REFLECTOR: fuel feed - my solutions
KeithHallsten
KeithHallsten at quiknet.com
Sun Feb 27 22:24:03 CST 2005
Jim,
What are the odds that we could identify a vent plugged by wasps during
preflight inspection? I have always assumed that visual inspection would
reveal their activity.
Keith
----- Original Message -----
From: "Jim Sower" <canarder at frontiernet.net>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, February 27, 2005 7:36 PM
Subject: Re: REFLECTOR: fuel feed - my solutions
> <...I suspect that an icing encounter sufficient to completely block ...>
>
> I don't worry about ice. I don't go there. I do worry about "dirt
> daubers" and other critters.
>
> And I've heard DOZENS of anecdotal blockages from such critters ... Jim S.
>
> KeithHallsten wrote:
>
> >With 3/8" vent lines, plugging is not really a high-probability failure
> >mode. It may well be that the check valve is "pink elephant repellent".
> >(Since I put that check valve in, I haven't seen a single pink elephant!)
> >Is there any verifiable history of plugging of a 3/8" vent line? Anyone
> >have even anecdotal evidence that an alternate vent is really necessary?
I suspect that an icing encounter sufficient to completely block the fuel
system vent would also be sufficient to so alter the canard airfoil that
flight would not continue anyway.
> >Keith Hallsten
> >
> >
> >----- Original Message -----
> >From: "Brett Ferrell" <bferrell at 123mail.net>
> >To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> >Sent: Sunday, February 27, 2005 2:25 PM
> >Subject: Re: REFLECTOR: fuel feed - my solutions
> >
> >
> >
> >
> >>As soon as the pump pulls some fuel out of the sump with a blocked vent
> >>line, the check valve will open and vent some air into the tanks. 1
> >>atmosphere versus vacuum will open nearly any check valve. I've done
some
> >>process safety work and seen industrial tanks collapsed from
> >>
> >>
> >under-pressure,
> >
> >
> >>and I think it would be foolish not to install the factory-recommended
> >>
> >>
> >check
> >
> >
> >>valve and allow your tanks to routinely run under vacuum.
> >>
> >>Brett
> >>
> >>----- Original Message -----
> >>From: "Jim Sower" <canarder at frontiernet.net>
> >>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> >>Sent: Sunday, February 27, 2005 3:53 PM
> >>Subject: Re: REFLECTOR: fuel feed - my solutions
> >>
> >>
> >>My figures indicate that .5 psi is the equivalent of about 165 kias. Bad
> >>news: they aren't going to vent a damned thing if the vent ices over.
> >>Good news: the fuel pump will generate plenty enough suction to overcome
> >>that (of course that underpressure would add to your chances of vapor
> >>forming in the vent line and/or cavitation at the pump face).
> >>Check valves are not the panacea some folks would have you believe ...
> >>Jim S.
> >>
> >>Wayne wrote:
> >>
> >>
> >>
> >>>I'm using two of the .5 jobs for an alternate air source in the top of
> >>>
> >>>
> >the
> >
> >
> >>>loop before the vent line goes to the bottom of the fuselage. If the
> >>>
> >>>
> >fuel
> >
> >
> >>>vent iced over I hope they will provide cabin air to the fuel tanks. If
> >>>the bird is upside down they shouldn't allow fuel to leak inside the
> >>>cabin.
> >>>Wayne
> >>>
> >>> ----- Original Message -----
> >>> *From:* Brian Michalk <mailto:michalk at awpi.com>
> >>> *To:* Velocity Aircraft Owners and Builders list
> >>> <mailto:reflector at tvbf.org>
> >>> *Sent:* Saturday, February 26, 2005 10:01 AM
> >>> *Subject:* RE: REFLECTOR: fuel feed - my solutions
> >>>
> >>> McMaster has a lot of check valves.
> >>> This one says less than .5 PSI cracking pressure.
> >>> The image
> >>> “http://www.mcmaster.com/catalog/111/gfx/large/47245kp1l.gif”
> >>> cannot be displayed, because it contains errors.
> >>> http://www.mcmaster.com/catalog/111/gfx/large/47245kp1l.gif
> >>> This one says 0 PSI cracking pressure.
> >>> The image
> >>> “http://www.mcmaster.com/catalog/111/gfx/large/7909kp1l.gif”
> >>> cannot be displayed, because it contains errors.
> >>> http://www.mcmaster.com/catalog/111/gfx/large/7909kp1l.gif
> >>> These came from this page:
> >>>
> >>> http://www.mcmaster.com/nav/enter.asp?pagenum=389
> >>>
> >>>
> >>>
> >>> Brian Michalk <http://www.michalk.com>
> >>> Life is what you make of it ... never wish you had done something.
> >>> Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
> >>> musician, home-brewer, entrepreneur and barely single
> >>>
> >>>
> >>> > -----Original Message-----
> >>> > From: reflector-bounces at tvbf.org
> >>> [mailto:reflector-bounces at tvbf.org]On
> >>> > Behalf Of Chuck Jensen
> >>> > Sent: Saturday, February 26, 2005 4:27 AM
> >>> > To: Velocity Aircraft Owners and Builders list
> >>> > Subject: RE: REFLECTOR: fuel feed - my solutions
> >>> >
> >>> >
> >>> > Jerry,
> >>> > All check valves has some pressure differential which we can ill
> >>> > afford to loose when the fuel head is measured in inches.
> >>> > Probably the strongest reason for leaving them off is if you do
> >>> > have a little non-uniform fuel flow during your flight, at least
> >>> > when you land, the tanks will self level for your next
> >>> > flight--assuming your on the level when you parked.
> >>> >
> >>> > Chuck
> >>> >
> >>> > -----Original Message-----
> >>> > From: reflector-bounces at tvbf.org
> >>> [mailto:reflector-bounces at tvbf.org]On
> >>> > Behalf Of Jerry.Brainard at anthem.com
> >>> > Sent: Friday, February 25, 2005 5:22 PM
> >>> > To: Velocity Aircraft Owners and Builders list
> >>> > Subject: Re: REFLECTOR: fuel feed - my solutions
> >>> >
> >>> >
> >>> >
> >>> > Just because I don't know - is there a reason not to put a check
> >>> valve in
> >>> > line on the strake feed lines? My thought is that this would
> >>>
> >>>
> >prevent
> >
> >
> >>> > retrograde flow into a tank that is on the low side (out of rig)
> >>> or has a
> >>> > leaking cap. I can think of many scenarios where one might be
> >>> confused as
> >>> > to what is happening, but it would seem to resolve any issue
> >>> with pulling
> >>> > fuel into a tank from the feed line. Of course there is also
added
> >>> > complexity and another failure mode to consider.
> >>> >
> >>> > -jerry
> >>> >
> >>> > 513-484-1328
> >>> > 513-336-5949
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> > Don19dw at aol.com
> >>> >
> >>> > Sent by: To:
> >>> > reflector at awpi.com
> >>> >
> >>> > reflector-bounces cc:
> >>> >
> >>> > @tvbf.org Subject:
> >>> > REFLECTOR: fuel feed - my solutions
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> > 02/25/2005 04:38
> >>> >
> >>> > PM
> >>> >
> >>> > Please respond to
> >>> >
> >>> > Velocity Aircraft
> >>> >
> >>> > Owners and
> >>> >
> >>> > Builders list
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> >
> >>> > As a result of my accident in June 1999, caused by a leaking
> >>> fuel cap, I
> >>> > made the following changes.
> >>> > 1) Added the sump tank "low fuel" warning system per Velocity
> >>> > plans, except
> >>> > located float slightly lower. The "low fuel" warning would have
> >>> allowed we
> >>> > to reach an airport prior to fuel exhaustion from right tank and
> >>> sump
> >>> > tank.and thus prevented the accident.
> >>> > However then during later flights, especially in turns would get
> >>> flashing
> >>> > "low fuel" warnings which made me very nervous. To trouble shoot
> >>>
> >>>
> >the
> >
> >
> >>> > problem I removed the rear seats and spar cover so I could
> >>> visually see
> >>> > sump tank in flight. Using "T" fittings I added a vertical clear
> >>> > sight tube
> >>> > between top sump vent port and bottom outlet port plus a light
> >>> shinning on
> >>> > the tube to see fuel level from my pilots seat. As Scott Swing
> >>> suggested,
> >>> > the sloshing of the fuel in the sump tank was causing the
> >>> flashing "low
> >>> > fuel" warning with little or no lowering of fuel level.
> >>> > 2) In order to solve flashing "low fuel" warning, I added a time
> >>> delay
> >>> > relay set at 6 seconds, before warning light went on, and have
> >>> > not had that
> >>> > problem since.
> >>> > 3) Installed a manual shut off valve in fuel line from each
> >>> strake into
> >>> > sump tank. These left and right shut off valves are actuated by
> >>> cables and
> >>> > small levers on each side of keel at pilots hip. These valves
> >>> > could be used
> >>> > in flight to isolate either strake tank from the sump if the
> >>> fuel level in
> >>> > one side or the other is seen to be dangerously low. If the sump
> >>> vent is
> >>> > closed, the fuel pump should "suck" fuel from the open fuel
> >>> > strake. However
> >>> > the argument for a closed sump vent is valid "to suck fuel" only
> >>> if empty
> >>> > tank is shut off, otherwise air is "sucked" from the empty tank,
> >>> rather
> >>> > than fuel sucked from the other tank. That apparently is what
> >>> happened
> >>> > prior to my accident. So far have never used my added valves in
> >>> flight.
> >>> > (However these valves are handy during servicing and I recommend
> >>> adding
> >>> > them for that reason alone)
> >>> > 4) Added an instrument panel note: " Warning: at least every 30
> >>> minutes,
> >>> > check fuel level in each strake tank. If an unusual balance is
> >>> > seen, ASSUME
> >>> > fullest tank is unusable"
> >>> > 5) After rebuilding the airplane, discovered the turn and bank
> >>> > indicator in
> >>> > the instrument panel, was not installed vertical, about 1/2
> >>> bubble off
> >>> > vertical. Once that was corrected, had to shim left rudder out
> >>> 1/4 inch at
> >>> > trailing edge. Plane now flies perfectly level and straight and
> >>> have not
> >>> > had any unusual fuel level problems since.
> >>> > 6) Finally check fuel caps are tightly closed and properly
> >>> lubricated.
> >>> >
> >>> > This may have been suggested to Jim already. During flight, have
> >>> you held
> >>> > slight pressure on one rudder or the other, to see if fuel tank
> >>> levels
> >>> > equalize? If that occurs, then I strongly suspect plane is not
> >>> flying
> >>> > perfectly level and straight.
> >>> > Don White N19DW XL/RG
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> >
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