Electrical System ULP V06

After several comments/mail and reading books about this stuff, I think I'm finally converging to something usable.

The primary system is taken straight out of the ULPower manual. I have added the fuel pump 2 and manual switches for fuel pump 1 and 2. The isolation switch is a manual one installed with the battery (this may change, not sure yet).

The Mascot 8660 is removed. The reason is it will be impossible to isolate all the components from the common ground. The RDAC needed for EGT, CHT and MAP must be grounded to the engine, or it wont be able to read anything, and so on. Ideally all the RDACs should be in the primary system, and communications should be optical (fiber), maybe in 100 years. With a common ground, all isolation is gone. The 8660 would really only function as a current limiting device. Another reason is the 8660, when taking into account the efficiency (81%) will be too small. This could be fixed by dividing the system and install another ECB, but then things gets too complex for this little aircraft.

Electrical system ULP v02-03

Studied the manuals a bit more yesterday. I have been mistaken about a few things. The new diagram:

FP1 and FP2 are just manual switches. FP1A is the ECU governed relay switch. This makes much more sense. Normal operation: FP1 = ON, and the ECU runs the thing. FP2 is backup and can be run in addition or instead of FP1.

If I draw the diagram "as recommended" by UL, it will look like this:

I don't understand the use of that 30A fuse. All engine systems are connected to the ECU. Also, the starter button is always "hot", even though it won't start without FP and ECU switches "ON". The 60A fuse seems way over-sized. Both the 8660 and the Mascot charger have fuses.

IMO the philosophy must be that the primary system runs the engine, and it should contain no protective devices for the secondary system. The engine should run even though the master switch is "OFF", similar to the AeroVee. The ECU, FP1 and FP2 switches should be more than enough. The revised diagram will look like this (I think):

The master switch isn't really a master switch, it's a switch for the secondary system. The ECU switch is the "master" sort of.

Electrical system ULP

The installation manual for the ULPower engine has several diagrams for how the electrical system is recommended to be set up. It is different than the Aerovee in several aspects.

• The starter and regulator shall always be directly connected to the battery (no switches or fuses).
• The battery is in parallel with a huge 65k micro F capacitor.
• The battery is recommended to have an isolation switch.

The ECU have a separate on/off switch and ignition switches. The fuel pumps have an option to have relays that are governed by the ECU. In addition each one has a manual switch. The idea of ECU governed switches is that they will be "on" whenever the engine is running, and will shut of the fuel when the engine is stopped. In an accident they will shut off automatically. If only one pump is used, the whole system runs automatically. I'm not sure that option is a good idea, it also means each pump relies on two relays to work.

Further, the ECU has a CAN bus where most data are sent. I believed this would enable direct link to the CAN bus on the MGL EFIS, but that is apparently not the case. An additional MGL ULP DAC has to be installed. This box talks to the ECU, but transform the data to some pseaudo analog data before it sends them to the EFIS/EMS on the CAN/RS232 bus. Seems a bit odd to me.

EGT, CHT and MAP are not send by CAN bus. A normal XDAC is needed for those. Seems that I need yet another "box". Where to put them all?

 

Small EFIS fixes and thoughts about power supply

Added time variables to the EFIS. UTC, local time, flight time and stop watch. This also includes a count down timer that pops up, like on the default screen 1,2 etc.

But it's getting a bit cluttered. Perhaps bar graphs (big fat ones) and numbers would be better than these round dials and numbers. I have to try, I still have a couple of pages left in the EFIS. Programming it, once understanding the principles, is really easy though, rather fun actually.

The optically isolated DC-DC solution (Aviogard) may take some time to mature it seems. The Aviogard from MGL is not a viable solution as of today. There is one other guy doing something similar (I think), but not very much of details other than a battery charger as of yet. Its a really interesting site though. Experimental Avionics. If I have learned anything from this, it is that the backup battery MUST be on the isolated side, so it will supply power to the avionics also if the DC-DC converter should fail (a very real scenario as I have experienced). This also means a real battery charger solution must be in place. And while doing that, why not install a modern type of battery, NiMH or LiFePO4. (having said that, I have already ordered a Mascot DC-DC charger, and will rebuild the Aviogard with a new UQQ, configured in accordance to the specs, and try it on the kitchen table at least).

Anyway, a plan B is obviously needed, or building will stop. The obvious plan B is a traditional system, but with a backup battery for avionics. Plan B basically consist of removing the Aviogard, replacing it with a simple switch, essentially what is called an "avionics (master)/switch" in most certified aircraft. I will lose the galvanic protection completely, but:

• I will be able to isolate the avionics when starting the engine AND have power to everything through the backup battery.
• The backup battery is charged by the main system, and can be turned on and off.
• I can switch on and off the backup battery switch and avionics switch to see the voltage from each directly on the EFIS, monitoring each system without an extra gadget (IEFIS Extender)
• I can isolate the avionics in flight running only from the backup battery if needed.

The plan B will look something like this:

The reversed biased schottky diode is mainly to prevent accidentally starting the engine with the backup battery, which will completely overload the backup battery and wires. No power should ever run from the secondary system to the primary system. This will also simplify the backup mode.

• Starting:
• PM ON
• SM OFF
• SB ON
• Normal operation
• Everything ON
• If everything in the primary system goes down, the diode will assure all power from the backup is going to the avionics. The engine runs fine on mags alone.
• Testing
• SM ON/OFF - reading V from backup battery and main 

Brakes, vent and electrical

Got lots of stuff from different places. Finished the brakes.

Purchased Vans vents, from Vans... They only come in pairs, but I only need one. Very good design and construction, but I have to wait until all the cables are in place, so I dont cut a hole in the wrong place.

Made a drawing for the electrical system. It is fairly standard with the exception of perhaps the Aviogard and ECB.