« Archives in September, 2011

Grounded. Not.

6 hours.

Yesterday and today was an ugly mess. I had to pull the wiring harness to try to figure out a couple of things, first and foremost, why is my radio dumping RF energy into my EFIS? I’ve checked all the grounds, twice, three times, both at radio, both ends of the antenna, and the EFIS itself. I grounded the shields of the ARINC connector as well, while I was in there. It seems to be a little better. I get no clicking of relays, but I still have the Bermuda Triangle effect whenever I key the mic. I’ve also got no mic audio. I don’t know if that’s my headset, which, at last outing, proved itself extremely unreliable in the mic department. My other headset looks like the foam muff on the mic dissolved itself into the actual microphone somehow, so I doubt that one works. This just gets weirder and weirder.

One thing I’m not too sure about: If I place one probe of my multimeter against the inner conductor on the antenna’s BNC connector and the other one on the antenna rod, I get no beep. I thought an antenna had one pole connected to the center conductor and the other pole connected to a ground plane. It may be that I have a defective antenna, which would suck, but better than a fried radio or EFIS.

Looks like I’ll be ordering yet another antenna from ACS, but until then, my old RAMI whip antenna will have to do for now.

Big day!

6 hours.

Avionics installed! Everything powered up, no smoke! It also appears that I’ve connected everything correctly, with notable exception: One, I can’t seem to get any audio signal from the EFIS. This could be because I’ve connected the wrong wires to the RCA plug, or something is misconfigured in the EFIS software. It’s also entirely possible that the pins are in the wrong spot on the audio panel connectors. I think I used either the ADF or DME connection, but I have to check my notes to make sure. I definitely screwed up the pilot side mic connection. If you plug the mic in, it keys the mic. With nothing plugged in, the stick-grip push to talk trigger works fine. I’m going to try with my other headset, but I suspect it’ll be the same.

The GNS430W seems to be working OK. I can’t hear SMO or LAX tower, but I can hear aircraft overhead talking to them. ARINC data connection from the 430W to the EFIS seems to be working OK as well, at least there are messages being passed back and forth. I can’t pick up the SMO VOR either. It’s a weak signal, and there are a couple of hills between me and it. If I had a flatbed trailer, I’d put the fuselage on it, tow it up to the airport parking lot and to some tests there. Those devices aren’t designed to transmit to ground targets, so I’m not surprised I’m not picking it up. Had a bit of a scare though. At some point the large frequency knob stopped working. I could change the point frequencies with the small knob, but the major frequencies wouldn’t change. After going through several power cycles and various configurations, it started working. I think I had some kind of remote control enabled, but it’s working as of now.

Transponder lights up, but shows no altitude encoding from the EFIS. That’s probably a configuration issue as well, and I didn’t spend a lot of time on it.

I didn’t get all the antennas done, I just put a BNC end on the COMM antenna cable so I could test the radio without risking frying the thing by keying the mic and dumping all that RF energy right into the box itself. The location of the COMM antenna might be a problem. When I key the xmit, the EFIS shows me descending at 500fpm and a 20 degree yaw to the right. Since the plane is still in the guest house, this is clearly incorrect. I think I can swap the transponder antenna for the COMM antenna (this is why I got a new COMM antenna with a BNC connector) and get the COMM antenna the recommended 6 feet from the EFIS. The question then is, will the transmitted signal interfere with the operation of the autopilot pitch servo? I’ve still got a couple feet of antenna cable to spare on each end, so I can move that antenna all over the place and still be OK. I’m just trying to avoid punching any more holes in my airplane. Of course, in retrospect, using that cheesy audio cable to carry the AHRS data instead of a proper shielded two-conductor cable may have been a mistake. I so want to be done with this…

Before I put the EFIS back in, I made a new LED warning light for the panel. This one’s chrome and screwed in properly unlike the cheesy plastic one I had before. Much more solid. That LED is friggin’ bright, though. Apparently 800mcd is bright enough to get your attention in bright light, which is fine, since this will be primarily a daytime aircraft.

I still need to test the GPS transmit to the ELT and ground the ELT as well.

ELT wires run.

1.5 hours

Whoever decided that the 5-pin mini-DIN plug was a good idea for connecting the ELT to the shielded GPS cable needs to be pulled apart by 4 out-of-tune Harleys. Finicky, tiny little wires attached to miniscule pins with freaking solder. Couldn’t use a d-sub crimp-type connection, no, that would make too much sense. To add insult to injury, you need to make a pigtail off the GPS receive wire so you can check operation by, get this, making a tester out of an LED light and a 300 ohm resistor. The panel components are fastened with 4-40 screws, the only things aboard to do so.

I guess what sucked the most was after waiting 6 freaking months for the ELT itself, it has to go and be one of the most painful installs I’ve run into yet. At this point, I’m almost ready to get back into fiberglass.

But the wires are run, and I now have to join them to the big bundle going from the spar up the firewall to the panel. I also have to run the extra PTT wire at the same time, but that’s not such a big deal. The next few days will involve that, remounting the EFIS, and wiring the power and audio for the radio stack. With any luck, I should be able to hear Santa Monica ground and tower by Sunday night.