Electrical, Avionics and Panel
Panel design, done in Visio. Main panel for instruments and avionics, lower panel for switches and breakers.
Click here to got to the
web page that provides my complete electrical system design.
Presentation
on Avionics design (Oct 6, 2004)
Current
load/alternator size estimate spreadsheet
Here's a way to get 1/2" wiring holes drilled in the seat ribs. First, using an angle drill, drill a #30 pilot hole; then using a #30 countersink, drill all the way through the rib. Install SB-500 snap bushings, and presto, more ways to run wires.
Subpanel drilled with switches temporarily mounted.
Breakers temporarily mounted. These are P&B W28
series breakers, mounted on 0.75" centers.
Switch field. First position is a BNC connection to the dimmer bus for a goosneck lamp; next two holes are for lamp dimmer pots; next is the master (2 position), then the primer button, pitot, nav, strobe, landing, taxi and flash lights. The last position is the fuel pump switch. Out of the picture are the Avionics Master switch and the Standby Alternator switch.
Subpanel in place, fit checked.
See the design for the
subpanel and side panels (MS Visio)
See the mockup for the
main panel (MS Visio)
Side panel fitted. Obvious improvement to be made would
lengthen the subpanel a bit more (3/16") to move the side
panel attachment screw in a bit. I could also have lined up
this screw with the second screw from the bottom to make
everything appear symmetical. On the other hand, when you
try too hard, it can accentuate any misalignments as well.
The side panel will hold headphone jacks, power, handheld radio
inputs (antenna, audio, power). Copilot side with have a
music input and a PTT switch instead of the handheld radio
inputs.
Breaker array with wiring harness near completion.
Notice the 12V cigar lighter on the side panel. Above it is
a stereo audio input.
Switch array and harness. Dual light dimmers mounted to forward (aka sub) panel.
View looking aft of switch array and wiring harness.
View looking aft of breaker array and harness.
This is the barrier terminal block for the panel dimmer bus
that will connect to the various instruments.
Grounding terminal block mounted to firewall, with instrument
ground wires attached. Switch/Breaker panel has been
removed, leaving the harnesses in place.
Mic, headphone and aux +12V jacks will be mounted on an angled
panel on the armrests.
Exposed wiring in the cockpit is protected with polyethylene
tubing, wherever possible.
Rocky Mountain engine micromonitor kit being assembled. I decided on this engine monitor after a '747 pilot suggested that a multi-channel unit was overkill for an O-320. Simplify! I also like the split between external fuel gauges and the totalizer in the Rocky Mountain unit-- redundancy, redundancy! Also, it fits nicely in a radio rack, is simple and the display is quite legible. Missing switch was a a problem that Ron at Rocky Mountain corrected right away. Notice the aluminum tray is grounded for ESD protection.
Boards assembled in case.
Display with ambient lighting, looks good.
Backlit display-- a bit blotchy due to backlight
imperfections, but acceptable. Dim numbers are 'flashing'
(low fuel, low current).
**Update** I replaced the LED backlight (under warranty) and most
of the blotchiness disappeared.
Here's a product designed to be used with the Rocky Mountain Micromonitor. It replaces over 100 hand crimped connections and really tidies up the wiring and makes it more reliable and easier to maintain. It's available from Vx Aviation at www.vx-aviation.com. It's proven to be very popular so far.
The plans call for the vent shrouds to be attached with screws and fiber nuts. I'm going to install plate nuts instead to simplify assembly/disassembly of panel.
Strobe Power Supply mounting brackets fabricated out of 3/4 x 3/4 x 0.063 Aluminum angle.
Strobe supply mounted in place under baggage floor. There is about 1/16" height clearance from the floop panel to the top of the power supply in this position. It's hard to see, but the white wire is a grounding lug that will connect to the strobe cable shields.
AK ELT Installation on floor rib. Critical clearances: aft to allow for extraction of hand-held antenna (if wanted) and forward to allow future installation of autopilot pitch servo (ca-ching!). Wires in forground may be re-routed. The ELT remote extension cable needs to be cut to feed through snap bushings, shortened, then spliced. Kind of a cheesy system.
Cutting the panel. Panel punch makes short work of the holes,
but the rectangular cutouts and Garmin cutout took a lot of time.
Panels cut and painted. Using alkyd enamel, looks great, but takes forever to harden fully (weeks!)
Garmin GPSMAP 296 Mounting brackets, using yoke clip assembly provided with the GPS.
Close up of the assembly. Painted with flat black alkyd
aerosol enamel over Mar-Hyde self etching primer.
Panel cutout for the Garmin. Note the nice finish on the panel.
Back of panel with GPS in position. Back of panel is black-- my first attempt using aerosol gloss black alkyd enamel. Hardened up nicely, but shows everything! Decided to go to semi-gloss grey and spray with my HVLP.
Click on this link to
get a full size template of the GPSMap 296 panel cutout in .bmp
format suitable for printing.
Click on this link to get a
full size template of the GPSMap 296 panel cutout in .vxd format
suitable for editing (Visio).
Click on this link to get a
full size template of the GPSMap 296 panel cutout in .dwg format
suitable for editing (AutoCad).
This is the audio bus... 0.125" spade terminals connected to a small terminal block that I've been carrying around for 30 years (!). I new it would come in handy one day.
Nevertheless, I did not like the forest of tabs, so I used this product in it's place, now available from Vx Aviation http://www.vx-aviation.com. It provides every thing needed to hook a Sigtronics intercom into a typical panel.
Panel wiring in process. I'm using connectors (D-sub type and box type) to allow removal of panel by disconnecting fast-on terminals connected to switches and the D-subs connected to the autopilot, engine monitor and miscellaneous signal wires. Power or grounds are not connectorized. Power is a bolted lug, and the grounds connect via fast-on terminals at the firewall.
Panel wiring complete on repainted panel. Still waiting for Pictorial TC to finish up avionics. I wired the switched power output of the Dynon EFIS D10A to the Aux Battery position on the Rocky Mountain Micromonitor (with the internal charging circuit disconnected). This allows the internal EFIS battery to power the engine monitor. Coupled with the internal battery of the Garmin GPSMap 296, this means that my primary flight instruments, engine instruments and Nav instrument can all operate in the event of a power failure. With my hand-held comm on board this will allow the ability to safely get down to debug the primary problem.
Night view of the panel (TC is still missing).
Night view of the panel with map light on. Green glow is
because of the masking tape I put over the lens of the light,
since the dimmer is not hooked up for this photo.
Modification to the Micromonitor. Connect the External
Backup Battery (pin U) to the Dynon EFIS D10A Switched Power Out
(pin 12).
Single point grounding bus from B&C.
Map box, transponder antenna lead and traffic monitor antenna
lead. Blue and white wires are intercom PTT and ground.
Transponder antenna disconnect (top) and com 1 antenna
disconnect (bottom right). I subsequently relocated the com
1 routing to minimize interference with the wiring conduit.
Big black conduit is the grounding wire bundle
from the panel.
Pitot/Static/AOA tubing. Also shown are the dimmer regulators for the cabin and panel dimmers. Center bottom is the wig-wag flasher. Top left is the traffic monitor antenna lead. I will be drilling two more holes to simplify access to the Dynon EFIS D10A D-sub connector attachment screws.
A better view of the wig-wag flasher and the panel disconnect connector field.
Dynon, ASI and Mag switch. Missing is the Monroy traffic monitor, which I use as a portable unit.
(left) Sigtronics Intercom; (center) Garmin GSPMap 296 mount; (top right) Christmas tree warning lights; (bottom right) Trutrak Digitrak autopilot.
Back of Rocky Mountain micromonitor. I mounted a big D-sub connector onto the back of the tray so that I can disconnect the sensors and slide the instrument panel out. It worked, but I didn't like it... seemed difficult to maintain, and I was worried about all of those crimped connectors on the back of the Micromonitor, so...
I designed a circuit board that plugs on the back of the Micromonitor and cleans everything up. The production version of this board is available at the Vx Aviation web site http://www.vx-aviation.com.
This is all of the sensor wires with crimp pins attached. I use the machined pins from Steinair or B&C... work in Amp or Norcomp plugs and sockets.
I tested all of the sensors that I could, include the tach input. I used a pulse generator and a frequency counter. 40 Hz equals 2400 RPM at one pulse per revolution (electronic ignition setup).
Bottom right ventilator and cover plate/side panel. The bottom connector is a 12V 'cigar' plug; the small center connector is stereo audio input (but wired for a mono audio system), and the D-sub connector is the EFIS D10A programming port. Up top is the ventilator control knob.
Dynon Electronic Digital Compass (EDC) module mounted in aft fuselage. ThetaX, ThetaY and ThetaZ all adjustable to a small degree by oversize screw hoes and/or using shim washers. All hardware is brass except for D-Sub connector and screws. D-Sub shell is plated plastic. Remote thermal probe wiring runs to the tail section.
Another view showing tray construction.
Remote thermal probe location. It will be shaded by HS, and is out of (most) of the exhaust flow from the engine, so the temperature should be accurate. I could have put it on the underside of the wing, but the length of wire is critical and I wasn't sure if it would work well with a connector for wing disconnect. I etched/alodined the fuselage under the probe and used marine polyurethane sealant for bedding.
With the installation of the EDC and thermal probe, I am now ready to close up the aft fuselage (yeah!).
OK, here's a problem solved. The Van's dimmers are great, but run hot. I replaced the heatsink on the panel dimmer to ensure that the junction temperature of the regulator would not exceed 125 degrees C with a 50 C ambient with measured current loads. It still runs warm, but my math is conservative. Problem solved.
In order to have a removable panel, I needed to keyhole the control cable mounts in order to drop them down.
A view of the custom washers I made to allow the Throttle and Mixture controls to clear the label strip.
This is a keeper bracket to allow the power and audio signals for the traffic monitor to be secured. Attaches to the mounting screws on the side of the ATD-300.
Flap retraction modification. lever switch (15A rated) will shut off flap motor when flaps are fully retracted. Switch is mounted behind pilot's side baggage compartment flap pushrod housing (photos to follow).
Switch has no effect on flap extension operation. Failure mode (switch failure) is that you can extend your flaps, but not retract them. Easy to test on final approach or on ground.
Here's my wig-wag lamp wiring. TAXI and LANDING switches must be OFF and FLASH must be on for proper operation. The NTC devices are inrush current limiters that increase the life of the lamps, switches and breakers. They also require a longer flash cycle in order to come up to full brightness, so I popped open the Wig-Wag unit and increased the capacitor size to 10 uF.
Here's the fix for a pulsating alternator output, noticeable by flickering panel lamps and/or noise on the intercom and radio. The relay K3 is inserted into the regulator BUS circuit. Wire the B+ connection directly to the alternator output, the FIELDIN connection to the master switch field circuit, GND to firewall ground and FIELDOUT to the voltage regulator BUS input.
By connecting in this fashion, most of the voltage drops between the alternator output through the master bus, master switch and Bus wiring are eliminated. Flight testing shows a rock steady master bus voltage and no pulsating panel lamps or radio interference.
D1 is a snubber for the relay coil that protects the master switch, and D2 is secondary overvoltage protection that will blow F1 if primary overvoltage protection fails. The primary overvoltage protection circuit is aircraft dependent and not shown.
Here's as simplified application circuit. In this drawing the relay is K3 and the diodes are D16 and D17. D17 is not really required with the primary overvoltage protection crowbar (VR1 - OVM-14).
Carling Switch failure problems. Stay tuned....
Another aircraft's burned switches and fast-ons.
Replaced Carling switches with Honeywell/Micro Switch units. This photo shows main wiring bundles. Sheathed bundle carries the airframe wires.
Draft of my Ground Power design.
