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Rotax 914 Airbox / Fuel Pressure Differential

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flyingphil2

Joined: 04 Dec 2009
Posts: 117

Posted: Fri May 27, 2016 5:32 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

This is a question for those who have a 914 up at the front.



With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.  I'm looking for a simple and 'tried and tested' way of doing this.  Can anyone recommend a setup for this?  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential.



Any input or advice of what other people have done would be welcome.

rlborger(at)mac.com
Guest

Posted: Fri May 27, 2016 6:41 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

Phil,

I installed the UMA differential pressure gage:



http://www.aircraftspruce.com/pages/in/fuelinstrumentation_uma/fuelairboxdiff10-05562-3.php



A bit pricey but it works fine for me.



Blue skies & tailwinds,Bob BorgerEuropa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP3705 Lynchburg Dr.Corinth, TX  76208-5331Cel: 817-992-1117rlborger(at)mac.com (rlborger(at)mac.com)



 	  Quote: 	
		  On May 27, 2016, at 8:32 AM, flyingphil2 <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)> wrote:

--> Europa-List message posted by: "flyingphil2" <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)>This is a question for those who have a 914 up at the front.With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.  I'm looking for a simple and 'tried and tested' way of doing this.  Can anyone recommend a setup for this?  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential.Any input or advice of what other people have done would be welcome.

rehn(at)rockisland.com
Guest

Posted: Fri May 27, 2016 7:45 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

I have the UMA as well , easy to install, one gauge, been in for many years trouble free. 

Jerry



Sent from my iPad



On May 27, 2016, at 7:40 AM, Robert Borger <rlborger(at)mac.com (rlborger(at)mac.com)> wrote:

 	  Quote: 	
		  Phil,

I installed the UMA differential pressure gage:



http://www.aircraftspruce.com/pages/in/fuelinstrumentation_uma/fuelairboxdiff10-05562-3.php



A bit pricey but it works fine for me.



Blue skies & tailwinds,Bob BorgerEuropa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP3705 Lynchburg Dr.Corinth, TX  76208-5331Cel: 817-992-1117rlborger(at)mac.com (rlborger(at)mac.com)



 	  Quote: 	
		  On May 27, 2016, at 8:32 AM, flyingphil2 <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)> wrote:

--> Europa-List message posted by: "flyingphil2" <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)>This is a question for those who have a 914 up at the front.With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.  I'm looking for a simple and 'tried and tested' way of doing this.  Can anyone recommend a setup for this?  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential.Any input or advice of what other people have done would be welcome.

davidjoyce(at)doctors.org
Guest

Posted: Fri May 27, 2016 10:37 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

Phil, I am all for minimising the time you spend eyes down, (having experienced 5 mid air near misses with 3 probably fatal had I not been looking out!). From this point of view, I would doubt the value of a fuel pressure guage, as opposed to a low fuel pressure warning light, which shines a bright red light at you if pressure falls below a set level. To this end I sourced an on/off fuel pressure switch set to light up if pressure fell below 3 psi (as I remember it - but it should be easy enough to find a pressure well below normal running pressure and above what will stop you flying). This worked well for me in running my main tank dry. I found it came on in plenty of time for me to switch to reserve before the engine coughed. It would also, I guess, work well if you had a partially clogged filter and needed to switch on pump 2 and reduce power to limp home, as happened to the company demontrator in early days.  I cannot think of any very good reasons to need a fuel pressure gauge apart from these instances. 

Regards, David Joyce, GXSDJ 

   

 

On 2016-05-27 14:32, flyingphil2 wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "flyingphil2" <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)>



This is a question for those who have a 914 up at the front.



With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.  I'm looking for a simple and 'tried and tested' way of doing this.  Can anyone recommend a setup for this?  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential.



Any input or advice of what other people have done would be welcome.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=456603#456603



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brian.davies(at)clara.co.
Guest

Posted: Fri May 27, 2016 11:08 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

I donâ€™t often disagree with you David but I think a fuel pressure gauge is a very useful indicator of impending problems, including filter blockage and fuel vaporisation.Â  When the red light comes on it is all too late. 

 

Regards

 

Brian

 

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of davidjoyce(at)doctors.org.uk

Sent: 27 May 2016 19:36

To: europa-list(at)matronics.com

Subject: Re: Rotax 914 Airbox / Fuel Pressure Differential

 

Phil, I am all for minimising the time you spend eyes down, (having experienced 5 mid air near misses with 3 probably fatal had I not been looking out!). >From this point of view, I would doubt the value of a fuel pressure guage, as opposed to a low fuel pressure warning light, which shines a bright red light at you if pressure falls below a set level. To this end I sourced an on/off fuel pressure switch set to light up if pressure fell below 3 psi (as I remember it - but it should be easy enough to find a pressure well below normal running pressure and above what will stop you flying). This worked well for me in running my main tank dry. I found it came on in plenty of time for me to switch to reserve before the engine coughed. It would also, I guess, work well if you had a partially clogged filter and needed to switch on pump 2 and reduce power to limp home, as happened to the company demontrator in early days.  I cannot think of any very good reasons to need a fuel pressure gauge apart from these instances.

Regards, David Joyce, GXSDJ

 

 



On 2016-05-27 14:32, flyingphil2 wrote: 	  Quote: 	
		   	  Quote: 	
		  --> Europa-List message posted by: "flyingphil2" <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)> This is a question for those who have a 914 up at the front. With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.Â  I'm looking for a simple and 'tried and tested' way of doing this.Â  Can anyone recommend a setup for this?Â  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential. Any input or advice of what other people have done would be welcome.    	
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davidjoyce(at)doctors.org
Guest

Posted: Fri May 27, 2016 12:02 pm Post subject: Rotax 914 Airbox / Fuel Pressure Differential

Brian, I bow (to the point of grovelling in fact!) to your infinitely superior engineering knowledge, but have you in fact found a use for it practically? A theoretical value is all very well but I have found no practical value in 14 yrs flying a 914, other than the instances I cite, and I am entirely persuaded of the value of looking out the front, to avoid the other b*****rs coming straight at you whilst carefully working their way along their rows of dials, trying to remember what they should be saying or said last time they looked! One person's experience does  not a thesis make, but three occasions where a head on collision was only averted by me turning abruptly whilst the other party cruised straight on with no sign of having seen me, certainly persuades me of the value of designing one's panel to be able to spend as much time looking out as one would devote to it travelling down a busy motorway, where at least the likely collision candidates are going in the same direction! Looking at a gauge for impending problems , implies a lot of eyes down attention 

Regards, David 

   

 

On 2016-05-27 20:07, Brian Davies wrote:  	  Quote: 	
		    

I don't often disagree with you David but I think a fuel pressure gauge is a very useful indicator of impending problems, including filter blockage and fuel vaporisation.  When the red light comes on it is all too late.  

  

Regards 

  

Brian 

    

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of davidjoyce(at)doctors.org.ukSent: 27 May 2016 19:36To: europa-list(at)matronics.comSubject: Re: Rotax 914 Airbox / Fuel Pressure Differential 

 

 

  

Phil, I am all for minimising the time you spend eyes down, (having experienced 5 mid air near misses with 3 probably fatal had I not been looking out!). >From this point of view, I would doubt the value of a fuel pressure guage, as opposed to a low fuel pressure warning light, which shines a bright red light at you if pressure falls below a set level. To this end I sourced an on/off fuel pressure switch set to light up if pressure fell below 3 psi (as I remember it - but it should be easy enough to find a pressure well below normal running pressure and above what will stop you flying). This worked well for me in running my main tank dry. I found it came on in plenty of time for me to switch to reserve before the engine coughed. It would also, I guess, work well if you had a partially clogged filter and needed to switch on pump 2 and reduce power to limp home, as happened to the company demontrator in early days.  I cannot think of any very good reasons to need a fuel pressure gauge apart from these instances. 

Regards, David Joyce, GXSDJ 

   

  

 

On 2016-05-27 14:32, flyingphil2 wrote:  	  Quote: 	
		    	  Quote: 	
		  --> Europa-List message posted by: "flyingphil2" <flyingphil627-europastuff(at)yahoo.co.uk (flyingphil627-europastuff(at)yahoo.co.uk)> This is a question for those who have a 914 up at the front. With the 914uls the best way to monitor fuel pressure is to monitor the fuel / airbox differential pressure.  I'm looking for a simple and 'tried and tested' way of doing this.  Can anyone recommend a setup for this?  I see there are a variety of dual gauges available and also gauges that do the calculation for you (via sensors) and just have a single needle showing the differential. Any input or advice of what other people have done would be welcome.    	
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flyingphil2

Joined: 04 Dec 2009
Posts: 117

Posted: Tue May 31, 2016 5:25 am Post subject: Re: Rotax 914 Airbox / Fuel Pressure Differential

Thanks for all the replies and I think the UMA differential gauge seems to be the way to go.

That's a nice little task to work out how to fit that in with my current set up.



David, I take your point as well, especially as I also had an incident where I had to turn abruptly to avoid a midair.  That was in a glider so no fuel pressure gauge involved.

h&jeuropa

Joined: 07 Nov 2006
Posts: 645

Posted: Wed Jun 01, 2016 2:48 am Post subject: Re: Rotax 914 Airbox / Fuel Pressure Differential

Phil,



We also use the UMA sensor as an input to our GRT EIS and EFIS.  This way we have a red light warning, a fuel pressure warning displayed on the EFIS and the actual fuel pressure displayed on the EIS.  We also have the data available for download for analysis after landing.  Sort of the best of all worlds!



Jim & Heather

jan_de_jong(at)casema.nl
Guest

Posted: Thu Jun 09, 2016 8:40 am Post subject: Rotax 914 Airbox / Fuel Pressure Differential

I don't believe the differential pressure measurement carburetors vs. 

airbox will give much of an early warning.

By the time the pressure regulator is unable to maintain the small 

differential pressure the total (forward) flow, in the best case, is 

already down by more than half (total flow is normally at least twice 

the 33 l/h maximum carburetor flow, and many more times the actual 

carburetor flow in most conditions, f.i. in cruise at lower altitudes 

when fuel consumption is low and turbo pressure is low).

I see the differential pressure measurement as a check on the correct 

operation of the combination: pressure regulator + return line.



To get a really early warning of deterioration one would have to 

constantly measure the performance of all between tank and pressure 

regulator input; the 2 ingredients are: total flow and total pressure 

difference between regulator input and tank. A microcontroller would 

need to learn the reference curve (total flow vs. total pressure 

difference) when an installation is in "reference condition". A display 

would show actual total flow as a % of reference total flow at actual 

total pressure demanded (determined by actual turbo operation).



Jos once mentioned that he checked total forward flow (by defeating 

return flow pulses - or only their inclusion in the flow calculation - 

don't remember) as part of his before-takeoff checklist. This seems to 

me a good way to notice at least slow deterioration early (but higher 

altitudes would sometimes provide an excuse for a somewhat lower total 

forward flow than expected).



But I need to get on with building instead of daydreaming.



Jan de Jong

pestar

Joined: 11 Apr 2007
Posts: 61
Location: Auckland, New Zealand

Posted: Fri Jun 10, 2016 1:50 pm Post subject: Re: Rotax 914 Airbox / Fuel Pressure Differential

Real world experience.  I have the UMA differential fuel pressure sender which feeds into my MGL EFIS.  Recently after just taking off 500AGL I watched my fuel pressure disappear to zero, then the motor started missing and ultimately stopped.  I made a forced landing into a field which had many rabbit holes, one of which damaged my front leg.



What benefit did I get from having it - I had 16 seconds of time available to me after noticing the sagging fuel pressure, I swopped fuel tanks (didn't work), was able to get a MAYDAY call out and then flew the aircraft to the ground.  By having the gauge I knew straight away it was fuel problem and tried to plan in the time I had available to me which was not a lot.



Why did this incident happen - it was MY fault.  My 914 on a hot day is difficult to restart, I was on a AOPA fly around and flying into a number of sheep station strips that day.  To restart my 914 I turn both the primary and secondary fuel pumps off and turn the engine over, when it catches I turn the secondary pump switch on to maintain fuel flow.  My primary pump is always on and is turned on/off by an electronic ECB (button pushes on the EFIS) so it is a procedure to turn it on, I had done this in the many take-offs earlier in the day but this time rushing to line the aircraft with lots of others I did not.  SO when turning my secondary pump off after take-off (my SOP's state turn off secondary at 500'AGL -wrong) the fuel pressure indicator did what it did all very correctly.



To prevent this from happening again I have altered my checklist to include the primary pump, have a bright green (on) primary fuel pump indicator on the MGL EFIS and red when it is off and never ever turn my seconday off until 1000'AGL



So from a real world experience I am glad to have a fuel pressure gauge on my 914. 



I now also know how my wife reacts because she was with me.  Did not say or growl a word and jumped straight back into a Cessna 180 which took us back to our accommodation for the night after all this drama, I was impressed.



Cheers Peter

_________________
Peter Armstrong
Auckland, New Zealand
DynAero MCR-4S (Do not shoot me Smile

gilles.thesee(at)free.fr
Guest

Posted: Sun Jun 12, 2016 11:39 pm Post subject: Rotax 914 Airbox / Fuel Pressure Differential

Le 10/06/2016 à           23:50, pestar a écrit :

         

      	  Quote: 	
		          	  Quote: 	
		  --> Europa-List message posted by: "pestar" <peter(at)reivernet.com> (peter(at)reivernet.com)

  Recently after just taking off 500AGL I watched my fuel pressure disappear to zero, then the motor started missing and ultimately stopped.  I made a forced landing into a field which had many rabbit holes, one of which damaged my front leg. 	
     	
     

     Hi Peter,

     

     Just heard about your mishap during a seminar in Paris two days ago.     Nicolas attended too.

     Sorry about the damage to the airplane, and congratulations for     getting away unharmed.

      	  Quote: 	
		          	  Quote: 	
		  



  My primary pump is always on and is turned on/off by an electronic ECB (button pushes on the EFIS) so it is a procedure to turn it on, 	
     	
     

     This is a surprise to me. I believed your setup was identical to     ours with the main engine pump being turned on any time the ignition     switch is on ?

     

      

     -- 

       Best regards,

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

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