REFLECTOR:RE:check valves
Alexander Balic
reflector@tvbf.org
Mon, 28 Jul 2003 09:27:22 -0500
Yea,
I'm thinking that only IF I have some problem, I can easily go back and
install them anyway- I'll use the KISS principal in this one.........
-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
Behalf Of Brett Ferrell
Sent: Monday, July 28, 2003 8:10 AM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:RE:check valves
I'll bite. Although it *should* be OK, all thinngs being equal, I think
it's a bad idea because all things are never equal. There are a lot of ways
the tanks might get out of balance, and with open lines they can rebalance
themselves and avoid a lot of trimming.
I think in the example of the tip tanks, they're meant to be able to be
completely drained, and you wouldn't want them refilling in a steep
(uncoordinated) turn. You shouldn't routinely have the strakes running dry,
and even if you get a little undesirable cross flow, the moment arm isn't as
big a concern as with a tip tank.
Brett
Quoting Alexander Balic <alex157@direcway.com>:
> I was thinking of this also- about using check valves
> in the lines from the
> mains to the sump to keep the fuel always moving in
> the correct direction-
> anyone else done this? any other comments on why is a
> good/bad idea?
>
> -----Original Message-----
> From: reflector-admin@tvbf.org
> [mailto:reflector-admin@tvbf.org]On Behalf Of
> Larry Richter
> Sent: Monday, July 28, 2003 12:33 AM
> To: reflector@tvbf.org
> Subject: Re: REFLECTOR:Low fuel light
>
>
> Folks:
> Okay, I lurk too. I have been building for a long
> time (forever?)
> but do have plans to finish it (before I die of old
> age).
>
> My flying plane is a 1948 Bonanza with Flight Extender
> tip tanks
> installed in 1961. I've been flying her since 1984.
> This system uses
> no transfer pumps . There is a vent line consisting
> of a little tube
> extending down into the slip stream cut off at an
> angle with the bevel
> forward and a small hole on back side of tube ( to
> allow some venting if
> the the front ices over- so I have been told). This
> tube opens into the
> top of the tank. (Main tanks have similar vents).
> About 1/3 of the tip
> fuel is actually below the level of the fuel line in
> level flight with
> the line going out to the tip tank inside the wing and
> then down into
> the bottom of the tank. This system has a check valve
> in each fuel line
> from the tip tanks preventing fuel from
> porting/venting in the wrong
> direction. I have done all kinds of experiments over
> the years to try
> to get the tip tanks to unport or malfunction. To
> explain all of these
> would make this email very long. Suffice it to say,
> it has been
> totally reliable. Proper (but very simple)
> maintainance is mandatory
> to keep it working as the tip gas caps cannot leak and
> the vents must
> be open and working. (My wife occasionally sees me
> kiss the tip
> tanks--blow into the vent, feel the tank pressurize,
> and blow back at
> you when you let go). Newer "improved" versions of
> this system
> (Beryl'D Shannon is the latest) used various transfer
> pumps to eliminate
> problems that do occur if the old system isn't
> maintained. These
> systems become maintainance nightmares as they age and
> fail and end up
> in junk yards. They can also give you little thrill
> if you are careless
> and end up with 90lbs of fuel in one wing tip only to
> find out (too
> late) that the transfer pump on that side has failed.
> The only $
> maintainance I have had to do was replace the O-rings
> in the check
> valves 10 years ago when I discovered that they
> weren't "checking" after
> most of the tip fuel ended up on the ground after
> parking overnight on a
> slope with one wing higher. And I had to replace the
> tip gas caps after
> a certified mechanic "cleaned up them thar oily old
> gas caps n dried um
> out real nice". Want to ask me again why I am
> building my own airplane?
>
> Sooo,
> My Velocity has vent lines as per (my) manual with
> main tanks and
> sump vented to a common manifold on the front of the
> firewall. I used
> 3/8 inch lines. When I saw discussions regarding fuel
> sucking out of
> leaking gas caps and draining the sump and opposite
> tank, I looked at my
> 50+ year old reliable lady and added the check valve
> to the lines from
> the main tanks to the sump. It seems to my simple
> mind that this should
> be equally reliable. The check valve would obviously
> cause a problem if
> you expect fuel/air to go "backward" from sump to main
> tank.
>
> larry richter
>
> John Dibble wrote:
>
> > Yes, I agree that the pressure will be equal, under
> static
> > conditions. The problem is keeping the pressure
> equal under dynamic
> > conditions like climb, descent, and leaking caps. If
> connected
> > directly to the manifold, the sump pressure will
> change faster than
> > the tanks because there is very little air space in
> the sump.
> >
> > John
> >
>
>
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