I'm in the process of deciding which components to put on which bus. I feel like I have a nice plan in the works, but it'll require a large relay, and I'm not sure which direction to take. (more on that at the end of the post)
I'm planning on a Z-13 style setup, with the following objectives:
1) E-bus with capability to get me back on the ground in night IFR with the Master switched off.
2) Steady-state emergency load on e-bus less than 8A (for sustained operation w/SD-8 backup alternator), though intermittent loads may be >>8A.
3) Intuitive operation for the average IFR pilot (no weird "switchology" to start and operate the aircraft, minimal complexity to switch to reversionary modes)
3) Isolation of avionics during engine start
Conceptually, I'm thinking of feeding the e-bus from the avionics bus. The rationale is that the Master will energize only the equipment necessary for startup. Next, the avionics bus is energized, which in turn brings power to the remaining systems (radios+e-bus stuff). Simple to operate, good isolation, with the expected e-bus behavior. Nice, eh?
Here's the breakdown of my planned system:
Main bus equipment
(nominal operating current=~6A)
*battery contactor
*EFIS w/ engine monitor
*Fuel boost
*Fuel primer
Avionics bus equipment
(nominal operating current=~5A)
*Panel lights
*AP servos
*SL-40
*Intercom
E-bus equipment
emergency steady state current=~5A
"everything on" steady state current=~35A (all lights, pitot heat)
Peak current (radios blazing, flaps in motion, ...) >45A
*Backup EFIS
*430W
*327 transponder
*Nav lights
*strobe lights
*landing lights
*flaps
*pitot heat
Here's the rub: The avionics+ebus can draw a peak load of 50A or so (lights, pitot heat, flaps, ...). Normal loads will be much less, especially when switching it on or off, but I want to size things appropriately. For the e-bus feed from the avionics bus, I can use a good SCR-type power diode, so it'll be up to the task with manageable heat and voltage drop.
For switching the avionics bus, the best solutions I can think of at the moment are:
1) put a huge relay between the master bus and the avionics bus
2) move the lights to the main bus. This would take the maximum Avionics+e-bus load down to about 15a, but would make nav and landing lights unavailable when running on the e-bus, greatly complicating emergency procedures in some cases.
Thoughts or suggestions would be appreciated.
Thanks,
Matthew
I'm planning on a Z-13 style setup, with the following objectives:
1) E-bus with capability to get me back on the ground in night IFR with the Master switched off.
2) Steady-state emergency load on e-bus less than 8A (for sustained operation w/SD-8 backup alternator), though intermittent loads may be >>8A.
3) Intuitive operation for the average IFR pilot (no weird "switchology" to start and operate the aircraft, minimal complexity to switch to reversionary modes)
3) Isolation of avionics during engine start
Conceptually, I'm thinking of feeding the e-bus from the avionics bus. The rationale is that the Master will energize only the equipment necessary for startup. Next, the avionics bus is energized, which in turn brings power to the remaining systems (radios+e-bus stuff). Simple to operate, good isolation, with the expected e-bus behavior. Nice, eh?
Here's the breakdown of my planned system:
Main bus equipment
(nominal operating current=~6A)
*battery contactor
*EFIS w/ engine monitor
*Fuel boost
*Fuel primer
Avionics bus equipment
(nominal operating current=~5A)
*Panel lights
*AP servos
*SL-40
*Intercom
E-bus equipment
emergency steady state current=~5A
"everything on" steady state current=~35A (all lights, pitot heat)
Peak current (radios blazing, flaps in motion, ...) >45A
*Backup EFIS
*430W
*327 transponder
*Nav lights
*strobe lights
*landing lights
*flaps
*pitot heat
Here's the rub: The avionics+ebus can draw a peak load of 50A or so (lights, pitot heat, flaps, ...). Normal loads will be much less, especially when switching it on or off, but I want to size things appropriately. For the e-bus feed from the avionics bus, I can use a good SCR-type power diode, so it'll be up to the task with manageable heat and voltage drop.
For switching the avionics bus, the best solutions I can think of at the moment are:
1) put a huge relay between the master bus and the avionics bus
2) move the lights to the main bus. This would take the maximum Avionics+e-bus load down to about 15a, but would make nav and landing lights unavailable when running on the e-bus, greatly complicating emergency procedures in some cases.
Thoughts or suggestions would be appreciated.
Thanks,
Matthew