REFLECTOR: fuel feed - my solutions

Sat Feb 26 04:26:38 CST 2005

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                                                             
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                      @tvbf.org                Subject:  REFLECTOR: fuel feed - my solutions                                            

                      02/25/2005 04:38                                                                                                  
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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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