REFLECTOR: RE: asymmetric fuel feed

Ronnie Brown romott at adelphia.net
Thu Sep 30 13:22:08 CDT 2004 

Another data point:

My 173 Elite RG (four 3/8 lines feeding to sump) with IO360 flows about 20
gallons per hour through the sump, emergency shut off valve, 3/8" fuel
lines, check valves associated with the Airflow Performance aux fuel pump,
and then through the hose (-6) that connects to the AC engine driven fuel
pump.  This is with about 10 gallons in the fuel tanks. I have never
experienced less than 25 psi at the mechanical fuel pump outlet (aux pump
off) with full throttle - about 15 gph.

Ronnie


----- Original Message ----- 
From: "Chuck Jensen" <cjensen at dts9000.com>
To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
Sent: Wednesday, September 29, 2004 2:22 PM
Subject: REFLECTOR: RE: asymmetric fuel feed


| Larry,
|
| Your point is not just well taken, but even better, well-proven.  Even the
| IO-540 on takeoff won't gobble quite that much fuel.
|
| My earlier reference regarding concern about adequacy of fuel flow through
a
| single, 3/8" line was from a somewhat impeachable source, who was quoting
| another source...who had once dated Carmen Electra's, sister's cousin.
|
| When I balance the quality of information from the two sources, you may
know
| your's is somewhat weightier.  Are there any other data points out there
| showing adequate fuel flow through a 3/8" line?
|
| Chuck
|
|
| -----Original Message-----
| From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
| Behalf Of Laurence Coen
| Sent: Wednesday, September 29, 2004 11:51 AM
| To: Velocity Aircraft Owners and Builders list
| Subject: Re: asymmetric fuel feed was Re: REFLECTOR: Fuel Shutoffs
|
|
| Scott,
|
| I agree with your statements regarding asymmetric flow.  As a point of
| interest, fuel flow problems due to leaking fuel caps are not unique to
the
| Velocity.  I have a friend with a Debonair that had a bad "O" ring on the
| left tank.  He pulled enough of a vacuum to collapse the fuel bladder.
This
|
| in turn held the fuel sender float up, indicating 3/4 full when the tank
was
|
| empty.
|
| As to the fuel flow being marginal with the standard venting system I will
| pass along the results of some tests I ran.  I have a standard RG with
3/8"
| fuel lines and both tanks and the sump vented from a common manifold.  I
| have a carbureted Franklin engine.  I disconnected the fuel line at the
| carburetor.  This was to insure that I was indeed measuring fuel delivered
| to the engine with any restrictions to flow still in place.  I delivered
| fuel from the left tank and the lines from the right tank plugged.  Ten
| gallons in the left tank plus the sump (2.4 gal usable).  I ran the
electric
|
| (Faucet) fuel pump and measured flow with my fuel flow meter.  Initial
flow
| was 33.4 gal/hr and dropped to 30.5 gal/hr just before the pump ran dry.
| The Faucet pump is rated at 30 gal/hr.  The fuel totalizer indicated 12.4
| gal total.  This shows that you can get at least 30 gal/hr from a single
| tank till the system runs bone dry.  I see nothing marginal about that.
|
| Larry Coen
| SE/RG Franklin
| N136LC
|
| ----- Original Message ----- 
| From: "Scott Derrick" <scott at tnstaafl.net>
| To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
| Sent: Tuesday, September 28, 2004 6:07 PM
| Subject: asymmetric fuel feed was Re: REFLECTOR: Fuel Shutoffs
|
|
| > As I understand it, if you use the standard vent system of all tanks and
| > sump tied into one vent line and your lines are unobstructed there are
| > only two reasons for asymmetric fuel flow.
| >
| > 1.  leaking fuel cap. the low pressure over the cap pulling air out of
the
|
| > tank.  Get a new O ring or use fuel valve lube on the O ring to cure.
| >
| > 2.) Your airplane is skidding/slipping when in straight flight, ie not
| > trimmed with the ball in the center.  This is the most common reason.
| > Fix the skid by adjusting the correct rudder outboard and the tanks will
| > drain evenly within a couple gallons.
| >
| > stepping on the fuller tank with the same rudder for a short period will
| > equalize the tanks,
| > adding more valves and lights to fail is solving the symptom, not the
| > problem......
| >
| > Scott
| >
| > At 11:06 PM 9/27/2004, you wrote:
| >>If you don't vent the sump, the [marginal] gravity feed will be enhanced
| >>by the fuel pump sucking the fuel out of the strakes into the sump.
That
| >>said, if you have assymmetric feeding of the strakes (a common
occurrence
| >>in these airplanes) once one tank gets empty, the sump will vent through
| >>that strake vent and the strake that still has fuel will have only
gravity
|
| >>feed (which it has demonstrated is not working for it very well)
| >>available. Isolation valves would solve that problem.
| >>
| >><... a turn the wrong direction on take-off (away from the fuel outlet)
| >>could all contribute to less than adequate fuel flow ...>
| >>  Of course if you're in balanced flight (ball centered) the fuel has no
| >> way of knowing you're turning so fuel flow would not be affected.
| >>
| >>I had assymmetric fuel transfer from the strakes to the sump for the
| >>LONGEST time.  I tried everything (except 1/2" lines) to no avail.
| >>Finally solved the problem with electric "de-selection" valves that
light
| >>a LED on the panel when they are closed.
| >>
| >>If you vent your sump, all bets are off .... Jim S.
| >>
| >>
| >>
| >>Chuck Jensen wrote:
| >>>Regarding a dual fuel shutoff, I understand there was some work/testing
| >>>done on this years ago that raises an issue that is worth thinking
about.
|
| >>>It seems Velo (or someone) did flow tests from a single tank (with a
low
| >>>level of fuel in it) through the 3/8" fuel line and found the flow rate
| >>>was marginally greater than the expected fuel consumption of an IO-540
| >>>engine at max power.  Given that some installations are non-standard
and
| >>>less than optimal, there was thought that with low fuel, a turn the
wrong
|
| >>>direction on take-off (away from the fuel outlet) could all contribute
to
|
| >>>less than adequate fuel flow unless both tanks were feeding.  Since
then,
|
| >>>most have gone to 1/2" fuel lines, which should resolve the flow
capacity
|
| >>>from each tank--but not the exposed outlet from a flight turn.
| >>>
| >>>So, 1) I don't know if there is anything to it!, 2) on the side of
| >>>caution, item #86 on the checklist would be to confirm both tanks are
on
| >>>line.  With all that said, I wish I had dual isolation valves!
| >>>
| >>>Chuck
| >>>
| >>>-----Original Message-----
| >>>From: <mailto:reflector-bounces at tvbf.org>reflector-bounces at tvbf.org
| >>>[mailto:reflector-bounces at tvbf.org]On Behalf Of v350tx
| >>>Sent: Sunday, September 26, 2004 8:31 PM
| >>>To: <mailto:reflector at tvbf.org>reflector at tvbf.org
| >>>Subject: REFLECTOR: Fuel Shutoffs
| >>>
| >>>I have run into more than case when I wish I had put individual fuel
| >>>shut-offs in each tank.  I have one that shuts off the fuel after the
| >>>sump tank, but if you have a leak in the sump tank or any of its
fittings
|
| >>>individual shut-offs would be handy.  Dave Bertram  ( hop to have my
velo
|
| >>>V-8 flying in a couple of weeks.)
| >>
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| >
| >
| > "Those who sacrifice freedom to get security, deserve neither."
| > - Benjamin Franklin
| >
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