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I ran the remote compass line forward this week. I had to secure it in quite a few places, as I had to route it around several stringers, rudder cables, etc. I also took the time to secure another wire bundle in the under floor area.

Yesterday I put the connector on the front end of the remote compass cable. Several other Dynon users have reported that there is quite a bit of electrical noise from the remote compass module, and that this causes noise on the radios. Based on an idea from other users, I put a switch in the power line going to the remote compass module, so I can turn it off and kill the noise if needed. Yesterday afternoon I tried powering up the EFIS to check whether the remote compass module was working. If the remote compass module is not working the EFIS uses a magnetometer inside the EFIS case. I powered up the EFIS and waved a magnet near it - the heading moved erratically, which meant the remote compass module was not talking to the EFIS. :( I was pretty bummed out, so I left the garage in disgust and came in for a couple of beer.

I had nightmares last night about the possibility of having a broken wire in the remote compass cable and having to replace it. But I happily discovered that I had simply put the power line to the wrong pin in the connector at the remote compass module. It was a real pain getting the connector reassembled while lying on my back working way up over my head, but I finally managed to get everything back together.

The remote compass module works properly now. :) The indicated heading is withing a few degrees of the direction I think the aircraft is pointed. It is pretty preliminary, but I can't hear any noise on the radios.

I revisited the rear seat intercom wiring today. I had started to run the wires back to the rear seat awhile ago, but I wasn't happy with the routing, so I put it aside. Today my brain saw a great routing that I had missed before, so I ran the cable. Next I need to solder on the headphone jacks and wire the rear seat Push-To-Talk.

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I have learned a lot about aircraft electrical systems from Bob Nuckolls, his AeroElectric Connection book and the AeroElectric-List. One of the list subscribers put together a huge (310 page - 737 kB) Frequently Asked Questions based on the info posted on the List, and Bob Nuckolls has made it available on-line.

Date: Tue, 09 Mar 2004 14:20:39 -0600To: This email address is being protected from spambots. You need JavaScript enabled to view it.: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Frequently Asked Questions Compilation--> AeroElectric-List message posted by: "Robert L. Nuckolls, III"List reader L. Holt has sent me a copy of his efforts to compilea list of frequently asked questions from the Matronics archivesfor the AeroElectric-List. This was a really BIG effort on hispart. I'm pleased that he has offered to share the product ofhis efforts. I've posted the document at:

http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf

This is a BIG document . . . about 310 pages. You can usethe table of contents he crafted at the beginning to find whereparagraphs on a major topic have been gathered together -OR-you can use the word search feature in Acrobat Reader to findwords and phrases in the total work.            Bob . . .            -----------------------------------------            ( Experience and common sense cannot be )            ( replaced with policy and procedures.  )            (                  R. L. Nuckolls III   )            -----------------------------------------

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I attacked the mount for the Dynon remote compass sensor this week. I decided to fold the mount from a piece of sheet, as that should be lighter and stronger than making it from several pieces. I drew up a prototype on a piece of paper, folded it up and crawled into the rear fuselage to see how it fit. The first one had an interference problem with the static line, and the second one had another issue, but the third paper prototype looked promising. So I traced it onto some 0.032 sheet, cut it out, polished the edges and folded it up. It seemed to fit well when I held it in place

The installation instructions say to get the remote compass sensor aligned within 0.2° of the EFIS, on all three axis. I had carefully measured how level the fuselage was and determined that it was leaning to the right by 1°, as the garage floor slopes towards the garage door. So all I had to do was use my digital level to align the compass mount 1° off level when I drilled the holes. Wonderful plan, except I leaned it the wrong way. so it ended up 2° out of alignment with the EFIS. I could have used a 0.312" shim, but it would have bugged the heck out of me.

So I made another mount and carefully drilled it in place. It must have moved a tiny bit as I drilled it, as it ended up being about 0.7° out of line, but I could live with a 0.063" shim under the right side of the sensor. Then I finally measured the alignment in pitch. I had thought that the alignment in pitch would be a simple matter, as I had measured the orientation of the bulkhead and determined that it differed by 10° from the EFIS. So I made the mount to sit at a 10° angle. Well, the top of the bulkhead seemed to be tilted forward just a bit, so I needed a 0.063 shim under the front of the sensor. OK, what's one more shim at this point.


Then I tried a trial install of the mount with the compass sensor bolted in place on top of those shims. Horror - I found that the shims lifted the front of the sensor high enough that the cable connector was rubbing on the bulkhead. I had made the bracket as short as possible so that it would be stiff, and only allowed a small amount of room between the connector and the bulkhead. But I hadn't envisioned the possibility of shims.


So, I made yet another bracket, a bit longer. And I measured the last one so I could drill the mounting holes on the bench, where I had better control of the drill. The alignment worked out almost perfect laterally, and I may need a 0.020" shim to adjust it in pitch. The new bracket was longer to make lots of clearance between the bulkhead and the connector, so I added a diagonal brace to stabilize it. I'll prime it when warm weather arrives and bolt it in place with brass (i.e. non-magnetic) bolts.

I also make up the first end of the connection cable today, but I have yet to string it from the aft fuselage to the instrument panel area.

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Another builder is having problems with his magnetic compass - very large errors. He asked me if I knew anything about degaussing the roll bar. I have been saving info on degaussing for a number of years, as it is a potential problem that I may need to deal with once my aircraft is finished. I decided to put this info on my web page, as some other builders may find it useful.

First, the Sacramento Sky Ranch has some apparently good info on their web site - Degauss Instructions.

I've collected the following information from a variety of e-mail lists, but I have never actually used any of it. So I have no idea whether any of it is good stuff, or complete garbage. Use at your own risk. If you use any of it, I'd appreciate it if you let me know what worked and what didn't.

Read on for the collection of info.

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Well, true to form all the stuff I have been working on took longer than expected. But I am making progress.

I had the intercom harness modified to extend the length of the wires for the rear seat jack. I started putting it in, but got bogged down finding a good way to route the wires. I didn't want to just put the intercom wires in the main wire bundle, as that might be a recipe for having noise in the intercom. As I was puzzling out how to route those wires I noted that there was an issue with the way I had installed the altitude encoder. It was installed with the fitting for the static line on the top, which might mean that any moisture in the lines would drain in the encoder. Probably not a good idea. So I moved it so the fitting for the static line was on the bottom. That will also make it more accessible when I have it calibrated.

I finished the roll trim wiring yesterday. The trim indicators slip into the panel from the cockpit side, with the wire bundle connecting up behind the panel. The panel will have to come out eventually to be painted, once I've got all the holes in it. That means that I couldn't just use butt splices to connect the trim indicators to the trim system, as I wouldn't then be able to remove the panel. I didn't want to have to lie on my back under the panel and wire them up after the front upper skin is rivet on either. So I decided to put Molex connectors between the indicator and the trim wiring. That was a bit more work now, but it'll be much easier to slip the indicators in later and pop the connectors together. It also means that if the pitch trim indicator ever fails when I'm on the road I'll be able to replace it with the roll trim indicator, as that one is much less important.

My Electric Gyro Corp turn and bank indicator arrived a few days ago, so I hooked it up yesterday as well. There were no installation instructions in the box, and I couldn't find any markings on the connector that indicated which pin got the power and which one was the ground. I wasted twenty minutes surfing the web looking for that info, gave up, then noted that the nice bright white label on the top of the turn and bank not only had the model and serial number, it had a list of the connector pins and what had to be connected to each one.

I'm on the road a few days early this week, then I'll have to finish off the intercom wiring and attack the mount for the remote compass module for the EFIS.


You can see the LED bar displays for the pitch and roll trim indicators to the left of the GPS.

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This instrument panel lighting stuff gets more complicated the deeper I get into it. So far I've got two B&C Specialties solid state dimmers, one for a gooseneck map light/supplemental cockpit light/emergency instrument panel light, and one for two LED flood lights. These solid state dimmer modules vary the output between 4v and 14v (i.e. system voltage).

Microair 760 Com display back-lighting - it works well when connected to the same dimmer module as the LED flood lights, and the back-lighting only draws about 0.03 amps. However there is an LED indicator that illuminates when the radio receives or transmits, and it does not dim. This LED is very bright at night, so it will be a nuisance. I'll probably end up covering it with something at night.

GNS-430 - the display and key back-lighting are extremely customizable. It could be set up to be controlled by the same dimmer module as the LED floodlights. It can be set up to switch its control to a photocell once the dimmer goes to a predetermined low voltage - i.e if you put the dimmer control to its minimum setting in the daytime, the GNS-430 will automatically vary its display intensity to match the ambient light level.

GTX-327 - it is fairly customizable, but the voltage level at which it goes into daytime mode cannot be varied. It won't go into daytime mode until the input voltage drops to about 0.35v. I thought I had a bright idea to use a zener diode to drop the solid state dimmer module voltage down to less than 0.3v. I invested $0.39 in a zener diode today, but my idea didn't work when I tried it tonight. So, I started wiring a small 2.5k ohm rheostat. One end of the rheostat goes to ground, the other end to 14v, and the variable output will go to the GNS-430, GTX-327 and trim indicators. The rheostat will draw a constant 0.0055 amp, even in the daytime, but I'm going to lose any sleep over that.

Ray Allen electric trim indicators - The trim indicator intensity can be controlled, but they are set up quite strangely. They go to a fixed low intensity if the control voltage is present, and go to a high intensity if the control voltage is below about 0.35 volts. The solid state dimmers don't go to a low enough voltage to kick the trim indicators into bright mode, so they will need a rheostat.

Grand Rapids EIS-4000 - it's display back-lighting is not dimmable. It seems to be set at a constant medium level. Time will tell whether it is too bright at night.

Annunciator panel - I'm still struggling with what to do for the four annunciator lights I'm planning. I haven't found anything reasonably priced that looks as professional as I want. I want some sort of light with the legend right on the face. At the moment I'm considering some LED light bars from Stanley Electric. Some other builders have used them and seem to be happy. One other builder thinks they are not bright enough, but I suspect that depends on how much you are willing to overdrive the light bars by running them at more than the rated voltage. LEDs are fairly tolerant of being over-driven, and they won't be ON that often, so I don't need a super long life. I think I will order a couple to play around with. They will get their own Bright/Dim switch.

Other - the Garmin GI-106A CDI (0.3 amp), Van's engine instruments (0.15 amp each) and magnetic compass all have incandescent lighting. They will get their own solid state dimmer.

Two shipments of odds and ends arrived today, so I can re-attack the roll trim wiring, etc.