Stjohn's RV-7

6 hours.

Saturday and Sunday got the ELT installed. I’d been waiting for this thing for about 5 months, and it finally showed up.Of course this device goes back in the tailcone behind the baggage bulkhead, so it’s a lot of contortion and crawling around. I’m beginning to hate working back there almost as much as I hate painting. But it went fairly quickly, since I used the same technique I used for mounting the strobe controller, which is:

blind-rivet 2 angles along the J-stringers, then blind rivet a plate to that, with platenuts attached at the mounting points for the device. Easy. Only issue though is that the screws stick out far enough into the space between the side skin and the mounting plate for possible interference with the rudder cable. I’ll need to set it all up, but it’s not likely, and even if it is, I’ll make a guide of some kind. Somehow.

I also got my Odyssey battery charger and charged up my battery to full capacity. When the EFIS docs say 11-33 volts, they mean it. At 10.9v, my AHRS and compass no longer had sufficient power to provide data.

I’m still waiting on a connector kit from Steinair for my GMA340. When I get that, I can start wiring the avionics stack. Still not sure what to do about my stick grounds though. My PTT switch (the trigger) wants to be connected to the proper terminals on the audio panel and radio, but it’s currently got a positive and a ground, grounded at the airframe near the stick. This might have to change, because I’m not sure it’s cool to just pick up mic key ground from the airframe.

4 hours.

finally figured out the magic of crimping RG400 connectors on. With the standard cheapo coaxial stripper from Fry’s, the cuts aren’t exactly precisely what you need for RG400 cable, which is actually the same as RG142. For RG58, it works fine, but RG400 is a superior cable for this app. Less loss, better shielding, etc. RG58 is perfectly acceptable as antenna cable, but only the best for yours truly. It just means things are a little less straightforward. Eventually, I got the cutter tuned right (you can adjust the blades so they cut more or less deep), and figured out how to get the right length of conductor to go in the pin. I redid the transponder antenna connector because now that I think about it, I didn’t crimp the pin conductor, which is dumb. I got the TNC connector on for the 430W’s GPS antenna as well, which has been up in my grille for months. Now it’s done.

I cleaned up the wires in back and secured the sensor wire bundle, so that job’s totally done too. What I did get into was the antenna doublers for the marker beacon antenna and the comm antenna. The comm antenna is going in just forward of the main spar. Under the seat would have gotten it too close to the strobe cables, and since there’s a strobe connection nearby, I’d rather not risk it. Now we get to see if the comm radio makes the EFIS go all funny, and if that happens, I find a better solution than the RAMI bent whip antenna I currently have. It’s the only antenna in the collection that uses a soldered lug connection instead of a BNC or TNC, but it should work just fine as long as there’s not much stripped wire exposed at the connection.

What’s left is a ton of rivets to put in. I still have to rivet the AHRS bracket along the bottom skin, plus the two doublers I made for the antennas.

Then comes wiring the avionics stack itself. That’s going to be a hoot, let me tell you.

2 hours.

Almost done. Yesterday before 4th of July festivities, I was able to finish up the pax stick wiring. I ran to Fry’s and picked up a DB15 connector. Some of you oldschool computer geeks might remember this connector as the “game port.” It’s got enough contacts to handle all 11 stick wires, and it’s small enough that it doesn’t interfere with stick travel. I don’t have any photos of it right now, but it goes something like this:

Stick wires exit detachable stick through 3/8″ snap bushing. These wires go to the DB15 plug, where there are multiple layers of heat shrink tubing protecting and securing them at the connector. I even found heat shrink tubing large enough to go around the back side of the connector. Backshells were out; they took up nearly as much space as the CPC connector. On the stick side, the wires going to the terminal block were done in the same fashion, with the socket connector zip-tied to the base of the stick. When the connector is plugged in, the two holes normally used for the screws in the backshells will have zip-ties holding the connection together. I settled on this as a semi-permanent install. I don’t expect to take the pax stick out except for special occasions like XC trips where I need all that space for Shelley’s in-flight activities or cargo, so for the most part, it stays in.

Some questions though.

Will wiring a panel switch into the ground wire of the pax stick for Enable/Disable of the stick cause a big fat ground loop?
Is having the start relay (not the starter contactor) always live when the master switch is on a good idea?
Am I asking for trouble running the trim, trim sensor power, and flaps off the same power feed? The trim motors hardly draw anything (they use 24ga wire FFS).

I now get to move on to the ugly process of wiring the avionics stack, but after finishing up this job, I’m a lot more confident that I won’t let all the magic smoke out of $10k worth of gear.