Wing Tanks

Use this forum to discuss technical points relating to the Nipper and its ancilliaries.
Ross
Posts: 11

Wing Tanks

Postby Ross » Wed Aug 26, 2020 2:02 am

My Nipper has wing tanks which spill a lot of fuel out of the wire and cork fuel level gauge/breather ports. The fuel system operates on both wing tanks together or the main tank. If the plane is parked off level, fuel runs from one tip tank and overflows out the other. When its flying fuel gushes out of the breather. Has anyone else had this trouble and what ingenious fix did you come up with? also one tip tank empties way before the other, and yes I flew with the little black ball in the middle ha.

I'm thinking of getting rid of the crude wire fuel level gauges and fitting 'one way' check valves on the breathers (where the wire gauge used to come out of) this enables air to get into the tank but no fuel can escape out. Then I'll fit another electric pump and re-plumb the tip tank lines into the top of the main tank. That way I can use up all the fuel in the tip tanks and it wont matter if it sucks a bit of air as it is only topping up the main tank.
P.S. I could extend the breather tubes instead of check valves then it allows for expansion..
Any thoughts?
Happy flying regards Ross

Paul1954
Posts: 15
Location: Norfolk

Re: Wing Tanks

Postby Paul1954 » Thu Aug 27, 2020 7:25 am

Ross, what is condition of the cork floats? Have they been well dried and then re sealed?

If you have the later brass floats you should also check that they are still airtight and float in fluid.

Ross
Posts: 11

Re: Wing Tanks

Postby Ross » Mon Sep 07, 2020 2:49 am

Hi Paul, Thanks for the reply,
The problem seems to be the gap between the fuel level indicator wire and the small tube it slides up and down in, that's where the fuel sprays out from.
The floats seem okay.

Paul1954
Posts: 15
Location: Norfolk

Re: Wing Tanks

Postby Paul1954 » Mon Sep 07, 2020 9:59 am

Hi Ross,

I no longer have my Nipper tip tank drawing - I gave it to PG when I left Inverness in 2007.

Perhaps there needs to be a discussion as to a/c attitude when fuelling and post refuel. Is it possible the tanks are being overfilled and/or when the a/c tail goes down the fuel is then leaking from the vent/gauge tube?

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G-NIPR
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Re: Wing Tanks

Postby G-NIPR » Fri Sep 11, 2020 9:43 pm

Hello both,
A bit late to the party, but I am here now!
My experiences with tip tanks have been almost the same. This is how I sorted it...
Firstly the floats don’t work as expected. I tried and tried and couldn’t achieve reliability with them. Often they would ‘hang up’ and not drop as the fuel level dropped. The ram air from ninety odd knots of forward speed would push the float stems back and hold them against the outer tube stopping them from dropping.
I also suffered venting from the orifice as I flew. Purely Bernoulli in action I’m afraid. The very force that is keeping us aloft, is sucking out your fuel.
Solution: Do away with them, pop a plastic cap on top to stop venting, and work on known burn and time. 16 litres per hour on mine, and I take 45 mins out of each tip tank, leaving adequate and safe reserve of the 17.5 litre capacity.
I also had fuel passing between the tip tanks when parked up, and walked in to an emptied tank once, having poured out overnight. Solution for this was Andair one way valves on the tip fuel lines to prevent fuel passing ‘backwards’ to the tanks. They work very well, and in fact have just fixed an issue I had with my other aircraft.
Which leads me on to the next bit...
We had real issues with one tank feeding before the other, and nothing would reliably fix it. Some said it was side slip, some said it was sticky check valves, some said fuel selector issues...
I battled with this for ages, until Paul Grellier came up with the best fix. Switch to a four way Andair fuel selector! Now I have ‘LEFT TIP’ - ‘MAIN TANK’ - ‘RIGHT TIP’ - ‘OFF’. This puts the control entirely in the hands of the pilot, and again using known burn, a good dipstick, and a four way kitchen timer, I can plan my airborne fuel to the nearest litre and be confident with it.
My longest flight to date has been 3h31m from Solent to Eshott, and I still had fuel to play with.
Tip tanks are great when you work them this way.

Paul.
G-NIPR.

Paul1954
Posts: 15
Location: Norfolk

Re: Wing Tanks

Postby Paul1954 » Sat Sep 12, 2020 3:01 pm

No idea why this posted twice.
Last edited by Paul1954 on Sat Sep 12, 2020 3:06 pm, edited 2 times in total.

Paul1954
Posts: 15
Location: Norfolk

Re: Wing Tanks

Postby Paul1954 » Sat Sep 12, 2020 3:02 pm

Hi paul,

Attached photo - is this the type of arrangement you mean? Do you require a small vent hole in the cap to allow fuel to feed. I would have though that not having one would prevent fuel flow.

G- AVKK #3.jpg
G- AVKK #3.jpg (1.14 MiB) Viewed 1289 times

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G-NIPR
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Location: INVERNESS, SCOTLAND
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Re: Wing Tanks

Postby G-NIPR » Sat Sep 12, 2020 11:59 pm

Hi Paul,
I have fitted a pair of forward facing vents which probably create positive pressure within the tank. They both work very well.

A76479D2-3C69-4FE7-B304-C7C88E8DF563.png
A76479D2-3C69-4FE7-B304-C7C88E8DF563.png (798.12 KiB) Viewed 1280 times



Keep well,

Paul
G-NIPR.

Dellboy
Posts: 6

Re: Wing Tanks

Postby Dellboy » Mon Sep 21, 2020 6:41 pm

Hi Paul, when you fitted the Andair 4 way fuel tap did you do away with the balance tube that feeds between the tanks

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G-NIPR
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Re: Wing Tanks

Postby G-NIPR » Mon Sep 28, 2020 10:50 am

Hello,
I am not quite sure what was done, but I have asked Paul Grellier who did the job, to comment.
He should be along soon, I hope.
Paul.
G-NIPR.

Ross
Posts: 11

Re: Wing Tanks

Postby Ross » Thu Oct 15, 2020 1:10 am

Thank you everyone for your valuable input, Your solutions validate my thinking on how to remedy the problem.
Cheers Ross


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