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The Factory Fuel Sight Gauge

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carl(at)flyers.freeserve.
Guest

Posted: Sat Sep 08, 2007 5:50 am Post subject: The Factory Fuel Sight Gauge

Many builders avoided this nightmare and fitted a capaticance or other 

similar gauge.



We originally figured that fitting a fuel flow meter would be sufficient 

along with the factory sight gauge. Our reasoning was that as long as the 

rear wheel was raised such that the aircraft was level (we use a spirit 

level to check this) the sight gauge ought to be reasonably accurate - for 

refuelling purposes only.



Last weekend we fuelled the aircraft with 40 litres of fuel on top of the 15 

already in the tank (15 l is our minimum safety level - ie: 11 in the 

reserve plus 4). The sight gauge indicated 15 l beforewe refuelled and 55 l 

after which is what we expected.  The estimated flight time was just over 2 

hrs excluding arrival and departure.



As soon as we took off the sight gauge indicated the tank to be virtually 

empty which caused a degree of worry (you can never be certain there isnt a 

leak !!!). This lack of fuel continued throughout the flight and on the 

return. Before we put the plane to bed we re checked the levels and as 

expected there were 20 litres remaining (having used 35l according to the 

Fuel Flow meter). So far so good !!!



Yesterday we planned for a similar trip and started to refuell with 2x 20 

litre cans. About halfway through the second can the fller tube filled up 

and we ended with fuel everywhere. Assuming this was nothing more than an 

airlock we lifted the tailplane to shoulder height (it is a momowheel) in 

the belief that this would clear the blockage - IT DIDNT !. The tank 

appeared to be full whatever we did.



So we drained off 20 litres through the drain valve and rechecked the 

levels - guess what - 45 litres !!! The tank holds at least 75 litres (it is 

one of the originals). 75-20 should be 55 litres. So we put back all 20 

litres without any problem.



Then as soon as we took off the gauge indicated empty!



We should point out that as part of our refuelling check we first blow 

through the vent pipe (that enters at the top of the tank) to clear it and 

then we blow back the fuel down the sight gauge till air bubbles into the 

tank to clear any possible airlocks. In theory this should ensure an 

accurate reading.



The problem seems to be that the filler pipe has what is in effect a U bend 

which fills up with fuel and it seems that the breather pipe is prone to a 

similar problem - despite blowing through both to clear them.



If this theory is true then as soon as the fuel pumps start delivering fuel 

to the engine this will create a partial vacuum in the tank which would 

explain the low sight gauge reading.



Has anyone else had a similar problem or are we the only ones using the old 

style gauge. We are aware that some of the sight gauges are fitted to the 

seat backs but according to the above reasoning this problem would still 

exist.



Any suggestions ? (other than retrofitting another type of gauge). We have 

enough on our hands with mod 74 !



One thing we were considering is replacing the filler pipe with clear 

plastic fuel tube (it is available) - at least it would be easier to 

diagnose the problem.



Carl & Dot

G-LABS

EuropaXSA276(at)aol.com
Guest

Posted: Sat Sep 08, 2007 6:10 am Post subject: The Factory Fuel Sight Gauge

In a message dated 9/8/2007 8:51:27 AM Central Daylight Time, carl(at)flyers.freeserve.co.uk writes:

  	  Quote: 	
		  As soon as we took off the sight gauge indicated the tank to be virtually 

empty which caused a degree of worry (you can never be certain there isnt a 

leak !!!). This lack of fuel continued throughout the flight and on the 

return. 	
  Hi Carl

 Is the small Baffle / Restrictor inserted in the line between the sight gauge and tank? Part number FS02 

 It is there to minimize the sloshing around and help stabilize the sight gauge. 



 



  

 Brian Skelly

Europa XS TriGear #A276

North Texas USA

You can see my build photos at:

http://www.europaowners.org/BrianS



See what's new at AOL.com and Make AOL Your Homepage.

  [quote][b]

sidsel.svein(at)oslo.onli
Guest

Posted: Sat Sep 08, 2007 8:17 am Post subject: The Factory Fuel Sight Gauge

Carl,



I have experienced similar problem as you describe.  I have the sight tube

between the seat backs, and I often got the same mis-readings and sudden

drops in the air even though I first blew the vent tubes exactly as you

describe.



I suspected that fuel remained in the tube going over the fuel tank (under

the top of the cockpit module) and back up alongside the filler pipe.  Even

with my trigear, on the ground there is a slight aft-down pitch attitude, so

a "U" was formed there.  Evidently, fuel still remained there at level

cruise.



I have cured the problem by new routing of the gauge tube from the top front

of the cockpit module (where it used to go into the cockpit module).  I cut

the tube there, and instead used a copper tube going up along the front face

of the cockpit module, into the right head rest through a hole drilled in

the inner side near the fore left corner of the head rest, and continuing

always up-up-up through the outer side of the head rest near the rear right

corner and joining the original tube further up.  Joined to the original

sight tube both ends by inserting the copper tube into it and securing with

small hose clamp.  Painted copper tube where visible in colour matching the

upholstery.



Thus, I no longer have the "U" previously exisiting on top of the fuel tank,

and the gauge reads just fine.



///



Have you tried a good side slip after climb-out?  Another Europa (monowheel)

here in Norway does that to get rid of the fuel in his "U" in the gauge tube

(I tried it, but my "U" was probably too deep - or perhaps I did'nt dear to

slip hard enough!)



Best regards,

Svein

LN-SKJ (test flying completed - regular airworthiness certificate received)

carl(at)flyers.freeserve.
Guest

Posted: Sat Sep 08, 2007 9:40 am Post subject: The Factory Fuel Sight Gauge

---

carl(at)flyers.freeserve.
Guest

Posted: Sat Sep 08, 2007 9:53 am Post subject: The Factory Fuel Sight Gauge

The solution for us would seem to be in somehow re routing the pressure 

equalising tube to eliminate any U bends. At present there would seem to be 

no means of pressure equalisation within the tank itself. The sight tube and 

its return line would have little effect on this.



You seem to have cured your problem by re routing the return line of the 

sight tube but not sure if this would work for us as we dont have the sight 

tube against the seat back (as with yours).



What is most puzzling is that this is a relatively recent occurrence, having 

had 5 relatively trouble free years of flying with the present arrangement.



It is just possible that the extension tube which is fitted within the fuel 

tank (mod ???) to ensure the pressure equalisation tube is at the top of the 

tank has fallen off but it is relatively easy to check this.

---

ami(at)mcfadyean.freeserv
Guest

Posted: Sat Sep 08, 2007 11:37 am Post subject: The Factory Fuel Sight Gauge

Carl,

One possibility is that one or both of the seals on your filler cap is not 

effective.



The fuel gauge symptoms you describe are the same as leaving the fuel cap 

off altogether, whereupon the relatively low pressure in the vicinity of the 

fuel filler cap in flight immediately sucks the sight gauge to zero.



Duncan McF.

---

s.vestuti(at)virgin.net
Guest

Posted: Sat Sep 08, 2007 1:57 pm Post subject: The Factory Fuel Sight Gauge

Just Thought i would add my "short" experience with the standard 

sight gauge here, 

      i have a tri gear with a compleatly standard text book 

intallation with the tube visable in the port footwell, on the 

ground the gauge reads fine, airbourne it reads empty - it has done this 

from day one. i intend shortly to dissconnect it and fit a stop end to the tank as my fuel flow meter is accurate to within half a litre. 

could the empty reading in flight be due to acceleration as the tube runs forward B4 running verticaly?



Steve vestuti G-CEBV #573.

Visit -  www.EuropaOwners.org

carl(at)flyers.freeserve.
Guest

Posted: Sun Sep 09, 2007 6:39 am Post subject: The Factory Fuel Sight Gauge

It wouldnt matter if the seals worked or not. Early on we decided to drill a 

small hole in the filler cap - just under the locking handle (cant remember 

why). We have flown for several years with this configuration and it hasnt 

caused a discernible problem. It may as you have suggested cause an 

inaccurate reading. We have never relied on the sight gauge in flight as the 

fuel contents varies with how level the aircraft is flying.



I can understand what you mean by leaving the filler cap off which would 

create a considerable vacuum in the tank.



Thanks,



Carl



---

fklein(at)orcasonline.com
Guest

Posted: Sun Sep 09, 2007 10:40 am Post subject: The Factory Fuel Sight Gauge

On Sunday, September 9, 2007, at 07:58  AM, ALAN YERLY wrote:



 	  Quote: 	
		   Sight gauge woe's. The fix is to install the Mod 33 and use the drain 

 line as your lower sight gauge hookup point.  The static fuel at the 

 rear of the tank allows the site gauge to be quite stable in flight.  

 For those of you who put the sight gauge in the seat back like I have, 

 it works fine (tri-gear).  The longer tube lengths for those of you 

 with the sight gauge near the foot well, acceleration does cause the 

 fuel to move.  Remember to use the FSO2 to help stabilize the > readings.


	


I've been rassling w/ these issues...wanting to have a positive visual 

(reliable) for both in-flight fuel, as well as a simple visual 

reference when refueling...and now have the following set up. I'm 

installing both a modified factory sight gauge as well as one between 

the seat backs. My factory sight gauge T's off the main tank fuel drain 

with an FS 02 inserted, but where the line goes vertical at the 

footwell, I'm opting to use 90 degree barbed fittings top and bottom so 

that I can contain a small redux/micro sphere float (painted w/ bright 

yellow butyrate dope); sphere will be contained within the vertical w/ 

a bit of SS wool (at) the barbs. I can live with the extra clamps for the 

fittings. Vent line will continue to starboard (rather than port) and 

rearward just below the door sill before rising alongside the filler 

neck and venting below the flap as Bud described.



For the gauge between the seats, which also T's off the main tank drain 

line, I'm using a piece of rigid pipe (ACS P/N 03-54100); it will also 

have a redux/micro float. As I'm uncomfortable venting it between the 

underside of the top of the CM and the tank, I've made a T-shaped 

splash molding over foam which extends down to the tunnel; the 

"crossing" of the T provides a lip which dies into the head rests and 

provides a void in which the vent will reside before it penetrates the 

starboard head rest and eventually Ts into the other sight gauge vent 

line...this may sound complex, but it's really quite simple. Since my 

reason for the seat back gauge is solely as a visual reference when 

refueling, I want to be sure that it registers fuel level in the tank 

as fuel is poured in. I have some concerns that if an FS 02 restrictor 

is used, the fuel level in the sight gauge will lag behind the actual 

level in the tank, rendering its utility suspect, if the point of 

having it is to avoid spillage. Consequently, my thinking is to NOT use 

an FS 02 in this line, recognizing that stable readings in flight may 

result and if so would not affect the

footwell sight gauge at all.



I must confess to being a believer in redundancy for critical systems, 

as I have also installed the factory electric float gauge.



All just grist for the mill,



Fred

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paul.mcallister

Joined: 09 Jan 2006
Posts: 177
Location: Waukesha, WI USA

Posted: Sun Sep 09, 2007 3:22 pm Post subject: The Factory Fuel Sight Gauge

Hi all,



Over the years I have been subscribing to the forum one of the topics that

comes up pretty regularly is the subject of sight tubes.



On all of my reading it seemed like they we troublesome systems so I

ultimately left mine off and constructed the system designed by Tony K. This

system has a 0 ~ 1" pressure transducer in the lowest point in the fuel

system and measures the weight of fuel in the tank.  By using your laptop it

is possible to calibrate the 10 segment LED bar display to show 1.8 gallons

per segment, thus having a perfectly linear display, despite the shape of

the tank.  The advantage of this system is that no tank penetration is

required, and unlike capacitance gauges is reads correctly for Mogas or

100LL, and best of all its linear.



Mine has been in service for 3.5 years now and so far has been trouble free.

The downside of this is that Tony does not have a printed circuit board

layout available, so you need to have some ability to construct electronic

circuits on a patch board.



See http://www.kaon.co.nz/europa/fuelgaugev3.pdf



Paul

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