REFLECTOR: Uneven Fuel Flow

[Brooke Wolf]

AH HA!  So what you are saying Alex, is that a fuel cap leak could be large enough to overwhelm the plumbed fuel vent.  ie, more air could escape through the cap than could be replaced by the vent resulting in a vacuum which would inhibit in fuel transfer from the main tank to the sump.

For the record, the bottom of my vent is cut off parallel with the bottom of the fuselage.  I also have a one way check valve inside the cabin as an alternate vent.  So far, in my 45 hours of flying, I have had no fuel feed issues.  Both sides feed evenly.

Brooke 


> 
> From: "Alex Balic" <velocity_pilot at verizon.net>
> Date: September 29, 2011 3:14:09 PM EDTReply-To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
> Subject: Re: REFLECTOR: Uneven Fuel Flow
> 
> 
> Yes, there is a LOT of suction at the fuel cap area- it is the highest point
> in the chord- even though the vent is allowing air back in, there is enough
> of a pressure imbalance that with the slight head pressure of the tanks, the
> fuel would not feed evenly. Try blowing through 6 feet of 3/8 line by mouth,
> and you will see that there is quite a bit of resistance to flow- and that
> is without any fittings on there.  The vents are designed to allow pressure
> to equalize in the tanks based on fuel being removed by the engine running,
> not air being sucked out via the fuel cap.
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of John Abraham
> Sent: Thursday, September 29, 2011 9:37 AM
> To: 'Velocity Aircraft Owners and Builders list'
> Subject: Re: REFLECTOR: Uneven Fuel Flow
> 
> Above the fuel cap is a low pressure.  This creates a vacuum on the tank if
> the cap is loose.  If it is loose enough you will see fuel coming out of the
> tank.  Have you ever flown a piper when a fuel cap came off on take-off?  An
> entire tank will be sucked out in a matter of a minute or so.  Your fuel
> vent line is pressurizing the tank with ram air.  If you were to cut your
> vent flat or scarf it backwards then you can also create a vacuum on the
> tank that will not let the tanks feed very well.
> 
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Jones Nick
> Sent: Thursday, September 29, 2011 10:16 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Uneven Fuel Flow
> 
> I'm with you on this one. I hope someone can explain this.
> 
> Nick Jones
> XL-RG
> N10CN
> 
> 
> ________________________________
> From: reflector-bounces at tvbf.org [reflector-bounces at tvbf.org] On Behalf Of
> Brooke Wolf [bwolf1 at tds.net]
> Sent: Thursday, September 29, 2011 09:41
> To: reflector at tvbf.org
> Subject: REFLECTOR: Uneven Fuel Flow
> 
> 
> 
> Ok, at the risk of showing my ignorance, I need to chime in here.
> 
> How could a minute leak in a fuel cap affect fuel flow out of a tank when
> that same tank has about a 3/8 inch hole in it vented to the outside (aka
> fuel vents)?
> 
> Brooke
> 
> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20110929/c457dffe/attachment.htm>