REFLECTOR: Fuel Vent (used to be Odd Fuel Stain)

Brooke Wolf bwolf1 at tds.net
Mon Nov 21 14:40:07 CST 2011


I think they are talking about something like the attached photo.  The vent line goes up the firewall, then comes forward along the roof line inside the overhead plenum for about 4 feet.  Then it loops back to the firewall, then down and out the airplane.



Brooke 








> From: "Alex Balic" <velocity_pilot at verizon.net>
> Date: November 21, 2011 3:07:50 PM EST
> To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
> Subject: Re: REFLECTOR: Odd fuel stain?
> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> 
> 
> No- extend the loop on the vent system (which should currently go up the
> firewall to the top of the roof, then back down through the belly )foreword
> along the roof of the aircraft so when the aircraft is pitched up at say 45
> degrees, the foreword most part of the loop will be at a higher elevation
> than the front of the strakes where the fuel is located
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Robert Wood
> Sent: Monday, November 21, 2011 1:36 PM
> To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Odd fuel stain?
> 
> I think when saying extend the vent forward they are saying during the
> building process inside the tank. Am I wrong?
> 
> Bob Wood
> 
> On Nov 21, 2011, at 1:32 PM, "Bob Jackson \(Jax Tech\)"
> <bobj at jaxtechllc.com> wrote:
> 
>> John,
>> 
>> Can you translate your 500 fpm climb limit to a number of degrees nose up?
> 
>> 
>> Our normal full fuel, 160 KIAS climb to altitude (turbo IO-550N) is with
>> 1000 fpm and 7 degrees nose up.  We occasionally get a 'whiff' of fuel in
>> the cockpit after takeoff or touch-n-goes, but I normally do those with a
>> ~18 degrees nose up attitude (100 KIAS).  I assumed these were caused by
>> occasional fuel sloshing, not by a steady state venting problem!
>> 
>> Are you saying we need to either start climbing out at higher than 160
> KIAS,
>> or a lower power setting, or extend our vent line a couple of feet along
> the
>> top of the fuselage?
>> 
>> When this topic came up a while back, and I did rough calculations back
> then
>> I figured that in climbouts the fuel was going to be very close to the top
>> of our vent loop (which is as close to the top of the fuselage as we could
>> make it), but not over.  
>> 
>> I don't have the exact measurements here -- but the way I roughly figure
> it
>> is:  the top of the vent loop extends ~18" above the spar beam, and the
>> tanks are full and there is fuel at the front of the strake (and the
> strake
>> front is about 48" forward of the vent line), and that it would take a
> climb
>> angle greater than ~ 20 degrees (arctan[18/48])before you started venting.
>> I'll have to take some more accurate measurements.
>> 
>> Bob Jackson
>> Turbo IO-550N XL/RG
>> 
>> 
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> Behalf Of John Abraham
>> Sent: Monday, November 21, 2011 8:57 AM
>> To: 'Velocity Aircraft Owners and Builders list'
>> Subject: Re: REFLECTOR: Odd fuel stain?
>> 
>> General rule of thumb I use is no more than 500fpm climb when above 75%
>> tanks.  This helps prevent dumping fuel out your vent which you cannot
>> calculate very easily.  The only solution to this would be to run your
> vent
>> 1-2 feet forward so that your strake angle does not exceed the top of the
>> vent.  
>> 
>> IO-540 (260HP) RG should be climbing between 120-130kias, 300HP Lycoming's
>> and Continentals should be 130-145KIAS.  *Note that the IO-550 RG's at 135
>> will be above 500FPM so you may have to climb at a faster speed than 140.
>> Turbo charged aircraft with RG systems are between 145-165KIAS in a climb.
> 
>> 
>> FG aircraft, speeds in climb will vary about 10kts less.
>> 
>> Also, make sure your vent is scarfed into the wind so that you continually
>> pressurize your tanks and don't create a vacuum.  Vent lines in the back
>> should be treated the same as your main feed lines.  You want a continual
>> downhill slope into the tanks so that you don't have any low point in the
>> vent lines otherwise you may get some fuel stuck in the vent that cant
>> pressurize itself out very easily which will lead to uneven feeding.
>> 
>> John
>> 
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> Behalf Of Scott Baker
>> Sent: Monday, November 21, 2011 7:47 AM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Odd fuel stain?
>> 
>> Maybe not the negative-G, but very likely the steep pitch up maneuver.  I
>> have many times seen (from the ground) a vapor trail of fuel exiting the
>> vent tube from Velocity aircraft doing high performance takeoffs at
>> Sebastian.
>> Scott B.
>> 
>> ----- Original Message -----
>> From: "Scott Derrick" <scott at tnstaafl.net>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Sunday, November 20, 2011 7:18 PM
>> Subject: REFLECTOR: Odd fuel stain?
>> 
>> 
>>> So after design/install of a new forward cabin heater system I took the 
>>> bird for a test flight.  I as also testing a new oil temperature sensor 
>>> which is working fabulously!
>>> 
>>> Played around to the north of GNT getting the plane setup for LOP at 9500
> 
>>> and playing with different settings of the heater controls, there is a 
>>> separate control for pilot and co-pilot positions, plus the oil flap 
>>> provides full or reduced air flow.
>>> 
>>> The problem occurred when I did a walk around in front of the hanger
> after
>> 
>>> the flight and saw a bit of a fuel(blue) stain on the rear cowl! Thats 
>>> really odd I thought!  It started about a foot to the rear of the fuel 
>>> vent and was kinda wispy looking, about a foot+ long.
>>> 
>>> I was pretty upset as I don't like fuel leaks, who does, and we are 
>>> planning on flying to Tahoe Tuesday morning. I was contemplating where it
> 
>>> could have come from, There is no way it cam from the engine compartment,
> 
>>> it would have pooled at the low point in the bottom cowl and come out the
> 
>>> drain holes, and this was nowhere near that. Plus the fact, is was 
>>> directly in line with the fuel vent, but why would it spit fuel in
> flight!
>>> 
>>> Then I had an idea.
>>> 
>>> When I came back to the pattern the airport crowd requested a low pass, 
>>> you know an altimeter/compass check, so I sucked the gear back up and did
> 
>>> a 185 knot 100 ft pass down the runway.  Turning about 2600 RPM, at mid 
>>> field I pulled up into a  steeper than usual climb, about 4,000+ ft per 
>>> minute, the speed rapidly unwinding, the altimeter doing the reverse. At 
>>> the top, about 1,000 agl and now at 120 knots I pushed over a little more
> 
>>> aggressive than I usually do, going just a bit negative G for 5 seconds
> or
>> 
>>> so, leveled off and made a sedate pattern to landing.
>>> 
>>> My fuel tanks are almost full, about 26 gallons in 30 gallons tanks.
>>> 
>>> Now I wonder did the negative G maneuver cause the fuel to spit out the 
>>> vent?  Anybody else experience a similar thing?
>>> 
>>> Scott
>>> 
>>> -- 
>>> We are all here for a spell; get all the good laughs you can.
>>> Will Rogers
>>> _______________________________________________
>>> To change your email address, visit 
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>> 
>>> Visit the gallery!  www.tvbf.org/gallery
>>> user:pw = tvbf:jamaicangoose
>>> Check new archives: www.tvbf.org/pipermail
>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html 
>> 
>> 
>> _______________________________________________
>> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
>> 
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
> 
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> 
> 
> 
> 
> 
> From: Robert Wood <slvegl99 at aol.com>
> Date: November 21, 2011 3:12:05 PM EST
> To: reflector at tvbf.org
> Subject: Re: REFLECTOR: Odd fuel stain?
> Reply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> 
> 
> Ohh, OK. Mine is fine then.
> Bob Wood
> 
> 
> -----Original Message-----
> From: Alex Balic <velocity_pilot at verizon.net>
> To: 'Velocity Aircraft Owners and Builders list' <reflector at tvbf.org>
> Sent: Mon, Nov 21, 2011 3:08 pm
> Subject: Re: REFLECTOR: Odd fuel stain?
> 
> No- extend the loop on the vent system (which should currently go up the
> firewall to the top of the roof, then back down through the belly )foreword
> along the roof of the aircraft so when the aircraft is pitched up at say 45
> degrees, the foreword most part of the loop will be at a higher elevation
> than the front of the strakes where the fuel is located
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Robert Wood
> Sent: Monday, November 21, 2011 1:36 PM
> To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Odd fuel stain?
> 
> I think when saying extend the vent forward they are saying during the
> building process inside the tank. Am I wrong?
> 
> Bob Wood
> 
> On Nov 21, 2011, at 1:32 PM, "Bob Jackson \(Jax Tech\)"
> <bobj at jaxtechllc.com> wrote:
> 
> > John,
> > 
> > Can you translate your 500 fpm climb limit to a number of degrees nose up?
> 
> > 
> > Our normal full fuel, 160 KIAS climb to altitude (turbo IO-550N) is with
> > 1000 fpm and 7 degrees nose up.  We occasionally get a 'whiff' of fuel in
> > the cockpit after takeoff or touch-n-goes, but I normally do those with a
> > ~18 degrees nose up attitude (100 KIAS).  I assumed these were caused by
> > occasional fuel sloshing, not by a steady state venting problem!
> > 
> > Are you saying we need to either start climbing out at higher than 160
> KIAS,
> > or a lower power setting, or extend our vent line a couple of feet along
> the
> > top of the fuselage?
> > 
> > When this topic came up a while back, and I did rough calculations back
> then
> > I figured that in climbouts the fuel was going to be very close to the top
> > of our vent loop (which is as close to the top of the fuselage as we could
> > make it), but not over.  
> > 
> > I don't have the exact measurements here -- but the way I roughly figure
> it
> > is:  the top of the vent loop extends ~18" above the spar beam, and the
> > tanks are full and there is fuel at the front of the strake (and the
> strake
> > front is about 48" forward of the vent line), and that it would take a
> climb
> > angle greater than ~ 20 degrees (arctan[18/48])before you started venting.
> > I'll have to take some more accurate measurements.
> > 
> > Bob Jackson
> > Turbo IO-550N XL/RG
> > 
> > 
> > -----Original Message-----
> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> > Behalf Of John Abraham
> > Sent: Monday, November 21, 2011 8:57 AM
> > To: 'Velocity Aircraft Owners and Builders list'
> > Subject: Re: REFLECTOR: Odd fuel stain?
> > 
> > General rule of thumb I use is no more than 500fpm climb when above 75%
> > tanks.  This helps prevent dumping fuel out your vent which you cannot
> > calculate very easily.  The only solution to this would be to run your
> vent
> > 1-2 feet forward so that your strake angle does not exceed the top of the
> > vent.  
> > 
> > IO-540 (260HP) RG should be climbing between 120-130kias, 300HP Lycoming's
> > and Continentals should be 130-145KIAS.  *Note that the IO-550 RG's at 135
> > will be above 500FPM so you may have to climb at a faster speed than 140.
> > Turbo charged aircraft with RG systems are between 145-165KIAS in a climb.
> 
> > 
> > FG aircraft, speeds in climb will vary about 10kts less.
> > 
> > Also, make sure your vent is scarfed into the wind so that you continually
> > pressurize your tanks and don't create a vacuum.  Vent lines in the back
> > should be treated the same as your main feed lines.  You want a continual
> > downhill slope into the tanks so that you don't have any low point in the
> > vent lines otherwise you may get some fuel stuck in the vent that cant
> > pressurize itself out very easily which will lead to uneven feeding.
> > 
> > John
> > 
> > -----Original Message-----
> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> > Behalf Of Scott Baker
> > Sent: Monday, November 21, 2011 7:47 AM
> > To: Velocity Aircraft Owners and Builders list
> > Subject: Re: REFLECTOR: Odd fuel stain?
> > 
> > Maybe not the negative-G, but very likely the steep pitch up maneuver.  I
> > have many times seen (from the ground) a vapor trail of fuel exiting the
> > vent tube from Velocity aircraft doing high performance takeoffs at
> > Sebastian.
> > Scott B.
> > 
> > ----- Original Message -----
> > From: "Scott Derrick" <scott at tnstaafl.net>
> > To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> > Sent: Sunday, November 20, 2011 7:18 PM
> > Subject: REFLECTOR: Odd fuel stain?
> > 
> > 
> >> So after design/install of a new forward cabin heater system I took the 
> >> bird for a test flight.  I as also testing a new oil temperature sensor 
> >> which is working fabulously!
> >> 
> >> Played around to the north of GNT getting the plane setup for LOP at 9500
> 
> >> and playing with different settings of the heater controls, there is a 
> >> separate control for pilot and co-pilot positions, plus the oil flap 
> >> provides full or reduced air flow.
> >> 
> >> The problem occurred when I did a walk around in front of the hanger
> after
> > 
> >> the flight and saw a bit of a fuel(blue) stain on the rear cowl! Thats 
> >> really odd I thought!  It started about a foot to the rear of the fuel 
> >> vent and was kinda wispy looking, about a foot+ long.
> >> 
> >> I was pretty upset as I don't like fuel leaks, who does, and we are 
> >> planning on flying to Tahoe Tuesday morning. I was contemplating where it
> 
> >> could have come from, There is no way it cam from the engine compartment,
> 
> >> it would have pooled at the low point in the bottom cowl and come out the
> 
> >> drain holes, and this was nowhere near that. Plus the fact, is was 
> >> directly in line with the fuel vent, but why would it spit fuel in
> flight!
> >> 
> >> Then I had an idea.
> >> 
> >> When I came back to the pattern the airport crowd requested a low pass, 
> >> you know an altimeter/compass check, so I sucked the gear back up and did
> 
> >> a 185 knot 100 ft pass down the runway.  Turning about 2600 RPM, at mid 
> >> field I pulled up into a  steeper than usual climb, about 4,000+ ft per 
> >> minute, the speed rapidly unwinding, the altimeter doing the reverse. At 
> >> the top, about 1,000 agl and now at 120 knots I pushed over a little more
> 
> >> aggressive than I usually do, going just a bit negative G for 5 seconds
> or
> > 
> >> so, leveled off and made a sedate pattern to landing.
> >> 
> >> My fuel tanks are almost full, about 26 gallons in 30 gallons tanks.
> >> 
> >> Now I wonder did the negative G maneuver cause the fuel to spit out the 
> >> vent?  Anybody else experience a similar thing?
> >> 
> >> Scott
> >> 
> >> -- 
> >> We are all here for a spell; get all the good laughs you can.
> >> Will Rogers
> >> _______________________________________________
> >> To change your email address, visit 
> >> http://www.tvbf.org/mailman/listinfo/reflector
> >> 
> >> Visit the gallery!  www.tvbf.org/gallery
> >> user:pw = tvbf:jamaicangoose
> >> Check new archives: www.tvbf.org/pipermail
> >> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html 
> > 
> > 
> > _______________________________________________
> > To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
> > 
> > Visit the gallery!  www.tvbf.org/gallery
> > user:pw = tvbf:jamaicangoose
> > Check new archives: www.tvbf.org/pipermail
> > Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> _______________________________________________
> To change your email address, visit
> http://www.tvbf.org/mailman/listinfo/reflector
> 
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> 
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
> 
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
> 
> 
> _______________________________________________
> Visit the gallery!  tvbf:jamaicangoose

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