins are seated (causing a red LED to illuminate on the panel otherwise), but they will also be used in this lighting circuit. These proximity sensors basically act as a switch and will indicate when a door is opened. When opened, the overhead lights will come on full intensity, despite what they’ve been dimmed at, and stay on for a pre-determined time (somewhere around 15 minutes). Of course there will be an override button to disable this feature if you want/need to taxi with the doors open at night. I’ll also likely put an on/off switch on the circuit to be able to disable it during times where the doors may be open for long periods (i.e. annual condition inspection). I put together a quick video on my prototype of the circuit.
As I’ve mentioned previously when putting a fuel return port into my gas tanks, I plan to go full EFII (Electronic fuel injection and ignition). That means I’ll have an electrically dependent airplane and, being such, demands quite a bit of attention to the electrical architecture to have redundancy to always keep the fan turning. Fortunately, there is a guy by the name of Bob Nuckolls over at the AeroElectric Connection who has written a book outlining basic electrical principles (most of which I already know being an EE), and provides multiple different time-proven architectures having worked in the industry for many years.
Early on, I had really settled on his Z-14 architecture, which is a dual battery, dual alternator, split (redundant) bus architecture. In-depth schematics are located across 2 pages here and here for those interested. This allows one to take approx half of the load and run it on one bus independent from the other. The idea would be to have the left glass panel, #1Nav/Com, and a handful of other goodies on one bus, and have the #2 Nav/Com, the right-most glass panel etc.. on the other bus. That way you should always be able to navigate, communicate, and get on the ground even under IMC conditions. Additionally, the EFII system is redundant too in the sense that there are 2 ECU modules, 2 fuel pumps, 2 ignition coils, etc… so each of those would be powered off of their respective redundant power busses such that you always have power to at least one of the redundant pair. The 2 busses also have the ability to crossfeed, meaning that if a failure occurs which takes out one bus, it’s possible to continue to use it by having the 2nd bus feed it. That feed won’t be at the same overall capacity as you are now on a single battery and alternator, but most stuff should be able to be used after doing some non-critical load shedding.
I’m getting close to pluming in my brake and fuel lines and systems so I’ve recently started researching more details into the architecture and also the SDS EFII solution I have chosen. First off, I’ve ordered the Andair duplex fuel selector that I’ll need to both select and return fuel from one of the tanks.
I’ve also placed an order for my dual fuel pump module (shown below), filters, and pressure regulator.
One thing that I have discovered is the fact that there is only one set of injectors into each engine cylinder for the fuel injection (i.e. not redundant), so there becomes a need to be able to power those devices from either battery. I was figuring that I was going to need to diode-Or the two battery busses together in order to accomplish that. Fortunately there was some really good discussion on VAF about this very topic and various architectures for an EFII setup. The end result was a slightly modified Z14 architecture that provides just that. I am currently planning on going with this as the architecture for my plane.
Credit for the diagram goes to Dan Horton.
Ignore the alternator amperages for now. I will need to work out my exact electrical loading and size everything appropriately.
Talking to the architecture diagram, you have 2 separate batteries that provide their respective battery busses. These feeds are directly off the battery. The battery busses are then joined together via switches and diodes to form an Engine bus. One could simply put the fuel injectors on this engine bus and keep all the other redundant engine components on their respective battery busses, but the point was made that once you have to have an engine bus, you might as well put all critical engine components on it. The switches would provide a way to isolate the engine bus from either side if something really bad happened on one of the sides that it was impacting the engine bus somehow.
The upper part of the diagram shows each battery feeding a a main and aux contactor (what your master switch typically turns on) powering a main and aux bus which all of the other electrical devices will sit on. There is the cross-feed (cross tie) contactor which allows one bus to drive the other, and each bus has its own alternator.
There will be no single point of failure that can cause the engine to shut off, if something happens, the goal of the architecture is to be able to keep flying while diagnosing and planning to get on the ground as soon as practical. Another benefit of this is if there were ever smoke in the cockpit, the first reaction will be to shut off the master switches. This is still the response here. The panel will go dark, but the engine will still run.
There is still lots of work to do on specifics, but I feel like I have a solid foundation to work from.