SonexBuilders.net

Has anybody come up with a good working fuel level sight tube, or whatever, that will show the correct remaining fuel quantity from full and down to nothing?

When old #0525 was still young and beautiful, it rapidily became clear that the sight tube on the panel as specified in the drawings could be improved on. Consequently a Princeton sender was installed in the fuel tank and hooked up to a MGL Infinity fuel level instrument. Avgas 100LL was the only type of fuel used- those were the days!

Presently the 100LL is more or less gone, and Mogas is more often than not the only alternative. But the Princeton does not like Mogas at all- to the extent, in fact, that MGL presently discourages the use of capacitance fuel level senders in their latest installation manuals. The level readings are subject to large variations, depending on the actual fuel used. My experience is such that I can offer no arguments!

So what now? Ideas, please- practical solutions!

Thanks
Kai

I am going with a backlit, marked tank and a cheap backup camera. Jeff has a YouTube video showing his setup.

https://youtu.be/pnXE_hSvlJI

I like the sight tube with graduated marks for level flight (blue) and on the ground (red); I have a tail dragger. When the sight tube disappears into the bottom of the panel I have 5 gallons left (in flight). When my fuel gets there my rule is to be on the ground soon, or within the half hour at the latest, to make sure I still have a reserve. I guess I don't feel the need to know when I'm at 2 gallons or less. If I get that low then I'm getting close to being a fuel exhaustion statistic.

http://www.mykitlog.com/users/display_l ... 2339&row=1

Interesting comment about mogas. It's nearly impossible to find at an airport around me. In fact I can't think of even one. It's 100LL or nothing.

Mike,

Sorry- this is Europe! The environment friendly idiots that because of it's slight lead content have banned a product that constitutes 0,2% of total fuel consumption. Boy- are we healthy now!

Apart from that- where do you buy clear tubing that can handle all the different fuels that are now foisted upon us?

Thanks
Kai

Apart from that- where do you buy clear tubing that can handle all the different fuels that are now foisted upon us?

Aircraft Spruce sell a range of clear tubing https://www.aircraftspruce.com/menus/ap/fuel_line.html including one that is supposed to be alcohol resistant. I have used the blue polyurethane tubing with avgas and it appears to have a long life. The sight tube as shown in the Sonex plans is not much use. I extended mine further down than shown in the plans but it is not easy to read quickly and unless it shows quantity for the whole tank I think it's a waste of time. If you fitted a central extension to the instrument panel, enough to show the whole fuel range in a position that is easy to read it would be a useful fuel gauge. I have a centre control stick so that option is not viable. It also needs a flow restricting orifice in the lower fuel tank fitting to get reasonably steady readings.

I only use avgas and the Princeton sender works well but had lots of trouble with fuel leaks when I first fitted it, I think due to the load of fuel sloshing against the probe. I was able to fix it but probably it would have been better fixed with an Oops fitting.

Peter

I've used that blue fuel line from aircraft spruce in my older plane a few times. Works great with avgas but even after 1 x tank of premium unleaded it starts to discolour quickly. I've yet to find a good clear fuel line but I'm sure one is out there somewhere.

These are the "good stuff": https://www.aircraftspruce.com/pages/ap ... seline.php https://www.aircraftspruce.com/pages/ap ... seline.php

I could never get my electronic fuel gauge calibrated consistently so I eventually did away with it and only used the sight tube. Installing the sight tube as shown in the plans means you can't see the bottom half of its range. Instead I just ran the tube all the way down the front of the panel and then back to the tank. I marked the sight tube at 1 gal intervals for the first 5 gal and 5 gal intervals for the rest of it. I could see the fuel level down to the last couple of gallons, but like Mike above, when it got to 5 gals I was feeling the need to land. I installed a restrictor in the line to reduce sloshing in the sight tube. If you have trouble seeing exactly where the fuel is in the sight tube you can add a "barber pole" behind it.

Guys,

Thanks for the help- I was not aware of this Seline brand.

I realize the original design makes it impossible to read the last 5 gallon contents, but what if it does not go back to tank at the bottom of the panel, but a little lower through the fuselage side upright? The much prized orifice could be positioned here as well.

A 'barbers pole' behind the tube would undoubtedly do the trick, but what happened to the little ball we had in the J3 Cub sight glasses? Someone told me it was actually a pea- in that case it would probably dissolve in the ethanol?

Thanks
Kai

Kai wrote:Mike,

Sorry- this is Europe!

I see, said the blind man...

Now I get it :-)

radfordc wrote:I installed a restrictor in the line to reduce sloshing in the sight tube. If you have trouble seeing exactly where the fuel is in the sight tube you can add a "barber pole" behind it.

Me, too (to both of those).