REFLECTOR: fuel flow sensor

[nmflyer1 at aol.com]

Doesn't need to be that way in my setup. The fuel leaving the sump equals the fuel being burned.

Kurt 


-----Original Message-----
From: Scott Derrick <scott at tnstaafl.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Tue, 7 Apr 2009 6:12 am
Subject: REFLECTOR: fuel flow sensor



The fuel flow sensor needs to be between the fuel controller spider. 
hats the normal place to put it as all certified planes return fuel to
 sump tank.
Scott
nmflyer1 at aol.com wrote:
 Brian,

 My exit line from the sump goes thru my flowmeter, then through a Low
 hole in the forward gear bulkhead. Then through the filters to the
 pumps that sit on top of my Lower NACA scoop.

 When I was pondering a return line to the sump, I thought about
 running it through a down=tube in the corner of the sump, away from
 teh pickup line. Seemed to make sense to me, until Airflow told me not
 to bother as I would not have a problem with their design (previous
 post to Al).




 -----Original Message-----
 From: Brian Michalk <michalk at awpi.com>
 To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
 Sent: Mon, 6 Apr 2009 8:43 pm
 Subject: Re: REFLECTOR: Engine failure causes

 Al,

 Good comments.  For prime #1, I envision three fixes.
 First, would be as you point out to make the fuel shutoff valve a cable
 operated valve.  Second, rather than pick up off the bottom of the sump,
 and loop over the gear bulkhead, I would drill a hole near the b
ottom of
 the bulkhead and route the fuel to the pump with little height change.
 Third, I would ensure the fuel return flow doesn't compromise where I
 pick fuel up to the pumps.

 Al Gietzen wrote:
 > Prime suspect #1: Fuel starvation due to fuel shutoff v
 alve arrangement.
 >  I still need to inspect the hose for evidence of kinking.  The fuel
 > return hose from the pressure regulator did not have fuel in it during
 > post crash inspection.  My theory is that my aggressive climb at 90 kts
 > resulted in the shutoff valve being higher than the level of fuel in the
 > strakes.  This could be a combination problem coupled to other theories
 > I have.  A vapor bubble might have gotten to the fuel pump, and caused
 > it to lose prime, and then cavitate when I lowered the nose.
 > 
 > Brian:  I don’t like the idea of having that line come forward to the
 > valve, and back. Although normally not likely that the level of the
 > valve getting slightly above the level in the strake would result vapor
 > bubble.  But how big is the line? Pressure drop in that line and valve
 > could result in vapor lock when the pumps are drawing high flow rates.
 > In addition, fuel returning from the engine is warm, and warming the
 > fuel in the sump. Now you have warm fuel being pulled against a flow
 > restriction.  Not good. You want minimal restriction  between sump and
 > pump  You might consider putting an emergency shutoff back20at the sump
 > with a pull cable on a 90 degree ball valve.  Works for me.
 > 
 > Theory #2: Foaming fuel in sump tank
 >  It might be possible, but unlikely that the sump tank became full of
 > foaming
  gasoline.
 > 
 > I think this very unlikely; that’s a lot of foam.  Yes the flow is high,
 > but so is engine usage. I have FI pressure regulator bypass also
 > returning to the sump.  There was never enough foam to make the low fuel
 > float switch activate.  The fuel flowing in from the strake will force
 > the foam out the vent.  I did find evidence that some small amount foam
 > was going out the vent line, so I installed a small separator ‘tank’
 > replacing the vent manifold – problem solved.
 > 
 > Unlikely theory #3: Debris in the tanks clogging filters
 > I pulled the filters and inspected several weeks before flight.  They
 > were clean, and this is the first time since building the plane and
 > doing all taxi testing and ground runs that I had inspected the
 > filters.  The tanks were found to be very clean after the building process.
 > 
 > Of course you’ll check the filters.
 > 
 > All the best,
 > 
 > Al
 > 
 >  
 > 
 > 
 > ------------------------------------------------------------------------
 > 
 > _______________________________________________
 > To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
 > 
 > Visit the gallery!  www.tvbf.
org/gallery <http://www.tvbf.org/gallery>
 > user:pw = tvbf:jamaicangoose
 > 
 Check new archives: www.tvbf.org/pipermail <http://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 <http://www.tvbf.org/gallery>
 user:pw = tvbf:jamaicangoose
 Check new archives: www.tvbf.org/pipermail <http://www.tvbf.org/pipermail>
 Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

 ------------------------------------------------------------------------
 Save money by eating out! Find great dining coupons in your area
 <http://www.when.com/search?st=restaurant&has_gift_cert=1&ncid=emlcntuswhen00000001>.

 ------------------------------------------------------------------------

 _______________________________________________
 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



_______________________________________________
o change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
Visit the gallery!  www.tvbf.org/gallery
ser:pw = tvbf:jamaicangoose
heck new archives: www.tvbf.org/pipermail
heck old archives: http://www.tvbf.org/archives/velocity/maillist.html

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20090407/0e751611/attachment.htm>