REFLECTOR:Low fuel light
Chuck Jensen
reflector@tvbf.org
Thu, 24 Jul 2003 09:07:49 -0400
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Good stuff on the vent system. I've been greasing (petro jelly) the O rings
on the fuel caps but didn't even think about the O ring on the locking
lever. During a long cruise, I'll get a 9 gallon indicated differential
between the tanks, so these efforts might reduce that differential. I
wasn't too concerned as I understand some differential is almost expected.
Though I've never gone there, what happens when left tank is 0 and the right
is 9 gallons? Will the rest of the fuel draw from the right tank or will I
have to pull off on the side of the road and hitch a ride for gas? I'd hate
to think I was carrying 9-10 gallons of useless ballast in my tanks but I'm
not (intentionally) going to find out. Anyone been there, done that?
Chuck
XL RG 540
-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On Behalf Of
Ronnie Brown
Sent: Thursday, July 24, 2003 7:46 AM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Low fuel light
I think the two primary reasons for the fuel tank imbalance are (1) airplane
flying out of trim, i.e. one wing low; (2) a fuel tank cap leak.
Enlarging the vent system to 3/8" instead of the original 1/4" will greatly
improve the impacts from (2) a leaking fuel cap. 3/8 tubing has double the
area of a 1/4" tube and will pass twice as much air. The reason this
matters is that we are only talking about 2 feet of fuel level from the
bottom of the sump to the top of the tanks. This is less than 1 psi. It
doesn't take much of a cap leak to pull a slight vacuum on that tank which
causes that tank to fill up. Keep those O rings vaselined and also make
sure the cap is pulling all the way down (adjust the lock nut on the back
side of the cap). There is also a small O ring on the shaft of the locking
lever that needs to be lubricated. If you want to check how tightly your
caps are sealing, connect a tube to the vent line, blow in it (keep the
pressure less than 1 psi!) and spray the caps with a water-dish detergent
mixture.
The original Velocity design had separate vents for each tank - which led to
lots of problems. It is impossible to create two vent outlets that have the
same static pressure at 200 mph!!! Hence the single vent system now used.
It is also important that the vent tubing slope upward to the manifold or
you can trap some fuel and create a tank vent pressure imbalance which will
lead to different fuel levels in the tank.
Ronnie
----- Original Message -----
From: KeithHallsten <mailto:KeithHallsten@quiknet.com>
To: reflector@tvbf.org <mailto:reflector@tvbf.org>
Sent: Wednesday, July 23, 2003 11:20 PM
Subject: Re: REFLECTOR:Low fuel light
Yes! Everything you say "SHOULD" be true. Unfortunately, we continue to
get these reports from the flying population regarding odd behavior of the
fuel/vent system!
I think that at times the vent system supplies air to the sump tank just a
TINY bit more easily than the longer path through the strakes supplies fuel
to the sump tank. It's probably a transient event, just persisting long
enough to actuate the "low fuel" warning and scare the bejesus out of the
pilot. I see little risk in shutting the vent line to the sump tank,
thereby assuring that the flow into the sump tank must come from the strake
tanks.
----- Original Message -----
From: Ronnie <mailto:romott@adelphia.net> Brown
To: reflector@tvbf.org <mailto:reflector@tvbf.org>
Sent: Wednesday, July 23, 2003 6:55 PM
Subject: Re: REFLECTOR:Low fuel light
If the vent lines slope upward to the manifold from the three tanks, there
shouldn't be any problems trapping air or fuel. The fuel should go down and
the vent air goes up. And the fuel in the sump tank vent should seek the
same level as in the fuel in the main tanks, thereby keeping the sump tank
full and the alarm off.
Ronnie
----- Original Message -----
From: KeithHallsten <mailto:KeithHallsten@quiknet.com>
To: reflector@tvbf.org <mailto:reflector@tvbf.org>
Sent: Wednesday, July 23, 2003 8:51 PM
Subject: Re: REFLECTOR:Low fuel light
Rene',
I'm not flying yet, so my comments can be discounted accordingly. I plan to
install a manual vent shut-off valve between the sump tank and the vent
manifold. The result will be that the vent system can allow the main strake
tanks to drain, but can't introduce air into the sump tank. I have a theory
that the vent line to the sump tank causes more problems than it solves,
once the initial "burp" of air is allowed to escape from the sump tank
(before engine start).
Keith Hallsten
----- Original Message -----
From: Rene <mailto:rdugas@bayou.com> Dugas
To: reflector@tvbf.org <mailto:reflector@tvbf.org>
Sent: Wednesday, July 23, 2003 4:00 PM
Subject: RE: REFLECTOR:Low fuel light
Thanks Jack,
I felt that maybe the boundary layer was causing a vacuum allowing air to
enter the sump but not the tanks. I don not want to over pressure my tanks
and rupture them at high pressures. I can splice a gage into the line but
wanted to glean info from the informed (flying) few. Since all three tanks
are connected to the manifold I remain perplexed. Thanks for the info on
the Vision. Two engine builders told me significant fluctuations with the
engine pump are common but no pressure numbers were available. I talked to
Lycoming. He air might be in the line but I don't see how. Thanks
Rene'
-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org] On Behalf
Of Jack Sheehan
Sent: Wednesday, July 23, 2003 4:35 PM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Low fuel light
Rene'
I can not say much about the low fuel light except that I have not had that
on my XL-RG and I am not extending the vent. Mine is as you described in the
plumbing except the vent line under the belly is cut off almost flush with
the fuselage. I have tested my sump warning light durin the test flight
period by getting pretty low on fuel and then pushing the nose over and
maintain a dive for enough time for the sump light to start to flicker The
low pressure warning from the VM1000 is a common indication. I have spoken
with Vision micro about it and the good news is the VM1000 is working fine
and the bad news is the lack of pressure is real. it is the way the lycoming
pump works and if you have an analog system with low sensitivity you never
see it. They have sent me a snubber to install in the sensor line which will
in theory reduce thesensitivity. ther is a similar snubber device in the
manifold pressure system. I will let you know when I get some free time to
install it.
Jack
N55XL
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<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff size=2>Good
stuff on the vent system. I've been greasing (petro jelly) the O rings on
the fuel caps but didn't even think about the O ring on the locking lever.
During a long cruise, I'll get a 9 gallon indicated differential between the
tanks, so these efforts might reduce that differential. I wasn't too
concerned as I understand some differential is almost
expected.</FONT></SPAN></DIV>
<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff size=2>Though
I've never gone there, what happens when left tank is 0 and the right is 9
gallons? Will the rest of the fuel draw from the right tank or will I have
to pull off on the side of the road and hitch a ride for gas? I'd hate to think
I was carrying 9-10 gallons of useless ballast in my tanks but I'm not
(intentionally) going to find out. Anyone been there, done
that?</FONT></SPAN></DIV>
<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff
size=2>Chuck</FONT></SPAN></DIV>
<DIV><SPAN class=042432512-24072003><FONT face=Arial color=#0000ff size=2>XL RG
540</FONT></SPAN></DIV>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B> reflector-admin@tvbf.org
[mailto:reflector-admin@tvbf.org]<B>On Behalf Of </B>Ronnie
Brown<BR><B>Sent:</B> Thursday, July 24, 2003 7:46 AM<BR><B>To:</B>
reflector@tvbf.org<BR><B>Subject:</B> Re: REFLECTOR:Low fuel
light<BR><BR></FONT></DIV>
<DIV><FONT size=2>I think the two primary reasons for the fuel tank imbalance
are (1) airplane flying out of trim, i.e. one wing low; (2) a fuel tank cap
leak.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Enlarging the vent system to 3/8" instead of the original
1/4" will greatly improve the impacts from (2) a leaking fuel
cap. 3/8 tubing has double the area of a 1/4" tube and will pass twice
as much air. The reason this matters is that we are only talking about 2
feet of fuel level from the bottom of the sump to the top of the tanks.
This is less than 1 psi. It doesn't take much of a cap leak to pull a
slight vacuum on that tank which causes that tank to fill up. Keep those
O rings vaselined and also make sure the cap is pulling all the way down
(adjust the lock nut on the back side of the cap). There is also a small
O ring on the shaft of the locking lever that needs to be lubricated. If
you want to check how tightly your caps are sealing, connect a tube to the
vent line, blow in it (keep the pressure less than 1 psi!) and spray the caps
with a water-dish detergent mixture.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>The original Velocity design had separate vents for each
tank - which led to lots of problems. It is impossible to create two
vent outlets that have the same static pressure at 200 mph!!! Hence the
single vent system now used. It is also important that the vent tubing
slope upward to the manifold or you can trap some fuel and create a tank vent
pressure imbalance which will lead to different fuel levels in the tank.
</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Ronnie </FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=KeithHallsten@quiknet.com
href="mailto:KeithHallsten@quiknet.com">KeithHallsten</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=reflector@tvbf.org
href="mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, 2003 11:20
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low fuel
light</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Yes! Everything you say "SHOULD" be
true. Unfortunately, we continue to get these reports from the flying
population regarding odd behavior of the fuel/vent system!
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I think that at times the vent system supplies
air to the sump tank just a TINY bit more easily than the longer path
through the strakes supplies fuel to the sump tank. It's probably a
transient event, just persisting long enough to actuate the "low fuel"
warning and scare the bejesus out of the pilot. I see little risk in
shutting the vent line to the sump tank, thereby assuring that the flow into
the sump tank must come from the strake tanks.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> </FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=romott@adelphia.net href="mailto:romott@adelphia.net">Ronnie
Brown</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=reflector@tvbf.org
href="mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, 2003 6:55
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low fuel
light</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2>If the vent lines slope upward to the manifold from the
three tanks, there shouldn't be any problems trapping air or fuel.
The fuel should go down and the vent air goes up. And the fuel in
the sump tank vent should seek the same level as in the fuel in the main
tanks, thereby keeping the sump tank full and the alarm
off.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Ronnie</FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=KeithHallsten@quiknet.com
href="mailto:KeithHallsten@quiknet.com">KeithHallsten</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=reflector@tvbf.org
href="mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, 2003 8:51
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low fuel
light</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>Rene',</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I'm not flying yet, so my comments can be
discounted accordingly. I plan to install a manual vent shut-off
valve between the sump tank and the vent manifold. The result will
be that the vent system can allow the main strake tanks to drain, but
can't introduce air into the sump tank. I have a theory that the
vent line to the sump tank causes more problems than it solves, once the
initial "burp" of air is allowed to escape from the sump tank (before
engine start).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Keith Hallsten</FONT></DIV>
<DIV><FONT face=Arial size=2> </FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=rdugas@bayou.com href="mailto:rdugas@bayou.com">Rene
Dugas</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=reflector@tvbf.org
href="mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, 2003
4:00 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: REFLECTOR:Low fuel
light</DIV>
<DIV><FONT face=Arial size=2></FONT><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Thanks
Jack,</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I felt that
maybe the boundary layer was causing a vacuum allowing air to enter
the sump but not the tanks. I don not want to over pressure my
tanks and rupture them at high pressures. I can splice a gage
into the line but wanted to glean info from the informed (flying) few.
Since all three tanks are connected to the manifold I remain
perplexed. Thanks for the info on the Vision. Two engine
builders told me significant fluctuations with the engine pump are
common but no pressure numbers were available. I talked to
Lycoming. He air might be in the line but I don't see how.
Thanks </SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Rene'</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face=Tahoma
size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">-----Original
Message-----<BR><B><SPAN style="FONT-WEIGHT: bold">From:</SPAN></B>
reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org] <B><SPAN
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Jack
Sheehan<BR><B><SPAN style="FONT-WEIGHT: bold">Sent:</SPAN></B>
Wednesday, July 23, 2003 4:35 PM<BR><B><SPAN
style="FONT-WEIGHT: bold">To:</SPAN></B>
reflector@tvbf.org<BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> Re: REFLECTOR:Low fuel
light</SPAN></FONT></P>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT face=Arial
size=2><SPAN style="FONT-SIZE: 12pt"></SPAN></FONT> </P>
<DIV>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT
face="Trebuchet MS" color=#663333 size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: 'Trebuchet MS'">Rene'</SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT
face="Trebuchet MS" color=#663333 size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: 'Trebuchet MS'">I
can not say much about the low fuel light except that I have not had
that on my XL-RG and I am not extending the vent. Mine is as you
described in the plumbing except the vent line under the belly is cut
off almost flush with the fuselage. I have tested my sump warning
light durin the test flight period by getting pretty low on fuel and
then pushing the nose over and maintain a dive for enough time for the
sump light to start to flicker The low pressure warning from the
VM1000 is a common indication. I have spoken with Vision micro about
it and the good news is the VM1000 is working fine and the bad news is
the lack of pressure is real. it is the way the lycoming pump works
and if you have an analog system with low sensitivity you never see
it. They have sent me a snubber to install in the sensor line which
will in theory reduce thesensitivity. ther is a similar snubber device
in the manifold pressure system. I will let you know when I get some
free time to install it.</SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT
face="Trebuchet MS" color=#663333 size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: 'Trebuchet MS'">Jack</SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal style="MARGIN-LEFT: 0.5in"><FONT
face="Trebuchet MS" color=#663333 size=3><SPAN
style="FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: 'Trebuchet MS'">N55XL</SPAN></FONT></P></DIV></DIV></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
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