Matronics Email Lists :: View topic - Fuel Flow thru Facet pump

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Fuel Flow thru Facet pump

Matronics Email Lists Forum Index -> Kitfox-List

View previous topic :: View next topic

Author Message

clemwehner

Joined: 02 Feb 2009
Posts: 32

Posted: Mon Sep 02, 2013 11:57 am Post subject: Fuel Flow thru Facet pump

Fuel Flow thru Facet pump



My son and I just did the fuel flow testing on our classic KF-IV with 912 and plastic header tank behind the seat. Before we did the test we decided to determine the best case fuel flow. We simply connected a 5/16 hose to the fuel tank and routed it alongside the aircraft fuel line through the fuselage ending at the carb. There was only a facet fuel pump in the line and nothing else-- no fittings, no valves, etc. The flow was a measly 4 ounces per minute, way below the guideline of 20 oz/min (1.5 X fuel requirements of the 912 at takeoff power and attitude).  The results would undoubtedly be worse when running the fuel through the actual aircraft lines with its fittings, valves, and 912 pump. 



We suspected the facet pump was limiting the fuel flow, so we took the pump out of the line and used just hose from the tank. This produced 40 oz/minâ€”ten times more flow and double the flow test requirements. 



We disassembled the facet pump and found it to be very simple. It has two one-way valves, one in each direction. The valve on the inlet side is held closed by a very weak spring that is easily opened by about 1 psi or less. BUT!!! it only opens about 1/16th inch and allows only a small amount of fuel to flow through it.  Then the valve hits a much stronger spring that could open more, but only with the force generated by the running pump.  So, it is true that gravity flow will pass through a facet pump, but it is very limited in volume to just a small stream, really not much more than a trickle. 



Lots of people use facet pumps in their fuel systems, but I donâ€™t see how it is possible that they met the gravity flow requirements.  Does anyone have any experience with this that can offer some advice?  It seems that without a facet pump, gravity flow meets the flow requirements, but with a facet pump it doesnâ€™t even come close. Do pilots with this situation just ignore the test requirements?



Your thoughts most appreciated,



Clem 

KFIV 912

Oklahoma

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Mon Sep 02, 2013 12:15 pm Post subject: Fuel Flow thru Facet pump

there are many different facet pumps and their interior configuration is

different too. some have check valves, others don't. at least one shuts off

flow when the current is off[sounds like the one you have] . no one at acs

has a clue from what i could tell in my last conversation with them about

facet pumps. they sold me an inline backup elec. pump. when i turned off

the electric to my ''backup'' pump the fuel flow stopped instantly. very

different than the 40105 or 40104 which allow fuel to flow thru them. my

40104 easily allows flow thru it for a jab 3300 x 1.5

 bob noffs

On Mon, Sep 2, 2013 at 2:57 PM, clemwehner <clemwehner(at)sbcglobal.net> wrote:



[quote] 



 Fuel Flow thru Facet pump



 My son and I just did the fuel flow testing on our classic KF-IV with 912

 and plastic header tank behind the seat. Before we did the test we decided

 to determine the best case fuel flow. We simply connected a 5/16 hose to

 the fuel tank and routed it alongside the aircraft fuel line through the

 fuselage ending at the carb. There was only a facet fuel pump in the line

 and nothing else-- no fittings, no valves, etc. The flow was a measly 4

 ounces per minute, way below the guideline of 20 oz/min (1.5 X fuel

 requirements of the 912 at takeoff power and attitude).  The results would

 undoubtedly be worse when running the fuel through the actual aircraft

 lines with its fittings, valves, and 912 pump.



 We suspected the facet pump was limiting the fuel flow, so we took the

 pump out of the line and used just hose from the tank. This produced 40

 oz/min—ten times more flow and double the flow test requirements.



 We disassembled the facet pump and found it to be very simple. It has two

 one-way valves, one in each direction. The valve on the inlet side is held

 closed by a very weak spring that is easily opened by about 1 psi or less

clemwehner

Joined: 02 Feb 2009
Posts: 32

Posted: Mon Sep 02, 2013 1:04 pm Post subject: Re: Fuel Flow thru Facet pump

We have Facet 40105 and facet 40106 pumps and both deliver the same volume of fuel through them at the gravity flow below the header tank. 



We also get fuel flow through them at gravity flow, but the volume is only 4 oz per minute which is not nearly enough to meet the test requirements.



thanks,

Clem

_________________
Clem
Oklahoma
Kitfox IV-912, under construction since 1991

lcfitt(at)sbcglobal.net
Guest

Posted: Mon Sep 02, 2013 5:51 pm Post subject: Fuel Flow thru Facet pump

Clem,



This was recently discussed in another forum.  There was a link to the FAA 

site that gives the test procedures and necessary results.  What I took from 

it was that there are different requirements for Gravity Flow systems and 

Fuel Pump systems.  I think what I took from that is that some designs do 

not have any fuel pump in the system whatsoever.  Since ours does have the 

mechanical and some have the electric (facet) we might be comparing apples 

to oranges.



One question I have is, are you measuring flow with only fuel in the header 

tank, or are you measuring flow with minimal fuel in the  wing tanks as 

well.  One of the guys in the other discussion mentioned the numerous Rotax 

powered airplanes with low wings and essentially no head leading to fuel 

flow and they would have zero flow without the engine driven pump or an 

inline pump (facet).  The discussion also mentioned that the engine driven 

pump will lift fuel significantly.



Don't know for sure on all this, but it is something to think about.

Lowell



--------------------------------------------------

From: "clemwehner" <clemwehner(at)sbcglobal.net>

Sent: Monday, September 02, 2013 2:04 PM

To: <kitfox-list(at)matronics.com>

Subject: Re: Fuel Flow thru Facet pump



 	  Quote: 	
		   



 We have Facet 40105 and facet 40106 pumps and both deliver the same volume 

 of fuel through them at the gravity flow below the header tank.



 We also get fuel flow through them at gravity flow, but the volume is only 

 4 oz per minute which is not nearly enough to meet the test requirements.



 thanks,

 Clem



 --------

 Clem

 Oklahoma

 Kitfox IV-912, under construction since 1991





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=407938#407938

clemwehner

Joined: 02 Feb 2009
Posts: 32

Posted: Mon Sep 02, 2013 7:47 pm Post subject: Re: Fuel Flow thru Facet pump

Lowell,



We wanted to know what best case was with fuel flowing directly out of the wing tank, so we hooked a spare hose to the wing tank outlet and routed it thru the cockpit along the same path that the normal fuel lines run ending at the carb.  We tried it with just the hose and then tried it again going thru a spare facet pump that we have. We did not involve the header since we were looking for best case. 



Without the facet pump in the line there was plenty of fuel flow, but with the restriction of the facet pump (not running), there wasn't nearly enough to meet the test requirements for gravity flow.  A lot of guys use facet pumps and I wonder if they actually conducted the flow test. I can't see how anyone could get the required flow with a facet pump in the line at 25 degrees attitude, since we couldn't get it at 12 degrees attitude setting on the gear. 



Fuel will definitely gravity flow through a facet pump, but not nearly at the volume that's required.  The recent EAA webinar said that 70% of homebuilders never actually do the flow test, but just assume that it'll be fine since their airplanes are based on existing designs. That's scary.



So we're at the point of doing the test with the actual aircraft's plumbing and we know it will be worse than our best case test using just the hose and no fittings, valves, etc. 



I wonder if any Kitfox builders who have facet pumps have achieved the required 150% flow with actual testing.  If not, what did they do about it?  Would a bypass loop around the facet help, or do they just document the flow shortfall and make a flight restriction requiring use of the fuel pump in takeoff and high power climbs?



thanks for the help, 



Clem 

KF-IV, 912

Oklahoma

bobnoffs

Joined: 04 Jul 2012
Posts: 132
Location: northern wi.

Posted: Tue Sep 03, 2013 2:05 am Post subject: Fuel Flow thru Facet pump

as i mentioned in an earlier post some facet models shut off fuel flow when they are turned off. when i talked to the facet rep he said there is supposedly a very weak check valve in these that is supposed to open somewhat. i immediately sent this model [don't remember the model but i got it from acs] back.

 

  anyone out there with the #40104 like mine that won't flow adequately?



 a wing tank must have about 3 psi?



 bob noffs

 and no one at acs can give you any useable info about these pumps.

 

On Mon, Sep 2, 2013 at 10:48 PM, clemwehner <clemwehner(at)sbcglobal.net (clemwehner(at)sbcglobal.net)> wrote:

 [quote]--> Kitfox-List message posted by: "clemwehner" <clemwehner(at)sbcglobal.net (clemwehner(at)sbcglobal.net)>

  

 Lowell,

 

 We wanted to know what best case was with fuel flowing directly out of the wing tank, so we hooked a spare hose to the wing tank outlet and routed it thru the cockpit along the same path that the normal fuel lines run ending at the carb.  We tried it with just the hose and then tried it again going thru a spare facet pump that we have. We did not involve the header since we were looking for best case.

  

 Without the facet pump in the line there was plenty of fuel flow, but with the restriction of the facet pump (not running), there wasn't nearly enough to meet the test requirements for gravity flow.  A lot of guys use facet pumps and I wonder if they actually conducted the flow test. I can't see how anyone could get the required flow with a facet pump in the line at 25 degrees attitude, since we couldn't get it at 12 degrees attitude setting on the gear.

  

 Fuel will definitely gravity flow through a facet pump, but not nearly at the volume that's required.  The recent EAA webinar said that 70% of homebuilders never actually do the flow test, but just assume that it'll be fine since their airplanes are based on existing designs. That's scary.

  

 So we're at the point of doing the test with the actual aircraft's plumbing and we know it will be worse than our best case test using just the hose and no fittings, valves, etc.

 

 I wonder if any Kitfox builders who have facet pumps have achieved the required 150% flow with actual testing.  If not, what did they do about it?  Would a bypass loop around the facet help, or do they just document the flow shortfall and make a flight restriction requiring use of the fuel pump in takeoff and high power climbs?

  

 thanks for the help,

 

 Clem

 KF-IV, 912

 Oklahoma

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=407958#407958

 

 

 

 

 

 

 

 ===========

  target="_blank">http://www.matronics.com/Navigator?Kitfox-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 [b]

mikeperkins

Joined: 22 May 2007
Posts: 123

Posted: Tue Sep 03, 2013 5:25 am Post subject: Re: Fuel Flow thru Facet pump

There is a way around needing to meet the gravity-feed minimum-flow requirement â€“ two fuel pumps each capable independently of supply 1.5x max rate in all flight attitudes.

  

Think low-wing aircraft - none would pass a gravity-flow test. The FAA just wants two sources of fuel pressure, each sufficient on their own to operate the engine at full power in all flight attitudes. So for low-wing aircraft, the minimum is two fuel pumps or one pump plus a header tank, both of which separately meet the 1.5x requirement.  (Kitfoxes, with their low-mounted header tank, will usually not meet the 1.5x requirement.)



If your desire is to have two Facet pumps plus the engine-driven fuel pump (three sources of pressure),  one Facet pump could be switched on all the time but the other could be either on all the time or switched only switched on for TO and landing. For redundancy, the second pump naturally would be supplied by a separate switch and breaker. But for the FAA, a single Facet pump would be enough for their redundancy requirement. 



As long as there are at least two independent fuel sources that meet the 1.5x requirement, it doesnâ€™t matter that none of them are gravity-feed.

_________________
Mike Perkins
Havana, Illinois
Model I, 532, B gearbox, GSC prop

lcfitt(at)sbcglobal.net
Guest

Posted: Tue Sep 03, 2013 8:22 am Post subject: Fuel Flow thru Facet pump

This was essentially my take on the discussion on the other forum and what I 

gathered from reading the specs from the FAA.    I was led to understand 

that gravity flow requirements were not dependent on whether the airplane 

had high wing tanks conducive to gravity flow, but rather whether the fuel 

system had fuel pumps in the system.  A Sonex with Rotax 912, would not have 

to prove any level of gravity fed fuel flow.  We while flying the high wing 

Kitfox have a two fold redundancy with an engine driven fuel pump and high 

wings providing a level of gravity flow.  One poster in the other forum 

mentioned that he could maintain altitude with a failed engine driven fuel 

pump relying only on gravity fed fuel.

Lowell



--------------------------------------------------

From: "mikeperkins" <flybyewire(at)gmail.com>

Sent: Tuesday, September 03, 2013 6:25 AM

To: <kitfox-list(at)matronics.com>

Subject: Re: Fuel Flow thru Facet pump



 	  Quote: 	
		   



 There is a way around needing to meet the gravity-feed minimum-flow 

 requirement â?" two fuel pumps each capable independently of supply 1.5x 

 max rate in all flight attitudes.



 Think low-wing aircraft - none would pass a gravity-flow test. The FAA 

 just wants two sources of fuel pressure, each sufficient on their own to 

 operate the engine at full power in all flight attitudes. So for low-wing 

 aircraft, the minimum is two fuel pumps or one pump plus a header tank, 

 both of which separately meet the 1.5x requirement.  (Kitfoxes, with their 

 low-mounted header tank, will usually not meet the 1.5x requirement.)



 If your desire is to have two Facet pumps plus the engine-driven fuel pump 

 (three sources of pressure),  one Facet pump could be switched on all the 

 time but the other could be either on all the time or switched only 

 switched on for TO and landing. For redundancy, the second pump naturally 

 would be supplied by a separate switch and breaker. But for the FAA, a 

 single Facet pump would be enough for their redundancy requirement.



 As long as there are at least two independent fuel sources that meet the 

 1.5x requirement, it doesnâ?Tt matter that none of them are gravity-feed.



 --------

 Mike Perkins

 Havana, Illinois

 Model I, 532, B gearbox, GSC prop





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=407972#407972

n223rv(at)wolflakeairport
Guest

Posted: Tue Sep 03, 2013 10:02 am Post subject: Fuel Flow thru Facet pump

So what is the purpose of the low mounted header tank?  Why is the KitFox not designed with 2 lines (one from each tank) to a selector valve (left-right-both-off)?



Just curious.

-Mike



Sent from my iPhone



On Sep 3, 2013, at 12:21 PM, "Lowell Fitt" <lcfitt(at)sbcglobal.net> wrote:



 	  Quote: 	
		   This message cannot be displayed because of the way it is formatted. Ask the sender to send it again using a different format or email program. text/plain

mikeperkins

Joined: 22 May 2007
Posts: 123

Posted: Wed Sep 04, 2013 6:38 am Post subject: Re: Fuel Flow thru Facet pump

Mike, 



All header tanks are installed with the same intention: insure fuel flow in 1) a dive, or 2) with one tank empty and the other tank unported due to a slip or skid.



Once upon a time, in the Model 1 and 2 days, fuel lines were commonly being routed uphill, over top of the door and then down between the windshield and the door, then back up to a firewall-mounted header tank. The biggest problem with this installation was requiring the fuel to go uphill over the doors because of the extremely low head pressure, or even negative head pressure, at that point in the system. Pulling fuel like this with a pump leads to vapor lock. Vapor lock is often associated with high temperatures, so thinking of it as an expanding  "gas bubble" might be a better way to look at it. Anyway, to get around the problem of unreliable fuel flow, folks were resorting to installing primer bulbs over the doors, which had their own problems, and the whole thing was getting messy. 



The switchover to the rear-mounted header tank arrangement occurred about 1990. The intention was to encourage routing that kept the fuel constantly going downhill immediately after leaving the wing tanks to prevent vapor lock. I switched my system over from the old way to the new way after it had all been plumbed but not flown. When I installed the rear-mounted header tank, I also added a valve just above the seat between each wing tank and the header tank. And I installed a main shutoff just forward and below the left door. The system has worked well for 400 hours.

_________________
Mike Perkins
Havana, Illinois
Model I, 532, B gearbox, GSC prop

SWeidemann

Joined: 28 Jul 2007
Posts: 5
Location: Photographer

Posted: Wed Sep 04, 2013 7:29 am Post subject: Fuel Flow thru Facet pump

I agree with Mike's question.  Why is a header tank necessary for such  a system (Kitfox with low behind the seat header tank) where gravity should take  care of ALL your fuel pressure needs?  I have an ancient Luscombe with wing  tanks that uses Mother Nature's Gravity System and has no fuel pump  anywhere.

  

 Sko

  

 [quote][b]

_________________
WestSouthWest

mikeperkins

Joined: 22 May 2007
Posts: 123

Posted: Wed Sep 04, 2013 7:46 am Post subject: Re: Fuel Flow thru Facet pump

The Luscombe's updraft carb is located much farther below the wing tanks than the the Kitfox's side-draft carbs. So the Luscombe's head pressure at the carb is going to be a lot higher, and so will the gravity fuel flow rate. That's my guess anyway.

_________________
Mike Perkins
Havana, Illinois
Model I, 532, B gearbox, GSC prop

Display posts from previous:

	Matronics Email Lists Forum Index -> Kitfox-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum