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kesleyelectric(at)chooseb
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 Posted: Wed Jan 28, 2009 8:21 am Post subject: e-bus question |
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I am building a fairly simple VFR panel (comm., transponder, D-10A, UMA analog gauges) using Z13/8. The SD-8 aux. alternator will easily support everything on the panel (about 5.5 amps), except the position lights, strobes, and wig wag landing lights. I know that the intent of the endurance bus is to power the items necessary for the comfortable termination of the flight. Is there a downside to putting most of the panel, minus the external lighting, on the e-bus, as long as it can be supported? If so, what would be kept on the main bus, and why?
Thanks,
Tom Barter
Kesley, IA
Avid Magnum
[quote][b]
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rshannon
Joined: 05 Sep 2007
Posts: 62
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| Posted: Wed Jan 28, 2009 11:40 am Post subject: e-bus question |
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On Wed, Jan 28, 2009 at 7:54 AM, Tom Barter <kesleyelectric(at)chooseblue.coop (kesleyelectric(at)chooseblue.coop)> wrote:
| Quote: |
I am building a fairly simple VFR panel (comm., transponder, D-10A, UMA analog gauges) using Z13/8. The SD-8 aux. alternator will easily support everything on the panel (about 5.5 amps), except the position lights, strobes, and wig wag landing lights. I know that the intent of the endurance bus is to power the items necessary for the comfortable termination of the flight. Is there a downside to putting most of the panel, minus the external lighting, on the e-bus, as long as it can be supported? If so, what would be kept on the main bus, and why?
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One perspective is that at some point, an E-bus becomes unnecessary. The main purpose of an E-bus is to allow you to rapidly reduce loads with one switch. If you can rapidly reduce loads with two switches, at most, then building an E-bus just to be able to rapidly reduce loads with one switch probably isn't worth doing.
If the above list is really all you're going to have, then at most you'd be switching off position and strobe lights. (If you're on approach with landing lights ON when the alternator/regulator goes south... you probably won't want or need to switch them off immediately, especially if they're LED's.) If you have low draw LED position lights, you might just keep them ON too if conditions warrant. At worst, LED position lights' draw is so small that there's no big rush to turn them off manually. At least some of the other things you might want to have (small panel GPS, intercom, etc.) might stay ON in a low voltage scenario as well. On the other hand, it may be worthwhile to include an E-bus now if you think you may add additional gear in the future, or for future resale to a buyer who may want to add more gear, etc.
My hunch is that in a VFR Avid equipped as you describe, you don't really need a separate E-bus. You could put the extra pound or so of weight it might take to include an E-bus into a little bit bigger battery instead.
Ron
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Wed Jan 28, 2009 1:36 pm Post subject: e-bus question |
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At 01:12 PM 1/28/2009, you wrote:
| Quote: | On Wed, Jan 28, 2009 at 7:54 AM, Tom Barter < kesleyelectric(at)chooseblue.coop (kesleyelectric(at)chooseblue.coop)> wrote:
I am building a fairly simple VFR panel (comm., transponder, D-10A, UMA analog gauges) using Z13/8. The SD-8 aux. alternator will easily support everything on the panel (about 5.5 amps), except the position lights, strobes, and wig wag landing lights. I know that the intent of the endurance bus is to power the items necessary for the comfortable termination of the flight. Is there a downside to putting most of the panel, minus the external lighting, on the e-bus, as long as it can be supported? If so, what would be kept on the main bus, and why?
One perspective is that at some point, an E-bus becomes unnecessary. The main purpose of an E-bus is to allow you to rapidly reduce loads with one switch. If you can rapidly reduce loads with two switches, at most, then building an E-bus just to be able to rapidly reduce loads with one switch probably isn't worth doing.
If the above list is really all you're going to have, then at most you'd be switching off position and strobe lights. (If you're on approach with landing lights ON when the alternator/regulator goes south... you probably won't want or need to switch them off immediately, especially if they're LED's.) If you have low draw LED position lights, you might just keep them ON too if conditions warrant. At worst, LED position lights' draw is so small that there's no big rush to turn them off manually. At least some of the other things you might want to have (small panel GPS, intercom, etc.) might stay ON in a low voltage scenario as well. On the other hand, it may be worthwhile to include an E-bus now if you think you may add additional gear in the future, or for future resale to a buyer who may want to add more gear, etc.
My hunch is that in a VFR Avid equipped as you describe, you don't really need a separate E-bus. You could put the extra pound or so of weight it might take to include an E-bus into a little bit bigger battery instead. |
The "E" stands for "endurance." The goal is not necessarily
to accomplish "rapid" load reduction. If one waited to finish
a cup of coffee before switching to the endurance mode, the
likely outcome of the flight would probably not be altered.
I'll refer the reader to chapter 17 of the 'Connection
were simple-ideas behind the e-bus are discussed in
detail. In a nutshell, the e-bus . . .
(1) provides TWO pathways to ALL equipment useful for
en-route phase of flight . . . one of which does
not depend on a functioning battery contactor.
(2) a gathering place for en-route mode electrics
operating BATTERY only in a configuration most likely
to offer battery-only endurance equal to or greater
than fuel endurance.
(3) isolation of the battery contactor load in the
en-route phase of flight . . . 0.8A of battery
contator draw would run two to four solid state
radios in the receive mode!
(4) adding the SD-8 raises en-route loads to 8.0A
without taxing the battery. This allows one to
reserve 100% of battery capacity for approach to landing.
Obviously, if you can reduce main-bus + contactor
loads to some value less than 8 amps, then one
might decide that the separate e-bus was not necessary.
However, the dual pathway for power described in
(1) would be given up . . . meaning that loss of
a battery contactor walls off the battery as a source of
energy and runs the risk of loosing a main alternator
if you "stall" it with something like a landing light
inrush load. Now, if you've included the self-excitation
mode for the SD-8, you can probably fiddle with the
switches and get things back up and running.
The problem is that NOT configuring an e-bus as
shown tosses out a simple manipulation of switches
after loss main alternator. A simple procedure
that eliminates in flight troubleshooting and
switch-flipping and offers a predicable outcome
of flight under plan-b.
The E-bus is not a nifty, stand-alone feature of
the OBAM aircraft electrical system. It is but
one component of a SYSTEM that has evolved over
the past 15 years and represents one of several
recipes for success in meeting design goals.
If your goals are to design, own and operate
your airplane as if it were a C-150 with an SD-8
added, that's fine too. I'll suggest that the
well considered decision requires an understanding
of the respective design goals.
Bob . . .
[quote][b]
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rshannon
Joined: 05 Sep 2007
Posts: 62
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| Posted: Wed Jan 28, 2009 3:20 pm Post subject: e-bus question |
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My mistake, Bob. I forgot about the main contactor.
Ron
On Wed, Jan 28, 2009 at 1:05 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]
At 01:12 PM 1/28/2009, you wrote:
| Quote: | On Wed, Jan 28, 2009 at 7:54 AM, Tom Barter < kesleyelectric(at)chooseblue.coop (kesleyelectric(at)chooseblue.coop)> wrote:
I am building a fairly simple VFR panel (comm., transponder, D-10A, UMA analog gauges) using Z13/8. The SD-8 aux. alternator will easily support everything on the panel (about 5.5 amps), except the position lights, strobes, and wig wag landing lights. I know that the intent of the endurance bus is to power the items necessary for the comfortable termination of the flight. Is there a downside to putting most of the panel, minus the external lighting, on the e-bus, as long as it can be supported? If so, what would be kept on the main bus, and why?
One perspective is that at some point, an E-bus becomes unnecessary. The main purpose of an E-bus is to allow you to rapidly reduce loads with one switch. If you can rapidly reduce loads with two switches, at most, then building an E-bus just to be able to rapidly reduce loads with one switch probably isn't worth doing.
If the above list is really all you're going to have, then at most you'd be switching off position and strobe lights. (If you're on approach with landing lights ON when the alternator/regulator goes south... you probably won't want or need to switch them off immediately, especially if they're LED's.) If you have low draw LED position lights, you might just keep them ON too if conditions warrant. At worst, LED position lights' draw is so small that there's no big rush to turn them off manually. At least some of the other things you might want to have (small panel GPS, intercom, etc.) might stay ON in a low voltage scenario as well. On the other hand, it may be worthwhile to include an E-bus now if you think you may add additional gear in the future, or for future resale to a buyer who may want to add more gear, etc.
My hunch is that in a VFR Avid equipped as you describe, you don't really need a separate E-bus. You could put the extra pound or so of weight it might take to include an E-bus into a little bit bigger battery instead. |
The "E" stands for "endurance." The goal is not necessarily
to accomplish "rapid" load reduction. If one waited to finish
a cup of coffee before switching to the endurance mode, the
likely outcome of the flight would probably not be altered.
I'll refer the reader to chapter 17 of the 'Connection
were simple-ideas behind the e-bus are discussed in
detail. In a nutshell, the e-bus . . .
(1) provides TWO pathways to ALL equipment useful for
en-route phase of flight . . . one of which does
not depend on a functioning battery contactor.
(2) a gathering place for en-route mode electrics
operating BATTERY only in a configuration most likely
to offer battery-only endurance equal to or greater
than fuel endurance.
(3) isolation of the battery contactor load in the
en-route phase of flight . . . 0.8A of battery
contator draw would run two to four solid state
radios in the receive mode!
(4) adding the SD-8 raises en-route loads to 8.0A
without taxing the battery. This allows one to
reserve 100% of battery capacity for approach to landing.
Obviously, if you can reduce main-bus + contactor
loads to some value less than 8 amps, then one
might decide that the separate e-bus was not necessary.
However, the dual pathway for power described in
(1) would be given up . . . meaning that loss of
a battery contactor walls off the battery as a source of
energy and runs the risk of loosing a main alternator
if you "stall" it with something like a landing light
inrush load. Now, if you've included the self-excitation
mode for the SD-8, you can probably fiddle with the
switches and get things back up and running.
The problem is that NOT configuring an e-bus as
shown tosses out a simple manipulation of switches
after loss main alternator. A simple procedure
that eliminates in flight troubleshooting and
switch-flipping and offers a predicable outcome
of flight under plan-b.
The E-bus is not a nifty, stand-alone feature of
the OBAM aircraft electrical system. It is but
one component of a SYSTEM that has evolved over
the past 15 years and represents one of several
recipes for success in meeting design goals.
If your goals are to design, own and operate
your airplane as if it were a C-150 with an SD-8
added, that's fine too. I'll suggest that the
well considered decision requires an understanding
of the respective design goals.
Bob . . .
| Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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