Feb 23, 2024     Schematics - (2 hours)       Category: C22 Electrical

Gathering into one entry the schematics that are distributed into project entries, both pdf's and dwg's.

  Dec 02, 2020     13. cabin side - part 1 - (60 hours)       Category: C22 Electrical

The Cozy firewall is a non-magnetic stainless steel sheet over Fiberfrax. A lot of planning goes into the layout of both the engine side and the cabin side. The engine side is designed for ease of service, engine layout and clearance. The cabin side is about short runs, logical flow and ease of service.

A lot goes on the cabin side of the firewall. I made up a template and did the layout of components – battery, contactors, relays, battery and engine busses, et al. Cables and connectors come up from the lower corners, then run on the outside of the curve. I aim to have the runs to alternator and starter use the passthrough fittings below the right side of the picture (pilot side). The electronic ignition runs will use the passthrough below the left side of the picture (passenger side).

Ground - Engine side. The alternator grounds through its case to the engine mount. A #2 AWG cable connects an engine case bolt to a brass bolt passing through the firewall and becoming the cabin ground. That brass bolt is the fat point ground on the firewall, connects to a non-magnetic steel firewall by direct contact. Also on the engine side is a supplemental ground for the starter - it grounds through its case to the engine, and also through a #2 AWG cable to an engine case bolt.

Grounds - Cabin side. The busses are grounded by a brass bolt / fat point penetrating from cabin to engine side of the firewall. On the cabin side it is connected to battery negative with a #10 AWG cable. The starter contactor grounds, through two short brass bolts passing through the firewall. A #10 AWG cable connects one of the bolts to a field of tabs. The field-of-tabs has a brass bolt pass through to a second field-of-tabs on the engine side of the firewall.

Power - Engine side. The _normal_ power source is a 60a alternator (B&C LX60). Consistent with the Nuckolls schematic "Z101b", a #8 AWG wire runs from the B lead through a lower right side access port to the cabin side. The field wire is a brown plug on the forward side of the alternator, with a lead running alongside the other power wires, throught the lower right side access port. The _auxilary_ power souce is a permanent magnet generator (B&C SD-8), made to fit the vacuum pump port on the accessory case with a rated output of 8.4a at 3500 rpm (2700 engine RMP). The Nuckolls schematic allows for a generic aux alternator, while his text endorses the B&C generator. I followed the B&C instructions for the SD-8 generator, so that the aux power wiring differs slighting from the Nuckolls schematic (see below). In the future I may choose to replace the 8a with the 30a version from Monkworkz (also mounted on the vacuum pad). See https://monkworkz.com/product/mz-30l/ .

Power - Cabin side. The 60a alternator is fused by a 12AWG fusible link used next to the contactor connection (see schematic detail below). The alternator regulated by the B&C LR3D-14 'controller', consistent with the template schematic Z101. In the detail photo below, the LR3 is the silver box below the red tray. The LR3 is 1) a linear regulator, generating no audio or radio noise; 2) a solid-state, crowbar over-voltage protection circuit; and 3) low-voltage monitoring and warning (yellow light flashing at the panel). The controller also has overvoltage protection, a capacitor to smooth the current delivered and a relay to switch between main and backup alternator. At the panel a clear-yellow warning light that will illuminate if the crowbar over-voltage protection module is tripped or when the alternator switch is left off.

Above the B&C controller is a red tray. It holds a regulator for the backup alternator (B&C model PMR1C), which is a _switching_ series rectifier with a rectifier bridge, adjustable solid-state regulator circuitry, and built-in heat sink. At full load (8.4 amps output) it "rejects" ~20 watts of heat. Per Nuckolls, "The power-path components depend on thermal conductivity of the potting compound for heat rejection. The rectifier/regulator's service life is tied to optimizing thermal management." The installation instructions warn against mounting to a composite surface - the red tray is an aluminum platform for the unit. (On an aluminum tray at 8a output the B&C test results point to a max temp of 125F. Since aux power operations are last only until a safe landing, the heat seems a reasonable risk.) The large blue capacitor below the red tray has two functions – it presents the SD-8 generator with the starting polarity, and it smooths out the noise that comes from a switching regulator. Also on the red tray is a relay, switching the alt aux alt bus feed to the main bus. There are diodes protecting each of the relays and a diode bridge protecting the engine bus (the silver box above the red tray).

[I'm not overly confident that 8a of backup alternator can do the job. There is an alternative for a pad-mounted backup - the Monkworkz 30a. I'll check it out at SnF and can make a final decision after wiring the SDS system.]

4/16/2023. This evening I finished the power lines described above. It continues to seem nutty to have the heaviest cables (#2 AWG) used for the very short term task of starting the engine, while much lighter cables (#8 and #14) carry the power from the alternator and generator.

===============================================

Lots of learning. I had used several methods to secure fasteners (rivet nuts & click bond studs) to the cabin side of the firewall: marine adhesive, epoxy & BID, flox & BID, marine adhesive on aluminum plate holding an installed rivet nut, et al. I decided to test the security of the components. Results were terrifically inconsistent, with some click bond studs easily twisted off with pliers and others pried off with a paint scraper and elbow grease. Bottom line, I need to find a new way to secure components to the cabin side of the firewall.

The new approach is to build the system on the bench, firmly securing everything to a sheet that can then be attached to the firewall, using the existing holes. This will sharply reduce the number of firewall penetrations - I won't be drilling two dozen holes to secure everything. I then prepared such sheets using stainless steel, a coreplast board and my own layup (1/2 foam with 2 layers BID each side). The 22 gauge non-magnetic stainless steel was heavy (3 lb 13 oz). Coreplast was 2 lb 4 oz, my own layup 1 lb 14 oz (before trimming). 22 gauge aluminum was 1 lb 13 oz (after trimming) and it's easier to set fasteners in the aluminum. I'll go with the aluminum.

  Dec 29, 2023     06. Panel Final (?) - (48 hours)       Category: C22 Electrical

My panel plan has had major changes over the past few years, but now the changes are smaller and driven by market pricing of alternatives.

Structurally, the plans composite panel is replaced by aluminum. Thickness of the aluminum is .041. I don't know the alloy, but suspect 2024. Composite "piers" tie the aluminum to the fuselage at the right, left and bottom center. The radio stack ties the panel to the F25 behind it, again adding stiffness. Aluminum angle at the top carries red LED's and adds stiffness.

A busy panel with old school round guages and small screens is now glass panels + ipad. Switches are now (mostly) a row at the top of the panel - see the photot of the test fit. I will work on some other parts of the build, then buy the avionics and cut the final panel. After mounting everything I will set the fuse block locations and do wiring.

(Sooner or later I have to buy a lot of electronics. But not today!).

  Nov 08, 2023     08 - back up com - (12 hours)       Category: C22 Electrical

I came across a Becker com radio that was thought to be working. It wasn't, and taking it apart did not show anything obvious I could repair. I am lucky that the comapny is based here in Florida, and they were able to quickly repair and return the unit. The spend including shipping was the radio ($85) + repair ($190) + break-out connectors for the male and female DB-15 connectors. I know where in the panel I want it, and now I have to build the mounting tray. (A shout out to Becker - these units are beautifully made and packaged, and the most durable brand I know. Because the US is still a 760-channel environment, we can use these older models. 5 watt transmit. )

  Jul 19, 2020     Transponder + ELT antennas - (62 hours)       Category: C22 Electrical

Transponder + ADSB + ELT = 3 antennae.

The Dynon transponder unit is "SV-Xpndr-261" and the antenna connection is a TNC male from the antenna locking onto TNC female on the back of the unit. The Dynon ADSB unit is "SV-ADSB472 and needs a BNC male connector locking onto the BNC Female on the back of the unit. The ELT unit is likely to be the Artex ELT 345 with a BNC male connector locking onto the BNC female on the back of the unit.

Along the way to my antenna install I took a few detours and learned a bit. I bought and figured out how to use a vector network analyzer - it was a fun way to master a slick piece of test gear. After carefully making 2 high tech annular antennae, I decided to use the simpler "ball on a stick", and then I made and discarded 3 different kinds of ground planes. I then removed and discarded my homemades in favor of something small, pre-made and inexpensive listed on Amazon (found by Del Schier). See the attached Word file for pictures. As sent from the manufacturer, it worked well only on 1090 MHz and the newer all-in-one transponders seem to require an antenna that works on both 978 MHz and 1090. Del created a simple mod and now it works on both frequencies with < 1.2:1 VSWR. "...I simply soldered .65 mm brass extensions onto both sides of one of the pair of dipoles and it now resonates at both frequencies. See attached photo of the mod and the VSWR plot. Note: the little triangles on the plot are at 978 and 1090." In place of soldering onto the circuit board, I used copper foil with a conductive adhesive. Per Del: "It should have the same performance as a 1/4 wave rod or any BIG $$ dual frequency TSO'd antenna and it is very light and does not require a ground plane." As installed, I have SWR's of 1.2 (ADSB) and 1.3 (transponder). Rather than make cables with SMA connectors, I'll buy those online.

Today's ELT's operate on both the old 121.5 Mhz and the new 406 Mhz (typically with a GPS locator signal). I did a Jim Weir-specified dipole with legs of 22.5" and 6.3" and installed it on back of the pilot seat. Looking at pictures of the Artex ELT 345, I see a BNC connector, so I made up an RG400 coax with one end a male BNC and the other split between center and sleeve, each soldered to the long leg of the copper foil tape. The short leg of the dipole was electrically connected with a conductive adhesive copper foil.

  May 09, 2023     CO detector - (1.5 hours)       Category: C22 Electrical

Aircraft need a CO detector. The cool new thing is active detectors like the "CO Guardian" ($640) or the newest, a CO detector embedded in the headset. I went with the most common solution, a $4 2"x2" card with a dot that changes color in a CO danger condition, replaced at annual.

  Jan 13, 2021     14. Firewall - cabin side - (12 hours)       Category: C22 Electrical

This design certainly has evolved - a dozen drafts of how to arrange the components on cardboard, 3 ways to fix components to the aircraft, 4 versions of how to make the removable panel. One of the very last changes came from Ross Farnum at SDS. Seems it takes 6" of clearance for the cables going into the EM-5 electronic ignition modules. I did a last minute juggle to create a clear field for the cables. No, a right angle DB25 won't work. I think all is final, and I'm drilling for the fasteners.

On the fastener map, the green dots are click bond studs, a 10-32 thread and the pink X's are 6-32 rivet nuts. Both use 3/16ths holes in the aluminum, drilled and deburred. I want to prevent turning of stud or rivet nut. The click bond studs were notched and the notch aligned with a 1/16th hole drilled in the aluminum, then set with JB Weld, taped firm against the aluminum during cure. The holes for the rivet nuts are lightly notched before the squeeze, aiming to reduce risk of turning. Back to the fastener map - the purple hex shapes are the through bolts that use existing firewall penetrations. I will put the head of the bolt on the engine side and secure from the cabin side, with AN hardware and thread locker.

Contactor basics and wire size. Contactors are powered switches that control high amperage flows. The battery contactor draws 0.7a continuous, with power flowing from the battery terminal, to a post of the magnet wiring, around the magnet, out through the second post and then through the battery master switch to ground. The starter contactor draws 3.5a intermittent, flowing from the battery to the starter button to the starter contactor, then out through the contactor case to the battery ground. For ease of recognition I used red and black twisted pair, in 16 AWG. Over the 14' run from panel to firewall the 20 AWG is rated for 15a intermittent, 7a continuous.

  Jun 14, 2020     00. 12v, dual alternators, single battery, Nuckolls Z101 - (25 hours)       Category: C22 Electrical

Wiring this airplane will involve a lot of learning. I'm hoping that acknowledging ignorance will protect me in this part of the project. And maybe I'll come away with a better understanding - the FAA says I'm allowed to do build an airplane for research and education. Here's hoping some education happens.

Reliability is darn important. The A3B6D has two mags mounted on one shaft - it has only a little more reliability than a single mag system. I used this engine (on a BD-4) with that mag + a first generation electronic ignition system made by Light Speed Engineering (Klaus Savier). For the Cozy I plan dual EI and the more modern SDS system - weight savings, more powerful spark, said to be more durable, etc.. Dual EI means that if I lose electricity I lose spark, and I'm guessing the Cozy is a poor glider. Therefore, this all-electric airplane needs a fault tolerant electrical design.

Like most builders, I stand on the shoulders of Bob Nuckolls - 50+ years of designing electrical systems for aircraft and probably 30 years of sharing the information through the AeroElectric Connection (first a book and then a forum). Bob recently refreshed his schematic for all electric aircraft - the "Z101" using dual alternators and a single battery. See the drawing below. It is his most recommended design and my starting point.

Continuing the homage to Bob K., a snippet from his "getting Started" (in full at http://www.aeroelectric.com/articles/Getting_Started.pdf):
__________________________

RULE 9A:
A single point ground system shall be established behind the instrument panel with sufficient attach points
for all accessories in the cockpit area. In deference to RULE 2, a forest-of-fast-on-tabs ground block similar
to . . . http://www.aeroelectric.com/Pictures/Grounding/gnd_bus.jpg

The threaded stud on the ground block assembly would penetrate the firewall and be used to terminate
battery (-) leads on either side of firewall and the crankcase ground strap on the engine side of the firewall.
In the case of canard pushers with the battery up front, the ground bus would be mounted forward of the
instrument panel. If the airplane's firewall is metallic, then a brass bolt and appropriate washers and nuts
would be used to provide an engine compartment ground stud and connection of the ground lead to the
firewall. A ground strap like . . .http://aeroelectric.com/Pictures/Wiring_Technique/bbs.jpg or http://www.aeroelectric.com/Pictures/Wiring_Technique/sbl.jpg
. . . will be used to connect the crankcase to the firewall ground stud.

The welding cable illustrated in the photo would also be used to make the short, VERY flexible jumpers from battery (+) and (-)
terminals.

Any ground straps provided around the rubber biscuits of an engine mount will be removed. Engine mounts
are for holding engines on airplanes and not use for any part of the electrical system.
-------------------------------------------------------
RULE 9B:
Avionics and other electrowhizzies on the panel would benefit from an “avionics/panel ground bus” as
described in the latest revision of the ‘Connection. See:
http://aeroelectric.com/articles/Rev11/18Audio_R11.pdf
and . . .
http://aeroelectric.com/articles/Rev11/AppZ_R11J.pdf
and illustrated in . . .
http://aeroelectric.com/Pictures/Grounding/AGB_V.jpg
http://aeroelectric.com/Pictures/Grounding/AVG_RA.jpg
http://aeroelectric.com/Pictures/Grounding/Avionics_Bus_3.jpg
http://aeroelectric.com/Pictures/Wiring_Technique/Avionics_Ground_3.jpg
--------------------------------------------------
RULE 10:
Tefzel wire used throughout with the exception of cranking circuit fat wires where 4AWG or 2AWG
welding cable would be used. An alternative FAT wire could be one of the new copper-clad aluminum wires.
These new materials are as solderable and crimpable as pure copper conductors.
_______________________________________________________

In the next entry I will repeat the electric system build log created by Chad Robinson - he's a skilled engineer and his work deserves consideration. Also, it may help me identify circuits in the tangle of wires I see in the cockpit!

  Apr 06, 2023     95. Manuals       Category: C22 Electrical

see the attached.

  Feb 07, 2021     97. Expansion bus - (8 hours)       Category: C22 Electrical

One fun thing - I ran and will set aside a 12-line expansion block, running firewall to instrument panel. I bought 5 meters of 12 conductor shielded cable, with tinned copper conductors. The individual wires have a conductors with a cross section of 0.75 mm, just slightly bigger than 19 AWG. It's not a perfect choice since individual wires are shielded in PVC rather than tefzel. Bob Nuckolls notes that PVC was used in a generation of Cessnas and he sees it as appropriate for use on the cold side of a firewall. That works for me. One end of the cable was wired on the bench, the other standing at the side of the airplane. I made it once with the full length of the cable, figuring I would have a big service loop. I thought better of it, and cutting to length saved 11 oz. Tested for continuity and cross feed and no problems.

The rear end is at the lower left of the cabin side of the firewall. The forward end is on the passenger side of the panel, secured to the panel with rivet nuts (great when working the aluminum!). I built and installed the one end, then figured out I needed to set the path of the cable to travel alongside my 4 AWG runs. Solution? Chop it off and do it again.
The shorter cable did save 11 oz., and I understand it takes that kind of weight discipline to make this project a success.

  Aug 07, 2021     05 switches - (4 hours)       Category: C22 Electrical

Hardware.

Carling toggle switches, with actuators of either the nylon paddle or steel bat. The switch guards protect
- switches that would affect engine spark
- switches that control the fuel pumps and
- the defeat of the autoextend module for the landing gear.

Battery Contactor / "Master". Battery contactors are the "master" switch, and I used the standard wiring - the panel switches the ground while power is a direct connection from the battery post. So long as the ground is connected the battery will flow 18 watts of power to the contactor. The electromagnet will stay in the raised position and the contactor will stay closed. The panel switch is off-1-both, where the #1 circuit completes the link to the battery ground. I used 16 AWG for the ground connection (a red & black twisted pair) at the switch - on an all electric airplane this is a peace-of-mind matter. The "both" position brings the alternator online by sending the field signal to the alternator. Note that another switch, described below, changes the power source to the backup alternator. Alternator field is a 3a circuit.

Start Contactor / "start button". Using electronic ignition I have a start button and a 1-2-both switch for coil packs. The starter load is intermittent, and that FAA chart allows for 20 AWG. I made a red (starter) & black (battery) twisted pair for the contactors, using 16 AWG - on an all electric airplane this is a peace-of-mind matter.

Buss fuse blocks usign ATC style blade fuses.

  Oct 11, 2020     03 Panel - drafts and discards - (58 hours)       Category: C22 Electrical

I learn and re-learn the common sense stuff:
1) Know and comfortable with CAD? You're way ahead of me. In my case, I need to stay on paper and cardboard for as long as possible. But if y ou can outsource panel cutting with a reliable CAD file, it would be a lot easier than my 8 iterations (paper, cardboard, thin plywood and then aluminum).
2) Aluminum is better for panels because of the design of the avionics mounts. 2024 is everywhere but bending 6061 is lot easier than 2024.
3) The project I acquired had the standard madness of a composite panel cut to spiderweb by all the instrument holes. A spiderweb cannot add strength or stiffness to the structure. Now a radio stack ties the panel to F28 (fore-aft stiffness) and a bit of square tube runs across the panel bottom, tying together the right and left fuselage side.
4) If I knew for certain what my layout would be, I might make it modular. But maybe not – most of the wiring is across the natural panels, and it's just as easy to pull displays as to pull a module.
5) I should have created a wiring channel before I wired anything other than the 4AWG power and ground cables. I clipped open the ugly bundles and am doing it over, threading wire through jumbo Adel clamps hanging on the bottom of F28. The upside is that I have yet another chance to test all my connections.

I worked the last wood template near to death - when I made mistakes I patched it with flox and tried again. I found and solved all my clearance issues and changed the layout multiple times. With the wood perfected I started working on aluminum sheet, first with .063 2024-T3 then .050 6061. See below on aluminum alloys. I worked through multiple colors before setting on flat black with labels of white text on black. Lesson - don't trust "paint and primer in one" over any existing finish and don't spray a clear over anything from another family. To secure the panel to the composite perimeter frame I like AN3 bolts and 10-32 machine screws into 2-lug nut plates, floxed to small pieces of G10 and topped with a layer of fiberglass tape. These suckers hold, and the compressive load is the aluminum sheet on one side and the G10 on the other.
________________________________

Side bar on aluminum alloys....The former panel was aluminum alloy 2024 - readily available and easy to cut and drill. Even so it is easier to work with the recommended alloy, 6061. After the rolling mill 6061 is a lumpy mix of magnesium, silicon, and other elements in aluminum. Solution heat treatment is done by raising the alloy temperature to about 980 degrees F and holding it there for about an hour. This dissolves all the alloying elements into a solid solution in the aluminum. Then quench the alloy in water - cool it rapidly enough to prevent the alloying elements from precipitating on cooling. at room temperature. This is called the T4 temper. If we take this material and heat treat it at a temperature between 325 and 400 degrees F, the alloying elements begin to form ordered arrays of atoms in the aluminum matrix. These arrays are called GP zones, and they strengthen the aluminum considerably. This is T6 temper and how I bought it. Heat it again, the ordered arrays break down and the sheet bends easily. Now the clock is running...an age hardening process takes place at room temperature over a time period of four to five days, with 90% of the hardening occurring within the first day. Because of this effect, aluminum parts often need to be shaped soon after a heat treatment process.

Here's the mechanics of annealing in the home shop. Mark the bend line, then use a candle to put light soot on that line. Think through the bending jig and handling hot sheet, _then_ use another heat source to burn off that soot line. I have a propane torch, and w/o an O2 feed it burns at 2000 F - I play the flame over the bend area to raise the temp gradually. The soot line burns off at 700F, and then I use a spray bottle to quench. I clamp along the bend line and the annealed 6061 bends with hand pressure. To get a crisper bend I use wood blocks and soft hammers. It aircools over 5 days, and is reported at 90% strength within 24 hours. I understand this is a T5 condition, not T6, but has the rigidity I want.
________________________________

For layout I repeatedly used the Cozy template in X-Panel software, muttering all the while. I do not recommend X-Panel - expensive and the ability to export a CNC file is even more expensive. The template doesn't fit this airplane. The outline view is _not_ a cutting guide - it will show the instrument's total dimensions but not the panel hole.

Below is a template I found useful for my steam guages. Print it (use the "original size" option, paste it on a bit of aluminum sheet, market the center and corners, and outer edges of the standard instrument. Save it forever!

  Apr 08, 2023     96. Regulator test rig - (2 hours)       Category: C22 Electrical

Following instructions posted on AeroElectric Connection, I used an automotive regulator to build a test rig. If and as I suspect a regulator problem, I can easily put this in place of the installed one, then test the resulting performance.

  Mar 13, 2021     02 panel - patch & repaint - (6 hours)       Category: C22 Electrical

Getting the labels and switches just right was the path to seeing that the panel color was too dark. I loved the hammered bronze look, but you have to look 2x to read the label, and that won't work. And a poorly fitted notch for the altimeter adjustment could look better, so let's get it done. I removed the panel and instruments (30 minutes?) and used a flox / G-Flex epoxy mix to fill the mis-cut. See the circled area below. Once it cures I'll carefully file the notch for the adjustment knob, and then move ahead with the repaint.

FYI, I'm going with a light grey / dark silver. That goes well with the painted interior and with the labels.

Now in April 2023 I'm recutting the panel. I want a more standard layout, and that means
- engine and aux alternator switches separate from lights and accessories
- lights & accessory switches in the normal location along the top edge, moving engine and aux alternator switches to left edge
- built in red night lighting along top edge (probably a piece of right angle riveted to top edge)
- bottom edge extended full length, with the leg hole cut outs folded back for a longer shelf
- fuse blocks moved to the longer shelf
- round guages in a column to the right of the radio stack
- refinement in the switch alignment - using a blueprint sized print of instruments on a standard Cozy panel
- 6061 alloy! The 2024 was hell to bend and this should be much easier.

I'll change the paint scheme one more time - a flat buff might work well.

  Nov 17, 2020     83. Shore Power - (64 hours)       Category: C22 Electrical

I installed a "Piper" shore power socket, and wired the matching plug to a set of jumper cables. Below you can see the Nuckolls article that describes how to wire the socket, which includes another continuous duty contactor and "crowbar" circuit. In addition to what Nuckolls described, in place of crowbar circuit that blows the fuse, I went with a smart voltage detection circuit, such as would be used in a modern control system. The gist of it is
- flip a toggle switch and the voltage detector runs with a power drain of 3 milliamps - on par with a quartz watch.
- The inserted plug connects to the socket, which has its voltage detected and compared against low (9v) and high (15.7v) thresholds. This is protection against a battery cart trying to send a GA-standard 24v.
- If between the two values, the detector closes a (normally open) relay and power goes to the contactor. Power flows to the battery.
- If and as socket voltage spikes, the relay opens, the contactor opens and the socket is disconnected from the battery. Any fingers inside the socket can get pinched, but not shocked.
- As a final protection, when the toggle is "OFF", there is no power to the voltage sensing relay and it goes back to its normal open, which removes voltage from the battery contactor.

I've found that sometimes I don't want to bother with the socket and I just use a batter charger or jumper cables. In that case, positive goes on the battery side of the contactor and ground clips to the socket cover. Seems to work quite well...

If I were doing it again I would install the unit in the forward hatch - easier access, no need to get the cabin wet on a rainy day, and further from any prop.

  Oct 31, 2020     15. wiring EI - (1 hour)       Category: C22 Electrical

Backtesting the switch layouts.... The instrument panel cutouts plan on using the "Design1" programmer. This is a newish model, and so far SDS has posted the switching and fuses to-from the older style panel-mounted controller head. This looks consistent with what I understood when I did the switch layout. Looks like two electrical cables run from the control head back to the firewall one for the coil packs and one for the main harness. I'm guessing the panel switches are wired into those harnesses, and the harness will be custom built to fit my project. For purposes of the firewall arrangment, the single ECU dimensions are 3.875 x 8.5 x 1 inches, gold anodized, 6061T6, CNC'd billet. I'm doing double, so figure it at 2" tall.

More electrical redundancy - this is a dual alternator system with a single battery. The Nuckolls design standard calls for sufficient redundancy to complete the planned flight. The SDS EFI system draws 1.5 amps and the fuel pumps draw 4.5 amps in normal ops (14 gph), 5.5 at the max expected draw (20 gph) = 5.5-6.5 a. Add 4a for the avionics = a total draw of 9.5 - 10.5 a. The PC680 battery has 16 amp hours, so I get 1.5 hours in which to notice the flashing lights and change to the back up alternator, cut high drain items (not many of those) and plan for a landing. This is an all electric engine in an airplane that "glides" at 150 mph, so the circle in which to find a safe landing is ~200 miles radius. I'm certainly safe, but the next step would be a move to a higher capacity b/u alternator - the Monkworkz ML-30z 30a permanent magnet, also using the vacuum pad. That will shift duration back to fuel remaining.

  Oct 04, 2020     Cabin Lights - (40 hours)       Category: C22 Electrical

For cabin lights I went through 3 iterations before going final with aluminum panels of LED strips fed from a single pulse width modulating dimmer and a selector switch (red-off-white) mounted on the panel. There are red panels in the strakes + instrument panel lip, and white panels in the strakes and overhead rear. Each panel is 0.5 meters long, and 10 strips of 36 LED's, for a panel of 360 LED's. The max draw is 5.3a for the 3 white panels at full output. Below I show both the LED strips and the amperage test set up. The wire runs are short, and I used 20 awg from main bus (15a) to dimmer to red-white switch, and then switch to the point where the current is split right-left-rear. From that point I used 22 awg.

  Oct 16, 2020     05 panel - mounting trays and supports - (32 hours)       Category: C22 Electrical

I ended up spending a week fussing with the supports and stiffeners around the panel. It is shaping up as a stiff, strong box with very little flex, while also being fully removable.
- The instrument panel is .063 aluminum bent into an "L", and right, left and bottom center of the panel are tied to the old plans panel with machine screws into my home made G10 nut plates, floxed.
- I have a 1/2" square aluminum tube running across the remnants of the plans i-panel, screwed in on the right, left, and center support. The bottom edge of the panel attaches to the lower edge of the square aluminum tube, using nut plates attached to the top of the tube and machine screws coming up through the tube.
- The top of the panel screws into another piece of square tube, increasing stiffness at the top and across the center.
- Side panels of the radio stack attach to the IP and the cross member used for lift pins into the canard. It's as strong as anything not called a spar. There was some experimentation and dead ends in the shape of the supports, but I finally got where I need to be.
- The audio panel and the 2" GPS-Comm are held in manufacturer-supplied mounting trays, them selves screwed into rivet-nuts on the side panels. The mounting trays add rigidity.

Theoretically I can disassemble and pull out the panel in one piece - I have to take out 2 machine screws from the top edge, three across the face from the bottom and 4 from the leg openings. That is not super easy, and maybe I overbuilt this.

  Dec 08, 2020     98. Discarded - copper tubing connections - (6 hours)       Category: C22 Electrical

I wanted short distances for all the main power connections, and certainly achieved it. On the firewall I have a vertical stack of the battery, my "fat wire point", the battery contactor and the battery bus. The total distance is 5 inches, and the longest segment is 2 inches. It is clumsy to have distances that short connected with cable and lugs.

Consistent with advice in AeroConnection, I am connecting these parts with solid copper, formed from sections of copper tubing. The hydraulic crimper has multiple dies. Reversing a pair to get a flat surface, the 3/8 inch pipe is crushed to a flat of 14 mm x 1.2 mm = 16.8 square mm cross section. This is the same cross section as #5 AWG. which has a resistance of .00103/meter. 5 inches is .127 of a meter, so the length has resistance of .000156. Using an online calculator, at 14 volts it can carry better than 3000 amps while losing less than 1 volt. Yeah, I think it will work for my system.

A headache in using solid copper is the alignment of the attach point - each of the 3 connections has ends perpendicular to each other. Cut it, crimp it, test fit, modify, test fit... there is no time savings here. Once fitted, cover with shrink tubing for some insulation - getting zapped is a PITA. A better approach might be to make the copper bar and put twists in it in order to get the alignment - I'll try that if I have any connection problems.

  Feb 12, 2021     07 - Avionics Bus - (18 hours)       Category: C22 Electrical

I made, installed, removed and then repurposed two power conditioners. The more versatile of the two is now used to condition the 5v power that runs to the LIDAR sensor. The brown-out device is still available, and I may use it as a supplemental power input on the Garmin GPS-Comm or the Dynon. I appreciate the several rounds of consultation with Charlie England (AeroConnection guru, #2 to Nuckolls).

At the front of the plane I have gone through a heck of a lot of circuits, and decided to organize them onto 3 buses - a 20-fuse main, a switched 8-fuse for cabin accessories, and an always-on 6-fuse dedicated to the radio stack. At the rear of the plane I have a 6-fuse main and a 14-fuse engine bus. All in, that's 50+ circuits!

  Jan 20, 2021     82. Making cables - (10 hours)       Category: C22 Electrical

I've been making my own power cables, connecting battery to contactor, contactor to starter, main fuse block (rear firewall) to the front fuse block (instrument panel), et al. I started with the Bob Nuckolls recommendation for fat wires - make cable ends from copper pipe. The result was great in carrying current, but way to difficult to get good looking ends with smooth bolt holes. I bought an assortment lug ends and a hydraulic crimper. The result has been much better.

One of the lug ends had too small a hole, so I had to replace it. That was a chance to cut into the lug and check how my squeezing was doing. OK! See the two photos below. The first one shows the cable just outside the lug. You can see the individual wires of the 4AWG cable. The second photo shows a cross cut in the center of the lug. Under compression the wires merge into a solid mass, and there is no space between the copper and the tinned copper wall of the lug. I didn't get that solid metal look all the way across the cable, but there is still one heck of a low resistance connection. I don't know that all the cable ends are this good, but this one looks acceptable.

The spend was on a hydraulic crimper (Klutch brand from Northern Tool) and an assortment of lug ends (Amazon, their larger assortment). Make sure to get copper, tinned, with a tang end opening so you can add solder if you want to.

  Jul 12, 2020     Lights: Nav, Strobe, Land and Taxi - (16 hours)       Category: C22 Electrical

I started with the Whelen wing tip lighting, the "Microburst III". There are less expensive choices, but I spent a lot of time in the CT aviation crowd, and learned respect for the Whelen team and products. Worth the $450? I'll find out over the long haul. The sooner you install the lights the sooner the lenses will break. I'm getting all the connections ready, but I won't do final install until I am at the airport. At the wingtip the connectors are DB pins, crimped, with shrink tubing with inner glue used for strain relief. DB pins are rated for 5 amps in low density loads. This load is significantly less than the rating of the DB pin connection. The connections at the wing root are shelled DB connections - there is room for a connector and it is possible the wings will come on and off several times.

The FAR's governing this area were clarified with Advisory Circular 43-217 dated 12/12/2018. At section 11.7.1 the AC says the required light intensity is in 23.2530, which says "Any position and anti-collision lights, if required by part 91 of this chapter, must have the intensities, flash rate, colors, fields of coverage, and other characteristics to provide sufficient time for another aircraft to avoid a collision." The AC also says that Part 23 aircraft certified prior to August 30, 2017 comply with 23.1405, which gives a table for required output measured in "effective candela value". At a measuring distance of 1 meter, the values for candela (lumen per steradian) and lux (lumen per m2) are the same and a candela is to 1 lumen x square meter per steradian. Per the FAR's, the light should put out 400 ECV at the 0 horizon. My non-calibrated light meter shows light output of 421 lux, so I believe I comply with both standards.

Wire sizing From AC43.13-1b: "Wires must be sized so that they: have sufficient mechanical strength to allow for service conditions; do not exceed allowable voltage drop levels; are protected by system circuit protection devices; and meet circuit current carrying requirements." With a nominal 14 volt system the allowable voltage drop is 0.5v continuous, 1v intermittent. As applied to the wingtip lights....... Total amp draw at 14v = nav 0.25 continuous + strobe 0.2 average and 1.2 intermittent. Each wing 14', total single wire run estimated at 16' x round trip = 32'. Fig 11-2 (continuous) says 22 awg handles 1a for 30', so redundant for the nav and average strobe draw. Figure 11-3 (intermittent) says 22 awg will handle intermittant 1.5A in a 40' run, so good for the strobe intermittant. The ground has to handle both loads, so 0.45a average and 1.45 intermittent. I upgraded the shared ground to 18 awg - better safe - and fused the 2 circuits (Nav & Strobe) at 5a each. The old fashioned strobes handled a lot of current and created interference for the com circuits. LED strobes are low current, but still a strobe and run alongside antenna wires. For the wing portion a good twist in the wires, and at the wing root it connects to shielded twisted pair. As a caveat to the tables, I note that Whelan manufactures these lights with 4 leads of AWG 28 or so - those are surprisingly fine wires.

The nose holds landing and taxi lights, a pair of 6-LED lights in aluminum cases which are finned to act as heat shields, with shock resistant design (intended for use on ATV's). I modded the cases for fit in the nose cavity, then attached to the bottom and side ribs with dabs of flox. Connectors are DB pins, crimped, with shrink tubing with inner glue used for strain relief. DB pins are rated for 5 amps in low density loads. This load tests at 0.9 amps at 12.8 significantly less than the rating of the DB pin connection. The wire run is about 3 feet x 2 = 6, so 22 AWG is redundant, fused at 5a.

I made and rejected multiple lenses - 5 in plexi and one in Lexan, before learning how to make a good Lexan lens (heat very slowly, nudging up the oven temperature to a soft slump. The lens was trimmed with bandsaw, then sanded to final profile and attached with silicone. The nose compartment is unventilated and the LED's generate heat. I placed a probe between the lights, sandwiched between the radiator fins. The LED's raised the fin temp from 88F (garage temp) to 120 (15 minutes) and then 141F (30 minutes). The fins were uncomfortably hot to touch. The surrounding composite surfaces were only slightly warmer than the air. With landing and taxi lights typically on for less than 15 minutes and a transition temperature of 165F (50C), I am satisfied that this solution works for this application.

10/18/20 - I came back to the lens and decided it needed a better shape. I rebuilt the base with 2 plies of BID, then a foam micro slurry, then micro. That was sanded flat. I cut the existing lexan lens to have a matching flat, and attached with the flexible and durable "Shoe Goo". See photo. I then faired with a wood flour + epoxy mix.

  Sep 26, 2021     Cabin Accessories       Category: C22 Electrical

Several of the accessories are switched at the device or somewhere other than on the instrument panel. I created a separate bus to handle these loads:
right USB port (3a) left USB port (3a)
right seat heater (5a) left seat heater (5a)
cabin heat blower (3a) defrost blower (7.5a)

I had just finished the radio stack and immediately put the sub bus on the side of the radio stack, and moved the ground out from under the radio stack. The new look is easier to service, with the tradeoff that removing the radio stack now requires disconnecting that cabin accessories bus.

  Sep 15, 2020     cabin heat - (2 hours)       Category: C22 Electrical

There are two blowers that address cabin heat.

A plans blower moves heat across the exhaust muff and pulls it forward. That is done with a marine sump blower, drawing a max of 1.2a and fused at 5 amps. The harness appears to be equivalent to 24 awg. I will follow the FAA rules on load, distance and allowable drop. I will install a heat duct from the engine compartment forward to the passenger footwell, with the motor forward of the passenger rudder controls.

A defrost / avionics fan pushes air across the radio stack and then washes the front of the canopy. This is a 6 amp rotary fan The two work well together, able to spin the motor at all settings and drawing 6v at the half-way setting and full battery voltage at the "max" setting. The manufacturer wired the fan with 24 AWG; my wiring will be to-from the IP connect points, fused at 7.5 amps, wire as per the FAA rules.

I also picked up a nice 10 amp pulse width modulation rotary switch. It is ideal for these motors, but I'm not sure it makes sense. When you want heat or defrost, you want it full on. Is there a use for the switch?

  Dec 08, 2020     Aux Alt tray - (6 hours)       Category: C22 Electrical

I'm using the permanent magnet alternator spec'd in the Nuckolls architecture, manufactured by B&C Electric and sold as the "SD-8". The kit includes the SD-8, over-voltage protection, a 20 amp relay, regulator, capacitor and instructions. I installed it consistent with the instructions - horizontal on aluminum. (I spent a week of 1-2 hour sessions doing this 4x.) At the end, what you see below - scrap aluminum turned into a tray to hold the switchery of the aux alternator. Two rivet nuts in the aluminum plate catch 6-32 screws holding the red tray to the firewall. Using the tray allows me to horizontally mount the regulator on a cooling surface, and, of course, to do the connections at the bench.

The big blue cylinder is a capacitor, included in the PM-8 kit sent from B&C. That plan was intended for lighter weight engines - think an O-235 in a Long EZ. With the cap the alternative alternator has a starting charge. If and as I had to hand prop the engine, I could switch to the auxiliary alternator and this cap would support the rectifier. There's not much reason to take it out, but it's not in the Nuckolls diagram and not something I'd do again. Nuckolls said not to worry about it - it certainly won't harm anything (so long as I don't lick the terminals!).

  Oct 13, 2020     04 Panel - Labels - (40 hours)       Category: C22 Electrical

Wow, this took a long time, with several dead ends. I ended up finding a clear material which I can print on a desk jet printer. ("Octago Inkjet Transparency Paper" available on Amazon.) I tweaked and changed layout repeatedly, using an Excel spreadsheet to keep alignment. The Excel-based layout was converted to a screen shot, saved it as a jpg, reversed in a photo editor, and pasted it into a Word document. From there I could print the picture on the transparency. Now the printing is on the inner side with a protective film.

Notes on what didn't work.
- I have a panel in a non standard size. If there was an easy way to digitize the dimensions I would chase having one watercut and engraved. With no easy path to the right dimension I went old school, hand cutting all the holes.
- Label tapes can't fit good descriptions. Yes, it fits the FAR, but I can do better
- Print shops are able to print any pdf onto Mylar. I found that clear Mylar is opaque, and looks only a little better than label tape
- it should be possible to engrave the image onto the thin, layered plastic used for nameplates. The local shop was unable to give a quote on this job.

I'll keep the alternatives handy if this solution fails.

  Jul 04, 2020     01 Fitting a panel - (20 hours)       Category: C22 Electrical

Cutting, fitting, trimming. Repeat.

When I took the project the old panel was a disaster - cut and recut until there was no structure dealing with twisting loads. That's pretty much guaranteed to give a rotten feeling when you throw a switch or turn a knob. Pretty clear it needs a rethink and another, better effort.

I'm trying for a larger leg opening, since the plans one is too darn small for normal size people. That means taking advantage of the vertical clearance, so long as I don't lose visibility over the nose and can still close the canopy...you can see the tradeoffs. Add in the comments of others about needing to angle the panel, and it gets to be too much for sketches - I have to sit in the airplane, pull down the canopy and see if the part fits. I've been through 4 panel templates, trying to nail down exactly how much room I have under the non-standard canopy. #4 is the wood template in the back of the stack.

I could build this panel from some foam and fiberglass. But it's easier to test fit wood (nature's composite) and easier to mount instruments on aluminum. I'm pretty sure this ends up a composite plane with a metal panel! But I like the look of the wood so I'll sand out the blood stains, seal this piece and use it as the long term template and/or final panel.

Ended up going with aluminum - the strength/weight relationship is just too good to pass up.

  Oct 17, 2020     02. Out with the bad - (8 hours)       Category: C22 Electrical

A lot of wires with no labels and 3 surprises: 1) the existing wiring assumes the battery and central wiring hub will be immediately behind the front seat. Well, that changes. 2) the wiring used was not milspec. 3) all power and ground was run from battery to behind the panel in a single (18 AWG?) pair, then instead of a fuse block there are big solder joints with a bunch of leads heading their own ways. I need to replace that with normal runs to blade fuse blocks and the "field of tabs" ground blocks.

There was some milspec, but of the wrong size and in the wrong place - two long runs of 2 AWG running up the heater duct to the backrest, with one to the battery (described above) and one to a marine battery power switch located where the plans call for a fuel selector. I gather that the prior builder intended to use that marine switch as the DC master, and avoid having a battery contactor.

There were also a number of firewall penetrations that I don't understand - perhaps they had to do with the prior (incomplete) installation of a Mazda engine. I reused 3 of them, one being a pass-through for the field-of-tabs ground and the other two used to secure the aluminum firewall I installed over the fiberglass + plywood (as the project was delivered, the firewall was built as per the plans). My own planned firewall penetrations are limited:
- 2 AWG cable run to the main alternator, something lighter to the backup (8 amp) alternator.
- 2 AWG from the starter contactor (cabin side of the firewall) to the starter
- A pass through bolt ties together the ground field-of-tabs on each side of the firewall.

I plan to use the firewall wiring ports located low on the right and left sides, under the engine mount holes.

  Jul 12, 2020     81. Tools & Tricks - (15 hours)       Category: C22 Electrical

Tools. I started with some automotive style crimpers. Nope. Dean Psiripoulos is a hangar neighbor and Honeywell rockets guy. He told of chasing bad connections and steered me to buying a set of tools from Stein Air. Done. I also bought a SteinAir connector assortment and an assortment of milspec wire from an auto racing firm. Following Nuckoll's guidance I went with 4 awg welding cable for the run from power center (cabin side of firewall) forward to a single location just forward of the instrument panel. I used the F22 bulkhead.

Following Keith Spreuer's advice I ran multi-conductor from the firewall forward to F22 - I have a dozen shielded 19 AWG tefzel coated wires ready for future use, with quick connect terminal blocks at each end.

I have experimented with click bond studs and click bond nutplates. I come back to the Nick Ugolini zip tie loops - see http://nickugolini.com/blog/?p=1490. For completeness, I'll repeat some of what's there. Below, the pictures from my first set, cast around square tube aluminum. My next set will be half height and a set to hold the O2 bottles. My "mold release" was packing tape and hair spray.

From Nick's blogpost:

Light weight, easy to make ZL's make it easy to attach almost anything to your fiberglass structure.

ZTL's are made by taking 3 layers of wetted glass and laying them over a rod or some square material (1/4? x 1/4? I would recommend at least 1/4? high. After curing I used my radial arm saw to cut the slots in the long strip and a pair of scissors to separate the loops. After you fabricate them (which takes very little time) you can secure them anywhere on your structure by just gluing them in place with a little bit of flox. They are so light you dont even need to secure them or hold them in place while the floxis curing. Just wet the back side and postion. They are also easy to remove. Just apply a little heat from a heat gun, and the epoxy softens and you can remove them.

ZTL's are very light weight and extremely strong. testing has proven that NO zip tie (or even doubling up the strongest zip tie I have) is as strong as the ZL. I built test rigs and have tested them to over 75 lbs of pull (tensile strength) before failure. Once cured, they will self destruct before they will come loose - I discovered the ZL will always tear through the loop before separating from the base IF you bond them directly to sanded fiberglass. If you bond them to a painted surface the attachment strength of the ZL will only be as strong as the surface material strength.

Cut the ZL to the desired length (using the fence of the bandsaw). Generally I like to cut my ZTL's about 1/2” wide. I also make them from 1/4” (for just a few wires), to 5/8” wide if I have something heaver that I want to mount such as heavy cables, or a filter. I even have a set that are 1" wide and 1/2" tall, for paired electrical cables and paired fuel and return lines. I find it's always nice to have a layup to work on, so I find these a fun part of the electrical and fuel line work.

  Apr 13, 2009     99. Prior builder writeup - (41.5 hours)       Category: C22 Electrical

Step 1 - Main Design

My electrical system is a single-alternator, dual-battery configuration with a manual battery switch. The batteries are identical 20Ah Panasonic batteries, installed just behind the front seatback, on the floor. The battery switch is a Blue Sea Systems 9002e, a 4-position marine-rated device with alternator field disconnect. This is a very simple setup with only a single bus to worry about.

I printed out a full-size, color copy of the current instrument panel design, then cut it out and taped it onto the panel. Looks pretty good! Do you want to do the same thing yourself? If so, click here for a synopsis of how I used Inkscape to do this! You can also Click Here to download an SVG file of my panel template. Download Inkscape (it's free!) and use it to open this file. The panel is to scale (actual size) and per plans. That means you can import (File->Import) pictures of avionics/instruments, set their widths/heights in the top toolbar, and play with their locations on the panel. It's fast and easy - no need for a panel builder!

Step 2 - Main System Wiring

The batteries and main switch are installed. The plans call for batteries either in the nose or above the spar. In the nose requires less ballast for solo pilots, but limits your weight and balance range if you fly with passengers. Above the spar gives you more flexibility, but flying solo you have to ballast the nose all the time. I went with a middle-ground solution - behind the front seat back! I'm a relatively light pilot (less than 160lbs, depending on proximity to Christmas), and the weight of my batteries more or less right behind my butt just makes me a heavier pilot. I'll still need nose ballast, but maybe a FEW pounds less, so I might save a few bucks in gas over the long haul without sacrificing much CoG range.

But the real reason is noted above - my design has a manual battery switch, which eliminates the load from the main contactor(s). It's located in the middle of the front seat back, about where the fuel valve would normally be placed. I don't need a fuel valve there because I have a Mazda Rotary (see the engine chapters for details).

One battery is behind each seat, for redundancy. The switch connects to a fuse panel just below it (easy access), and there is a grounding panel just behind the pilot's battery. You can see a lot of grounds here because I'm using a single-point star configuration grounding system, which helps eliminate noise. Larger cables run back to the firewall, where it will connect to the alternator and the starter contactor.

I still need to make upper covers for the batteries to prevent them from sliding out if I'm ever inverted (such as during a crash), but otherwise this system is basically done.

2009-05-21 (0.50 hours):

First switch installed

OK, it's a minor bit of progress but an important one to me. Until now I've kept all my switches and wires and such on a small temporary panel. This let me work on things without actually installing them, but was sort of an anti-commitment thing, too. This switch controls the speed brake - I'll install the landing gear switch next, but I need to rewire the interface because I want to remove the AEX unit. I'm not happy with how that thing behaves.

2009-07-02 (5.00 hours):

Gear Switch

I know it doesn't seem like a big step, or something that should have taken this long. But today I installed the switch for the Wilhelmson nose gear lift.

Several years back, when I purchased this unit, I also bought the AEX1 auto-extension module. I quickly came to hate it - every time I turned on the power, it wanted to extend the gear, and nearly caused several accidents in the build process because of that. And I didn't like the standard answer of adding a breaker or switch - what good is a safety device that you can disable? This also came with a big rats-nest of wires, some of which didn't even match the supplied wiring diagram. For instance, "white" for me was actually grey. Blue was purple. It took a while to wire, and it looked like a mess. I never did get it neatened up to my satisfaction.

Today I cut all the wires out of the rats nest, removed the AEX1, and rewired the unit with the bare minimum of wires. I kept everything neat, bundled all wire bundles together with heat shrink tubing, and now I have a clean and simple installation that I'm finally happy with! The only thing I have left to do is replace the LED grommets - they're just sort of sitting there right now. I need deeper grommets for my instrument panel. I'll address all the LEDs at once when I do the full panel setup later. Besides, I'd just have to remove them anyway when I do my panel overlay (which I may do with carbon fiber trim sheets off eBay.

2011-11-27 (9.50 hours):

Installing Avionics

Avionics are something you usually leave until the last possible moment, because every month of the build brings new innovations (and price reductions). I'm glad I did - I started the build before Dynon Avionics existed -- even before Blue Mountain (remember them?)!

But you can't wait forever because once you start wiring and laying out things like controls and switches you need to be able to plan the back of the panel. My panel has changed a bit since earlier "dreaming" posts (I still can't afford SL-30 radios), but I'm happy with it, so I decided to install a few instruments to get the ball rolling.

The "quad" you see here are 2-1/4" instruments intended mainly to act as backups to the Dynon panels I will be installing. I chose these four units for two reasons. First, three of the four (compass, altimeter, and airspeed) require no power or vacuum at all, so they're obvious choices as backup units. Second, the electric turn and bank is a solid-state unit with few moving parts and no gyro to tumble. All of them are very light and make a nice quad together.

I had hoped these units would install easily, and they did... sort of. The holes must be drilled very precisely, and even then I found slight variances in my instruments that I needed to work around - the compass had an adjustment-screw slot on the bottom, two instruments had top lighting bumps, etc. Thanks to Jim at RST Engineering for a nice set of downloadable PDF templates for this task!

Step 4 - Overvoltage Module

Jim Weir of RST Engineering was kind enough to publicly post a circuit diagram and documentation for a crowbar overvoltage module. This device basically shorts its power feed to ground if it sees a voltage exceeding a trip point. The idea is to put it on the tail end of a fuse or circuit breaker leading to the alternator regulator, the primary cause of overvoltage events. By shorting to ground, it blows the fuse or trips the breaker, taking it offline and preventing damage to the rest of the devices on the bus. (This all happens pretty quickly.)

I decided to build my module based on Jim's plans, but made one change. I replaced all of the devices selected with equivalent surface-mount components. I didn't really spend a lot of time shoving this into the smallest form factor possible. For example, I chose size 1206 resistors to make soldering easy - why sweat for a quarter of an inch in this particular module? It's about 1.5"x1" even with four 5mm holes for mounting posts, so I didn't do too badly. I have one backside track, which can be replaced by a simple jumper wire, and only four holes (not counting the mounting holes).

Bill of Materials:

Designation Digikey P/N Value Description Cost

C1 PCE3574CT-ND 10uF Electrolytic capacitor, 5000hr life $0.6360
D1 S1BDICT-ND 100V 1A Diode $0.48
D2 S1BDICT-ND 100V 1A Diode $0.48
D3 1SMA5918BT3OSCT-ND 5.1V 1.5W Zener Diode $0.40
R1 311-470ECT-ND 470 ohm Resistor $0.078
R2 311-10.0KFCT-ND 10k ohm Resistor $0.088
R3 P5C102CT-ND 1k ohm Trim Potentiometer $0.31
R4 311-10.0KFCT-ND 10k Resistor $0.088
R5 311-4.70KFCT-ND 4.7k Resistor $0.088
R6 311-1.00KFCT-ND 1k Resistor $0.088
SCR1 S4010DCT-ND 400V 10A SCR $1.64
U1 296-1014-1-ND Dual op amp $0.49
Total $4.87

The plan is to build this on a single-side PCB and pot it in epoxy, with space allocated for the mounting studs. It only has two wires, one to the bus and one to ground. I'll probably make a bunch of these all at once, so if you want one holler, and I'd consider making a few for people willing to cover my costs and shipping. And by all means, check out Jim Weir's site, he has a lot of very useful information for aircraft builders, and a number of great kits for DIY-ers.

This device is really cheap to build. The $10.00 estimate would cover PCB, solder, potting epoxy, testing, and the need to buy 5-10 of some of the parts above (single single quantities are not always available, even through DigiKey - who wants to buy a single $0.088 resistor?)

Step 5 - Install Instruments

I've been playing with instrument panel layouts for a while now, watching the available options on the market evolve. This is where I am so far. Qty Description Cost (ea) Total

1 ASA Flight Timer $40 $40
2 Eyeball Swivel Vents $150 $300
2 Dynon NextGen EFIS $4000 $8000
1 Dynon 2-axis Autopilot $1700 $1700
1 2-1/4" Attitude Gyro $3300 $3300
1 2-1/4" UMA Airspeed $200 $200
1 2-1/4" UMA Altimeter $275 $275
1 PS Engineering PMA9000ex Audio Panel $2100 $
2 Garmin SL30 NAV/COM Radios $3600 $7200
1 Garmin GTX327 Transponder $1900 $1900
1 RealWorldSolutions Engine Controller $950 $950
1 RealWorldSolutions Engine Monitor $475 $
N/A Miscellaneous Switches and Indicators $300 $300

Total: $26,740

That sounds like a lot, but this is also a dream installation. I can (and probably will) cut the number in half by installing less expensive radios, only one EFIS display, and no electric backup attitude gyro. Then, as funds permit, the remaining items can be installed or upgraded as necessary.

Basic Backup Instruments

My panel design includes a Dynon glass panel and engine monitor, a fairly standard radio stack, a top row of switches, and room for Rotary Aviation's EC2 control panel. There are four backup instruments included. Today I installed the most fundamental pair: the altimeter and airspeed units in 2-1/4" format.

I knew for sure I'd be installing these because they don't even require power - they're a nobrainer, really. I was surprised at how light they were. I have a standard 3-1/8" altimeter, and it's easily twice the weight of the 2-1/4" model. Note that this unit is not the sensitive type. The Dynon install will include an encoder - this is just a backup. For the other two units I'll probably install a compass and a turn coordinator. TruTrak makes a cost-effective 2-1/4" option here.

  Jan 30, 2021     Securing large wires - (16 hours)       Category: C22 Electrical

There are 3 kinds of large wires traveling forward and back in the plane:
- a positive and negative 4 AWG (welding) cable from firewall forward to instrument panel,
- a 12-conductor expansion bus from firewall forward to instrument panel
- a positive and negative 4 AWG (welding) cable from the shore power "Piper" socket to the firewall

Wires are to be secured every 4 inches. In some locations I took that approach (see forward of the panel, where lines curve to the terminal blocks). In others I decided to make a cover - in the rear seat the lines could be kicked or shoved by a passenger. Below is how I molded a cover for use in corners. Other surfaces used different molding jigs and a similar process.

A jig was made of scrap wood, whcih was then covered in packing tape. Wires/ cables of appropriate size were fixed on the board and covered with packing tape. Two lengths of BID tape were cut to the length of the jig and wetted out between two sheets of polyethylene. THe tapes were laid over the cables and edges defined by boards clamped or weighted during the curing process. When cured, the part was released, inspected, cut to fit and #4 screw holes drilled.

  Nov 04, 2020     Waiting for components - (5 hours) Category: C22 Electrical

My orders are hostage to the slow down at the USPS and overseas trade. I've got 8 or so components that were ordered more than 30 days ago, and I wait and wait. Aircraft Spruce, Northern Tool, eBay and TomTop all owe me parts I need to finish the backbone (not the high $$$ avionics) of the electrical system. PITA.

  Jul 06, 2020     Com Antennas - (12 hours)       Category: C22 Electrical

It took some research, some time running wires and some review of the plans. I know where the antennae are located!
- nav antennas: one in each rudder, with a coax cable currently hanging at the wing tip end of the wire conduit. The location is consistent with the plans. I will made a coax connection at the nav light end and run a line back to the strake. Add another join there and use the existing coax run to the planned radio location.
- com antennas: one in each wing, mid-wing and on the bottom, with a coax cable currently hanging at the _strake_ end of the wire conduit. I bought the good stuff - RG-400 - and the BNC hardward and ran the connection to the planned radio location.
- marker beacon: under the pilot, emerging from the floor just forward of the instrument panel. Marked "MB" and stubbed off
- glide slope: under the co-pilot, emerging from the floor just forward of the instrument panel. Marked "GS" and stubbed off.

I got my instrument ticket and figured out it's not much fun - I want IFR capability in case a mistake takes me into IFR conditions. GS and MB are parts of precision instrument landing systems, and largely replaced by LPV approaches (localizer performance with vertical guidance). Pretty much every IFR GPS is WAAS enabled and allows the 200' LPV minimum. That's background on why I stubbed out the GS and MB antennae - they are preserved for future use by someone else, or if and as those antenna can be matched to some new capability (10th gen wifi?).

I need a transponder antenna, and spent too long screwing around with ground planes and making my own antennae. See that separate entry.

Still to install:
- I need two and possibly 3 GPS antennae, feeding the transponder, the Dynon Skyview and one the GPS navigator. I know Dynon can accept the feed from the WAAS enabled GPS.
- if there is a reasonable way to do it, I'd like to have a good ELT antenna ground. I don't plan to use it, but the device is required, so I might as well one that works well. Note that the smart money says to do a check-the-box install on the ELT and carry both a cell phone and a personal beacon. Add in flight following and it's a heck of a lot better than an ELT.