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SV: Re: SV: fuel flow and return line status

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sidsel.svein(at)oslo.onli
Guest

Posted: Fri Feb 22, 2013 8:06 am Post subject: SV: Re: SV: fuel flow and return line status

Hello Clive,



Impossible to know without actually measuring, but perhaps our restrictors

have different openings?  Probably not, though.



On longer flights and with the engine (I assume) operating at or near the

same power each time, I realize that the error in total consumption for the

flight may not be too large.  The consumption at idle and taxiing is of

relatively short duration, so that even though the indicated flow rate may

be quite wrong during ground operations, it does not have a big influence

percentagewise on the displayed total consumption.



Regards,

Svein

clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Fri Feb 22, 2013 9:07 am Post subject: Re: SV: Re: SV: fuel flow and return line status

Hi Svein,



I have the std restrictor, so I guess its the same as yours.  I think that compared to the 'average' K factor figure for the actual fuel flow rate at taxi and under full power are probably out, but for an 'average' flight - which accounts for my airframe drag, prop type (I've a fixed pitch warpdrive) and the power settings I tend to use, the average useage stacks up (now) with the observed consumption based upon measured full tank and bowser meter quantities to refill it.  I do get a readout of about 9lit/hr at idle and just over 20 at full power - and a readout of around 15lit/hr in the cruise around 115kts.



I simply dial in the known quantity in the tank into my Stratomaster at the beginning of each flight (if I've added fuel).  I did try to get it to sense the actual quantity in the tank using the fuel probe, but never got it to work.

sidsel.svein(at)oslo.onli
Guest

Posted: Sun Feb 24, 2013 9:36 am Post subject: SV: Re: SV: fuel flow and return line status

From the two replies to my first message, and reading once again Bud Yerly's detailed explanation last fall on how he set up a one-sender unit, I now understand how one sender can be made to work accurately enough to show fuel consumed/remaining.  As I indicated in my second message, the reading error at flows outside the normal cruise power evidently are of too short duration to give much error in the flow x time = consumption calculation.  The attached illustration shows this clearly, I think (it is fairly accurate to scale).

 

I therefore regret my earlier statement that  one single transducer will serve only one useful purpose: with the engine stopped and the electric feed pump running, one can check that the return line is open.  In actual fact, this feature is an additional feature to keeping good enough track of fuel consumed (provided that a K-factor has been found that gives true consumption for a typical flight time).

 

With my two-sender system (one in feed and one in return line), I cannot check that the return line is open unless I somehow disconnect momentarily one of the senders.  I have therefore asked Electronics International in which wire I can introduce a push-to-break pushbutton mounted next to the display unit.  This return flow check will then become an item in my pre-engine-start checklist.

 

I will then also be able to inform the List about actual return flows at various power settings and tank levels, for those who share my sometimes too deep interest in the mysteries of our aircraft!

 

Regards,

Svein

LN-SKJ

Fuel_flow_-_One_sender.pdf

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sidsel.svein(at)oslo.onli
Guest

Posted: Sun Feb 24, 2013 10:17 am Post subject: SV: Re: SV: fuel flow and return line status

Hi Tim,

 

I stand corrected.  Very decent of you to make me aware of the spelling error, so that I can avoid it in the future!

 

Actually, the graph is not typical of my own landings, especially not on grass strips.  I really have a problem seeing them from above, and once I did a 360 on final descent ( J ) just to have time to verify that I was approaching the right strip of open land (maybe not good aviation practice …….).  But, having the benefit of a two-sender fuel flow system, I always know how much fuel I have left!

 

Regards,

Svein

 

Do not archive 	  Quote:

sidsel.svein(at)oslo.onli
Guest

Posted: Wed Feb 27, 2013 9:11 am Post subject: SV: Re: SV: fuel flow and return line status

Thank you, Bud.

 

For anyone interested, attached is the modification that I will do to the wiring of my installation,  OK’d by Electronics International.  

 

I will use a 12 volt relay with two contact sets.  In normal operation, the relay is not energized.  The white wires from both the Feed and the Return flow transducers are connected to the Differential module as per the original wiring diagram.  Net flow = consumption is displayed on the instrument.

 

When I energize the relay, the white wire connection from the Feed transducer is cut, and the white wire from the Return transducer is connected to the Feed white wire going up to the Differential module.  The display now shows the return flow.

 

I will use a momentary pushbutton switch (closed contacts when pushed and held in the “in” position) so that I do not risk leaving the relay energized.  No chance of upsetting the totalizer function in this way.

 

As mentioned, I will post some return flow readings on this List when my flying season begins later in the spring.

 

Regards,

Svein

LN-SKJ

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Remi Guerner

Joined: 14 Dec 2010
Posts: 284

Posted: Thu Feb 28, 2013 3:13 am Post subject: Re: SV: Re: SV: fuel flow and return line status

Hi Svein,

I am looking fwd seeing your measured return flow in flight. Years ago, I made some measurements of return flow with the engine stopped using the electric pump only and testing several restrictor diameters. It will be interesting to compare our respective figures.

Regarding  a possible plugged restrictor, I experienced just that years ago. When I stopped the engine, the fuel pressure stayed where it was and it took a few minutes before dropping very very slowly. That is because the fuel trapped in the lines between the mechanical fuel pump and the carbs has  (almost) no way to escape due to the blocked restrictor. 

So now while shutting down the engine, I monitor  the fuel pressure to make sure it drops to zero  instantly.    

Remi Guerner

F-PGKL Monowheel , 912ULS, 996 hours

clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Thu Mar 14, 2013 10:48 pm Post subject: Re: SV: Re: SV: fuel flow and return line status

Hello Svein,



Thinking more about the single fuel flow setup - would you agree that another way of checking the restrictor is not blocked, is simply to monitor that there IS fuel flow without the engine running but with the boost pump running?  I get around 9L/hr.



Assuming the float chambers are full and there are no external leaks, not sure where else fuel can go if it is not being consumed by a running engine. . .



Clive

clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Fri Mar 15, 2013 1:13 pm Post subject: SV: Re: SV: fuel flow and return line status

Hi Svein,



Thanks for your reply.  I regret that the 9lit/hr indicated figure I gave in

my last email is actually wrong - 9lit/hr is indicated with the 912ULS

running at idle and with boost pump 'on'.  I just checked the boost

pump-only flow rate (my a/c is in the garage next door for the winter), and

it reads just over 4Lit/hr with a K factor of 17030 - which I think all

tallies rather well with your comments about 'spot' flow rates vs totalised

flow rates and the 9 lit/hr figures you have found.  My K factor will be

specific to the sensor/Stratomaster setup of course, other combinations may

easily have different K factors.



Regards,

Clive.



--

Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Sat Mar 16, 2013 1:40 am Post subject: Re: SV: Re: SV: fuel flow and return line status

Try the bush mechanic's method to test the restrictor.  If you have the restrictor near the carb end of the line, try the following.... disconnect the line, blow down it with very strong pressure, you should eventually hear the bubbling from the bottom of the tank.  If you don't, the restrictor is blocked.  If it is blocked, get a piece of locking wire and unblock it.  Job done.  It worked for me.

Best

Richard

Classic 5Y-LRY, Kenya

clivesutton

Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH

Posted: Sat Mar 16, 2013 2:11 am Post subject: Re: SV: Re: SV: fuel flow and return line status

Does anyone have a view on the way around the FS02 needs to go into the return line?  



I seem to remember that it has a recess on one side of the through-hole - should this recess be facing the engine or the fuel tank side?  Can't find anything about this in my manual.  



I did wonder if its orientation has any influence on its tendency to block or not . . .



I also wondered if there is anything to prevent the restrictor from moving down the length of the hose under pressure over time?

john.heykoop(at)gmail.com
Guest

Posted: Sun Mar 17, 2013 8:51 am Post subject: SV: Re: SV: fuel flow and return line status

Hi Clive



The k factor of 17030 you are using for your single transducer setup is roughly 53 percent of the standard Flowscan k factor of 32000. 



On the strength of that I have just set the initial k factor of new my red cube transducer to 36000 (53 percent of the standard red cube k factor of 68000). I switched on the boost pump and guess what - the indicated fuel flow is 4ltrs/hr, exactly the same as yours.



Many thanks for posting this information, it will give me a head start when I get my Europa back in the air. My k factor will, of course, need further fine tuning but it is good to start off with an initial k factor that is broadly correct.



Regards



John

G-JHKP mono

(Rotax 912ULS with single red cube transducer fuel flow measurement)

On 15 Mar 2013, at 21:13, "Clives email" <clive.maf(at)googlemail.com> wrote:



[quote] 

 

 Hi Svein,

 

 Thanks for your reply.  I regret that the 9lit/hr indicated figure I gave in

 my last email is actually wrong - 9lit/hr is indicated with the 912ULS

 running at idle and with boost pump 'on'.  I just checked the boost

 pump-only flow rate (my a/c is in the garage next door for the winter), and

 it reads just over 4Lit/hr with a K factor of 17030 - which I think all

 tallies rather well with your comments about 'spot' flow rates vs totalised

 flow rates and the 9 lit/hr figures you have found.  My K factor will be

 specific to the sensor/Stratomaster setup of course, other combinations may

 easily have different K factors.

 

 Regards,

 

 

 Clive.

 

 --

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