Installed Garmin GTN 635 Antenna

I stopped by my avionics shop over lunch today and picked up the GA 35 antenna for my GTN 635.  Dynon recommends installing any GPS antennas at least 1′ from the ADAHRS, and Garmin recommends installing the GPS antenna with at least 7.5″ ground plane all the way around the antenna.  These two recommendations necessitated moving the antenna behind the F-707 bulkhead.  I fabricated a doubler from 0.040″ aluminum that matches the outline of the antenna and then installed it to the fuselage.

Here’s where the antenna is relative to the aft window.  The ADAHRS is roughly under the aft edge of that piece of paper, putting it roughly 18″ from the GPS antenna.

Afterward, I crimped on a TNC connector and ran the antenna cable along the underside of the upper rib next to the Dynon network cable.

Tidied Up Wiring

I spent a little time tonight tidying up some wiring runs under the seats.  I installed an adel clamp on the wires to the left of the center tunnel.  I haven’t tightened either of these down fully yet since I want to wait until the GPS antenna cable is adjusted to length and I still need to run the wires for the control sticks.

I installed the adel clamp supporting the wires coming out of the left conduit and added a couple of zip-ties to tie everything together.  It’s amazing how solid these wire bundles become when zip-tied together.

I added an adel clamp to keep the pitot/AOA lines held down to avoid interfering with the aileron push tube.  I might have been able to use a zip-tie base attached with a pop-rivet, but I really don’t want there to be any possibility of anything coming loose around the flight controls.  You can also see at the top of this picture that I took all of the snap bushings out of the forward holes in each seat rib.  I have no idea why Van’s has you drill holes here.  It’s a really poor place to put them since they’d have to snake around the control stick brackets.

I also tidied up the wiring aft of the baggage bulkhead.  Everything is firmly secured and well supported.

Ordered Avionics Stack

I ordered my avionics stack today.  I’m going with a PS Engineering PMA8000BT audio panel and Garmin GTN 635.  I went back and forth about both units a bit.  I was originally going to install the PMA5000EX audio panel, but ended up deciding the Bluetooth functionality would be worth it for making phone calls and listening to music.  I was also originally planning on installing the GTN 650, but ultimately didn’t think I would use the VOR/Loc/Glideslope functionality much.  Switching to the 635 not only saved me about $1,000, but the unit is 0.8 lbs lighter and I probably saved another several pounds of antennas and wiring (not to mention hours of time that I would have spent hooking up the additional antennas).

Installed Throttle Cable Bracket

For some reason, I decided to install the throttle cable bracket tonight.  I fabricated this bracket months ago, but it needed to be powder coated before it could be installed.  I sprayed a couple of coats of white powder coat on it and baked it for awhile in my toaster oven.

I then drilled the heads of a couple of coarse thread AN4 bolts and installed the bracket to the boss on the front right of the engine.  It was a little tight getting the safety wire installed, but I managed to get it done on the first try.

I’m not sure why I took this picture, but here’s a shot of the other side.

Worked on Cowl Attachment and Dynon GPS Antenna Mount

Now that I know where the side hinges will rivet to the firewall, I riveted the sides of the firewall flange above that point.

Then riveted the hinges on below that.  The bottom seven rivets can’t be reached with the squeezer, so I’m going to have to shoot and buck them somehow.

I’ve been planning on mounting the Dynon GPS antenna under the cowl.  Most builders fabricate a little shelf that runs between the engine mount and the firewall, but that would get in the way when changing the oil.  Since I only have one antenna to mount, I decided to fabricate a small mount that will attach directly to the engine mount.  I placed the straightedge between the top of the firewall and the spinner to see how high I can go.  The actual cowl in convex through here and will actually provide more clearance than this.

The mount is just a short piece of Z channel that I trimmed to fit the antenna.  I’ll drill a couple of holes in the bottom flange and attach it to the engine mount with a couple of adel clamps.

Started Countersinking Cowl

I started countersinking the cowl for the rivets used to attach the hinges.  I was originally planning on using a permagrit countersink, but I tried my regular countersink and it did a great job.  I’ve heard it can dull them, but buying a new one would be cheaper than a permagrit countersink so I don’t think it’s worth it.

Finished Tailcone Wiring

With the ELT shelf riveted in, I wanted to finish up all of the tailcone wiring.  One of the final items on the list is the cabin light wiring.  I ran three 22awg wires from the front up through the top of the baggage bulkhead.  This will be inside the cabin frame support and will connect to a small LED spotlight that will have both white and green lights in it (hence the two red wires and one black ground wire).

I then secured all of the wires from the left conduit with an adel clamp on the ELT shelf rib and some zip ties.

I also ran an additional RG-400 cable through the right conduit for the Garmin GTN-635 GPS antenna.  I had originally planned to mount both GPS antennas (the Garmin and the Dynon) under the cowling, but the Garmin install manual stipulates that GPS antennas not be installed closer than 9″ from each other and require a 7.5″ minimum radius ground plane under the antenna.  Though under the cowling would likely work just fine most of the time (and I’m still going to mount the Dynon antenna there), I want the highest possible antenna performance for my primary IFR navigator.

I finished all of the wiring runs up to the area behind the subpanel, though the cabin light ground is the only wire I could actually hook up to anything.

Finished Sealing Cowl and Riveted ELT Shelf

I got up early this morning and finished sealing the inside of the lower cowl.  It doesn’t look like applying tinted epoxy is going to work very well.  The coats of epoxy are so thin that they’re translucent.  It would take so many coats to make an opaque white layer that it would be pretty heavy.  I’m going to end up just painting this white like most builders do.  The epoxy and filler still did a great job sealing the surface to keep oil from soaking into the fiberglass though.

My buddy Andre stopped by mid-morning and helped me finish riveting in the ELT shelf.  Afterward, I reinstalled the ELT.  We also riveted in the transponder antenna doubler that I fabricated and then I installed the antenna cable.

Finished Wiring Exterior Lights

With the final trimming of the cowl complete, I pulled the forward top skin off so that I could do some further wiring.  All of the exterior light wires have been coiled up on the cabin floor for the last couple of weeks.  With access to the VP-X again, I finished running all the wiring runs.  I’m probably done with 80% of the load wiring at this point.  I mostly just have the avionics left to do.

I also ran the static tubing up behind the panel so that it can be plumbed to the alt-static switch.

It comes up the firewall with the other wires and then heads over to the left side of the plane and then aft to the instrument panel.

Worked on Cowl and Mounted Com Antenna

I mixed up some epoxy and microlight filler along with some white tint and applied it to the inside of the bottom cowl.  It started stiffening up before I could finish, but I got about half of it down.  This fills in the pattern left by the honeycomb core to provide a smooth finish and fill in any pinholes.  I’ll seal this with some neat epoxy tinted white to provide an easy to clean surface.

I decided to go ahead and mount the com antenna.  My wife gave me a hand with the nuts since you can’t reach both sides at the same time.

I then installed a BNC connector on the coax and installed it on the antenna.

I also fabricated a doubler for the transponder antenna.  I’ll need a little help riveting this on.

Finally, I fabricated the transponder antenna cable.  It has a BNC connector on one end and a TNC connector on the other.

Finally, I vacuumed out this bay and reinstalled the shelf in preparation for riveting it in place.