The Murphy Builders Site

Went flying this weekend and had some fuel management issues that
I still don't totally understand, so thought I would share with
the group, as it might affect you one day, too.

Usually in the winter, I transition from mogas to avgas, and was
last flying with one tank avgas and using up the last of the
mogas in the other. Anyway, I didn't get it quite empty on my
previous flight, so decided to drain the last of it (only 2 gal
left) through my gascolator, so I could fill up that tank, too,
with pure avgas.

While draining the mogas tank, I, of course, closed the other
avgas tank fuel valve. When finished, I closed the empty tank
valve and opened the other avgas tank again, and started the
engine to go fuel up my empty tank at the pumps. The engine
started fine, and I began my taxi. Well, I barely got going when
the engine quit. And I could not start it, no matter what. It
fired up a couple of times, but would not continue running. I
then opened up the closed empty tank, and after a short wait
(maybe 20 seconds) I then started and was able to continue on to
the fuel pump without further interruption.

This has actually happened to me before, while still on the
ground, with similar circumstances after draining a tank, but
wasn't exactly sure if it was a fluke or what. The fact that it
happened again, makes me very leery of ever running one tank dry
in the air. The tank that I switched to had exactly 15 US g, so
it wasn't anywhere near empty. What was interesting is that I
couldn't get the engine started until I opened the other empty
tank. So my theory is, it allowed the air to escape up there, and
then the fuel was able to flow freely from the full tank. My
tanks are plumbed so that the shut off valves are up top at the
tank outlets, and the lines are not tee'd together until just
before the gascolator on the firewall. I also have a fuel flow
sender that is on the output of the gascolator, that I believe
costs at most 0.5 PSI to operate. No fuel pumps, just gravity
feed.

Anyway, I think I have heard Bob P say, and maybe others that
they have run one tank dry in the air, and no problem. So my
question is, how exactly did you do that and exactly how low was
the fuel in the new tank? As I said, mine was 15 g, and it still
didn't start. When you opened the good tank, did you first close
the empty tank, or was it still open? I am just wondering what is
the better procedure. From my ground experience, it would seem
that it is better to leave the empty tank open until the engine
is running fine on the new tank.

I often fly with one tank, and switch tanks in flight, but have
never run one dry. When I do get low in one tank, as I did in my
previous flight (only 2 gal left) I switch to both before
landing, or when I am not over water. So I would like to
understand this better before I try running one tank completely
dry.

OK, that was one fuel issue. On the same day, when I took off,
after fuelling, I had another, that may or may not be related.
Here is what happened. I did my run-up, with both tanks now open,
and proceeded to the runway, but had to hold about 5 minutes
while other planes landed, and another ahead of me waited his
turn also. It's not normally that busy here, but it was a rare
nice day, and of course everybody decided to go flying. Anyway,
right after take-off, I noticed my rpm fluctuate and drop to low
2400's and even into the 2300's for a couple of seconds. I didn't
notice that it ran rough, just not full power. I climbed to about
300 feet and then abandoned our noise abatement path and started
a left turn so I could catch the crosswind grass runway if I had
to. It continued to climb though, and then resumed its usual
climb rpm of 2550, and ran just fine after that. The rest of my
flying that day was uneventful, but needless to say, I wasn't
happy with what happened.

I have a couple of theories on this last issue. One is that I
still may have had some air in my lines after bringing the second
tank online after fuelling. My run-ups are only at 1800 rpm
because of my amphib brakes. The other is that I may have got
some carb ice after sitting at idle so long waiting for my turn
to take off. OAT on the ground at that time was about 5 C (40F).
Or maybe my plugs fouled up a bit with lead with the long idle.

Any thoughts? I don't like mysteries of this kind.

Walter




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Went flying this weekend and had some fuel management issues that
I still don't totally understand, so thought I would share with
the group, as it might affect you one day, too.

Usually in the winter, I transition from mogas to avgas, and was
last flying with one tank avgas and using up the last of the
mogas in the other. Anyway, I didn't get it quite empty on my
previous flight, so decided to drain the last of it (only 2 gal
left) through my gascolator, so I could fill up that tank, too,
with pure avgas.

While draining the mogas tank, I, of course, closed the other
avgas tank fuel valve. When finished, I closed the empty tank
valve and opened the other avgas tank again, and started the
engine to go fuel up my empty tank at the pumps. The engine
started fine, and I began my taxi. Well, I barely got going when
the engine quit. And I could not start it, no matter what. It
fired up a couple of times, but would not continue running. I
then opened up the closed empty tank, and after a short wait
(maybe 20 seconds) I then started and was able to continue on to
the fuel pump without further interruption.

This has actually happened to me before, while still on the
ground, with similar circumstances after draining a tank, but
wasn't exactly sure if it was a fluke or what. The fact that it
happened again, makes me very leery of ever running one tank dry
in the air. The tank that I switched to had exactly 15 US g, so
it wasn't anywhere near empty. What was interesting is that I
couldn't get the engine started until I opened the other empty
tank. So my theory is, it allowed the air to escape up there, and
then the fuel was able to flow freely from the full tank. My
tanks are plumbed so that the shut off valves are up top at the
tank outlets, and the lines are not tee'd together until just
before the gascolator on the firewall. I also have a fuel flow
sender that is on the output of the gascolator, that I believe
costs at most 0.5 PSI to operate. No fuel pumps, just gravity
feed.

Anyway, I think I have heard Bob P say, and maybe others that
they have run one tank dry in the air, and no problem. So my
question is, how exactly did you do that and exactly how low was
the fuel in the new tank? As I said, mine was 15 g, and it still
didn't start. When you opened the good tank, did you first close
the empty tank, or was it still open? I am just wondering what is
the better procedure. From my ground experience, it would seem
that it is better to leave the empty tank open until the engine
is running fine on the new tank.

I often fly with one tank, and switch tanks in flight, but have
never run one dry. When I do get low in one tank, as I did in my
previous flight (only 2 gal left) I switch to both before
landing, or when I am not over water. So I would like to
understand this better before I try running one tank completely
dry.

OK, that was one fuel issue. On the same day, when I took off,
after fuelling, I had another, that may or may not be related.
Here is what happened. I did my run-up, with both tanks now open,
and proceeded to the runway, but had to hold about 5 minutes
while other planes landed, and another ahead of me waited his
turn also. It's not normally that busy here, but it was a rare
nice day, and of course everybody decided to go flying. Anyway,
right after take-off, I noticed my rpm fluctuate and drop to low
2400's and even into the 2300's for a couple of seconds. I didn't
notice that it ran rough, just not full power. I climbed to about
300 feet and then abandoned our noise abatement path and started
a left turn so I could catch the crosswind grass runway if I had
to. It continued to climb though, and then resumed its usual
climb rpm of 2550, and ran just fine after that. The rest of my
flying that day was uneventful, but needless to say, I wasn't
happy with what happened.

I have a couple of theories on this last issue. One is that I
still may have had some air in my lines after bringing the second
tank online after fuelling. My run-ups are only at 1800 rpm
because of my amphib brakes. The other is that I may have got
some carb ice after sitting at idle so long waiting for my turn
to take off. OAT on the ground at that time was about 5 C (40F).
Or maybe my plugs fouled up a bit with lead with the long idle.

Any thoughts? I don't like mysteries of this kind.

Walter




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Hi,

I kind of like the air in the lines theory for both issues. I thought of
some closed vent possibility but that doesn't seem likely if you have run
this tank open while the other is close before.

As for the Gravity Theory, always doubted it.

I like the electric fuel pump theory better, as I learned in boot camp:
What doesn't go with force, goes with more force... :)

Ted
----- Original Message -----
From: "Walter Klatt" <Walter.Klatt@shaw.ca>
To: "Rebel-Builders" <rebel-builders@dcsol.com>
Sent: Monday, December 13, 2004 8:22 PM
Subject: Rebel Fuel Management

Went flying this weekend and had some fuel management issues that
I still don't totally understand, so thought I would share with
the group, as it might affect you one day, too.

Usually in the winter, I transition from mogas to avgas, and was
last flying with one tank avgas and using up the last of the
mogas in the other. Anyway, I didn't get it quite empty on my
previous flight, so decided to drain the last of it (only 2 gal
left) through my gascolator, so I could fill up that tank, too,
with pure avgas.

While draining the mogas tank, I, of course, closed the other
avgas tank fuel valve. When finished, I closed the empty tank
valve and opened the other avgas tank again, and started the
engine to go fuel up my empty tank at the pumps. The engine
started fine, and I began my taxi. Well, I barely got going when
the engine quit. And I could not start it, no matter what. It
fired up a couple of times, but would not continue running. I
then opened up the closed empty tank, and after a short wait
(maybe 20 seconds) I then started and was able to continue on to
the fuel pump without further interruption.

This has actually happened to me before, while still on the
ground, with similar circumstances after draining a tank, but
wasn't exactly sure if it was a fluke or what. The fact that it
happened again, makes me very leery of ever running one tank dry
in the air. The tank that I switched to had exactly 15 US g, so
it wasn't anywhere near empty. What was interesting is that I
couldn't get the engine started until I opened the other empty
tank. So my theory is, it allowed the air to escape up there, and
then the fuel was able to flow freely from the full tank. My
tanks are plumbed so that the shut off valves are up top at the
tank outlets, and the lines are not tee'd together until just
before the gascolator on the firewall. I also have a fuel flow
sender that is on the output of the gascolator, that I believe
costs at most 0.5 PSI to operate. No fuel pumps, just gravity
feed.

Anyway, I think I have heard Bob P say, and maybe others that
they have run one tank dry in the air, and no problem. So my
question is, how exactly did you do that and exactly how low was
the fuel in the new tank? As I said, mine was 15 g, and it still
didn't start. When you opened the good tank, did you first close
the empty tank, or was it still open? I am just wondering what is
the better procedure. From my ground experience, it would seem
that it is better to leave the empty tank open until the engine
is running fine on the new tank.

I often fly with one tank, and switch tanks in flight, but have
never run one dry. When I do get low in one tank, as I did in my
previous flight (only 2 gal left) I switch to both before
landing, or when I am not over water. So I would like to
understand this better before I try running one tank completely
dry.

OK, that was one fuel issue. On the same day, when I took off,
after fuelling, I had another, that may or may not be related.
Here is what happened. I did my run-up, with both tanks now open,
and proceeded to the runway, but had to hold about 5 minutes
while other planes landed, and another ahead of me waited his
turn also. It's not normally that busy here, but it was a rare
nice day, and of course everybody decided to go flying. Anyway,
right after take-off, I noticed my rpm fluctuate and drop to low
2400's and even into the 2300's for a couple of seconds. I didn't
notice that it ran rough, just not full power. I climbed to about
300 feet and then abandoned our noise abatement path and started
a left turn so I could catch the crosswind grass runway if I had
to. It continued to climb though, and then resumed its usual
climb rpm of 2550, and ran just fine after that. The rest of my
flying that day was uneventful, but needless to say, I wasn't
happy with what happened.

I have a couple of theories on this last issue. One is that I
still may have had some air in my lines after bringing the second
tank online after fuelling. My run-ups are only at 1800 rpm
because of my amphib brakes. The other is that I may have got
some carb ice after sitting at idle so long waiting for my turn
to take off. OAT on the ground at that time was about 5 C (40F).
Or maybe my plugs fouled up a bit with lead with the long idle.

Any thoughts? I don't like mysteries of this kind.

Walter




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-----Original Message-----
From: mike.davis@dcsol.com
[mailto:mike.davis@dcsol.com]On Behalf Of
Legeorgen@aol.com
Sent: Monday, December 13, 2004 8:08 PM
To: rebel-builders@dcsol.com
Subject: Re: Rebel Fuel Management


Hi Walter,

How is the avgas tank vented? Maybe it was plugged.
Or, Like you said, there
may have been some air trapped between the avgas
flowing in and the carb. An
electric fuel pump would have been nice to use if you
have one.

It would make sense to open the full tank right before
the low tank is run
dry, so you don't trap air, if that is what's happening.

Do you lean when you,re idling to prevent lead fouling?

I would check the gascolator screen, maybe it is dirty
from running the one
tank dry.

Bruce




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----------

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

At 08:41 PM 12/13/2004 -0800, you wrote:

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

Hi Walter I've run one tank dry in flight a few times on long cross
countries when I'm getting near maximun range for the fuel
carried. I feel
better having all my remaining fuel in one tank rather than split
between 2
just because I've also had the problem of unporting the intake
pipe with
low fuel when cranking and banking close to the ground. My vent is
at the
wing root on the pilots side and that tank seems to feed a little
fasterthan the other one. so it's easier to manage just one tank
at a time.
Drew





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Check out this article on AVWeb - Suggests to run the tanks dry so
you know
where you stand - Not that I have ever done it but it seems
reasonable -
What if it happens accidentally? Will it restart?

http://www.avweb.com/news/columns/182044-1.html

Britt - SR194


-----Original Message-----
From: mike.davis@dcsol.com [mike.davis@dcsol.com] On Behalf Of Drew
Dalgleish
Sent: Tuesday, December 14, 2004 8:27 AM
To: rebel-builders@dcsol.com
Subject: RE: Rebel Fuel Management

At 08:41 PM 12/13/2004 -0800, you wrote:

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

Hi Walter I've run one tank dry in flight a few times on long cross
countries when I'm getting near maximun range for the fuel
carried. I feel
better having all my remaining fuel in one tank rather than split
between 2
just because I've also had the problem of unporting the intake
pipe with
low fuel when cranking and banking close to the ground. My vent is
at the
wing root on the pilots side and that tank seems to feed a little
fasterthan the other one. so it's easier to manage just one tank
at a time.
Drew





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Check out this article on AVWeb - Suggests to run the tanks dry so
you know
where you stand - Not that I have ever done it but it seems
reasonable -
What if it happens accidentally? Will it restart?

http://www.avweb.com/news/columns/182044-1.html

Britt - SR194


-----Original Message-----
From: mike.davis@dcsol.com [mike.davis@dcsol.com] On Behalf Of Drew
Dalgleish
Sent: Tuesday, December 14, 2004 8:27 AM
To: rebel-builders@dcsol.com
Subject: RE: Rebel Fuel Management

At 08:41 PM 12/13/2004 -0800, you wrote:

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

Hi Walter I've run one tank dry in flight a few times on long cross
countries when I'm getting near maximun range for the fuel
carried. I feel
better having all my remaining fuel in one tank rather than split
between 2
just because I've also had the problem of unporting the intake
pipe with
low fuel when cranking and banking close to the ground. My vent is
at the
wing root on the pilots side and that tank seems to feed a little
fasterthan the other one. so it's easier to manage just one tank
at a time.
Drew





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Went flying this weekend and had some fuel management issues that
I still don't totally understand, so thought I would share with
the group, as it might affect you one day, too.

Usually in the winter, I transition from mogas to avgas, and was
last flying with one tank avgas and using up the last of the
mogas in the other. Anyway, I didn't get it quite empty on my
previous flight, so decided to drain the last of it (only 2 gal
left) through my gascolator, so I could fill up that tank, too,
with pure avgas.

While draining the mogas tank, I, of course, closed the other
avgas tank fuel valve. When finished, I closed the empty tank
valve and opened the other avgas tank again, and started the
engine to go fuel up my empty tank at the pumps. The engine
started fine, and I began my taxi. Well, I barely got going when
the engine quit. And I could not start it, no matter what. It
fired up a couple of times, but would not continue running. I
then opened up the closed empty tank, and after a short wait
(maybe 20 seconds) I then started and was able to continue on to
the fuel pump without further interruption.

This has actually happened to me before, while still on the
ground, with similar circumstances after draining a tank, but
wasn't exactly sure if it was a fluke or what. The fact that it
happened again, makes me very leery of ever running one tank dry
in the air. The tank that I switched to had exactly 15 US g, so
it wasn't anywhere near empty. What was interesting is that I
couldn't get the engine started until I opened the other empty
tank. So my theory is, it allowed the air to escape up there, and
then the fuel was able to flow freely from the full tank. My
tanks are plumbed so that the shut off valves are up top at the
tank outlets, and the lines are not tee'd together until just
before the gascolator on the firewall. I also have a fuel flow
sender that is on the output of the gascolator, that I believe
costs at most 0.5 PSI to operate. No fuel pumps, just gravity
feed.

Anyway, I think I have heard Bob P say, and maybe others that
they have run one tank dry in the air, and no problem. So my
question is, how exactly did you do that and exactly how low was
the fuel in the new tank? As I said, mine was 15 g, and it still
didn't start. When you opened the good tank, did you first close
the empty tank, or was it still open? I am just wondering what is
the better procedure. From my ground experience, it would seem
that it is better to leave the empty tank open until the engine
is running fine on the new tank.

I often fly with one tank, and switch tanks in flight, but have
never run one dry. When I do get low in one tank, as I did in my
previous flight (only 2 gal left) I switch to both before
landing, or when I am not over water. So I would like to
understand this better before I try running one tank completely
dry.

OK, that was one fuel issue. On the same day, when I took off,
after fuelling, I had another, that may or may not be related.
Here is what happened. I did my run-up, with both tanks now open,
and proceeded to the runway, but had to hold about 5 minutes
while other planes landed, and another ahead of me waited his
turn also. It's not normally that busy here, but it was a rare
nice day, and of course everybody decided to go flying. Anyway,
right after take-off, I noticed my rpm fluctuate and drop to low
2400's and even into the 2300's for a couple of seconds. I didn't
notice that it ran rough, just not full power. I climbed to about
300 feet and then abandoned our noise abatement path and started
a left turn so I could catch the crosswind grass runway if I had
to. It continued to climb though, and then resumed its usual
climb rpm of 2550, and ran just fine after that. The rest of my
flying that day was uneventful, but needless to say, I wasn't
happy with what happened.

I have a couple of theories on this last issue. One is that I
still may have had some air in my lines after bringing the second
tank online after fuelling. My run-ups are only at 1800 rpm
because of my amphib brakes. The other is that I may have got
some carb ice after sitting at idle so long waiting for my turn
to take off. OAT on the ground at that time was about 5 C (40F).
Or maybe my plugs fouled up a bit with lead with the long idle.

Any thoughts? I don't like mysteries of this kind.

Walter




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I took the Champ up one fine day in Winter a couple of years ago.
I landed at Hampton (grass field) and when I left about a half
hour later, I had to wait awhile before the runway was clear for
takeoff. There was a lot of ice in the taxi area, so while I
waited I ran around 1200 RPM, and because of the ice I didn't do a
runup. I barely cleared the trees (lucky for me the air was cold),
and as I limped around the pattern tried carb heat to no avail.
But it was carb ice. Ten minutes on the ground and the radiant
heat from the engine melted the ice. I taxied with carb heat to
takeoff, and had no problems that time.

-------------- Original message from Walter Klatt
<Walter.Klatt@shaw.ca>: --------------

Went flying this weekend and had some fuel management issues

that

I still don't totally understand, so thought I would share with
the group, as it might affect you one day, too.

Usually in the winter, I transition from mogas to avgas, and was
last flying with one tank avgas and using up the last of the
mogas in the other. Anyway, I didn't get it quite empty on my
previous flight, so decided to drain the last of it (only 2 gal
left) through my gascolator, so I could fill up that tank, too,
with pure avgas.

While draining the mogas tank, I, of course, closed the other
avgas tank fuel valve. When finished, I closed the empty tank
valve and opened the other avgas tank again, and started the
engine to go fuel up my empty tank at the pumps. The engine
started fine, and I began my taxi. Well, I barely got going when
the engine quit. And I could not start it, no matter what. It
fired up a couple of times, but would not continue running. I
then opened up the closed empty tank, and after a short wait
(maybe 20 seconds) I then started and was able to continue on to
the fuel pump without further interruption.

This has actually happened to me before, while still on the
ground, with similar circumstances after draining a tank, but
wasn't exactly sure if it was a fluke or what. The fact that it
happened again, makes me very leery of ever running one tank dry
in the air. The tank that I switched to had exactly 15 US g, so
it wasn't anywhere near empty. What was interesting is that I
couldn't get the engine started until I opened the other empty
tank. So my theory is, it allowed the air to escape up there,

and

then the fuel was able to flow freely from the full tank. My
tanks are plumbed so that the shut off valves are up top at the
tank outlets, and the lines are not tee'd together until just
before the gascolator on the firewall. I also have a fuel flow
sender that is on the output of the gascolator, that I believe
costs at most 0.5 PSI to operate. No fuel pumps, just gravity
feed.

Anyway, I think I have heard Bob P say, and maybe others that
they have run one tank dry in the air, and no problem. So my
question is, how exactly did you do that and exactly how low was
the fuel in the new tank? As I said, mine was 15 g, and it still
didn't start. When you opened the good tank, did you first close
the empty tank, or was it still open? I am just wondering what

is

the better procedure. From my ground experience, it would seem
that it is better to leave the empty tank open until the engine
is running fine on the new tank.

I often fly with one tank, and switch tanks in flight, but have
never run one dry. When I do get low in one tank, as I did in my
previous flight (only 2 gal left) I switch to both before
landing, or when I am not over water. So I would like to
understand this better before I try running one tank completely
dry.

OK, that was one fuel issue. On the same day, when I took off,
after fuelling, I had another, that may or may not be related.
Here is what happened. I did my run-up, with both tanks now

open,

and proceeded to the runway, but had to hold about 5 minutes
while other planes landed, and another ahead of me waited his
turn also. It's not normally that busy here, but it was a rare
nice day, and of course everybody decided to go flying. Anyway,
right after take-off, I noticed my rpm fluctuate and drop to low
2400's and even into the 2300's for a couple of seconds. I

didn't

notice that it ran rough, just not full power. I climbed to

about

300 feet and then abandoned our noise abatement path and started
a left turn so I could catch the crosswind grass runway if I had
to. It continued to climb though, and then resumed its usual
climb rpm of 2550, and ran just fine after that. The rest of my
flying that day was uneventful, but needless to say, I wasn't
happy with what happened.

I have a couple of theories on this last issue. One is that I
still may have had some air in my lines after bringing the

second

tank online after fuelling. My run-ups are only at 1800 rpm
because of my amphib brakes. The other is that I may have got
some carb ice after sitting at idle so long waiting for my turn
to take off. OAT on the ground at that time was about 5 C (40F).
Or maybe my plugs fouled up a bit with lead with the long idle.

Any thoughts? I don't like mysteries of this kind.

Walter




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Drew, can you give me a couple more specifics about your fuel system. Do

And when you run a tank dry, exactly what order do you open and close the

Walter

----- Original Message -----
From: Drew Dalgleish <drewjan@cabletv.on.ca>
Date: Tuesday, December 14, 2004 7:26 am
Subject: RE: Rebel Fuel Management

At 08:41 PM 12/13/2004 -0800, you wrote:

Both caps have forward facing tube vents, and the tanks are
connected with a vent tube through the cabin. I do not lean when
idling, which is why I thought, too, that it might have been lead
fouling. I drained the tank dry through my gascolator, so if
there was any crap, it would have shown up then. I also did a
final fuel sampling from all my drains and gascolator after
fuelling, and again no water or crap.

I'm sure my first issue was because of air trapped in the lines
as Wayne described. And that was cleared up by opening the empty
tank valve. But that just raised my question of how some people
(Bob P or others?) have done it in flight without any problems.

So far now, I will continue my current practice of not ever
running one tank dry in flight. And again just as Wayne
described, when low on fuel, I may shut one down to get them
balanced, but use both when really low, or flying over hostile
terrain.

I will also remember Wayne's suggestion of using the primer to
relieve air, if I ever encounter that situation again.

Walter

Hi Walter I've run one tank dry in flight a few times on long cross
countries when I'm getting near maximun range for the fuel
carried. I feel
better having all my remaining fuel in one tank rather than split
between 2
just because I've also had the problem of unporting the intake
pipe with
low fuel when cranking and banking close to the ground. My vent is
at the
wing root on the pilots side and that tank seems to feed a little
fasterthan the other one. so it's easier to manage just one tank
at a time.
Drew





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