REFLECTOR: fuel feed - my solutions
Scott Baker
sbakr at comcast.net
Mon Feb 28 06:04:26 CST 2005
Keith,
Assuming the vent line is poking through he bottom of the fuselage, I think
the chances are excellent that a dirt-dobber (mud dobber) can block the line
and the pilot would see it during a preflight inspection.
SB
----- Original Message -----
From: "KeithHallsten" <KeithHallsten at quiknet.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, February 27, 2005 11:24 PM
Subject: Re: REFLECTOR: fuel feed - my solutions
> 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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