REFLECTOR: FUEL FEED [heur]
Ron Brown
romott at adelphia.net
Tue Feb 15 14:31:11 CST 2005
Tom,
I don't think it is a good idea to vent the fuel system into the engine
compartment, especially if you happen to flip upside down during a crash
landing. You will have lots of fuel draining out the vent system into the
hot engine compartment.
With the factory designed fuel vent line routed up to the top of the
firewall then back down to exit the bottom of the fuselage, fuel will not
leak out of the vent system when the airplane is upside down.
One other thought on uneven fuel flow, even if the vents are tied together
and the plane is flying level/ball centered: there is a possibility that an
air bubble trapped in the vent line with fuel on either side of the bubble
can cause an uneven venting of the tanks. This wouldn't happen if the vent
lines always slope upward to the manifold. I think this may be the scenario
that Jim Sower is seeing from time to time. I have had it happen a couple
of times on long trips after filling the tanks nearly full. After landing
and parking in my hanger, the fuel tanks were 5 or so gallons different and
remained that way until I opened the fuel caps. STRANGE! Wings are level
when parked in the hanger. Another experiment - I placed a 2 x 6 under one
main tire, simulating a wings down. Guess what - the fuel level difference
was MUCH LESS than I have seen in the air.
But again, it could be fuel caps that are not always sealing perfectly for
every flight.
Ronnie
----- Original Message -----
From: "Tom Martino" <tmartino at troubleshooter.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Tuesday, February 15, 2005 12:23 PM
Subject: RE: REFLECTOR: FUEL FEED [heur]
My plane flies perfectly. Not my opinion, it is the assessment of my
test pilot. The ball is in the center and the plane flies "hands off"
straight and level.
I will keep looking.
-----Original Message-----
From: Scott Derrick [mailto:scott at tnstaafl.net]
Sent: Tuesday, February 15, 2005 9:18 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: FUEL FEED [heur]
A leaking gas cap can cause uneven fuel flow but is not the prime
culprit. A bit of fuel valve lube applied to the O ring once a year will
insure this doesn't happen.
A miss-rigged airplane is most likely the cause. Shim your rudders so
the ball is right in the middle and you will get perfect fuel flow.
To test, be sure your turn and bank is installed correctly first,
garbage in garbage out. Then fly, this is the fun part.. Once you see an
uneven condition, press on the rudder that will put the ball in the
middle. If you want to even up the tanks fast, press on the correct
rudder so the ball is on the other side for a couple minutes, you'll see
the fuel even up and even go into the opposite imbalance if you keep the
rudder depressed. Then hold the rudder so the ball is centered, fuel
will flow as it was designed to.
Scott
Tom Martino wrote:
> Well, now that I'm in my test flying mode ... I will really be asking
> a lot of questions.
>
> Here are some of them, as they relate to my fuel system:
>
> 1. What makes the fuel tanks feed unevenly to the header tank/engine?
> (My right tank is feeding twice as fast as my right tank.)
>
> 2. Will that cause a problem when the fast-feeding tank runs out?
>
> 3. I used the larger vent lines for my tanks and tied them al together
> with a manifold, then vented the entire system out through the top of
> my firewall in the engine compartment (about four inches below my naca
> duct). Do you think the system gets enough venting there?
>
> 4. Is there a need for a "whistle" hole in any of the tank vents ...
> for additional venting (like we do with the crankcase breather?
>
> Any help is appreciated from my more experienced Velocitologists J
>
> Tom
>
> N173EX
>
> (A mere 6 hours)
>
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