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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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 Posted: Tue Nov 09, 2021 11:43 am Post subject: RV-10 Electrical Review with Electric AC and FlyEFII |
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On 11/8/2021 5:10 PM, melstien wrote:
| Quote: |
Hello,
I am looking to finalize my electrical system prior to running wires and electronics.
Mission - IFR cross country trips with my wife around the US
Airplane Specifics:
-RV-10
-BPE IO-540 D4A5 with 9:1 compression
-Fly EFII System 32 with dual controller and electronic injection and ignition
-BnC Primary belt driven alternator and controller
-BnC rear spline driven alternator and controller
-VPX-Pro to run most electronics, the engine will not be on the VPX Pro
-Electric Air Conditioner 12 volts DC at 40 Amps Max
-Electronics are all Garmin 2 screen with GTN750, audio panel, second radio, remote transponder, and 3 axis autopilot
-IBBS batteries (qty2) to keep critical flight electronics running when -Master(s) are turned off
-Batteries planned to be in rear as per plans (Earthx ETX900) qty 2 planned.
-Fly LED works Package plus one extra dual LED landing light in the cowing
Summary of electrical schematic: I have leveraged the Z101 architecture and added a second battery and master switch for it, mostly for separate Air Conditioner control and second battery charging/isolation. The AC connection is a relay or contactor and is on the hot side of the second battery master. This was done to isolate the second battery from all other ships power when needed, like when running AC on the ground or during take-off and landing operations. During flight I can turn on the second master, re-charge the second battery, run the AC off the alternator and have the extra capacity available if needed for emergency flight ops.
Alternators: Only one will be providing power at any one time. The second one on the vac pad will be set to a lower voltage and will only output power when the primary alternator voltage goes low or craps out. I may not have the sense wire or field wires correctly connected. I wish to have them both active/standby at the same time. Can one switch do this or is it best to have two switches?
Loads. The engine will require 11 Amps at full load to run the dual ECUs, 6 injectors and 3 quad coil packs and misc. engine instruments, according the manufacturer. I have individual fused power wires from each injector and each coil going to the engine bus.
One EarthX ETX900 will run a 16 amp load for close to 60 minutes.
Mission critical electronics will be powered in an emergency from the IBBS batteries if no other power is available.
I do have a hot buss that is used only for some minor items.
Example of emergency: Fire/smoke in the cockpit- both masters off, fuel off. Engine gets really quite. Select location and turn to it for landing and stabilize the aircraft in a best glide. Smart glide will be useful. If needed and if advisable, I could turn on the Emergency engine power switch and energize the engine bus. The engine buss isolated from the main power feeds using diodes.
I have read many discussions about the EFI systems vs mechanical/traditional systems. I am not asking for feedback on that aspect unless there is new information or facts that can contribute to the discussion.
One additional idea I was thinking about was to just add the second battery to the firewall and have it run just the engine in an emergency. The cable runs will be much shorter and keep everything a bit more location contained. W&B will be impacted and needs to be considered.
I welcome and appreciate feedback on the design based on my mission.
Michael
Hi Michael,
|
Some stuff I'd look at:
The ETX900 is rated at 16AH. While lithium tech does better at
maintaining voltage deep into discharge than lead-acid, the AH rating is
still real. I wouldn't trust one to supply 16A for an hour when it was
brand new, and I certainly wouldn't expect it when the battery has some
age on it. Might not be an issue with dual alternators, but I wouldn't
plan on a full hour without alternator power.
Smoke/fire: My choice with my electronic injection engine is to have a
totally separate engine bus, with its own switching, and a 'cross-tie'
switch from the main airframe bus as the power source backup. I have one
alt tied to the main bus and the other alt tied to the engine bus. My
process for smoke will be to 1st shut off the airframe (leaves the
engine running, just like carb/mags system). If still smoke, *then* shut
down the engine bus and pray for a landing spot.
Circuit protection: Like Joe said, setting circuit protection anywhere
near the potential demand of the load is inviting 'nuisance trips',
which get a lot bigger than nuisance level if it's the engine. I chose
to use a soldered-in fusible link for the primary supply on the engine
bus feed from the battery. I did the same as you on the injectors/coils,
but I'm seriously considering going to fusible links there, too.
I'd consider that 11A figure for engine amps somewhat optimistic, based
on typical fuel pump & injector power consumption. I'd verify before
trusting.
VPX Pro: Can't address the VPX brand directly from memory, but there are
some electronic control boxes on the market that have multiple 'single
points of failure' inherent in their design that can shut down
everything attached to them. Might be worth a deep dive, especially for
an IFR platform.
I've never had the luxury of air conditioning in an a/c, but IIRC,
certified stuff specs turning it off for takeoff. Have you run the
numbers on how much it will suck out of one of those 16AH batteries
while running battery-only, and what the lithium battery will do to
alternator output if it's significantly discharged when it's tied back
into the system? I think I've read accounts of the smaller EX battery
drawing 50-60 amps, if it was even slightly discharged when it came on line.
Alternators: I don't see circuit protection shown at the feed from the
battery(s), and both alt B leads are tied together at the dual diodes
feeding the engine bus. Any fault on any B lead could take out both alts.
I might have misinterpreted or misread some stuff; if I did I apologize.
Charlie
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Ceengland
Joined: 11 Oct 2020
Posts: 391
Location: MS
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| Posted: Tue Nov 09, 2021 5:23 pm Post subject: RV-10 Electrical Review with Electric AC and FlyEFII |
|
|
On 11/9/2021 1:47 PM, Charlie England wrote:
| Quote: | On 11/8/2021 5:10 PM, melstien wrote:
>
>
> Hello,
>
> I am looking to finalize my electrical system prior to running wires
> and electronics.
>
> Mission - IFR cross country trips with my wife around the US
>
> Airplane Specifics:
> -RV-10
> -BPE IO-540 D4A5 with 9:1 compression
> -Fly EFII System 32 with dual controller and electronic injection and
> ignition
> -BnC Primary belt driven alternator and controller
> -BnC rear spline driven alternator and controller
> -VPX-Pro to run most electronics, the engine will not be on the VPX Pro
> -Electric Air Conditioner 12 volts DC at 40 Amps Max
> -Electronics are all Garmin 2 screen with GTN750, audio panel, second
> radio, remote transponder, and 3 axis autopilot
> -IBBS batteries (qty2) to keep critical flight electronics running
> when -Master(s) are turned off
> -Batteries planned to be in rear as per plans (Earthx ETX900) qty 2
> planned.
> -Fly LED works Package plus one extra dual LED landing light in the
> cowing
>
> Summary of electrical schematic: I have leveraged the Z101
> architecture and added a second battery and master switch for it,
> mostly for separate Air Conditioner control and second battery
> charging/isolation. The AC connection is a relay or contactor and is
> on the hot side of the second battery master. This was done to
> isolate the second battery from all other ships power when needed,
> like when running AC on the ground or during take-off and landing
> operations. During flight I can turn on the second master,
> re-charge the second battery, run the AC off the alternator and have
> the extra capacity available if needed for emergency flight ops.
>
> Alternators: Only one will be providing power at any one time.
> The second one on the vac pad will be set to a lower voltage and will
> only output power when the primary alternator voltage goes low or
> craps out. I may not have the sense wire or field wires correctly
> connected. I wish to have them both active/standby at the same
> time. Can one switch do this or is it best to have two switches?
>
> Loads. The engine will require 11 Amps at full load to run the dual
> ECUs, 6 injectors and 3 quad coil packs and misc. engine instruments,
> according the manufacturer. I have individual fused power wires
> from each injector and each coil going to the engine bus.
> One EarthX ETX900 will run a 16 amp load for close to 60 minutes.
>
> Mission critical electronics will be powered in an emergency from the
> IBBS batteries if no other power is available.
>
> I do have a hot buss that is used only for some minor items.
>
> Example of emergency: Fire/smoke in the cockpit- both masters off,
> fuel off. Engine gets really quite. Select location and turn to
> it for landing and stabilize the aircraft in a best glide. Smart
> glide will be useful. If needed and if advisable, I could turn on
> the Emergency engine power switch and energize the engine bus. The
> engine buss isolated from the main power feeds using diodes.
> I have read many discussions about the EFI systems vs
> mechanical/traditional systems. I am not asking for feedback on
> that aspect unless there is new information or facts that can
> contribute to the discussion.
>
> One additional idea I was thinking about was to just add the second
> battery to the firewall and have it run just the engine in an
> emergency. The cable runs will be much shorter and keep everything a
> bit more location contained. W&B will be impacted and needs to be
> considered.
>
> I welcome and appreciate feedback on the design based on my mission.
>
> Michael
Hi Michael,
Some stuff I'd look at:
The ETX900 is rated at 16AH. While lithium tech does better at
maintaining voltage deep into discharge than lead-acid, the AH rating
is still real. I wouldn't trust one to supply 16A for an hour when it
was brand new, and I certainly wouldn't expect it when the battery has
some age on it. Might not be an issue with dual alternators, but I
wouldn't plan on a full hour without alternator power.
Smoke/fire: My choice with my electronic injection engine is to have a
totally separate engine bus, with its own switching, and a 'cross-tie'
switch from the main airframe bus as the power source backup. I have
one alt tied to the main bus and the other alt tied to the engine bus.
My process for smoke will be to 1st shut off the airframe (leaves the
engine running, just like carb/mags system). If still smoke, *then*
shut down the engine bus and pray for a landing spot.
Circuit protection: Like Joe said, setting circuit protection anywhere
near the potential demand of the load is inviting 'nuisance trips',
which get a lot bigger than nuisance level if it's the engine. I chose
to use a soldered-in fusible link for the primary supply on the engine
bus feed from the battery. I did the same as you on the
injectors/coils, but I'm seriously considering going to fusible links
there, too.
I'd consider that 11A figure for engine amps somewhat optimistic,
based on typical fuel pump & injector power consumption. I'd verify
before trusting.
VPX Pro: Can't address the VPX brand directly from memory, but there
are some electronic control boxes on the market that have multiple
'single points of failure' inherent in their design that can shut down
everything attached to them. Might be worth a deep dive, especially
for an IFR platform.
I've never had the luxury of air conditioning in an a/c, but IIRC,
certified stuff specs turning it off for takeoff. Have you run the
numbers on how much it will suck out of one of those 16AH batteries
while running battery-only, and what the lithium battery will do to
alternator output if it's significantly discharged when it's tied back
into the system? I think I've read accounts of the smaller EX battery
drawing 50-60 amps, if it was even slightly discharged when it came on
line.
Alternators: I don't see circuit protection shown at the feed from the
battery(s), and both alt B leads are tied together at the dual diodes
feeding the engine bus. Any fault on any B lead could take out both alts.
I might have misinterpreted or misread some stuff; if I did I apologize.
Charlie
followup/edit:
|
Just noticed the ANLs drawn next to the alternators. They need to be at
the battery-end of the B leads; not at the alts. Electrically it *looks*
the same, but the physical location matters. The danger to the wire is
from the battery. The wire should be sized large enough to handle
anything the alternator (which is self-limiting at slightly above rated
amps) can throw at it, but the battery can throw hundreds (a thousand?)
of amps at the wire.
I think Joe mentioned the 15A CB that feeds the engine bus. Another
concern with it would be that if you for any reason lose the B lead
connection to the main bus, it looks like that feeder would be the path
from alts to the main bus. If that's the case, loss of the main B lead
would put you on battery power if alt output exceeds CB rating by very much.
One thing I've seen recommended is to play 'what if' with any proposed
wiring diagram. Likely worthwhile to build a spreadsheet while doing it.
The process is to pick a wire, open it, and ask what happens; is it a
problem, and what alternative is available to work around it. Then short
it to ground and ask the same questions. Repeat for each wire in the
diagram. It will usually reveal issues & limitations in the diagram.
Charlie
--
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http://www.matronics.com/Navigator?AeroElectric-List |
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_________________
Charlie |
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