Today's Message Index:
----------------------
1. 04:56 PM - Fuel flow question (John Franklin)
2. 06:10 PM - Re: Fuel flow question (shad bell)
3. 06:19 PM - Re: Fuel flow question (taildrags)
4. 08:03 PM - Re: Fuel flow question (Rick)
5. 08:07 PM - Re: Re: Fuel flow question (Ken Bickers)
Message 1
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| Subject: | Fuel flow question |
I'm building a GN-1 with a Corvair engine, fed by a gravity-fed fuel system. The
fuel tank is from Aircraft Spruce, built for a Swift airplane, and is listed
as a 16-gallon tank. I placed it in the compartment where the passenger would
normally be, having decided to build a single-seat Aircamper. The 3/8" fuel
tubing is routed downhill from the main shutoff valve in the cockpit to the
gascolator at the bottom of the firewall.
Today I did a fuel-flow test as recommended by Tony Bingelis' books. With the
plane level and about three gallons of fuel in the tank, I get a most generous
29 gal/hour flow rate. However, when I lowered the tail until the fuselage was
at a 16 degree angle, the fuel flow dropped to a miserable 1.5 gal/hour.
Since I've never flown an Aircamper, I don't know if 16 degrees is a reasonable
angle to test, it looked pretty steep to me and I doubt if the plane could sustain
that kind of nose-up attitude for long, but really don't know. Since the
fuel flow is so high at level height, I would think that would rule out any
restrictions.
I would appreciate any comments and/or suggestions. I could raise the tank maybe
another inch or two, but no more than that. I suppose I could add a fuel pump
but of course that adds complexity, weight, etc.
Thanks,
John Franklin
Prairie Aire 4TA0
Needville, TX
Message 2
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| Subject: | Re: Fuel flow question |
John, If I am understanding correctly you have the tank back in the front c
ockpit area ( above the front seat )?- If you have it that far back you a
re loosing head pressure due to where the tank is relitive to the carburato
r in the nose up attitude.- If you move the tank forward (just behind fir
ewall) it should help the flow rate.- The farther back the tank the worse
the flow will be with a positive pitch attitude.-- For the corvair I w
ould estimate 8-9GPH at full power, so you want at least 14 GPH.- I just
did the same thing on the Baby Lakes I am finishing, it gets nerve racking
when you time that first gallon of gas flowing thru.=0A-=0AShad=0A=0A=0A_
_______________________________=0AFrom: John Franklin <jbfjr@peoplepc.com>
=0ATo: Piet_List <pietenpol-list@matronics.com> =0ASent: Saturday, January
25, 2014 7:55 PM=0ASubject: Pietenpol-List: Fuel flow question=0A=0A=0A-->
Pietenpol-List message posted by: John Franklin <jbfjr@peoplepc.com>=0A=0AI
'm building a GN-1 with a Corvair engine, fed by a gravity-fed fuel system.
- The fuel tank is from Aircraft Spruce, built for a Swift airplane, and
is listed as a 16-gallon tank.- I placed it in the compartment where the
passenger would normally be, having decided to build a single-seat Aircampe
r.- The 3/8" fuel tubing is routed downhill from the main shutoff valve i
n the cockpit to the gascolator at the bottom of the firewall.- =0A=0ATod
ay I did a fuel-flow test as recommended by Tony Bingelis' books.- With t
he plane level and about three gallons of fuel in the tank, I get a most ge
nerous 29 gal/hour flow rate.- However, when I lowered the tail until the
fuselage was at a 16 degree angle, the fuel flow dropped to a miserable 1.
5 gal/hour.- =0A=0ASince I've never flown an Aircamper, I don't know if 1
6 degrees is a reasonable angle to test, it looked pretty steep to me and I
doubt if the plane could sustain that kind of nose-up attitude for long, b
ut really don't know.- Since the fuel flow is so high at level height, I
would think that would rule out any restrictions.=0A=0AI would appreciate a
ny comments and/or suggestions.- I could raise the tank maybe another inc
h or two, but no more than that.- I suppose I could add a fuel pump but o
f course that adds complexity, weight, etc.=0A=0AThanks,=0AJohn Franklin=0A
=========================0A
- - - - - - - - - - - - -Matt Dralle, List Admin.
====
Message 3
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| Subject: | Re: Fuel flow question |
John; since you're building a GN-1, I can't offer direct advice or assistance (my
airplane is a Piet). However, my experience with the 16 gallon tank up ahead
of the passenger in my airplane is that with a gravity feed system, the last
couple of gallons in my tank are unusable except in an emergency, and then only
in level flight. I can cruise on past the 12 gallon mark and dig into that
last few gallons of reserve, but if I raise the nose to full-stall the airplane
or try to power out in a climbing go-around with minimum fuel, I may not have
sufficient fuel flow to sustain engine operation. It does sound like your
test is pretty extreme though I think I've heard of 12 degrees as the nominal
design three-point attitude, which would also be the climb out angle at just
above minimum controllable airspeed.
Although it is certainly simpler and easier to keep your system as-is, gravity
feed only, if you run a Corvair you'll also run a battery and electrical system,
so you can include an electric fuel pump feeding fuel from your main tank to
a small header tank that gravity-feeds the carb. Alternatively, your fuel pump
can continuously feed the carb and the overflow can return to the tank.
Just BS'ing here.
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=417601#417601
Message 4
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| Subject: | Re: Fuel flow question |
John,
I have a 19 gal in the nose on my Corvair powered Piet. With the fuselage at a
20 deg. angle of attack, I got a fuel flow of 22.5 gph. This fuel flow was maintained
with only 1/2 gallon of fuel in the tank. All of the fuel was useable
except for 4oz. The FAR's require the fuel flow to be 150% of the max fuel burn
at max angle of attack. I think you can easily climb at a 16 degree angle, especially
after a shallow dive. I would be very concerned about your fuel flow
rates.
If the max fuel burn is 9 gph on a Corvair, as Shad says you need a flow rate of
at least 13.5 gph.
Regards,
Rick Schreiber
On Jan 25, 2014, at 6:55 PM, John Franklin <jbfjr@peoplepc.com> wrote:
>
> I'm building a GN-1 with a Corvair engine, fed by a gravity-fed fuel system.
The fuel tank is from Aircraft Spruce, built for a Swift airplane, and is listed
as a 16-gallon tank. I placed it in the compartment where the passenger would
normally be, having decided to build a single-seat Aircamper. The 3/8" fuel
tubing is routed downhill from the main shutoff valve in the cockpit to the
gascolator at the bottom of the firewall.
>
> Today I did a fuel-flow test as recommended by Tony Bingelis' books. With the
plane level and about three gallons of fuel in the tank, I get a most generous
29 gal/hour flow rate. However, when I lowered the tail until the fuselage
was at a 16 degree angle, the fuel flow dropped to a miserable 1.5 gal/hour.
>
> Since I've never flown an Aircamper, I don't know if 16 degrees is a reasonable
angle to test, it looked pretty steep to me and I doubt if the plane could
sustain that kind of nose-up attitude for long, but really don't know. Since
the fuel flow is so high at level height, I would think that would rule out any
restrictions.
>
> I would appreciate any comments and/or suggestions. I could raise the tank maybe
another inch or two, but no more than that. I suppose I could add a fuel
pump but of course that adds complexity, weight, etc.
>
> Thanks,
> John Franklin
> Prairie Aire 4TA0
> Needville, TX
>
>
>
>
Message 5
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| Subject: | Re: Fuel flow question |
Reading through Firewall Forward by Tony Bingelis (pp. 171-172), Mikee's
uncle Tony indicates that for a gravity system, the fuel system should
provide 150% of the take-off fuel consumption. This, he says, should be
verified at maximum climb out angle at the minimum fuel level. On page
176, he describes a procedure for conducting this test, which basically
involves chocking the plane at max climb angle. Starting with an empty
tank, add fuel until it just begins to flow steadily from the disconnected
fuel line (keeping the open end at the same height as the carb inlet). That
establishes the unusable fuel amount. At that point, he recommends to start
the stopwatch and add a gallon of fuel to the tank, measuring how many
minutes it takes to drain back out.
Cheers, Ken
On Sat, Jan 25, 2014 at 7:19 PM, taildrags <taildrags@hotmail.com> wrote:
>
> John; since you're building a GN-1, I can't offer direct advice or
> assistance (my airplane is a Piet). However, my experience with the 16
> gallon tank up ahead of the passenger in my airplane is that with a gravi
ty
> feed system, the last couple of gallons in my tank are unusable except in
> an emergency, and then only in level flight. I can cruise on past the 12
> gallon mark and dig into that last few gallons of reserve, but if I raise
> the nose to full-stall the airplane or try to power out in a climbing
> go-around with minimum fuel, I may not have sufficient fuel flow to susta
in
> engine operation. It does sound like your test is pretty extreme though
=85 I
> think I've heard of 12 degrees as the nominal design three-point attitude
,
> which would also be the climb out angle at just above minimum controllabl
e
> airspeed.
>
> Although it is certainly simpler and easier to keep your system as-is,
> gravity feed only, if you run a Corvair you'll also run a battery and
> electrical system, so you can include an electric fuel pump feeding fuel
> from your main tank to a small header tank that gravity-feeds the carb.
> Alternatively, your fuel pump can continuously feed the carb and the
> overflow can return to the tank.
>
> Just BS'ing here.
>
> --------
> Oscar Zuniga
> Medford, OR
> Air Camper NX41CC "Scout"
> A75 power
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=417601#417601
>
>
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