REFLECTOR:Low fuel light
Ronnie Brown
reflector@tvbf.org
Thu, 24 Jul 2003 07:46:19 -0400
This is a multi-part message in MIME format.
------=_NextPart_000_002A_01C351B7.ABD601E0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Re: REFLECTOR:Low fuel lightI 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. =
=20
Ronnie=20
----- Original Message -----=20
From: KeithHallsten=20
To: reflector@tvbf.org=20
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! =20
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.
=20
----- Original Message -----=20
From: Ronnie Brown=20
To: reflector@tvbf.org=20
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 -----=20
From: KeithHallsten=20
To: reflector@tvbf.org=20
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
=20
----- Original Message -----=20
From: Rene Dugas=20
To: reflector@tvbf.org=20
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=20
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
------=_NextPart_000_002A_01C351B7.ABD601E0
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD><TITLE>Re: REFLECTOR:Low fuel light</TITLE>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
<META content=3D"MSHTML 5.50.4134.600" name=3DGENERATOR>
<STYLE>@font-face {
font-family: Tahoma;
}
@font-face {
font-family: Trebuchet MS;
}
@page Section1 {size: 8.5in 11.0in; margin: 1.0in 1.25in 1.0in 1.25in; }
P.MsoNormal {
FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman"
}
LI.MsoNormal {
FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman"
}
DIV.MsoNormal {
FONT-SIZE: 12pt; MARGIN: 0in 0in 0pt; FONT-FAMILY: "Times New Roman"
}
A:link {
COLOR: blue; TEXT-DECORATION: underline
}
SPAN.MsoHyperlink {
COLOR: blue; TEXT-DECORATION: underline
}
A:visited {
COLOR: purple; TEXT-DECORATION: underline
}
SPAN.MsoHyperlinkFollowed {
COLOR: purple; TEXT-DECORATION: underline
}
SPAN.EmailStyle17 {
COLOR: navy; FONT-FAMILY: Arial
}
DIV.Section1 {
page: Section1
}
</STYLE>
</HEAD>
<BODY lang=3DEN-US vLink=3Dpurple link=3Dblue bgColor=3D#ffffff>
<DIV><FONT size=3D2>I think the two primary reasons for the fuel tank =
imbalance=20
are (1) airplane flying out of trim, i.e. one wing low; (2) a fuel tank =
cap=20
leak.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Enlarging the vent system to 3/8" instead of the =
original 1/4"=20
will greatly improve the impacts from (2) a leaking fuel =
cap. =20
3/8 tubing has double the area of a 1/4" tube and will pass twice as =
much=20
air. The reason this matters is that we are only talking about 2 =
feet of=20
fuel level from the bottom of the sump to the top of the tanks. =
This is=20
less than 1 psi. It doesn't take much of a cap leak to pull a =
slight=20
vacuum on that tank which causes that tank to fill up. Keep those =
O rings=20
vaselined and also make sure the cap is pulling all the way down (adjust =
the=20
lock nut on the back side of the cap). There is also a small O =
ring on the=20
shaft of the locking lever that needs to be lubricated. If you =
want to=20
check how tightly your caps are sealing, connect a tube to the vent =
line, blow=20
in it (keep the pressure less than 1 psi!) and spray the caps with a =
water-dish=20
detergent mixture.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>The original Velocity design had separate vents for =
each tank=20
- which led to lots of problems. It is impossible to create two =
vent=20
outlets that have the same static pressure at 200 mph!!! Hence the =
single=20
vent system now used. It is also important that the vent tubing =
slope=20
upward to the manifold or you can trap some fuel and create a tank vent =
pressure=20
imbalance which will lead to different fuel levels in the tank. =20
</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Ronnie </FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DKeithHallsten@quiknet.com=20
href=3D"mailto:KeithHallsten@quiknet.com">KeithHallsten</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, 2003 =
11:20=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low fuel =
light</DIV>
<DIV><BR></DIV>
<DIV><FONT face=3DArial size=3D2>Yes! Everything you say =
"SHOULD" be=20
true. Unfortunately, we continue to get these reports from the =
flying=20
population regarding odd behavior of the fuel/vent system! =
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I think that at times the vent system =
supplies=20
air to the sump tank just a TINY bit more easily than the longer path =
through=20
the strakes supplies fuel to the sump tank. It's probably a =
transient=20
event, just persisting long enough to actuate the "low fuel" warning =
and scare=20
the bejesus out of the pilot. I see little risk in shutting the =
vent=20
line to the sump tank, thereby assuring that the flow into the sump =
tank must=20
come from the strake tanks.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2> </FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dromott@adelphia.net =
href=3D"mailto:romott@adelphia.net">Ronnie=20
Brown</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, =
2003 6:55=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low =
fuel=20
light</DIV>
<DIV><BR></DIV>
<DIV><FONT size=3D2>If the vent lines slope upward to the manifold =
from the=20
three tanks, there shouldn't be any problems trapping air or =
fuel. The=20
fuel should go down and the vent air goes up. And the fuel in =
the sump=20
tank vent should seek the same level as in the fuel in the main =
tanks,=20
thereby keeping the sump tank full and the alarm =
off.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Ronnie</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- =
</DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DKeithHallsten@quiknet.com=20
href=3D"mailto:KeithHallsten@quiknet.com">KeithHallsten</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, =
2003 8:51=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Low =
fuel=20
light</DIV>
<DIV><BR></DIV>
<DIV><FONT face=3DArial size=3D2>Rene',</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I'm not flying yet, so my =
comments can be=20
discounted accordingly. I plan to install a manual vent =
shut-off=20
valve between the sump tank and the vent manifold. The =
result will=20
be that the vent system can allow the main strake tanks to drain, =
but=20
can't introduce air into the sump tank. I have a theory that =
the=20
vent line to the sump tank causes more problems than it solves, =
once the=20
initial "burp" of air is allowed to escape from the sump tank =
(before=20
engine start).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Keith Hallsten</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> </FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- =
</DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Drdugas@bayou.com =
href=3D"mailto:rdugas@bayou.com">Rene Dugas</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Wednesday, July 23, =
2003 4:00=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: =
REFLECTOR:Low fuel=20
light</DIV>
<DIV><FONT face=3DArial size=3D2></FONT><BR></DIV>
<DIV class=3DSection1>
<P class=3DMsoNormal><FONT face=3DArial color=3Dnavy =
size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: =
Arial">Thanks=20
Jack,</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial color=3Dnavy =
size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I =
felt that=20
maybe the boundary layer was causing a vacuum allowing air to =
enter the=20
sump but not the tanks. I don not want to over pressure my =
tanks=20
and rupture them at high pressures. I can splice a gage =
into the=20
line but wanted to glean info from the informed (flying) few.=20
Since all three tanks are connected to the manifold I =
remain=20
perplexed. Thanks for the info on the Vision. Two =
engine=20
builders told me significant fluctuations with the engine pump =
are=20
common but no pressure numbers were available. I talked to =
Lycoming. He air might be in the line but I don’t =
see how. =20
Thanks </SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial color=3Dnavy =
size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: =
Arial">Rene’</SPAN></FONT></P>
<P class=3DMsoNormal><FONT face=3DArial color=3Dnavy =
size=3D2><SPAN=20
style=3D"FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: =
Arial"></SPAN></FONT> </P>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3DTahoma=20
size=3D2><SPAN style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Tahoma">-----Original=20
Message-----<BR><B><SPAN style=3D"FONT-WEIGHT: =
bold">From:</SPAN></B>=20
reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org] =
<B><SPAN=20
style=3D"FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Jack=20
Sheehan<BR><B><SPAN style=3D"FONT-WEIGHT: bold">Sent:</SPAN></B> =
Wednesday, July 23, 2003 4:35 PM<BR><B><SPAN=20
style=3D"FONT-WEIGHT: bold">To:</SPAN></B> =
reflector@tvbf.org<BR><B><SPAN=20
style=3D"FONT-WEIGHT: bold">Subject:</SPAN></B> Re: =
REFLECTOR:Low fuel=20
light</SPAN></FONT></P>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3DArial=20
size=3D2><SPAN style=3D"FONT-SIZE: =
12pt"></SPAN></FONT> </P>
<DIV>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3D"Trebuchet MS"=20
color=3D#663333 size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: =
'Trebuchet MS'">Rene'</SPAN></FONT></P></DIV>
<DIV>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3D"Trebuchet MS"=20
color=3D#663333 size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: =
'Trebuchet MS'">I=20
can not say much about the low fuel light except that I have not =
had=20
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=20
off almost flush with the fuselage. I have tested my sump =
warning light=20
durin the test flight period by getting pretty low on fuel and =
then=20
pushing the nose over and maintain a dive for enough time for =
the sump=20
light to start to flicker The low pressure warning from the =
VM1000 is a=20
common indication. I have spoken with Vision micro about it and =
the good=20
news is the VM1000 is working fine and the bad news is the lack =
of=20
pressure is real. it is the way the lycoming pump works and if =
you have=20
an analog system with low sensitivity you never see it. They =
have sent=20
me a snubber to install in the sensor line which will in theory =
reduce=20
thesensitivity. ther is a similar snubber device in the manifold =
pressure system. I will let you know when I get some free time =
to=20
install it.</SPAN></FONT></P></DIV>
<DIV>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3D"Trebuchet MS"=20
color=3D#663333 size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: =
'Trebuchet MS'">Jack</SPAN></FONT></P></DIV>
<DIV>
<P class=3DMsoNormal style=3D"MARGIN-LEFT: 0.5in"><FONT =
face=3D"Trebuchet MS"=20
color=3D#663333 size=3D3><SPAN=20
style=3D"FONT-SIZE: 12pt; COLOR: #663333; FONT-FAMILY: =
'Trebuchet =
MS'">N55XL</SPAN></FONT></P></DIV></DIV></BLOCKQUOTE></BLOCKQUOTE></BLOCK=
QUOTE></BLOCKQUOTE></BODY></HTML>
------=_NextPart_000_002A_01C351B7.ABD601E0--