Matronics Email Lists :: View topic - Fuel Pressure Indication

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 Pressure Indication

Matronics Email Lists Forum Index -> Europa-List

View previous topic :: View next topic

Author Message

hansjd(at)online.no
Guest

Posted: Sun Oct 17, 2010 9:13 am Post subject: Fuel Pressure Indication

During my studying in order to rectify my too high  fuel pressure indication (which for my 914 installation most probably is caused  by a restriction - one way or another - in the fuel return line), I'm astonished  to (re)learn that there is no requirement from Rotax to install a fuel pressure  instrument. 

  

 The Installations Manual states: "There is no  standard connection provided to measure the fuel pressure. For general  observation and at engine troubles fuel pressure readings would be helpful". The  text further describes how to go about fitting of an extra banjo bolt  etc.

  

 In other words: It's entirely up to the builder -  or to follow local country requirements - to install such an  indicator.

  

 Nevertheless: The Rotax Operations Manual issue a  warning (page 2-4) which says: "Exceeding the max admissible fuel pressure will  override the float valve of the carburetor and to engine failure".

  

 I would say that a check of the pressure would be  damned "helpful" in this respect! Or, how would I know at all of any ill  funktion before the donkey elects to stop over the biggest lake in  Norway???

  

 Now, can someone explain to me why the Rotax  factory has such an indifferent approach to this issue in the Installations  Manual, while the Operations Manual "paints the devil on the wall" in pointing  out the dangers. And, there is no follow up whatsoever in procedures or check  lists for high fuel pressure, as with other abnormalities. In other words: Rotax  issue a Warning based on an abnormality you wouldn't stand a chance to know - if  you didn't find it "helpful" to install the indicator system!

  

 This can't be right!

  

 Hans 

 LN-HJD, #334

  

   [quote][b]

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

rlborger(at)mac.com
Guest

Posted: Sun Oct 17, 2010 12:27 pm Post subject: Fuel Pressure Indication

Hans,



Tried to find the documentation from Rotax requiring the installation and use of the "Fuel/AirBox Differential Pressure Gauge" but can't find it right now.

In any case, Rotax now requires that a gauge and sensor system be installed to monitor the differential between fuel pressure and airbox pressure to ensure there is always sufficient fuel pressure to overcome airbox pressure in the carbs preventing fuel starvation issues.  It also allows detection of excess fuel pressure which can cause the problems you already described.

UMA makes the system.  I know that it is available from Aircraft Spruce:

http://www.aircraftspruce.com/catalog/inpages/umafuelairbox.php

And is probably available from other vendors as well.

Good luck in solving your fuel pressure problems.  As you previously stated, there is probably some restriction in your fuel return.

Check six,

 Bob Borger

Europa Kit #A221 N914XL, XS Tri-Gear, Intercooled 914, Airmaster C/S Prop

http://www.europaowners.org/forums/gallery2.php?g2_itemId=60232

http://www.biplaneforumgallery.com/index.php?cat=10046

Europa Flying!

3705 Lynchburg Dr.

Corinth, TX  76208

Home:  940-497-2123

Cel:  817-992-1117



 

 

On Oct 17, 2010, at 12:10, Hans J. Danielsen wrote:

 	  Quote: 	
		  During my studying in order to rectify my too high fuel pressure indication (which for my 914 installation most probably is caused by a restriction - one way or another - in the fuel return line), I'm astonished to (re)learn that there is no requirement from Rotax to install a fuel pressure instrument.

 

The Installations Manual states: "There is no standard connection provided to measure the fuel pressure. For general observation and at engine troubles fuel pressure readings would be helpful". The text further describes how to go about fitting of an extra banjo bolt etc.

 

In other words: It's entirely up to the builder - or to follow local country requirements - to install such an indicator.

 

Nevertheless: The Rotax Operations Manual issue a warning (page 2-4) which says: "Exceeding the max admissible fuel pressure will override the float valve of the carburetor and to engine failure".

 

I would say that a check of the pressure would be damned "helpful" in this respect! Or, how would I know at all of any ill funktion before the donkey elects to stop over the biggest lake in Norway???

 

Now, can someone explain to me why the Rotax factory has such an indifferent approach to this issue in the Installations Manual, while the Operations Manual "paints the devil on the wall" in pointing out the dangers. And, there is no follow up whatsoever in procedures or check lists for high fuel pressure, as with other abnormalities. In other words: Rotax issue a Warning based on an abnormality you wouldn't stand a chance to know - if you didn't find it "helpful" to install the indicator system!

 

This can't be right!

 

Hans

LN-HJD, #334

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

budyerly(at)msn.com
Guest

Posted: Sun Oct 17, 2010 12:41 pm Post subject: Fuel Pressure Indication

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Hans,

 You are right that they do not have a requirement, spelled  out, but it is implied.  Rotax does have parts for it  and information is in the new Rotax installation manual.  Copy  attached (check currency), page 69.

 I follow their instruction requirements very closely.   Part numbers are in the parts catalogue.  

  

 UMA does make a pressure differential gauge to measure airbox  vs. fuel pressure.  I can do the math so I just use the raw fuel pressure  and manifold pressure.

  

 Explanation: My normal fuel pressure is 4-5psi.   When I go to boost I glance at it to see if the pressure rose IAW the  boost.  

 We know that 29.92 in HG is 14.7 psi so 2 inches of Hg is  about 1 psi.  ISH OK.

 Example:  On takeoff,  at a boost pressure of  40 inches, that is 10 inches over atmosphere (that's 5 psi ish) so the fuel  pressure must be above 2.3 ish min plus 5 psi  or a min of 7.3 to keep  the fuel going to the carbs to prevent fuel starvation as the operations and  installation manuals state..

 If I cruise at a fuel pressure of 5 psi at 30 inches MP at low  altitude, that is OK, if I climb at 34 inches I'm looking for 6 ish and on  takeoff, 8.

 I don't cruise at high altitude normally, but as you climb,  the outside pressure decreases and that lowers the fuel pump inlet head a bit,  so as you climb your MP or outside pressure is around 17 inches HG at  15,000 MSL.  (Remember, you loose 1 in HG per 1000 or so.)  That means  outside air pressure is 8-9 psi or so in round numbers below sea level pressure  of 29.92 inches or 14.7 PSI.  If you push the MP above 30 inches then, the  engine may start to see some fuel starvation, so turn on the other pump when  going above 10,000 and you can run max continuous power up to 15000 or  so.  Above 15,000 I haven't gone, but I imagine that one has to pay  attention.  Let's see.  MP gauge reads 34 inches at 15,000 feet, minus  17 is 17 inches HG and that is about 8 psi, so 2.3 plus 8 is 10.3 at the fuel  pressure meter...  That needs both pumps to do, and it does it well.   

  

 So install a good MP gauge and a descent fuel pressure gauge  or buy one of the UMA differential gauges and press on.   I prefer to  know my raw pressure.  It is a preference for troubleshooting.  When  my math skills go, I'll buy the other gauge I guess.

  

 Hope this wasn't too confusing.  Check my math, I am  getting older.

  

 Bud Yerly

 Custom Flight Creations, Inc.

 [quote]   ---

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

914_Installationmanual_d03186.pdf

Description:

Download

Filename:

914_Installationmanual_d03186.pdf

Filesize:

2.79 MB

Downloaded:

4821 Time(s)

hansjd(at)online.no
Guest

Posted: Tue Oct 19, 2010 2:53 am Post subject: Fuel Pressure Indication

Thanks to those who supplied me with informations on this  subject. To Bud: I'm aware of the additional parts spelled out in the  Installations manual, I also have installed a fuel pressure instrument -  otherwise i wouldn't have detected my problem (too high fuel  pressure)!

  

 My issue was the lack of coherence between the  installations and operations manuals. (To give the builder  an advice of an  indicator system which "is nice to have" in one, while the other spells out  danger if you experience a condition you would know nothing about - if you did  not follow the advice).

  

 Now - this is not the airlines  (my background), but  I'm pretty sure they would detect and correct such a mismatch immediately.  

  

 This is definitely a safety related issue and should be  adressed by Rotax the sooner the better (to ammend the istallations manual to  REQUIRE a fuel pressure indications system). 

  

 As to my problem: I sorted it yesterday. It was of course  a pinched hose in there, and it was quite a feat to repair it! Now everything is  nice and green again.

  

 Cheers,

 Hans, LN-HJD, #334

  

  

  

  

  

 [quote] [b]

- The Matronics Europa-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Europa-List

Display posts from previous:

	Matronics Email Lists Forum Index -> Europa-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