REFLECTOR: fuel feed - my solutions
Jim Sower
canarder at frontiernet.net
Sun Feb 27 23:18:33 CST 2005
I don't really know. Early stages, perhaps very low. Later, the mud
might stick out the end of the vent line and be visible. Either way,
it's a near certainly that you'll [forget / decide not] to look (it does
after all involve crawling around in the dirt and grease).
And if you miss it, and your sump is vented, you're toast ... Jim S.
KeithHallsten wrote:
>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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