Today's Message Index:
----------------------
1. 06:07 AM - Re: Please review my electrical system (Deviation of Z-13) (John Morgensen)
2. 06:16 AM - Re: Fuel pump control (Joe)
3. 06:53 AM - Re: Please review my electrical system (Deviation of Z-13) (John Morgensen)
4. 07:05 AM - Re: Please review my electrical system (Deviation of Z-13) (Joe)
5. 08:25 AM - Re: Fuel pump control (Jeff Page)
6. 10:29 AM - EFIS backup battery switch wiring (messydeer)
7. 10:49 AM - Re: EFIS backup battery switch wiring (messydeer)
8. 11:50 AM - Re: EFIS backup battery switch wiring (edleg)
9. 12:16 PM - Re: Please review my electrical system (Deviation of Z-13) (user9253)
10. 12:25 PM - Re: Re: EFIS backup battery switch wiring ()
11. 12:26 PM - Re: Please review my electrical system (Deviation of Z-13) (Robert L. Nuckolls, III)
12. 12:58 PM - Re: EFIS backup battery switch wiring (messydeer)
13. 03:55 PM - Re: EFIS backup battery switch wiring (Robert L. Nuckolls, III)
14. 04:29 PM - Re: EFIS backup battery switch wiring (messydeer)
15. 07:12 PM - Re: EFIS backup battery switch wiring (edleg)
16. 07:37 PM - Re: EFIS backup battery switch wiring (messydeer)
17. 08:09 PM - Re: Re: EFIS backup battery switch wiring (Richard E. Tasker)
18. 08:49 PM - Re: Re: EFIS backup battery switch wiring (Kevin Horton)
19. 10:36 PM - Re: Re: EFIS backup battery switch wiring (Jay Hyde)
Message 1
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Subject: | Re: Please review my electrical system (Deviation |
of Z-13)
Message 2
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Subject: | Re: Fuel pump control |
The RV-12 has a mechanical fuel pump on the engine and an electrical
fuel pump near the fuel tank. The electric fuel pump runs continuously
whenever the master switch is on. There is no discrete switch for the
electric fuel pump. The pre-flight check is to turn on the master
switch and observe the fuel pressure to be sure the electric pump is
working. Then start the engine and watch for an increase in fuel
pressure to be sure that the mechanical fuel pump is also working. Yes,
it wastes electricity and wears out the electric fuel pump. On the
other hand, most automotive fuel pumps last the life of the vehicle.
Airplanes are used a lot less then cars. I would not expect the
electric fuel pump in the RV-12 to wear out soon. The big advantage of
wiring the electric fuel pump to run continuously is that it helps to
prevent mismanagement of the fuel system, a major cause of accidents.
The RV-12 fuel system does not have a fuel selector valve because there
is only one fuel tank. There is no mixture control. The only thing for
the pilot to mismanage is the emergency fuel shut-off valve handle that
is located on the floor. The handle must be pulled up to shut off. The
simpler the system is, the less chance for malfunction or error.
Joe
Message 3
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Subject: | Re: Please review my electrical system (Deviation |
of Z-13)
I investigated this earlier and this is what I found:
1. No harm is done with both alternators online. The theory that there
is a problem stems from twin engine systems with elaborate schemes to
deal with 2 alternators.
I am using Z-13/8 and there are only 3 switches:
Main: (off)- (battery contactor)-(battery+main alternator)
Aux feed: (off)-(on)
Aux Alt: (off)-(on)
The endurance bus can be powered by:
Battery only
Battery + Main Alternator
Battery + Aux Alternator
Aux Alternator only
The Aux Feed provides a path that does not include the battery contactor.
Hope this helps,
John Morgensen
Grumman AA1B 150hp - For Sale
RV4 - Flying
RV9A - wiring
Matthew Schumacher wrote:
> List,
>
> I've been working on the wiring diagram for my airplane (electric panel,
> IFR, plane power internally regulated main alt and a SD-8 backup). So
> I've been reading though Bob's book and am familiar with the Z-13 wiring
> diagram, however there are a two things about it that I don't like:
>
> 1. It is possible to turn on both alternators at once. It is my
> understanding that you don't want to have both alternators online at
> once and I don't want the pilot to be able to cause damage by not using
> the correct switches.
>
> 2. Alternate feed switches. Feed switches seem cumbersome since it
> requires the pilot to know something about the electrical system.
>
> I think I have a new wiring diagram that addresses these things, but I
> want to run it past this list and perhaps Bob so that others can help me
> find the problems.
>
> Here is how it works:
>
> The avionics bus is treated like the endurance bus since the avionics
> are the only things I care about if my alternator fails (I have mags and
> a mechanical fuel pump.) When the master switch is on, the battery
> pulls the battery contactor which brings the main alternator and battery
> into the system. Should something happen to the main alternator the
> battery will continue to power the system unless I switch the ALT switch
> to AUX. When the alternator switch is on AUX it takes out the main alt
> and powers up the SD-8 wired up with the self exciting hack. This will
> allow my aux alternator to power the avionics bus (when the Avionics
> master is on AUX) but will keep my master contactor and battery separate
> from the rest of the system. In the event that I want to charge my main
> battery I can turn the master switch off which will then allow me to
> charge my battery should I desire to try and bring the main alternator
> back after a dead battery.
>
> In order to clear up any confusion here are the basic switches,
> settings, and mode of operation:
>
> Master: on, Alt: main, Avionics: main; Normal operation running on the
> main alternator and battery.
>
> Master on, Alt: Aux, Avionics: Main; Aux alternator is online and master
> alternator is offline, battery is powering everything.
>
> Master on, Alt: Aux, Avionics: Aux; Aux alternator is powering avionics,
> main alternator is offline, and battery is powering everything except
> avionics.
>
> Master off, Alt: Main, Avionics: main; Nothing is powered up.
>
> Master off, Alt: aux, Avionics: main; Avionics are off, Aux alternator
> is online and is charging the battery.
>
> Master Off, Alt: aux, Avoinics: aux; Avionics are on aux alternator, aux
> alternator is online and is charging the battery.
>
> Perhaps it would be more intuitive if I name the switches like this:
>
> Battery: On | Off (Aux Charge)
> Alternator : MAIN | AUX
> Avionics: MAIN | OFF | AUX
>
> This setup reduces the panel down to 3 switches and gives the operator
> good control over the system, allows for the battery to be isolated or
> charged from the aux alternator, and gives a way for non critical
> devices to run off the battery.
>
> If this doesn't look sane to you please post some feedback. Any help I
> can get is greatly appreciated.
>
> Thanks,
> schu
>
>
Message 4
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Subject: | Re: Please review my electrical system (Deviation of |
Z-13)
Schu,
It is easier for me to visualize a circuit by looking at an
electrical schematic rather than reading about it. If I understand
correctly, you intend to have one switch control two alternators. It
seems like a single point of failure. What happens when the switch
fails? Switches probably fail about as often as alternators. It is my
understanding that it will not hurt to have two alternators on line at
once. Power will be drawn from the one with the highest voltage. Bob
will correct me if I am wrong.
Having one switch for the avionics is also a single failure point.
In Z-13/8, inadvertently turning on both the master switch and the E-Bus
Alternate feed switch will not hurt anything. The Endurance Bus will
draw from the highest voltage source. After engine shut down, it is
important to remember to shut off both the master switch and the E-Bus
Alternate Feed switch.
Keeping the electrical controls simple is a worthwhile goal. Having
options in case of a failure is another worthwhile goal. Aircraft
design is a matter of compromises. It is hard to improve on Bob's
designs. They have been scrutinized by many and have evolved over the
years.
Joe
Message 5
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Subject: | Re: Fuel pump control |
Thanks for everyone's replys. The following is exactly the trick I
was hoping for !
Jeff Page
Dream Aircraft Tundra #10
> From: Steve Ruse <steve@wotelectronics.com>
> Subject: Re: AeroElectric-List: Fuel pump control
>>
> It is pretty simple to do this if you use a fuel pump and relay coil
> that require the same voltage. Use a pressure sensor to control the
> relay. Connect the relay output to the fuel pump AND to the relay
> coil (input). That way when the fuel pump comes on (due to a low
> pressure signal), the relay locks itself on, regardless of the state
> of the pressure sensor. To turn the pump off, you would have a
> momentary switch in the circuit that would break the connection to the
> relay coil. This used to be called a "seal-in" circuit for industrial
> controls.
>
> Steve Ruse
Message 6
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Subject: | EFIS backup battery switch wiring |
Hello :-)
I have an MGL Enigma EFIS and will put in a backup battery. In regular operation,
both the main and backup battery are to be wired to the EFIS. The Enigma automatically
switches to backup when it senses a main battery low voltage.
I was thinking of maybe some wiring of a 2-10 that would do the following:
Down position: main buss to EFIS.
Middle position: backup battery to EFIS (for backup battery check)
Up position: both batteries to EFIS.
Or maybe just a two position switch, one position would be for both batteries,
the other just to the backup. The backup check position could be a momentary on,
I suppose, that just takes the main battery offline. Hold it in this position
and see if the EFIS still works, then release.
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273305#273305
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Subject: | Re: EFIS backup battery switch wiring |
Well, I got one possibility figured out using a 2-10. Figure attached.
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273310#273310
Attachments:
http://forums.matronics.com//files/enigma_efis_backup_switch_wiring_with_2_10_162.pdf
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Subject: | Re: EFIS backup battery switch wiring |
With one switch you are putting all your eggs (and faith) in a single point of
failure. What use is having emergency backup power if you can not use it if the
only switch is broken?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273314#273314
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Subject: | Re: Please review my electrical system (Deviation of |
Z-13)
Oops my mistake, there was no schematic in the daily digest that is emailed to
me. Now I see it on the online forum.
Most aircraft have the battery contactor and starter contactor wired in series
so that the starter can be shut off in case it welds shut. There is no way
to disconnect the main alternator from the battery. Moving the alternator wire
to the other side of the battery contactor will fix both issues.
Will the avionics momentarily lose power when the avionics master switch is
operated?
Do the master switch and alternator switch have a center off position? There
needs to be a way to kill power in case of smoke in the cockpit. Most pilots
are familiar with switches being off when in the down position. Switches that
accomplish your goals are available that are off when down.
The 22mfd capacitor should be 22,000mfd.
There is a hot wire from the battery to master switch terminal 5. If it starts
smoking inside of the cockpit, there is no way to shut it off.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273318#273318
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Subject: | Re: EFIS backup battery switch wiring |
Dan,
Turn the master on, turn the EFIS on . Turn the master off. If EFIS remains on
the systemn works.
Don VS RV7 flying
---- messydeer <messydeer@yahoo.com> wrote:
>
> Well, I got one possibility figured out using a 2-10. Figure attached.
>
> --------
> Dan
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=273310#273310
>
>
>
>
> Attachments:
>
> http://forums.matronics.com//files/enigma_efis_backup_switch_wiring_with_2_10_162.pdf
>
>
>
>
>
>
>
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Subject: | Re: Please review my electrical system (Deviation |
of Z-13)
At 08:52 AM 11/17/2009, you wrote:
>
>I investigated this earlier and this is what I found:
>
>1. No harm is done with both alternators online. The theory that
>there is a problem stems from twin engine systems with elaborate
>schemes to deal with 2 alternators.
Correct . . . and the "problem" was that light twins fitted
with alternators were plagued with inability to make two
alternators PARALLEL . . . i.e. share total loads. I've
developed several approaches to alternator paralleling. Quite
frankly, if you have TWO alternators capable of carrying
most if not all of total system loads, then Z-14 and
NO paralleling is the better way to go.
But the system is not placed at risk by having two
alternators on at the same time. Unless they are
calibrated to within millivolts of each other, the
device with the higher set-point "hogs" the load
until it reaches its output limit. The bus voltage
then sags until the alternator with the lower setpoint
picks up the difference.
Bob . . .
---------------------------------------
( It's MATRONICS FUND RAISER MONTH! )
( Do your part to keep this marvelous )
( tool sharp and available to all our )
( brothers in the OBAM aviation )
( community. )
---------------------------------------
Message 12
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Subject: | Re: EFIS backup battery switch wiring |
Turns out I had the wiring to the EFIS wrong. There are separate terminals for
the backup and main power inputs, so I've redrawn it. It looks like if I forgot
to turn off the EFIS switch, my backup battery would run dead. But I suppose
I otta notice that my screen is still powered up. I would think that would be
pretty obvious.
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273325#273325
Attachments:
http://forums.matronics.com//files/enigma_efis_backup_switch_wiring_with_2_10_150.pdf
Message 13
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Subject: | Re: EFIS backup battery switch wiring |
>I have an MGL Enigma EFIS and will put in a backup battery. In
>regular operation, both the main and backup battery are to be wired
>to the EFIS. The Enigma automatically switches to backup when it
>senses a main battery low voltage.
>
>I was thinking of maybe some wiring of a 2-10 that would do the
>following . . .
What does the manufacturer of the EFIS system
recommend?
Bob . . .
---------------------------------------
( It's MATRONICS FUND RAISER MONTH! )
( Do your part to keep this marvelous )
( tool sharp and available to all our )
( brothers in the OBAM aviation )
( community. )
---------------------------------------
Message 14
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Subject: | Re: EFIS backup battery switch wiring |
Thanks, Bob.
>From the manual:
"...One power switch for the main incoming 12 or 24 V feed (switch in positive
supply lead),
another for the backup battery.
In flight, both switches would be on allowing the charging of the backup battery.
Preflight check would involve switching main power on, then battery power on. Check
of
battery power would involve switching main power off and verifying that Enigma
continues
to operate. Voltage on the backup battery should be measured by means of the backup
voltage readouts which can be placed on any display..."
Imaged referred to attached.
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273357#273357
Attachments:
http://forums.matronics.com//files/mgl_enigma_odyssey_installation_198.bmp
Message 15
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Subject: | Re: EFIS backup battery switch wiring |
In simple terms... if the backup battery is not on its own switch it won't charge.
Two switches is simple. Trying to find a special switch to do all things at
once leaves you with a non-common fix if it fails away from your home airport.....
Two switches lets you troubleshoot power problems, and lets the EFIS be powered
fully during a voltage drop, like during an engine start.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273386#273386
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Subject: | Re: EFIS backup battery switch wiring |
Thanks, E., for bringing up the issue of single point of failure. Hadn't thought
about that, which makes me ask some questions about DPDT vs SPST switches.
Looking at the schematic of a DPDT switch it looks like there are two circuits,
an upper and a lower. Their terminals are separate but contained in the same
housing. They also use the same lever and the mechanism the lever connects to
that makes and brakes the contacts.
If the only way a switch failed was through these shared components, then a DPDT
would have the same reliability as a SPST, so there would be a single point
of failure.
And if DPDT's never failed at these shared components, then having one DPDT would
be just as reliable as having two SPST's, and there wouldn't be a single point
of failure.
I'm sure the truth lies somewhere between these two extremes. If it turns out that
a DPDT has 90% of the reliabilty as two SPST's, I might stick with just one
DPDT. If it has only 20% of the reliabilty of two SPST's, I might consider going
with two switches.
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=273392#273392
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Subject: | Re: EFIS backup battery switch wiring |
The issue is not so much about what the relative reliability is. The
issue is that if the DPDT switch fails you may not be able to connect to
either source of electrons. If one of the SPST switches fails, you
always have the other one.
Dick Tasker
messydeer wrote:
>
> Thanks, E., for bringing up the issue of single point of failure. Hadn't thought
about that, which makes me ask some questions about DPDT vs SPST switches.
>
> Looking at the schematic of a DPDT switch it looks like there are two circuits,
an upper and a lower. Their terminals are separate but contained in the same
housing. They also use the same lever and the mechanism the lever connects
to that makes and brakes the contacts.
>
> If the only way a switch failed was through these shared components, then a DPDT
would have the same reliability as a SPST, so there would be a single point
of failure.
>
> And if DPDT's never failed at these shared components, then having one DPDT would
be just as reliable as having two SPST's, and there wouldn't be a single
point of failure.
>
> I'm sure the truth lies somewhere between these two extremes. If it turns out
that a DPDT has 90% of the reliabilty as two SPST's, I might stick with just
one DPDT. If it has only 20% of the reliabilty of two SPST's, I might consider
going with two switches.
>
> --------
> Dan
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=273392#273392
>
>
>
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Subject: | Re: EFIS backup battery switch wiring |
What are the consequences of failure of both poles in that switch,
given how you will operate the aircraft (day/night and VFR/IFR) and
the backups you have installed? If you are certain that you will be
able to safely get the aircraft on the ground with an acceptable
workload, then the potential single point failure is acceptable.
Kevin Horton
Sent from my iPod
On 2009-11-17, at 10:36 PM, "messydeer" <messydeer@yahoo.com> wrote:
> >
>
> Thanks, E., for bringing up the issue of single point of failure.
> Hadn't thought about that, which makes me ask some questions about
> DPDT vs SPST switches.
>
> Looking at the schematic of a DPDT switch it looks like there are
> two circuits, an upper and a lower. Their terminals are separate but
> contained in the same housing. They also use the same lever and the
> mechanism the lever connects to that makes and brakes the contacts.
>
> If the only way a switch failed was through these shared components,
> then a DPDT would have the same reliability as a SPST, so there
> would be a single point of failure.
>
> And if DPDT's never failed at these shared components, then having
> one DPDT would be just as reliable as having two SPST's, and there
> wouldn't be a single point of failure.
>
> I'm sure the truth lies somewhere between these two extremes. If it
> turns out that a DPDT has 90% of the reliabilty as two SPST's, I
> might stick with just one DPDT. If it has only 20% of the reliabilty
> of two SPST's, I might consider going with two switches.
>
> --------
> Dan
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=273392#273392
>
>
Message 19
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Subject: | Re: EFIS backup battery switch wiring |
There is one quite important thing to note, no matter how one wires the
switches (I used two DPST switches in the Sling - one for the power to the
Enigmas and one to the backup batteries)- that is that the backups will not
charge unless the voltage to them is sufficiently high. Obvious of course,
but where this becomes a problem is if you have a diode between your main
bus and the e-bus. You get a 0.7v drop across it and then there are some
voltage drops inside the Enigma and the backup batt gets a voltage of
between 12.5 -13v.
To solve this we now run the aircraft with the e-bus alt feed permanently
on, which boosts the e-bus voltage back up sufficiently to charge the backup
battery.
Jay
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Kevin
Horton
Sent: 18 November 2009 06:43 AM
Subject: Re: AeroElectric-List: Re: EFIS backup battery switch wiring
What are the consequences of failure of both poles in that switch,
given how you will operate the aircraft (day/night and VFR/IFR) and
the backups you have installed? If you are certain that you will be
able to safely get the aircraft on the ground with an acceptable
workload, then the potential single point failure is acceptable.
Kevin Horton
Sent from my iPod
On 2009-11-17, at 10:36 PM, "messydeer" <messydeer@yahoo.com> wrote:
> >
>
> Thanks, E., for bringing up the issue of single point of failure.
> Hadn't thought about that, which makes me ask some questions about
> DPDT vs SPST switches.
>
> Looking at the schematic of a DPDT switch it looks like there are
> two circuits, an upper and a lower. Their terminals are separate but
> contained in the same housing. They also use the same lever and the
> mechanism the lever connects to that makes and brakes the contacts.
>
> If the only way a switch failed was through these shared components,
> then a DPDT would have the same reliability as a SPST, so there
> would be a single point of failure.
>
> And if DPDT's never failed at these shared components, then having
> one DPDT would be just as reliable as having two SPST's, and there
> wouldn't be a single point of failure.
>
> I'm sure the truth lies somewhere between these two extremes. If it
> turns out that a DPDT has 90% of the reliabilty as two SPST's, I
> might stick with just one DPDT. If it has only 20% of the reliabilty
> of two SPST's, I might consider going with two switches.
>
> --------
> Dan
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=273392#273392
>
>
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