More Antennas and Fittings

After giving things a lot of thought, I finally summoned enough resolve to drill some holes in the aircraft skin, and most, where none had existed before. You’ve got to do what you’ve got to do. Antennas, static ports and bulkhead connectors need holes. Now I’ve got them.

Determining the location of antennas is where most of the thought went. I tried to get the transponder blade antenna pretty close to the fuselage centerline – right in the middle as it turned out. Airframe shading and interference between antennas and other equipment are key concerns. The COM 2 antenna is also on the bottom of the fuselage, just behind the rear wing spar carry-through. I tried to keep it as far away as I could from the the transponder antenna and GMU 11 magnetometer. I didn’t get all of the separation distance called for in various installation documents, but what could I do? This is a tiny little airplane — not a King Air. Time will tell if it’s enough. Build on.

All of the antennas are made by Rami and came along as part of the package with my panel, harness and avionics. Some builders have made rather large doublers. For the moment I’m using only the doublers that came with the antennas. I may eventually go beyond those, but for now, everything is in place.

Of the 14 holes that were already in the ELT mounting tray, none were where I wanted them to be. I made 4 more in the tray that allow 4.0 x 10mm rivets, through the fuselage skin and into the tray, without interfering with the plastic case of the ELT itself.

I made an airframe ground lug from a 5/16″ brass bolt and installed it at the location where the KAI called for a 12 AWG avionics ground bus wire to be passed through a grommet in the firewall on it’s way to the negative battery terminal. I’ve decided to have a 10 AWG cable for the avionics ground bus to the lug (inside) and a 4 AWG cable from the same lug, on other side of the firewall, to the battery. I plan to attach a 6 AWG engine [starter] ground cable to the lug as well.

Rubber fuel lines penetrating the firewall through ordinary grommets, as the kit assembly instructions (KAI) call for, didn’t float my boat. I’ve gone with AN6 bulkhead fittings for the fuel supply and return lines. These fittings need smaller holes than the ones pre-punched in the firewall by the factory. I designed and fabricated a doubler out of steel and riveted over the original holes. The fittings are mounted there.

A set of step-drills is absolutely essential for making holes in sheet metal. I’ve got a cheap set but they’ve worked well.

I’ve set M6 rivnuts (with some JB Weld epoxy for good measure) in the fuselage rib, behind the parachute compartment, where the Rotax ECU goes. Getting the 3 large engine wire bundles and connectors in place, given the minimal space remaining with the LRU rack mounted, is going to be super tight. Fingers crossed.

As long as I had rivnuts and JB Weld handy, I decided to rework the Andair Duplex Fuel Selector valve to receive M4 rivnuts and then set them in place. These steps are called out in the KAI.

My factory quick-build fuselage came with not one – but two – static ports in the rear fuselage. However, the factory now says not to use them. They’ve also said they haven’t officially decided where the new location(s) should be either. They think it’s going to be finalized “soon” and anticipate that it’s going to be just in front of the fresh air NACA duct near the front of the fuselage. They sent me a picture and I’ve gone with that location.

The outside air temperature probe found its home in the LH fresh air NACA duct.

Panel Power On Milestone

I’m happy to report that the panel powered up with no apparent issues. All good!

At this point, I’ve got good reason to believe that the avionics and and wiring harness are happy and healthy. There’s still a long way to go, but I’ve got something to hang my hat on.

The engine management and engine information systems aren’t connected yet, but the Garmin G3X Touch avionics are up and running, along with the Vertical Power, VP-X Pro electronic circuit breaker system. Of course this was done during setup and testing at Midwest Panel Builders, but it’s very nice to see it happening – here and now.

I’ve confidence-checked about as much of the harness as I can at this point. I’ll be able to do more when my Rotax 912iS Sport engine is mounted and its Engine Management System (EMS) connected. Stay tuned for that.

Wiring Harness Placement

After careful study of the wiring harness, I think I generally understand how it should be positioned. All of the connectors and each of the individual wires have labels that match the names of the LRU connectors and appear in the schematic wiring diagrams that came with it all. Sweet!

The harness has a central “gooseneck” from which various connector bundles extend. The several sub-harness bundles have been made to reach corresponding LRUs where they are mounted behind the panel. Other portions of the harness extend to places in the center and rear fuselage to connect with lights and autopilot servos.

There are probably several ways that some of the harness extremities could be routed within the center fuselage (CF). Some routes are undoubtedly better than others. I’ve tried to find what I consider to be the most natural – and if you will – most elegant way to dress and eventually secure the wiring, while always considering guidance in FAA AC-43.13-2B.

So far, so good.

In the interest of keeping things both lightweight and tidy, I’ve opted to replace a heavier and bulkier firewall-mounted circuit breaker enclosure with a simple bracket. I also decided to locate the battery and pitot heat power C/Bs and the ammeter shunt on the LRU rack instead of inside the engine compartment.

IBBS Mounting

The navigation avionics and engine management systems each have a TCW Integrated Battery Backup System (IBBS). The backup systems provide essential power in the event that one or both alternators in the Rotax 912iS engine should fail. There are 2 battery power units that have to be mounted someplace. I’ve found a spot on the fuselage rib, behind the parachute compartment that is within comfortable reach of the associated wiring harness connectors.

I thought that the batteries could use more support than they would get, were they attached directly to the rib. I designed and fabricated doubler plates to reinforce the rib. The batteries are fastened to the doublers.

I’ve had to consider that one day the battery units will have to be replaced. It won’t be easy, but I will be able to get to them from the front, after I remove the pilot side display and the remote LRUs and vertical rack that sit behind it.

LRU Rack Fit and Mounting

Most of the remotely mounted avionics will be behind the instrument panel, on a custom designed and fabricated rack. Each Line Replaceable Unit (LRU) has a specific position on the rack and the harness is custom tailored to precisely reach and connect all of the units together, along with all of the other electrical systems in the aircraft.

I elected to have the harness and panel professionally designed and fabricated by Midwest Panel Builders in Lapeer, Michigan — specifically for my Sling 2 and its extensive Garmin G3X advanced IFR avionics suite. While I might have been able to manage the panel and wiring for a modest VFR setup, there was no way I was going to attempt it for this project.

Even with the custom-made harness, rack and panel there is still plenty of fitting and integration for me to do. This is no paint-by-numbers ELSA project. It’s full-on experimental amateur-built — all the way. I can’t wait to begin training for my IFR rating in this aircraft.

The LRU rack is a replacement for the one I received back in April. The original rack was the first of an all new design and needed several refinements.

The new rack needed to be fitted and the mounting points established. The center portion of the rack needed support. I designed and fabricated a bracket. Everything fits nicely.

Cabin and Firewall

With the firewall forward kit and the avionics, related tasks are accomplished.

Instrument Panel and Avionics Arrive

Boxes and boxes of Garmin avionics arrived along with my custom instrument panel and its plug-n-play wiring harness from Midwest Panel Builders. There’s lots to play with, but I still managed a few other tasks.

March – Spring Has Sprung

Man does not live by aircraft building alone. There are so many enjoyable things to do.

E-Biking on the Spruce Railroad Trail – Lake Crescent, Washington

Group Fly-Out to Forks, Washington – Mary Ann and I have some fun flying in our Warrior

Misc Rework – Firewall and Wingtip

Work on the RH wingtip continues. Getting a good fit (matching the wing airfoil) is what I’m after. It has to happen in small steps. I’m getting there.

The battery box reinforcement channel is going to be tricky to rivet to the firewall. That’s because the shape of the channel overhangs and blocks access for the rivet setting tool. A few of the holes can be riveted from behind, but a couple holes are only accessible from the front. I’ve asked the factory about it. (This channel really should have been mounted before the parachute box was assembled at the factory.)

I’ve decided in favor of having the full-airplane ballistic parachute. I’ve thought about it – long and hard. The terrain in Pacific Northwest Washington is very rugged – utterly unforgiving should the occasion of an emergency off-airport landing ever present itself. Having the parachute will give me some peace of mind. I think it will also open the door to some evening and night flights that I wouldn’t otherwise consider.

The parachute system adds weight and expense, but it likely adds a bit of safety margin and value, as well.

There are break-away skin panels that cover the parachute compartment. Mounting them will involve countersunk rivets. The flanges of the firewall, RIB-003 and the curved top-skin, in front of the windscreen need to be dimpled with a squeezer. To do that, I have to remove the top-skin that was partially riveted at the factory. I also have to countersink some of the holes in the narrow cowl mounting strips, using a 120 deg pilot-cutter and micro-stop cage. I’m doing this countersink rework on the plane, so it’ll be a freehand operation with my lithium battery-powered drill. Having the top-skin off will provide improved access for installation of the avionics rack and wiring harness.