Matronics Email Lists :: View topic

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 Pump Switch(es)

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

FLYaDIVE(at)aol.com
Guest

Posted: Tue Oct 17, 2006 8:48 am Post subject: Fuel Pump Switch(es)

Ed:

  

 With in the body of your email I inserted my responces.

  

 Barry

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

 Hi Frank,



I've been following this thread for a while. I like your idea for the 

fuel system.  Just a couple of questions.



I'm thinking of using a carbed lycoming.  Why couldn't I use a 

mechanical pump,  an off-left-right-both fuel valve, and two electric pumps?

  

 [Barry] - It depends on what type of plane.  You DO NOT run off BOTH with a Low Wing plane.  The reason is fuel flow is NEVER equal from both tanks.  When one tank runs dry before the other, the engine's fuel pump will SUCK AIR. 

 This does not happen on Gravity feed systems since gravity will keep the fuel flowing even when one tank is dry.

  

 Another reason for NOT running off BOTH is Fuel Management.  When the brain is FORCED to think about switching tanks it generally does a better job of keeping important thing foremost in the thought pattern.  This is something the FAA talked about in the WINGS PROGRAM.

  

  Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada



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

 ============================================



Normal Operation:

Fuel valve on both all the time (no valve to switch).

One or the other electric pump on to select tank used.

Tanks switched with the pumps.



Takeoff and landing.

Same as above but both electric pumps on.



Failures.

Electric pump failure.  Fuel selector switched to that tank if that fuel 

is needed.

Mechanical pump failure would NOT be noticed in this system but could be 

checked at startup (or in the air if you wanted to turn both pumps off).



All of the advantages you pointed out but would not be dependent on the 

electrical system or an electric pump failure.

I like simple systems.  I owned and flew a Beech Duchess (light light 

twin) for 14 years.  Left tank fed left engine, right tank fed right 

engine.  No switching fuel valves unless an engine failure.  Went back 

to a single engine three years ago, first time I had to switch tanks I 

wasn't happy having to fool with the fuel.  A year later in the same 

plane, my wife (a pilot also) switched tanks for me but commented that 

it didn't feel right going into the left position.  I looked down at the 

valve and saw that a loose nut from a screw was lodged between the 

handle and the stop preventing the valve from fully engaging.  Luckily 

the engine continued running , valve back to right, fish nut out,  valve 

to left then worked fine.  Should there be loose nuts in the airplane?  

No, but stuff happens.   Therefore  when I heard of your system,  I 

liked it immediately. 

  

  

  

  [quote][b]

frank.hinde(at)hp.com
Guest

Posted: Tue Oct 17, 2006 9:28 am Post subject: Fuel Pump Switch(es)

The way I ran this system  was to only run both pumps for TO and landing...Maybe batting around the pattern  I would leave both pumps running but generally would only do this if I had way  more fuel that I would burn on the flight.

  

 Normal cruise would be  one pump or the other...if the pump quit i simply flipped on the second  pump.

  

 What you are getting at  Barry is the fact that you have to understand the system is different and is  managed accordingly. But it is very simple and the only really nasty failure  mode I can think of is what happens in the event of a lightening  strike.

  

 Frank



   From: owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of  FLYaDIVE(at)aol.com

Sent: Tuesday, October 17, 2006 9:40  AM

To: aeroelectric-list(at)matronics.com

Subject: Re:  Fuel Pump Switch(es)

 

 Ed:

  

 With in the body of your email I inserted my responces.

  

 Barry

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

 Hi Frank,



I've been following this thread for a while. I like your  idea for the 

fuel system.  Just a couple of questions.



I'm  thinking of using a carbed lycoming.  Why couldn't I use a 

mechanical  pump,  an off-left-right-both fuel valve, and two electric pumps?

  

 [Barry] - It depends on what type of plane.  You DO NOT run off BOTH  with a Low Wing plane.  The reason is fuel flow is NEVER equal from both  tanks.  When one tank runs dry before the other, the engine's fuel  pump will SUCK AIR. 

 This does not happen on Gravity feed systems since gravity will keep the  fuel flowing even when one tank is dry.

  

 Another reason for NOT running off BOTH is Fuel Management.  When the  brain is FORCED to think about switching tanks it generally does a better job of  keeping important thing foremost in the thought pattern.  This is something  the FAA talked about in the WINGS PROGRAM.

  

  Barry

"Chop'd  Liver"



"Show them the first time, correct them the second time, kick them  the third 

time." 

Yamashiada



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

 ============================================



Normal  Operation:

Fuel valve on both all the time (no valve to switch).

One or  the other electric pump on to select tank used.

Tanks switched with the  pumps.



Takeoff and landing.

Same as above but both electric pumps  on.



Failures.

Electric pump failure.  Fuel selector switched to  that tank if that fuel 

is needed.

Mechanical pump failure would NOT be  noticed in this system but could be 

checked at startup (or in the air if you  wanted to turn both pumps off).



All of the advantages you pointed out but  would not be dependent on the 

electrical system or an electric pump  failure.

I like simple systems.  I owned and flew a Beech  Duchess (light light 

twin) for 14 years.  Left tank fed left engine,  right tank fed right 

engine.  No switching fuel valves unless an engine  failure.  Went back 

to a single engine three years ago, first time I  had to switch tanks I 

wasn't happy having to fool with the fuel.  A  year later in the same 

plane, my wife (a pilot also) switched tanks for me  but commented that 

it didn't feel right going into the left position.   I looked down at the 

valve and saw that a loose nut from a screw was lodged  between the 

handle and the stop preventing the valve from fully  engaging.  Luckily 

the engine continued running , valve back to right,  fish nut out,  valve 

to left then worked fine.  Should there be  loose nuts in the airplane?  

No, but stuff happens.    Therefore  when I heard of your system,  I 

liked it immediately.  

  

  

  

[quote]



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List



[b]

FLYaDIVE(at)aol.com
Guest

Posted: Tue Oct 17, 2006 10:42 am Post subject: Fuel Pump Switch(es)

Frank:

  

 The issue is NOT running the pumps, one or both ... BUT, running of BOTH tanks at the same time.  This is a No-No for low wingers.  It is easier to pump AIR than fuel so the pumps run dry ALL PUMPS electrical and mechanical.  For when a pump is given a choice of AIR Vs Fuel, such as in the 'Y' connection where both tanks feed the same engine mechanical pump, the pump takes the path of least resistance ... AIR.

  

 As far as the lighting strike ... I don't know for sure, but I would say you are TOAST. 

 But, I can guarantee 100% that a dry tank in a Low Wing Both configuration will lead to an emergency situation.

  

  Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

  

  

 =============

 The way I ran this system was to only run both pumps for TO and landing...Maybe batting around the pattern I would leave both pumps running but generally would only do this if I had way more fuel that I would burn on the flight.

  

 Normal cruise would be one pump or the other...if the pump quit i simply flipped on the second pump.

  

 What you are getting at Barry is the fact that you have to understand the system is different and is managed accordingly. But it is very simple and the only really nasty failure mode I can think of is what happens in the event of a lightening strike.

  

 Frank



   From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of FLYaDIVE(at)aol.com

Sent: Tuesday, October 17, 2006 9:40 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: AeroElectric-List: Fuel Pump Switch(es)

 

 Ed:

  

 With in the body of your email I inserted my responces.

  

 Barry

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

 Hi Frank,



I've been following this thread for a while. I like your idea for the 

fuel system.  Just a couple of questions.



I'm thinking of using a carbed lycoming.  Why couldn't I use a 

mechanical pump,  an off-left-right-both fuel valve, and two electric pumps?

  

 [Barry] - It depends on what type of plane.  You DO NOT run off BOTH with a Low Wing plane.  The reason is fuel flow is NEVER equal from both tanks.  When one tank runs dry before the other, the engine's fuel pump will SUCK AIR. 

 This does not happen on Gravity feed systems since gravity will keep the fuel flowing even when one tank is dry.

  

 Another reason for NOT running off BOTH is Fuel Management.  When the brain is FORCED to think about switching tanks it generally does a better job of keeping important thing foremost in the thought pattern.  This is something the FAA talked about in the WINGS PROGRAM.

  

  Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada



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

 ============================================

  [quote][b]

frank.hinde(at)hp.com
Guest

Posted: Tue Oct 17, 2006 12:36 pm Post subject: Fuel Pump Switch(es)

It is not a NO-NO  Barry....In an experimental airplane you can do what you want...And I have and  i'm happy with the system. I simply leave a small reserve in each  tank.

  

 As I said the only time I  run both pumps is for take off and landing. if you did suck a tank dry then you  screwed up...Simply turn off the low tank, not that it should have been running  with a nearly empty tank in the first place.

  

 I think if you focussed  on the benefits of the system (i.e fuel pumps in both both a cool place and in  the hydraulically correct place) then the small downside of sucking a tank dry  (that should never happen unless your asleep) is a minor  consideration.

  

 I did not suck a tank dry  in 400 hours...but as I said the system is not normally run with both pumps  running at the same time.

  

 Frank



   From: owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of  FLYaDIVE(at)aol.com

Sent: Tuesday, October 17, 2006 11:42  AM

To: aeroelectric-list(at)matronics.com

Subject: Re:  Fuel Pump Switch(es)

 

 Frank:

  

 The issue is NOT running  the pumps, one or both ... BUT, running of BOTH tanks at the same time.   This is a No-No for low wingers.  It is easier to pump AIR than fuel so the  pumps run dry ALL PUMPS electrical and mechanical.  For when a pump is  given a choice of AIR Vs Fuel, such as in the 'Y' connection where both tanks  feed the same engine mechanical pump, the pump takes the path of least  resistance ... AIR.

  

 As far as the lighting  strike ... I don't know for sure, but I would say you are  TOAST. 

 But, I can guarantee 100%  that a dry tank in a Low Wing Both configuration will lead to an emergency  situation.

  

  Barry

"Chop'd  Liver"



"Show them the first time, correct them the second time, kick them  the third 

time." 

Yamashiada

  

  

 =============

 The way I ran this system  was to only run both pumps for TO and landing...Maybe batting around the pattern  I would leave both pumps running but generally would only do this if I had way  more fuel that I would burn on the flight.

  

 Normal cruise would be  one pump or the other...if the pump quit i simply flipped on the second  pump.

  

 What you are getting at  Barry is the fact that you have to understand the system is different and is  managed accordingly. But it is very simple and the only really nasty failure  mode I can think of is what happens in the event of a lightening  strike.

  

 Frank



   From: owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of  FLYaDIVE(at)aol.com

Sent: Tuesday, October 17, 2006 9:40  AM

To: aeroelectric-list(at)matronics.com

Subject: Re:  Fuel Pump Switch(es)

 

 Ed:

  

 With in the body of your email I inserted my responces.

  

 Barry

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

 Hi Frank,



I've been following this thread for a while. I like your  idea for the 

fuel system.  Just a couple of questions.



I'm  thinking of using a carbed lycoming.  Why couldn't I use a 

mechanical  pump,  an off-left-right-both fuel valve, and two electric pumps?

  

 [Barry] - It depends on what type of plane.  You DO NOT run off BOTH  with a Low Wing plane.  The reason is fuel flow is NEVER equal from both  tanks.  When one tank runs dry before the other, the engine's fuel  pump will SUCK AIR. 

 This does not happen on Gravity feed systems since gravity will keep the  fuel flowing even when one tank is dry.

  

 Another reason for NOT running off BOTH is Fuel Management.  When the  brain is FORCED to think about switching tanks it generally does a better job of  keeping important thing foremost in the thought pattern.  This is something  the FAA talked about in the WINGS PROGRAM.

  

  Barry

"Chop'd  Liver"



"Show them the first time, correct them the second time, kick them  the third 

time." 

Yamashiada



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

 ============================================

[quote]



href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List



[b]

frank.hinde(at)hp.com
Guest

Posted: Tue Oct 17, 2006 12:38 pm Post subject: Fuel Pump Switch(es)

Oh BTW  this statement is incorrect...The air will simply vent through the float  bowl. Note the fuel; pumps are in the wingroots. The pump will not pump air  against the other pump that is pumping liquid...Can't happen.

  

 For a FI'd engine it  won't vent air through the injection system bu it still won't pump  air.

  

 Frank

  

  



   But, I can guarantee 100% that a dry tank in a  Low Wing Both configuration will lead to an emergency situation.

  

  Barry

"Chop'd  Liver"

[quote] [b]

khorton01(at)rogers.com
Guest

Posted: Tue Oct 17, 2006 5:29 pm Post subject: Fuel Pump Switch(es)

Barry's statement is true for most low wing light aircraft.  Frank's  

aircraft has an unusual fuel system design that shouldn't have a  

problem in this scenario, as fuel pumps generally do a pretty poor  

job of pumping air.  It would be good to do an actual test to  

demonstrate this mode of operation though, just in case there is a  

gotcha lurking.



Some other low wing aircraft (e.g. some Yaks) use gravity feed from  

both wings to a small header tank, and have the fuel pump sucking  

from the header tank.  This would also prevent an emergency if you  

run one wing dry with the fuel selector in Both.



But, on RVs with a "normal" fuel system, running one wing dry with a  

fuel selector on Both would lead to an engine failure.



Kevin Horton



On 17 Oct 2006, at 16:37, Hinde, Frank George (Corvallis) wrote:



 	  Quote: 	
		   Oh BTW this statement is incorrect...The air will simply vent  

 through the float bowl. Note the fuel; pumps are in the wingroots.  

 The pump will not pump air against the other pump that is pumping  

 liquid...Can't happen.



 For a FI'd engine it won't vent air through the injection system bu  

 it still won't pump air.



 Frank



 But, I can guarantee 100% that a dry tank in a Low Wing Both  

 configuration will lead to an emergency situation.



  Barry

 "Chop'd Liver"

FLYaDIVE(at)aol.com
Guest

Posted: Tue Oct 17, 2006 6:54 pm Post subject: Fuel Pump Switch(es)

In a message dated 10/17/06 4:40:18 PM Eastern Daylight Time, 

frank.hinde(at)hp.com writes:



 	  Quote: 	
		   It is not a NO-NO Barry....In an experimental airplane you can do what

  you want...And I have and i'm happy with the system. I simply leave a

  small reserve in each tank.

============================
	


Frank:



Experimental has nothing to do with it.  It is PHYSICS.  Do some simple 

experimenting.  Make up a 'Y' fitting have the Gas Tank on one side of the 'Y' and 

NOTHING but AIR on the other side.  Now put the pump at the bottom of the 'Y'. 

 What do you think will happen?  Lots of pump noise but NO FUEL.

Now, I know you are going to say: But I have the electric pump at the top of 

the 'Y' ... It does NOT matter.  Your mechanical engine pump is still at the 

bottom of the 'Y' and it will still suck air.  Yet you may be lucky and get 

some fuel mixed with air ... Gee in this case I'd take physics over luck.

As for your statement about the air leaking out the float bowl ... I agree 

100%.  It sure will ... Because AIR is the only thing that will be in the float 

bowl.



#2



Barry

"Chop'd Liver"



"Show them the first time, correct them the second time, kick them the third 

time." 

Yamashiada

frank.hinde(at)hp.com
Guest

Posted: Tue Oct 17, 2006 7:09 pm Post subject: Fuel Pump Switch(es)

I tested it on the ground but I think I'll avoid the temptation in

flight...



Frank 



--

frank.hinde(at)hp.com
Guest

Posted: Tue Oct 17, 2006 7:25 pm Post subject: Fuel Pump Switch(es)

Barry we have beaten this to death I think....Clearly I have not

conveyed the layout of the system.



I do not have a mechanical pump. I have two electric pumps...Each pump

is in the wingroot...I.e pushing on the fuel.



There is no point in the system that the fuel is under suck (except

right at the discharge of the tank)....Now the two pressure feeds from

each pump join at what was the selector valve...Its a simple tee

fitting. There is a check valve in each of these feeds.



Now if a pump goes dry it does not pump air against the head of the

other pump...I have proved this on the ground...Doesn't do the pump much

good and I would never intentionally run it dry because then you have

lost redundancy...I.e I'm down to a single electric pump only.



If I screwed up and ran a tank dry I would hope it would be running a

single pump (cruise mode) and I would simply flip on the other

pump...power restored no problem.



If I ran a tank dry with both pumping I would probably not know about it

because the dead pump won't pump air.



Now why did I do this your probably asking...Simple, its an almost

vapour lock proof system no matter what fuel you choose to run.



Cheers



Frank

--

echristley(at)nc.rr.com
Guest

Posted: Wed Oct 18, 2006 4:25 am Post subject: Fuel Pump Switch(es)

Kevin Horton wrote:



 	  Quote: 	
		   

 <khorton01(at)rogers.com>



 Barry's statement is true for most low wing light aircraft.  Frank's  

 aircraft has an unusual fuel system design that shouldn't have a  

 problem in this scenario, as fuel pumps generally do a pretty poor  

 job of pumping air.  It would be good to do an actual test to  

 demonstrate this mode of operation though, just in case there is a  

 gotcha lurking.


	


I've heard some anecdotal evidence that says these pumps don't like 

being run dry.  The person's complaint was that he had a few die in a 

couple different cars, and in each case it was soon after an incident of 

running out of gas, even though the pump had given years of reliable 

service.  Seems reasonable considering that the fuel provides cooling 

and lubrication.  This is in no way to be construed as scientific 

evidence, or a repeatable experiment, but I'd keep any such test very 

short (for some undefined value of "very short").



-- 

         ,|"|"|,              Ernest Christley       |

----===<{{(oQo)}}>===----    Dyke Delta Builder      |

        o|  d  |o        http://ernest.isa-geek.org  |

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-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