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Electric Fuel Pumps

Gasman
That filter looks good. How would it work to have one in each fuel line as
they run along in front of the spar just before the tank selector valve? Would
it then be safe/advisable to get rid of gascolator?

Jim

The gascolator is not needed. And Ken K. of Van's agrees. Set your pick-up tube to leave about 16 to 20oz of fuel in the tank. That's where the water will be. AND SUMP YOUR TANKS.

Anytime you place the filters before the shut off valve, you can't shut off the fuel to service the filters. If you want two filters, do what Frank said..... Two filters, two fuel pumps side by side then "T" them together after the outlet and run a single line to FFlow or firewall. You will pay about $45 for each pump and about $72 per filter. Less than $250 for a complete double fuel pump and filter system.

A mechanical fuel pump is about $210.00. Add a Andair gascolator for another $200.00........... Then ask yourself, what is a better system for today. Plus, the gascolator does not protect the back-up pump.

ps. The POWER SONIC model PS 1250 5 Amp Hr. is an AGM battery. It is safe.
 
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Gasman
That is a good looking battery and the website "Battery Plex" sells them for
$14.99. I initially planned to charge the back-up battery with external
charger but it was suggested that I charge from alternator and use a diode
to isolate the two batteries. Does anyone have specifics on the best way to
do this and size of diode needed for a 5 to 7 amp hour battery?
 
Gasman
That is a good looking battery and the website "Battery Plex" sells them for
$14.99. I initially planned to charge the back-up battery with external
charger but it was suggested that I charge from alternator and use a diode
to isolate the two batteries.
Does anyone have specifics on the best way to
do this and size of diode needed for a 5 to 7 amp hour battery?

Yes, you could set it up to charge automatically. You could also set up a system that will keep the oil topped off. This is a back-up battery. It should be checked for % of charge at every shut down. Due to my bench test of how well it held a charge, I would place it on a proper charger http://www.acichargers.com/technology.htm use the three amp model. Also good for your main battery. I would expect to charge my back-up battery about twice a year unless it was placed into service. K I S S.

My point is, it is my back-up battery for my fuel pump and ignition. I want to keep an eye on it.
 
Purely personally

If this is a basic VFR airplane, I would wire the second fuel pump direct to the second battery with a fuse and an on/off switch. If I had two electronic ignitions I would wire the second ignition the same way.

This is the simplest and least cluttered arrangement. The I would charge the second battary thrugh a shottkey diode..This is a specific type of diode that has a lot of capacity and very small forward voltage drop.

The shottkey may also be used in place of the rectifier that Bob Knuckolls proposes in hie aerolectric connection..This is what I did in my IFR set up.

I can't for the life of me remember where I bought the Shottkey from???
 
After I made the last post I by chance found the article by Bob N. that Frank just spoke of. I first just envisioned one diode between the two batteries but
it is more complicated than that and will just stick with my original plan to
externally charge but it will have to be a little more frequent as I will be
running both pumps during take-off and maybe landings. I am considering a
little larger battery PS-1270 7 AH which will have a little more capacity in
case of incomplete charge.
 
Frankh - what is the reasoning behind keeping the minimum 5 gallons of fuel reserve in each tank - insurance against opposite wing tank pump failure?

Also - do you have your pumps wired direct to the battery or on your buss through the master contactor? I'm thinking I would want to be able to hit the master if I have an electrical fault and kill everything but the pumps - which means either wire them direct or have an E-buss on a separate contactor just for the pumps (and/or other critical load).

I did end up putting both my pumps in the center floor where Vans recommends installing the boost pump. I had to stretch the boost pump housing a bit, but both pumps are in there with check valves so they can't back flow. Each tank flows through it's own filter and check valve before entering the pump, the output of the pumps are Tee'd together and go to the fuel valve, which is on/off/ferry with a port underneath to connect a ferry tank for long over-water legs.

1000327c.jpg
 
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I attempt to land with about 5 gallons in each tank for exactly the reason you describe..do I always do this?..No, especially if i am surounded by lots of airports.

We know the RV (even with flop tubes) has only a few ounces of unusuable fuel so a gallon of fuel will take you 20 miles or so.

Yes I use the Bob Knuckolls single battery, 2 alternator set up with both my pumps wired to the battery buss..I.e I always have the battry feed.
 
After I made the last post I by chance found the article by Bob N. that Frank just spoke of. I first just envisioned one diode between the two batteries but
it is more complicated than that and will just stick with my original plan to
externally charge but it will have to be a little more frequent as I will be
running both pumps during take-off and maybe landings. I am considering a
little larger battery PS-1270 7 AH which will have a little more capacity in
case of incomplete charge.

Well it depends on what you want. In my Zodiac it was not more complicated than I described..I simply had two batteries and a diode between them.

One pump from each battery and they both then charge from the single alternator.

Really very simple.
 
Nice

Frankh - what is the reasoning behind keeping the minimum 5 gallons of fuel reserve in each tank - insurance against opposite wing tank pump failure?

Also - do you have your pumps wired direct to the battery or on your buss through the master contactor? I'm thinking I would want to be able to hit the master if I have an electrical fault and kill everything but the pumps - which means either wire them direct or have an E-buss on a separate contactor just for the pumps (and/or other critical load).

I did end up putting both my pumps in the center floor where Vans recommends installing the boost pump. I had to stretch the boost pump housing a bit, but both pumps are in there with check valves so they can't back flow. Each tank flows through it's own filter and check valve before entering the pump, the output of the pumps are Tee'd together and go to the fuel valve, which is on/off/ferry with a port underneath to connect a ferry tank for long over-water legs.

1000327c.jpg

Looks good Greg, I think I would probably do it that way next time.
 
Looks great, Robert. But what's the output pressure of these pumps? Those of us running carbs need a lower pressure than the FI guys to my knowledge.
 
Well it depends on what you want. In my Zodiac it was not more complicated than I described..I simply had two batteries and a diode between them.

One pump from each battery and they both then charge from the single alternator.

Really very simple.


I was thinking one diode also until I saw the article by Bob N. from 1998.
He shows the alternator output going to a junction between TWO diodes
each diode allowing current to flow to its respective battery. The main
battery diode would have to carry full alternator output. If only one diode
was used it would prevent current from flowing from back-up battery
to main but not the reverse. The article titled "What's all this Battery
Isolator Stuff Anyway"
 
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I was thinking one diode also until I saw the article by Bob N. from 1998.
He shows the alternator output going to a junction between TWO diodes
each diode allowing current to flow to its respective battery. The main
battery diode would have to carry full alternator output. If only one diode
was used it would prevent current from flowing from back-up battery
to main but not the reverse. The article titled "What's all this Battery
Isolator Stuff Anyway"



Frank
While according to Bob Nuckles article and diagram a single Shotkey diode
would not be a true battery isolator it would prevent, as you stated, the main
battery or malfunctioning charging system from draining the back-up battery. I am going to look into a single shotkey diode and switch to
connect the backup battery to the charging system but keep turned off
except when a need exist to charge the back-up battery. This way it would
not be a issue during normal operation and would not be activated unless
it was observed that the main electrical was functioning normally.

Jim
 
Looks great, Robert. But what's the output pressure of these pumps? Those of us running carbs need a lower pressure than the FI guys to my knowledge.


Hi Kurt,
Good point, we have a dual electric pump for full return systems as with electronic fuel injection. We also have our Boost Pump for mechanical fuel injection which puts out 30psi.

The engines which don't have mechanical fuel pumps are a special case.
One attractive solution is to use our dual electric pump module which will give you a primary and a backup pump in a clean package. After the pump assembly, a bleed off type fuel pressure regulator is used to set the pressure after the pump and return the excess fuel back to the selected tank through a duplex fuel valve. This requires the extra complexity of a return fuel line, but it allows you to setup a low pressure fuel source for a carb or a high pressure fuel source for mechanical FI as well as offering the redundancy of the dual pump setup.
Robert
 
Dual electric fuel pump module

The Lyc engines which do not have provision for a mechanical fuel pump present an interesting challenge when it comes to the fuel system.
I have put together an application note that covers one solution using our dual electric fuel pump module.
The application note can be found here:
http://www.flyefii.com/add_components/FPM_App_Note_1.pdf
There is also a link to the App Note on the FPM info page here:
http://www.flyefii.com/add_components/additional_comp.htm

Robert
 
I have returned my 40108 pumps that I intended to run in series and
purchased two 40109 pumps and plumbed to run in parallel. After wasting
a lot of time and money on fittings I milled two aluminum manifolds from
3/4 inch square 6061 which made a more professional looking installation.
I also simplified the electrical hook-up for hopefully less chance of failure,
and hooked up as follows: Battery---W31 5amp Breaker switch---Pump
Repeated for Back-up battery and pump. Each totally independant of the
other and both directly connected to their respective batteries. During takeoff
and landing I plan to run both pumps which will mean the back-up battery
(a 7AH powersonic) will have to be recharged every so often. From the specs
it should run the pump for about 5 hours when fully charged. My question is
what would be the safety issues if I just added another switch to allow both
pumps to be run from main battery during takeoff and landing, making the
second battery purely back-up?
 
Complexity

From my perspective the twing electric fuel pump system has to be brain dead simple to operate..I.e your flying along and the pump dies..you throw one switch (2nd pump) and your back on line... Switching between batteries is asking to do fault finding, never under estimate the lack of your brain functionality when under extreem stress.

Both pumps are used for TO and landing of course.

This for me is why I advocate the shotkey diode between the main and alt batteries..its fit and forget and the second battery can't go dead.

Of course then you can run your second electronic ignition form the alt battery as well.

Frank
 
Frank
That's my thinking also. By having a back-up battery we are assuming that
something could happen to make the primary battery fail to deliver power
to the pumps. That's why during takeoff having both pumps on each powered
by its own battery is the only truly safe and redundant system. Whether I
charge on the bench/ground or charge using the plane's alternator I plan
to operate using both batteries during takeoff.
 
Robert,
Are these pumps able to handle E10 Auto gas (Auto gas with 10% ethonol)? Where can I get the adjustable fuel pressure regulator? Is it E10 compatable?

The Lyc engines which do not have provision for a mechanical fuel pump present an interesting challenge when it comes to the fuel system.
I have put together an application note that covers one solution using our dual electric fuel pump module.
The application note can be found here:
http://www.flyefii.com/add_components/FPM_App_Note_1.pdf
There is also a link to the App Note on the FPM info page here:
http://www.flyefii.com/add_components/additional_comp.htm

Robert
 
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Risk Assessment

Frank
That's my thinking also. By having a back-up battery we are assuming that
something could happen to make the primary battery fail to deliver power
to the pumps. That's why during takeoff having both pumps on each powered
by its own battery is the only truly safe and redundant system. Whether I
charge on the bench/ground or charge using the plane's alternator I plan
to operate using both batteries during takeoff.

Seems to me that the alternator is the primary source, with the main battery the reserve source. If you have a second battery you're adding more capacity and one more level of redundancy.

If you have an alternator failure the primary battery gives you time to land. If you have the back-up battery, you can tolerate one additional failure, that of the main battery. However, if you have a pump failure with the electrical system still happily making electrons, you don't have that additional failure tolerance any more - one more failure and you're dead-stick.

Assuming that you've done your electrical load analysis right and are keeping track of the condition of the primary battery, your electrical power source is one-fault tolerant, just like your pump system and your ignition. So why add a second level of redundancy to that system alone?

Real question, not just throwing darts. I'm wondering why you're choosing to have three layers in the electrical generation with two in the pumps and two in the ignition.

Dave
 
Robert,
Are these pumps able to handle E10 Auto gas (Auto gas with 10% ethonol)? Where can I get the adjustable fuel pressure regulator? Is it E10 compatable?

Hi Fred,
Yes, the pumps are fine with auto gas and Ethanol. They are automotive pumps.
The regulator listed in the app note can be purchased from summitracing.com.
It is fine with Ethanol as well.
Robert
 
Assuming that you've done your electrical load analysis right and are keeping track of the condition of the primary battery, your electrical power source is one-fault tolerant, just like your pump system and your ignition. So why add a second level of redundancy to that system alone?

Real question, not just throwing darts. I'm wondering why you're choosing to have three layers in the electrical generation with two in the pumps and two in the ignition.

Dave

I think we're getting into the area of personal risk tolerance here, for which there is no right or wrong answer that fits all. Independent redundancy (one backup for each primary, flight-critical system) is the standard in aviation, and seems to be widely accepted as the minimum acceptable risk tolerance in both certified and experimental ships. Of course, there are things like a propeller and an engine (on single engine aircraft) that have zero redundancy, and that is a risk that all of us single-engine pilots choose to accept each time we fly. More levels of redundancy are good, up to the point where they create undue levels of complexity in operations resulting in opportunity for mismanagement in an emergency.

Bottom line, once you have one redundant system for each primary, then decide for yourself if that's enough for your tastes or if you want more.
 
What is the worst that can happen when a alternator fails? Could the voltage
increase enough to damage the pumps or increase current flow thru them to
trip their circuit breakers? Could a sudden main battery internal short throw the alternator off-line?
 
As I understand it, alternator failure causing voltage spikes is extremely rare, and the vast majority of alternator failures are those that cause power output to drop off completely. But in the event it does happen, overvoltage protection (crowbar) in the alternator regulator, assuming you have one with that feature, will take the alternator field offline and prevent the voltage spike from getting too far outside normal range.

Sudden main battery internal short is a bit of a stretch, in my opinion. Perhaps the new LiFePo batteries that folks are playing with would be more of an unknown, but I'm not aware of any such failures with the Odyssey that most folks seem to use. I'd sure like to know if that IS a common failure mode so that I can plan accordingly.
 
Battery failure

Unheard of for an odyseey to have an internal short.

It is possible but if it did happen then it would be two cells shorting together which would bring down the battery voltage a little..then the altrnator would go to max current anyway and would maintain 10V or so..Still not enough to stop your pumps or electrnic ignitions.

But as I say I have not seen a single report ofan Odyssey failing that way. In fact Bob Knuckolls 2 alt, 1 battery system (which I have) relies on the fact.

I run two electric fuelpumps (no mechanical pump), 2 electronic ignitions and fly IFR.

Frank
 
Seems to me that the alternator is the primary source, with the main battery the reserve source. If you have a second battery you're adding more capacity and one more level of redundancy.

Dave

Thats pretty much where I got to..I.e the alternator going phut was far more likely than a battery failing. Hence I ended up with a small standby alternator and a single battery.

I only got to this point because it is conceivable to have and alternator go bad and be flying along in IMC with the need to fly for another hour before I could land. I would rather not declare an emergency unless I have to.

Personally the two battery or two alternator system is a little overkill for a VFR airplane..if (BIG IF) you have a cast iron way of detecting the failure...Not knowing your alternator died because you couldn't see the little red light in bright sunshine and now your fuel pressure is waning because the fuel pump is slowing down is not acceptable.

In my case I use the Dynon with the audible warning set to 12.5V.

So having said all that..why would you install a second battery on a VFR airplane with two electric fuel pumps and an audible warning?

Well because its easy, cheap, light weight and if done right will not add any more complexity..So why wouldn't you?

Frank
 
One of the better rules in engineering is "get it good enough and move on."

That's why not.

There might be things which for the same cost, weight and complexity might improve safety even more. For example, a redundant pitot tube (or anti-icing on the only one you have), or additional fuel tankage, or a real honest 406 ELT with its own built-in GPS.

Dave
 
One of the better rules in engineering is "get it good enough and move on."

That's why not.

There might be things which for the same cost, weight and complexity might improve safety even more. For example, a redundant pitot tube (or anti-icing on the only one you have), or additional fuel tankage, or a real honest 406 ELT with its own built-in GPS.

Dave

A pitot tube is not required to finish the flight. Fuel and ignition are required. You give a poor example. If you can't fly your aircraft without an ASI then it's not good enough, and don't move on.
 
In my case I use the Dynon with the audible warning set to 12.5V.

Frank

Frank, at 12.5 volts, your battery is already down to 75%. If you want to catch the alternator failure ASAP, set your Dynon warning to 13 volts.
 
A pitot tube is not required to finish the flight. Fuel and ignition are required. You give a poor example....

You're right, good catch.

Since this is for IFR, and assuming that the plane has an EFIS, then please replace my suggestion of a redundant pitot tube with a second ADAHRS.

There!

Dave
 
Sure thing, Bob. Glad to help.

I'd sure like to see a schematic of the fuel system you're planning with those pumps. Any chance you're willing to share?

I have what I think is a great system in mind, but you've got more engine, RV, etc. experience than I'll probably ever have.
 
Its in my head. Pretty simple. Two 40109 pumps in series in each wing root, plumbed to a tee in the center tunnel, with inline filters before the pumps. The 40109's have check valves built in. No fuel selector. No mechanical pump. From there straight to the Rotec TBI. Normal usage is one in each wing root is on at all times, the other two are backups. Four pump switches, L/R and L/R backup.
 
Sounds good, Bob. Hope you don't mind if I ask a question for my own (and others') education.

Since the pumps have built-in check valves, why not parallel them at each wing root? My thinking is this: presumably you would want to have both the main and the backup pump on during takeoff and landing. With both on, and in series, the output pressure doubles, potentially sinking the carb float or causing some other carb problem. If they were in parallel, the output pressure would be the same as having a single pump on. Plumbing issues are easier, of course, with them in series though.

Edit - never mind, I just re-read and saw you have a TBI. It can probably deal with the excess pressure.

Edit again - wouldn't just the most downstream pump in each wing need to have the check valve?
 
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Sounds good, Bob. Hope you don't mind if I ask a question for my own (and others') education.

Since the pumps have built-in check valves, why not parallel them at each wing root? My thinking is this: presumably you would want to have both the main and the backup pump on during takeoff and landing. With both on, and in series, the output pressure doubles, potentially sinking the carb float or causing some other carb problem. If they were in parallel, the output pressure would be the same as having a single pump on. Plumbing issues are easier, of course, with them in series though.

Edit - never mind, I just re-read and saw you have a TBI. It can probably deal with the excess pressure.

Edit again - wouldn't just the most downstream pump in each wing need to have the check valve?

If you run them in parallel one check valve failure will render the whole fuel system unusable. Highly unlikely two in series would ever fail. The TBI will handle pressures in excess of 10psi, so the additional pressure won't cause any problems.
 
Fantastic, Bob, thanks. I've got a carb, so I'm planning on two paralleled 40109 pumps immediately downstream of the fuel selector. Dual alternators are also planned, with a single bus. The only single point of failure I can imagine, besides the Andair fuel selector becoming blocked in some fashion (unheard-of?) would be if my Odyssey battery were to somehow shed a terminal.

To be complately fault-tolerant I'm now considering running one of the pumps off its own, smaller, battery that is charged by the electrical system like the main Odyssey.

Opinions welcome!
 
Apologies, my turn to have not done the "express myself clearly* bit. Let me try and elaborate.

There is only one tank shut off valve. The output of the pumps are teed together before the inlet of the shutoff valve and a pipe is taken from the output of the pumps to the inlet of the single ON OFF (Not Left Right) shutoff valve. A pipe feeds fuel from the output of the shutoff valve to the fuel injection. One pump is fed from the left tank the other pump is fed from the right tank. The pumps are mounted close to the left and right wing roots to alleviate vapour locking by keep pipe runs from the tank short. Feed back of fuel through the pumps is prevented by check valves (included in Andair pumps).

It is possible for the system I have described for one or both pumps to run against a blocked line. In this case the fuel is going nowhere and the pumps continue to run. I have not done any tests but I suspect the current consumption of the pumps would rise. Overheating may happen in time but as I said your attention would be drawn to the lack of sound coming from the front end for that to be any extended length of time. Running the pump against a closed valve is less of an issue for me. I want to avoid vapour locks by pushing fuel as much as possible rather than pulling it. With proper checklist consultation on the ground with respect to turning on the fuel valve, running against a closed valve is next to impossible

I hope this is more clear now.


frankh has been running a similar system. This is not my original idea and I do not want to steal his cudos.

My set-up is similar to yours Anthony (again thanks to Franky H), with a filter and pump in each wing root (each pump has a check valve) and no mechanical pump. And a "'T" before a on/off valve. Each pump has a on/off switch so the tanks are selected by the right or left switch.

I have a "SD8" alternator and a very small battery, as a back-up system. This back-up system only runs the fuel pumps (one at a time as selected), incase the master solenoid or something else in the primary charging system fails.

The Rotec TBI has no problem with both pumps running as a booster system. The left pump has a slightly higher fuel pressure and I've found with both pumps on the pressure is no higher than the left pumps pressure.
 
The Rotec TBI has no problem with both pumps running as a booster system. The left pump has a slightly higher fuel pressure and I've found with both pumps on the pressure is no higher than the left pumps pressure.

Paul @ Rotec told me that they will handle 10psi no problem. I rigged up some 40185 pumps I have and indeed the regulator didn't have any problem holding about 14psi. I did note that it took more negative pressure on the air side of the regulator to make it flow fuel at that pressure but it did work. What that tells me is that in a case of inadvertent high pressure it might quit at idle but I have no way of quantifying that.
 
Paul @ Rotec told me that they will handle 10psi no problem. I rigged up some 40185 pumps I have and indeed the regulator didn't have any problem holding about 14psi. I did note that it took more negative pressure on the air side of the regulator to make it flow fuel at that pressure but it did work. What that tells me is that in a case of inadvertent high pressure it might quit at idle but I have no way of quantifying that.

Bob, we did find after landing sometimes the engine would quit, or run very uneaven before applying power to taxi. What you have just pointed out could have been the cause. We were having a hot start problem where it would run rough for a while (I am talking about an extremely hot day here in the tropics), but once in the air it would clear itself. I fitted a blast tube directed on the TBI fuel inlet. This solved the hot start problem as it now only runs rough for about 5-10 seconds at 1000-1200 rpm. This also solved the uneaven idle or quitting after landing problem. The blast tube mod also seems to have given the 0-235 more power.

Bob
 
After all the work getting ready to use dual electric pumps I have just
purchased a second 0235 C2C with only 897 hrs since new. It is from
a American Yankee and has all the parts needed to go with mechanical
pump plus my IA friend just realized he has a yellow tagged fuel pump
still in box he will sell me. This engine has been sitting for years and I
have torn down for complete rebuild and all looks good. If anyone needs
two new 40109 pumps let me know.

Jim Miller
 
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