REFLECTOR: fuel feed - my solutions
Jim Sower
canarder at frontiernet.net
Mon Feb 28 13:23:29 CST 2005
The C-A list is replete with folks who have had vents stopped up and
missed it. I suggest that if some critter did stop up the vent, it
might or might not be visible standing on the tarmac, and might possibly
not be visible if you crawled down there and looked. I further suggest
that the inconvenience of meticulous (crawling under the airplane and
looking right in there) inspection greatly increase the probability that
such an inspection would be skipped on a regular basis.
But that's just my opinion - no science to support it - just life
experience ... Jim S.
Scott Baker wrote:
> 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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