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Fuel Pump Switch(es)
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frank.hinde(at)hp.com
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PostPosted: Fri Sep 15, 2006 9:25 am    Post subject: Fuel Pump Switch(es) Reply with quote

Correct,

The airflow performance pump in the Standard airplane setup has a very
fine mesh filter in front of it.

I assume the is a bypass around the pump should this plug?

On the wingroot pump method I have a fine filter at the inlet of each
pump...Should one plug there is the other one.

At the first oil change (10 hours?) I will junk these cheap paper
filters and change to the sintered bronze deal on each pump.

There is debate that one should not use paper as a filter because it
could swell if it encountered water...Not sure I believe that would be a
problem in real life but hey, if you got the choice might as well do the
right thing.

Frank

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oldbob(at)BeechOwners.com
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PostPosted: Fri Sep 15, 2006 10:22 am    Post subject: Fuel Pump Switch(es) Reply with quote

Good Afternoon Frank,

Just as a point of conversation, you might be
interested in Steve Wittmans's personal philosophy of
fuel filtering.

He told me once that the majority of his engine
failures had been due to crud or water in the fuel. It
would clog up those little filters on the gascolators
that were so ubiquitous on Cubs, T-Crafts, and the
like.

Therefore, Steve eliminated all of the filters down
stream of the fuel tank. None in the gascolator and
none in the carburetor.

He made a tent in the bottom of his fuel tank out of
the same material as the little filters in the
gascolator were made from. For a two foot long round
fuel tank (the type favored by Steve) he ended up with
a section of screen approximately two feet long and
four inches wide. The tent walls were each about two
inches high.

In addition to that, he made a tubular unit out of the
same screen material that would fit down into the
fueling port. It was about six inches long and was of
a diameter that would easily fit in the opening. There
was a section of screen soldered to the bottom of the
tube and a suitable collar soldered around the top
such that the tube would not fall into the tank.

Steve would always fuel his airplane through that tube
while he watched carefully for any water or other crud
in the filling tube.

Whatever managed to get by that setup was, hopefully,
blocked out of the system by the large area screen in
the bottom of the tank. The fuel pick up was inside
the "tent".

Obviously, our fuel is a lot cleaner than it was forty
or fifty years ago when Steve was having problems, but
it was, nevertheless, a neat solution to the problems
he had encountered.

Happy Skies,

Old Bob
Stearman N3977A
Downers Grove, Illinois
LL22

--- "Hinde, Frank George (Corvallis)"
<frank.hinde(at)hp.com> wrote:

[quote]
Frank George (Corvallis)" <frank.hinde(at)hp.com>

Correct,

The airflow performance pump in the Standard
airplane setup has a very
fine mesh filter in front of it.

I assume the is a bypass around the pump should this
plug?

On the wingroot pump method I have a fine filter at
the inlet of each
pump...Should one plug there is the other one.

At the first oil change (10 hours?) I will junk
these cheap paper
filters and change to the sintered bronze deal on
each pump.

There is debate that one should not use paper as a
filter because it
could swell if it encountered water...Not sure I
believe that would be a
problem in real life but hey, if you got the choice
might as well do the
right thing.

Frank

--


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frank.hinde(at)hp.com
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PostPosted: Fri Sep 15, 2006 11:02 am    Post subject: Fuel Pump Switch(es) Reply with quote

Wow that's quite a solution...Smile

I went the "large as I could get filters" method but even those would
not prevent a catastrophic contamination event. Filtering the fuel on
the way in is a pain but it looks like Staev has a workable solution
there.

Thanks for the tip Bob

Frank

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N6030X(at)DaveMorris.com
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PostPosted: Fri Sep 15, 2006 11:46 am    Post subject: Fuel Pump Switch(es) Reply with quote

Filtering it going into the tank is great, but I'm not sure how he
would clean the "tent" filter.

How about those nice huge high-flow Fram HPG-1 filters? I'll bet it
would take a real mess to clog one of those puppies. They are also
pretty heavy.

Dave Morris

At 01:20 PM 9/15/2006, you wrote:
[quote]
<oldbob(at)beechowners.com>

Good Afternoon Frank,

Just as a point of conversation, you might be
interested in Steve Wittmans's personal philosophy of
fuel filtering.

He told me once that the majority of his engine
failures had been due to crud or water in the fuel. It
would clog up those little filters on the gascolators
that were so ubiquitous on Cubs, T-Crafts, and the
like.

Therefore, Steve eliminated all of the filters down
stream of the fuel tank. None in the gascolator and
none in the carburetor.

He made a tent in the bottom of his fuel tank out of
the same material as the little filters in the
gascolator were made from. For a two foot long round
fuel tank (the type favored by Steve) he ended up with
a section of screen approximately two feet long and
four inches wide. The tent walls were each about two
inches high.

In addition to that, he made a tubular unit out of the
same screen material that would fit down into the
fueling port. It was about six inches long and was of
a diameter that would easily fit in the opening. There
was a section of screen soldered to the bottom of the
tube and a suitable collar soldered around the top
such that the tube would not fall into the tank.

Steve would always fuel his airplane through that tube
while he watched carefully for any water or other crud
in the filling tube.

Whatever managed to get by that setup was, hopefully,
blocked out of the system by the large area screen in
the bottom of the tank. The fuel pick up was inside
the "tent".

Obviously, our fuel is a lot cleaner than it was forty
or fifty years ago when Steve was having problems, but
it was, nevertheless, a neat solution to the problems
he had encountered.

Happy Skies,

Old Bob
Stearman N3977A
Downers Grove, Illinois
LL22

--- "Hinde, Frank George (Corvallis)"
<frank.hinde(at)hp.com> wrote:

>
> Frank George (Corvallis)" <frank.hinde(at)hp.com>
>
> Correct,
>
> The airflow performance pump in the Standard
> airplane setup has a very
> fine mesh filter in front of it.
>
> I assume the is a bypass around the pump should this
> plug?
>
> On the wingroot pump method I have a fine filter at
> the inlet of each
> pump...Should one plug there is the other one.
>
> At the first oil change (10 hours?) I will junk
> these cheap paper
> filters and change to the sintered bronze deal on
> each pump.
>
> There is debate that one should not use paper as a
> filter because it
> could swell if it encountered water...Not sure I
> believe that would be a
> problem in real life but hey, if you got the choice
> might as well do the
> right thing.
>
> Frank
>
> --


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rv8ch



Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

PostPosted: Sat Sep 16, 2006 10:50 am    Post subject: Fuel Pump Switch(es) Reply with quote

OldBob Siegfried wrote:
Quote:

He made a tent in the bottom of his fuel tank out of
the same material as the little filters in the
gascolator were made from. For a two foot long round
fuel tank (the type favored by Steve) he ended up with
a section of screen approximately two feet long and
four inches wide. The tent walls were each about two
inches high.

It seems the car manufacturers have learned from Steve Wittman, as most
cars now use a type of "filter bag" at the fuel inlet connected to the
in-tank fuel pumps. This provides a very large surface area for
filtering, and the agitation inside the tanks helps keep crud from
clogging up the filter.
--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive


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trigo(at)mail.telepac.pt
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PostPosted: Sat Sep 16, 2006 11:32 am    Post subject: Fuel Pump Switch(es) Reply with quote

Hi Mickey

Long time you haven't posted.
Back in "business"? Still in CH? Still finishing the -8?

Carlos
Do not archive

---


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rv8ch



Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

PostPosted: Sat Sep 16, 2006 12:28 pm    Post subject: Fuel Pump Switch(es) Reply with quote

Quote:
Long time you haven't posted.
Back in "business"? Still in CH? Still finishing the -8?

Carlos

Still finishing, and unfortunately the fun stuff (wiring) is almost
done. Then on to the cowl - ugh! At one point I really dreaded the
wiring, but this list and Bob's book made that a real pleasure.

--
Mickey Coggins
http://www.rv8.ch/
#82007 finishing
do not archive


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khorton01(at)rogers.com
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PostPosted: Sat Sep 16, 2006 1:21 pm    Post subject: Fuel Pump Switch(es) Reply with quote

On 15 Sep 2006, at 10:18, Gary Casey wrote:

Quote:

<glcasey(at)adelphia.net>

Kevin previously wrote:
> "If you don't do the test then, someday you may
> stumble across that condition when you hadn't planned it. If the
> system works as expected, then everything is OK. But if the system
> does not perform, then you may lose the aircraft.

Good points, but what "assumptions" do you have in mind that should
be tested?

I'm not familiar enough with the assumptions that your fuel system
design was based on, so I can't make any specific recommendations.

If I understand properly, you looked at the conventional design fuel
system, but were not satisfied with some aspects of its operation, in
normal or abnormal conditions. E.g., "In situation A, if event B
occurs, the conventional design fuel system will not operate
adequately". Then you designed a fuel system that you believe should
work better in each of those situations. If your fuel system
actually functions as expected in each of those situations, then you
it should prove satisfactory in service. But, if it turns out that
it in fact performs differently than you assume it will, then maybe
there could be an accident or incident.

If you want to identify any potential problems during the test
program, find a way to create all the "situation A" + "event B" from
above. You have also considered all the conceivable normal and
abnormal operation scenarios, and determined that your fuel system
design should work properly. This should be validated by test.
Obviously, the tests must be conducted so that there will be a safe
outcome, even if the fuel system proves to not function as expected.

Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8


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ed(at)muellerartcover.com
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PostPosted: Wed Sep 20, 2006 9:31 am    Post subject: Fuel Pump Switch(es) Reply with quote

Hi Frank,

I've been following this thread for a while. I like your idea for the
fuel system. Just a couple of questions.

I'm thinking of using a carbed lycoming. Why couldn't I use a
mechanical pump, an off-left-right-both fuel valve, and two electric pumps?

Normal Operation:
Fuel valve on both all the time (no valve to switch).
One or the other electric pump on to select tank used.
Tanks switched with the pumps.

Takeoff and landing.
Same as above but both electric pumps on.

Failures.
Electric pump failure. Fuel selector switched to that tank if that fuel
is needed.
Mechanical pump failure would NOT be noticed in this system but could be
checked at startup (or in the air if you wanted to turn both pumps off).

All of the advantages you pointed out but would not be dependent on the
electrical system or an electric pump failure.
I like simple systems. I owned and flew a Beech Duchess (light light
twin) for 14 years. Left tank fed left engine, right tank fed right
engine. No switching fuel valves unless an engine failure. Went back
to a single engine three years ago, first time I had to switch tanks I
wasn't happy having to fool with the fuel. A year later in the same
plane, my wife (a pilot also) switched tanks for me but commented that
it didn't feel right going into the left position. I looked down at the
valve and saw that a loose nut from a screw was lodged between the
handle and the stop preventing the valve from fully engaging. Luckily
the engine continued running , valve back to right, fish nut out, valve
to left then worked fine. Should there be loose nuts in the airplane?
No, but stuff happens. Therefore when I heard of your system, I
liked it immediately.

Hinde, Frank George (Corvallis) wrote:
[quote]

Exactly!

And now back to the one pump in each wingroot solution....left tank
...switch left pump on...Right tank switch right pump on... Both tanks
(TO and landing).. Both switches on. Pretty simple I think.

The other advantages are...
No selector valves to switch.
Highly resistant to Vapour lock...Biggest driver to use auto fuel
SIMPLE
No single point of failure anywhere...OK the fuel line, servo and
battery is (assuming you don't have an isolated twin battery setup)
Plug a fuel filter...Who cares?

Downsides

Uses more electrical power.
Have to design the "what happens if the alternator craps out" failure
mode...I have dual alternaors...8 amp back up is just big enough for a
radio, tansponder and one fuel pump
Extra 3 feet of pressurised fuel line in the cockpit.

Frank
RV7a 4 hours

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PostPosted: Wed Sep 20, 2006 10:58 am    Post subject: Fuel Pump Switch(es) Reply with quote

Hello Ed,

With a carb you have the advantage that you don't have to mess with the
pressure relief valve and tank return...not that you mess with it in
flight but is more work to install. You also have a few seconds of
reserve fuel in the float bowl plus if somehow you pumped air to the
floatbowl it does'nt care because the air gets vented thru the floatbowl
harmlessly. Pretty good setup.

Yes you can use a Facet solid state pump in your wingroots and I believe
these are rated to 30GPH each.

There two failure modes that I am not sure of in your suggested
setup...I bet it is perfectly OK but I don't know for sure.

1) What happens if the mechanical pump rutures a diaphram...where does
the fuel go?
2) Are there any other failure modes that would stop the Facet pump from
pumping thru the dead mechanical pump?
3) can you suck thru two dead facet pumps with your mecahnical pump?...I
think you can and the point is a little moot anyway. As long as you wire
the pumps independantly the chances of loosing both pumps is very
unlikely..In a way you triple redundancy.
I personally would avoid a selector valve with left and right only
selections...One day you will get it wrong and have the wrong pump on
with the wrong tank...Simply replace it with an on/off valve, join the
outputs of the pumps together with a Tee fitting and make sure there is
a check valve in each line...This will stop cross feeding to the no used
tank.

Ahh...I just seen the issue with this...If you have an on/off valve with
a mechanical pump and both facets are offline you will likely suck air
to your floatbowl...That wouldn't be good...But should still suck thru
the pump you turned off.

Hmm seems to me the meachanical pump is not a good idea with this system
and will require a selector valve which adds complexity and the very
single point of failure you had trouble with before.

I wouldn't use this system but it should work. Personally I don't see
the advantage over the standard mechanical/electric pump with selector
valve...Unless you intend to use Mogas of course.

Frank

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PostPosted: Wed Sep 20, 2006 1:26 pm    Post subject: Fuel Pump Switch(es) Reply with quote

Hinde, Frank George (Corvallis) wrote:
Quote:


Hello Ed,

With a carb you have the advantage that you don't have to mess with the
pressure relief valve and tank return...not that you mess with it in
flight but is more work to install. You also have a few seconds of
reserve fuel in the float bowl plus if somehow you pumped air to the
floatbowl it does'nt care because the air gets vented thru the floatbowl
harmlessly. Pretty good setup.

Yes you can use a Facet solid state pump in your wingroots and I believe
these are rated to 30GPH each.

There two failure modes that I am not sure of in your suggested
setup...I bet it is perfectly OK but I don't know for sure.

1) What happens if the mechanical pump rutures a diaphram...where does the fuel go?

I thought the electric pump was a backup for the mechanical pump on cert

airplanes. Isn't it designed so the electric can pump if the mechanical
fails?
Quote:
2) Are there any other failure modes that would stop the Facet pump from
pumping thru the dead mechanical pump?

Same as above?

Quote:
3) can you suck thru two dead facet pumps with your mecahnical pump?...I
think you can and the point is a little moot anyway. As long as you wire
the pumps independantly the chances of loosing both pumps is very
unlikely..In a way you triple redundancy.

I wasn't sure about this other than it works this way on my cert

airplane when the electric is off. Unless a dead pump would be different?
Quote:

I personally would avoid a selector valve with left and right only
selections...One day you will get it wrong and have the wrong pump on
with the wrong tank...Simply replace it with an on/off valve, join the
outputs of the pumps together with a Tee fitting and make sure there is
a check valve in each line...This will stop cross feeding to the no used
tank.

Under normal operations you would not move the selector valve. You

would use the pumps for tank selection. Remember, this would be an
off-left-right-both valve (ACS ANDAIR FUEL VALVE FS20X4M). The
advantage of this valve would be in the event of an electrical pump
failure, the system would operate much like a cert system so that you
could get fuel out of the dead pump tank..
Quote:
Ahh...I just seen the issue with this...If you have an on/off valve with
a mechanical pump and both facets are offline you will likely suck air
to your floatbowl...That wouldn't be good...But should still suck thru
the pump you turned off.

If one tank had fuel and the mechanical pump is working, putting the

fuel selector on that tank should give fuel.
Quote:
Hmm seems to me the meachanical pump is not a good idea with this system
and will require a selector valve which adds complexity and the very
single point of failure you had trouble with before.

The mechanical pump becomes the backup. The selector valve is only used

in the event of electric pump failure.
Quote:
I wouldn't use this system but it should work. Personally I don't see
the advantage over the standard mechanical/electric pump with selector
valve...Unless you intend to use Mogas of course.

I don't understand this comment. The advantages would seem to be:

Both tanks feeding for critical flight phases such as takeoff and landing.
No need to use the selector valve except in an emergency.
Could use auto gas if desired.

The whole system would be almost identical to the systems in cert
planes. You would be adding one extra electric fuel pump and gaining
the advantages.

Ed

[quote] Frank

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ed(at)muellerartcover.com
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PostPosted: Wed Sep 20, 2006 5:34 pm    Post subject: Fuel Pump Switch(es) Reply with quote

Hinde, Frank George (Corvallis) wrote:
Quote:


Hello Ed,

With a carb you have the advantage that you don't have to mess with the
pressure relief valve and tank return...not that you mess with it in
flight but is more work to install. You also have a few seconds of
reserve fuel in the float bowl plus if somehow you pumped air to the
floatbowl it does'nt care because the air gets vented thru the floatbowl
harmlessly. Pretty good setup.

Yes you can use a Facet solid state pump in your wingroots and I believe
these are rated to 30GPH each.

There two failure modes that I am not sure of in your suggested
setup...I bet it is perfectly OK but I don't know for sure.

1) What happens if the mechanical pump rutures a diaphram...where does the fuel go?

I thought the electric pump was a backup for the mechanical pump on cert

airplanes. Isn't it designed so the electric can pump if the mechanical
fails?
Quote:
2) Are there any other failure modes that would stop the Facet pump from
pumping thru the dead mechanical pump?

Same as above?

Quote:
3) can you suck thru two dead facet pumps with your mecahnical pump?...I
think you can and the point is a little moot anyway. As long as you wire
the pumps independantly the chances of loosing both pumps is very
unlikely..In a way you triple redundancy.

I wasn't sure about this other than it works this way on my cert

airplane when the electric is off. Unless a dead pump would be different?
Quote:

I personally would avoid a selector valve with left and right only
selections...One day you will get it wrong and have the wrong pump on
with the wrong tank...Simply replace it with an on/off valve, join the
outputs of the pumps together with a Tee fitting and make sure there is
a check valve in each line...This will stop cross feeding to the no used
tank.

Under normal operations you would not move the selector valve. You

would use the pumps for tank selection. Remember, this would be an
off-left-right-both valve (ACS ANDAIR FUEL VALVE FS20X4M). The
advantage of this valve would be in the event of an electrical pump
failure, the system would operate much like a cert system so that you
could get fuel out of the dead pump tank..
Quote:
Ahh...I just seen the issue with this...If you have an on/off valve with
a mechanical pump and both facets are offline you will likely suck air
to your floatbowl...That wouldn't be good...But should still suck thru
the pump you turned off.

If one tank had fuel and the mechanical pump is working, putting the

fuel selector on that tank should give fuel.
Quote:
Hmm seems to me the meachanical pump is not a good idea with this system
and will require a selector valve which adds complexity and the very
single point of failure you had trouble with before.

The mechanical pump becomes the backup. The selector valve is only used

in the event of electric pump failure.
Quote:
I wouldn't use this system but it should work. Personally I don't see
the advantage over the standard mechanical/electric pump with selector
valve...Unless you intend to use Mogas of course.

I don't understand this comment. The advantages would seem to be:

Both tanks feeding for critical flight phases such as takeoff and landing.
No need to use the selector valve except in an emergency.
Could use auto gas if desired.

The whole system would be almost identical to the systems in cert
planes. You would be adding one extra electric fuel pump and gaining
the advantages.

Ed

[quote] Frank

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