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fallowdeer

Low fuel warning light

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Thanks for the reply. I will see what I can find was thinking of an old motorcycle carby float and cutting it down.

 

 

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That would probably work.

 

I recall my original bing carby on the jab had the foam type float. Later ones have a hollow plastic type.

 

But it was coated with a layer of some sort of paint or something that presumably kept the fuel out of the air cells.

 

you'd probably want to coat it with something - maybe epoxy or epoxy paint. My original floating balls were not sealed and they lasted about a month or so and they absorbed the petrol and just sank.

 

I found the uncoloured ones worked well but were virtually invisible in the fuel. I found fluoro yellow was equally invisible in AvGas.

 

I run exclusivley on AvGas which is 100Low Lead formulation its coloured blue-green.

 

I would guess what colour works best will depend on the colour of whatever fuel you use.

 

I tried different fluoro paints but they had all sorts of effects on the epoxy. Making it not cure etc.

 

I would guess if you sand down some carby float foam to little balls and then paint it then seal with epoxy they would probably work.

 

I don't know why I didn't try foam myself instead of having to make the Q Cell balls. Target fixation I guess.047_freaked.gif.8ed0ad517b0740d5ec95a319c864c7e3.gif

 

 

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Thanks for the reply. I will see what I can find was thinking of an old motorcycle carby float and cutting it down.

Don't use a modern Rotax float! Apparently they sink, I have to change mine before I can start my new engine.

 

 

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Wish I'd read this thread three years ago. I wasted mobs of time trying to find some brightly coloured plastic that floats in petrol. I never thought of cutting up an old plastic float. Eventually I ordered three red float bubbles from an American firm (sorry, name long lost). They were about 10mm long by about 4mm and fitted neatly inside my sight tubes. Why three? I tested one to destruction, which wasn't hard- they're hollow and flimsy.

 

One is working well, even though the sight tube is at about 30 degrees off horizontal. The other gave up and sank.

 

I'd never thought of making my own with filler, but it's a great idea. Vinyl Ester is probably the best resin to use. It copes with most fuels better than epoxy.

 

 

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If you want to see the level in a plastic tube you could try having diagonal yellow and black lines painted in the background behind the tube. 25mm thick lines at 45 degrees would work. Where the fuel level is shows up as a change in the slope of the lines.

 

I don't know the theory, but it does work.

 

 

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Hi Phil

 

I fitted the clear 'Pulse fuel line' 1/4" ID and have no trouble seeing the fuel level. Its listed in the Aircraft Spruce cataloge. Have a look at mine any time. Even if i'm not there have a look. Cheers Mike

 

395051775_CopyofP1100422.JPG.5853f4d95aacaa05b4dda12fae9e4867.JPG

 

Hi jaba-who,I have a sav and I was thinking of putting some floating balls in my fuel level sight tubes for easier fuel level sighting but could not find any to use. Do you know where I can get some from please?

 

Phil

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Appreciate this is an old thread but....

 

Was flying over the mountains at 7500 ft when the fuel warning light came on...

 

I have four individual tank feeds and was running on the right inner with about 15 liters remaining.  I had been level for about 3 minutes.  Power around 5200 for the last 15 minutes.

 

Vent pipe goes from top of 6 liter header to left inner tank.  Tank vents are hockey sticks in caps with thick non original cap seals. Vents regularly blown through.

 

Selected left inner along with the right and fuel light went out.

 

I regularly run on right inner only without issue.  With left and right inners selected left tends to drain first.  

 

Have since test run 15 minutes at 5200 at 2000 feet without issue so must assume altitude had something to do with it.

 

Left inner had 25 liters so the vent pipe was well above the fuel level. All tank feeds checked as part of build all gave adequate flow.

 

My physics is not up to an explanation....

 

Savannah S, 15 months 230 hours..

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Most likely it could be the altitude but what you think you have left in the tank in real terms of fuel amount at the pickup maynot be so. Savannahs tend to fly level in a nose down attitude. check the underside of your wing when flying level (no loss of altitude) and look at the position of the underside to the horizon. I bet it will be nose down. With that attitude your 15 litres is now running very close to the tank pickup feed. The pickups are not at the very bottom of the tank. If you had shifted the nose up to have the wing tip level then most likely the light would have gone out

 

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Thanks Kyle -  That would mean each tank would have around 15 litres of unusable fuel.  ( 4 x 15 = 60) Descent with less than 15 litres would require frequent leveling off.  Based on the trials I have conducted I don't believe that is the case.  I became reasonably familiar with the fuel system during the build and have not experienced the fuel light coming on, when not expected, at other times.  It is actually quite a useful way of ensuring I use most of the fuel in a tank.

 

I was just wondering how the reduction in pressure a bit higher up might cause the issue..

Thanks again. 

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The higher you are the more chance of a vapor lock and the liquid is lighter than water and even lighter at altitude 

I have much better than std sight gauges and when the aircraft was on the ground I measured quantity in the tanks and marked the gauges accurately. The tanks when you install them are usually never actually flat with the bottom of the wing they are slightly kicked up at the back so you will never get any where near all the fuel out of them. I have had the fuel light come on many times on a slow decent yet I was sure I had plenty of fuel but realistically you have about 10 litres that are not useable on level flight to decending flight..well that you can count on. Its very manageable though just slow up and raise the nose and the sump will fill back up again. Well thats what happens in mine anyway. You can always measure that amount thats there of course with the 4 taps. As soon as the light comes on in level flight turn that tank off and then use your others. When you get back turn all the taps off then drain the sump. Then turn on that tank and drain the fuel out and measure it with the aircraft sitting on its tail to make sure. I think full tanks are 35 or 36 litres to the top. Its the only real way to be sure what you actually are carrying on board but is it actually useable. I havent actually measured what was left as I always take well more fuel than I need anyway. But it is a bit of a trap in the savannahs

 

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