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jpspencer(at)cableone.net
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 Posted: Mon Nov 23, 2009 7:22 pm Post subject: Electric fuel pump behind seat of 701 |
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The reason a backup electric fuel pump is needed on a 912s equipped 701 is that the pitch attitude possible in a light weight max performance climb puts the engine above the level of the fuel tanks, or potentially so...if the engine driven fuel pump fails when operating at such a steep attitude gravity feed won't work; compounding the problem is that the failure would probably occur at low altitude when trying to clear a close in obstacle on takeoff. If I am doing a max effort climb I turn it on...if not I don't. I also turn it on before engine start to check operation of the pump, then turn it off for start
Mine is on the left side floor near the sidewall where any leaks would show.
Joe
[quote][b]
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ggower_99(at)yahoo.com
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| Posted: Mon Nov 23, 2009 11:53 pm Post subject: Electric fuel pump behind seat of 701 |
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Questions to the owners (engine already working or actually flying) that have the extra electric pump:
1.- Are you sure the final gas pressure (both pumps working) is less than the floats can stop?
2.- Do you have a gasoline pressure dial (could be an EIS) installed in the carb side if the fuel system?.
In case the pressure is too high (danger of push the floats down).
3.- Did you installed a gas pressure regulator (another gadget that can potentialy fail)betwen the mech pump and the carburators?
4.- Do you know (where to look for) the max pressure that the carb floats can stop without danger of flooding?
5.- Did you installed a "crash switch" in case of a take off or landing incident/accident the electric pump will turn instantly off?
If not will have lots of prssurized gas, flowing in case of fire...
Geee, is getting more complicate and dangerous than safe, in my humble opinion...
Dont have to answer to the list,,, Just be sure you have the answers.
This is not to bother anyone, just my best way to clear doubts in this high redundant instalation.
Saludos
Gary Gower
Not negative thinking. Just hoping all answers are OK (Safe) in all particular cases.
--- On Mon, 11/23/09, Joe Spencer <jpspencer(at)cableone.net> wrote:
From: Joe Spencer <jpspencer(at)cableone.net>
Subject: Electric fuel pump behind seat of 701
To: Zenith701801-List(at)matronics.com
Date: Monday, November 23, 2009, 10:21 PM
The reason a backup electric fuel pump is needed on a 912s equipped 701 is that the pitch attitude possible in a light weight max performance climb puts the engine above the level of the fuel tanks, or potentially so...if the engine driven fuel pump fails when operating at such a steep attitude gravity feed won't work; compounding the problem is that the failure would probably occur at low altitude when trying to clear a close in obstacle on takeoff. If I am doing a max effort climb I turn it on...if not I don't. I also turn it on before engine start to check operation of the pump, then turn it off for start
Mine is on the left side floor near the sidewall where any leaks would show
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jpspencer(at)cableone.net
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| Posted: Tue Nov 24, 2009 10:12 am Post subject: Electric fuel pump behind seat of 701 |
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Questions to the owners (engine already working or actually flying) that ha
ve the extra electric pump:
1.- Are you sure the final gas pressure (both pumps working) is less than t
he floats can stop?
Yes, on mine it is. I selected an electric pump that puts out less psi than the ED pump
2.- Do you have a gasoline pressure dial-(could be an EIS) installed in t
he carb side if the fuel system?.
In case the pressure is too high (danger of push the floats down).
Yes
3.- Did you installed a gas pressure regulator (another gadget that can pot
entialy fail)betwen the mech pump and the carburators?
No need on mine
4.- Do you know (where to look for) the max pressure that the carb floats c
an stop without danger of flooding?
My ED fuel pump puts out about 5 psi. My electric aux pump puts out about 3 psi. The 2 together put out the higher of the 2, or 5 psi.
5.- Did you installed a "crash switch" in case of a take off or landing inc
ident/accident the electric pump will turn instantly off?-
If not will have lots of prssurized gas, flowing in case of fire...
The battery master switch. It was already in the plane
-
Geee, is getting more complicate and dangerous than safe, in my humble opin
ion...
GA planes(and usually homebulits as in the RV line) that I am familiar with that won't gravity feed always have an engine driven fuel pump and a backup electric pump. This is no big deal, IMO, but if I didn't like it I wouldn't install it. Also if you aren't running a 912s and/or don't plan on doing the very steep climbouts that it is capable of you probably don't need it. Your call of course
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Dont have to answer to the list,,,- Just be sure you have the answers.
-
This is not to bother anyone, just my best way to clear doubts in this-hi
gh-redundant instalation.
normally redundant in a non gravity feed system
-
Saludos
Gary Gower
Not negative thinking. Just hoping all answers are OK (Safe) in all particu
lar cases.
[quote][b]
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