The ability to instantly imagine the worst possible outcome (one of the few skills in which I have proven expertise) can be useful in some circumstances and professions. Much more useful, however, is the ability to recognize that the worst possible outcome is unlikely. While still working on that, another example of its utility has appeared.

After anticipating a multi-day effort to fix the flap control system wiring, necessitating deconstruction of multiple components on and around the relay shelf, I was pleased to find that just by taking the cover off the relay box (as I'd recently done to resolve the LVWAABM issue) I was able to easily reach the terminals of Relay #3, and easily swap a couple of wires to remedy my error. A great relief. It was also gratifying to find that prior planning (leaving extra play in the wire runs) and construction practice (solder tinning the ends of bare wires going into screw down terminal strips) made this easy modification possible. The extra play in wire runs allowed swapping wire positions at two terminals. The solder-tinned ends were still solid and reusable, whereas mere bare wires would have been mangled by the screw down terminals, requiring trimming the wire ends to get new metal, etc. The hardest part was doing this while bundled up against the cold like the Michelin Man.

This afternoon I'll bundle up again, put things back together, and might even get the center panel section propped up in place, ready for hookups. All things considered, a good outcome. Onward!

About ten days ago, BIA [before ice age], I was finally able to test the complete flap control system. I couldn't do that before then because testing required at least a) the flap controller, b) the external relay, c) the flap operation switch, and d) the flap mode switch to be installed and, prior to about ten days ago, they were not all in and wired. Unfortunately there was a pesky fault. All seemed well except the fuse would blow in one and only one state -- when selecting down flaps while in AUTO mode.

Today, after several hours spent hovering over the schematics and notes, I did finally figure it out -- at least I'm 99% sure I've figured it out. Turns out I managed to misread the external flap relay schematic when wiring one side of the D-sub connector on the relay box, resulting in miswiring two connections to the external flap relay inside the box. Fixing it will either take either 2-3 hours, or a day or more, depending on how much I can access with just the relay box cover off. Let's hope that will do it, because otherwise I'll have to take the whole relay box out, which means taking several other things out first. 

The good news is that A) comprehensive notes of the "as built" configuration made it possible to eventually track down the error without having to pull everything apart for a diagnosis, and B) I won't have to pay a commercial avionics shop to fix this. 

Looking up at the rear of the right side panel. The harness end of the 9-pin D-sub for audio remains to be done. The wire bundle arriving at the top center is from the firewall area. The nylon spiral wrap is wrapped with red silicone "rescue tape" to keep the tie wrap from sliding into the slits of the spiral wrap. All the red terminals at the bottom center are quick tabs on the ground power relay switch. Just below that, you can see a smaller bundle curving back toward the panel. The bundles going down the door panel exits the picture at the very bottom. The first one there is the "merge lane" transition bundle from the horizontal to the vertical. The rubber channel is visible on the panel's bottom flange, angling up toward the right. About half way up, there are some masking tape labels on the ends of the Co-Pilot volume control wires, which will be connected to the harness side of the 9-pin D-sub. Above the masking tape, two other bundles are tied together, again with black silicone tape under the tie wrap. Moving up the rubber channel, the blue terminals are attached to the two auxiliary power sockets. The Hobbes meter is above those, but is not visible here. The D-sub in the upper right connects to the multi-I/O inverting relay box, and the D-sub near top center is connected to the RS-232 serial port at the rear of the CO monitor. At the top center there is a streak of light. That's the trimmed edge of the corner wrap flange, which was scooped out for clearance of the CO monitor's D-sub connector.

Coming down the stretch with wiring and, as things get bundled up, I'm even more mindful of preserving options for the future. Working on the right side panel, wiring up the two auxiliary power sockets (switched and unswitched) I decided that I would put "piggy back" quick tab terminals on these sockets. These terminals came from Mouser, although SteinAir sells some sizes. They will make it possible to tap into either the MAIN BUS and/or BAT BUS from the right side of the panel in the future without having to rebundle new wires all the way back to the left side -- if necessary. I'll put a little light heat shrink on the piggy back tabs until they're needed, to reduce the "live" metal surface a bit.

Piggy back quick tab terminals on the two auxilary power sockets on the right side panel, will allow tapping into either MAIN BUS or BAT BUS from those points in the future, if necessary.

The completed right side panel audio harness.

As usual, I'm waiting on a couple small parts (LED paraphenalia) for the center panel, so I got started on the right side panel, wiring the stereo audio IN jack. (Unfortunately, the PS Engineering PMA4000 audio panel on the center panel is just monaural, so right and left channels will be combined... oh well.) This teeny jack has (5) pins, and is "normally closed." That means a signal (source #1, XM radio in this case) can be routed through the jack to the entertainment audio input by default when nothing is plugged into the front side. When something is plugged in on the front of the panel (source #2, an iPod or whatever) the existing normally closed connection is broken, and the new plug signal is fed back to the audio panel, instead of source #1.

The jack's solder lug terminals are very tiny. With careful cutting and twisting of the metal strands, these 24AWG wires just barely fit through the solder lugs. After soldering, each wire and solder lug is covered with heat shrink -- the beginning step in providing as much strain relief as reasonably possible.

The next photo shows that about 1.5" out from the jack, a short length of larger diameter heat shrink joins the five tiny heat shrinked wires into one audio cable that will go to a 9-pin D-sub interconnect, along with three wires from the Co-Pilot volume control potentiometer to the left. The (5) wires from the 3.5MM stereo audio IN jack have been twisted -- in hopes of adding a modicum of noise cancellation -- with the twists held every 3" or so by a 1/2" length of heat shrink. Then the new "twisted cable" has then been tie wrapped around the nearby threads of the big cigarette lighter socket, to provide strain releive for the audio jack's delicate solder lug terminals. Of course, there's a good layer of heat shrink over the cable, underneath the black tie wrap, to protect those small wires from the socket threads and the tie wrap itself.

Finally, the completed right side panel audio harness. The three 22AWG wires coming from the Co-Pilot volume control add a lot of strength and stability to the final assembly, not to mention a festive motif. 

Tomorrow (Yikes! It's late!) I'll wire up the ground power switch to the left, and a small harness over on the right to connect the Hobbes to the MIOIR and this panel will be ready to install.

This shot shows the (5) wires from the stereo audio IN jack that have been twisted -- hoping to proved a modicum of noise cancellation, and tie wrapped around the nearby threads of the big cigarette lighter socket, to provide strain releive for the delicate audio jack solder lug terminals.

Wiring the stereo audio IN jack. This one has (5) pins, and is normally closed. That means a signal can be routed through the jack when nothing is plugged in (source #1, XM radio here) and when something's plugged in on the front of the panel (source #2, an iPod or whatever) the existing normally closed connection is broken, and the new plug signal is fed back to the audio panel instead of Source #1. The pins are very tiny. These 24AWG wires just barely fit through the solder lugs. After soldering, each wire and solder lug is covered with heat shrink and, about 1.5" out, a larger heat shrink joins the five wires into an audio cable that will go to a 9-pin D-sub interconnect, along with the three wires from the Co-pilot volume potentiometer to the left.

Throughout the wiring of the airplane, I've used several D-sub connectors for connections to avionics, to a custom chassis into which I've put relays and monitors, as well as for inline connections of bundles of wires. I've put together a collection of random notes about D-sub connections that may be useful to someone who's doing some of this work for the first (or second or third) time, which can be found in the Library, Project Documents, Design, Electrical section. Feel free to add comments with other suggestions, tips or tricks you may know about.