Fuel tanks unequal feed

[compsci]

The left wing fuel tank on my J230 does not feed fuel when both wing tanks are set to on. However, the left wing fuel tank does feed fuel when I shut off the right wing tank. I would normally expect that the wing tanks will not feed equally but don't understand one tank not feeding at all. Is this normal for the J230?

 

 

[Guest Decca]

Hi Compsci.

 

I can’t help you yet, but would like to research your problem. It’s an all too common one, and may not be restricted to the J230 or even J aircraft, according to other threads on these forums.

 

To start with (I have not done any of this myself yet); Have you communicated with Jabiru or their agents on this issue?

 

Have you referred to the maintenance manual for any reference to the problem?

 

Is your hourly fuel burn the same as the fuel used from the right tank? Need to know this to make sure there is no fuel transfer from right to left tank and subsequent loss of fuel from overflow.

 

There are other possible contributing factors I’ll just touch on here but I need to familiarise myself first with the maint manual & aircraft. These are how the vent system is set up, so that one tank doesn’t have more pressure than the other, & the aircraft flies straight & level with balance ball middled.

 

Thanks, Decca.

 

 

[frank marriott]

Unequal feed is normal - There is 4 J230s here, one kit built and three factory and all the same. The factory ones can't select individual tanks so you just get used to it. The guages (especially in rough weather) indicate a larger difference then is the actual case. I use a fuel log to be happy.

 

Frank

 

 

[Jabiru Phil]

The Australian factory built has no wing tank taps, only one main tap.

 

The kit has the two wing tank taps.

 

My experience with both types I found it possible to even the tank quantity by flying out of balance for a short time. watch the gauges and they will indicate this.

 

The two tap version (plus main) is a problem with full tanks as it tends to overflow from the lower wing. I always only ran one wing tank at time. Caution, more fuel management is required.

 

 

[Guest Decca]

Thanks Frank.

 

Do you and/or the other owners have answere to the above questions in post2?

 

Also is it always the left tank feeds slowest or last?

 

And just made a note for myself to see if there's a return line in the system from the carby area.

 

Decca.

 

 

[Guest Maj Millard]

The Jab engineers ?, need to look at the Savannah fuel system with it's 10 lts sump tank, and warning light, absolutly bulletproof...60% of all engine failures are due fuel problems...it's important...fix it !!.

 

 

[Captain]

The left wing fuel tank on my J230 does not feed fuel when both wing tanks are set to on. However, the left wing fuel tank does feed fuel when I shut off the right wing tank. I would normally expect that the wing tanks will not feed equally but don't understand one tank not feeding at all. Is this normal for the J230?

G'day comsci.

 

This has been debated to death in earlier threads here, and not just for 230's, so a search might find something there that might be of interest.

 

My 230 used to feed unevenly ..... then I really worked hard at keeping the ball in the middle, particularly in the early stages of a flight (takeoff to about an hour) and the issue went away.

 

My conclusion is that you don't have to be very far at all off totally coordinated flight for the tanks to feed selectively in the early stages .... and I mean that the ball just needs to be a bees dick (width not length) off centre to have an influence.

 

Hope that helps.

 

Regards Geoff

 

 

[GraemeK]

My conclusion is that you don't have to very far at all off totally coordinated flight for the tanks to feed selectively...

I second that - in my early stages of learning in the 160 my instructor would point to the fuel gauges and say "you're not keeping the ball in the middle!". Even a slight deviation and one tank will be a lot lower than the other, especially in circuits.

 

Now I'm improving with the rudder, the problem's gone away.

 

PS The header tank on the Jabs works well, but check the POH for what can happen in unblanced flight:

 

 

 

 

 

Flying “1 ball” out of balance (see Figure 7.14.1) causes the fuel in the tanks to slosh in to one side by an angle of about 8°. This leads to uneven fuel feeding – 1 tank emptying before the other. In extreme cases, this can cause fuel starvation & engine stoppage while there is significant fuel remaining in one wing tank. Care must be taken to fly the aircraft in balance at all times.

[Vev]

Same experiance in my 160 ... the trick is to use the rudder and stay coordinated as per the last couple of posts.

 

Cheers

 

Jack

 

 

[jetjr]

The Jab engineers ?, need to look at the Savannah fuel system with it's 10 lts sump tank, and warning light, absolutly bulletproof...60% of all engine failures are due fuel problems...it's important...fix it !!.

Most Jabirus with wet wings have the similar setup and have had for a long time, 10L header tank under PAX seat or back behind the rear curtain, most have red light too - still draws unevenly

 

Leave electric pump on helps

 

Dont worry about it too much as they drop the level difference sorts itself out, in ones where you can switch one side off, if you do it for a few minutes they then read level once both are back on again.

 

Old problem, most planes fly leaning left a bit, pilot weight and perception bias.

 

Jab tanks are long and flat, make problem seem worse

 

Make sure vents are all clear is another cause.

 

JR

 

 

[Guest Andys@coffs]

G'day comsci.My conclusion is that you don't have to be very far at all off totally coordinated flight for the tanks to feed selectively in the early stages .... and I mean that the ball just needs to be a bees dick (width not length) off centre to have an influence.

I agree entirely with Captain, this is exactly what I see in my J230. That all said I think we are simplifying to say that it doesnt feed from one tank or the other, rather I think what we are seeing is fuel transfering from one tank to the other. Fuel feed from both wing tanks, to the header tank is probably still occuring without issue. When unbalanced flight occurs then I believe there is fuel transfer occuring and additionally if the fuel moves to one end of the wing tank due to the off center ball, then on one side the guage will over read, while at the same time the other end will under read.

 

eg balanced = -G G-

 

unbalanced = /G G/ or \G G\

 

G= Guage, -,/ and \ all = top of fuel in tank with balanced and then unbalanced flight.....hope that makes sense.

 

Andy

 

P.S, while much has been said of this issue over the years, to me, once you understand it, its generally a non issue in my experience. I have yet to hear of anyone in a Jwhatever, with wet wings, ever suffer a fuel starvation prob where there was significant fuel still in one wing. Anyone ever heard of such a thing occuring where there was no other contributory factors?

 

 

[jcamp]

I have yet to hear of anyone in a Jwhatever, with wet wings, ever suffer a fuel starvation prob where there was significant fuel still in one wing. Anyone ever heard of such a thing occuring where there was no other contributory factors?

Pre JSB024-1 Fuel Line Routing Jan 9, 2009 I had an engine failure due fuel (engine died, fuel pressure light on and booster working hard). Restarted with some extreme unbalanced flight and landed ~ 5 min later. 18 liters came out of the system.

 

 

[Captain]

I agree entirely with Captain, this is exactly what I see in my J230. That all said I think we are simplifying to say that it doesnt feed from one tank or the other, rather I think what we are seeing is fuel transfering from one tank to the other. Fuel feed from both wing tanks, to the header tank is probably still occuring without issue. When unbalanced flight occurs then I believe there is fuel transfer occuring and additionally if the fuel moves to one end of the wing tank due to the off center ball, then on one side the guage will over read, while at the same time the other end will under read.

There is another wrinkle on this issue and that is that with your tanks chockers and uncoordinated flight immediately after takeoff it is possible to pump a good number of litres out of the filler vent, and if the circuit is busy with a few tight turns needed just after takeoff it makes watching the ball that bit more difficult.

 

I deliberately left my breather line visible between the 2 tanks in 2 easily monitored places and it is quite interesting to watch the direction of flow in that line when the ball is not in the centre.

 

Watch the ball ........... and have a ball. That's what I reckon I reckon.

 

Hope this helps.

 

Regards Geoff

 

 

[Vev]

Hi Geoff,

 

Isn't the fuel tank vent a one way valve on the Jabs ... it lets air in to displace the volume to prevent an air lock but wont let fuel/vapour escape?????

 

I didn't think it possible for fuel to escape out of the fuel filling vent during flight???

 

Cheers

 

Jack

 

 

[Captain]

Hi Geoff,Isn't the fuel tank vent a one way valve on the Jabs ... it lets air in to displace the volume to prevent an air lock but wont let fuel/vapour escape?????

 

I didn't think it possible for fuel to escape out of the fuel filling vent during flight???

 

Cheers

 

Jack

G'day Jack,

 

If that is right then mine must leak from around the O-ring on the filler cap in the example I gave 2 posts before, and when on uneven ground.

 

My vents are just a stand-pipe on each filler cap with what I thought to be a drilled out alloy cap on the top with a few small holes in the side of it. When I assembled that I didn't notice any one-way valve, but I was getting a bit excited by that stage of the build.

 

I have always considered that to be an open breather, only, so will be interested to hear what other have to say about it .... and I'll check mine further at the hangar today.

 

Regards Geoff

 

 

[Vev]

Hi Geoff,

 

The little cap on top of the breather snorkle is actually a surge valve which should have a 3/16 ball inside... lets air in, no fluid out.... if you give the cap a shake you should hear the ball in it rattle.

 

Every now and then i blow and suck through the small holes at the top of mine just make sure it's working.

 

I hate to think what I would be doing when I slip the jab to drop some hieght if it wasn't working.

 

Cheers

 

Jack

 

 

[biggles]

Yes Jack , you are quite right , however the earlier Jab's , certainly J160's anyway , had nothing to prevent reverse flow . My hangar partners kit built , around 2006 , does not have, but mine purchased Nov 2006 does have the small poly balls . Often if you see an early J160 with full tanks , and doing some fairly tight turns directly overhead , on a reasonably cool clear day , the vapor trail from each vent will be clearly visible . Good idea to test with blow/suck to ensure the balls aren't gummed up . And Geoff, it is possible to get a vapor around the fillers particularly with full , nearly full tanks , with the a/c on a lean . I use a smear of Vasolene around the 'o' ring and also on the contact area . This can help , but then again maybe it is time for a new 'o; ring !

 

Regards

 

Bob

 

 

[Yenn]

If you set up the vents so that port tank vents on stbd side and stbd tank vents on port side they should not drain when parked on a slope, because the lowest tank has the highest vent.

 

 

[biggles]

Yenn ,

 

I don't believe that is possible . The vents going to each tank come off a common connection from the head tank ( located under the passengers seat or, in the case of a factory build , behind the passengers seat ) and can vent into either or both tanks .

 

Bob

 

 

[quentas]

When I had the first 100 hourly done on my J230, my LAME found the rear fuel feed line from the right tank had a kink (from factory build) that stopped fuel flow completely from that line. Luckily the front feed was ok but I reckon that had a bearing on the way the fuel fed. To check this, you have to remove the wing root covers and have a good look with a small 'dentist' mirror. This can happen as the lines are fitted THEN the wings mated up and bolted.

 

 

[Captain]

Hi Geoff,The little cap on top of the breather snorkle is actually a surge valve which should have a 3/16 ball inside... lets air in, no fluid out.... if you give the cap a shake you should hear the ball in it rattle.

 

Every now and then i blow and suck through the small holes at the top of mine just make sure it's working.

 

I hate to think what I would be doing when I slip the jab to drop some hieght if it wasn't working.

 

Cheers

 

Jack

Thanks for pointing that out Jack,

 

I blew and sucked through my filler cap vents when I refuelled last night and there is no restriction either way, so mine doesn't have the one way set-up. Will have to see about upgrading them.

 

I wonder how much improvement they will make when parked on a bit of a slope with full tanks.

 

Yenn

 

The tank vents are in each filler cap. Can't do what you suggest.

 

There is a vent/balance line between the 2 wing tanks that has the vent from the header tank connected into it so that the header tank vents into the wing tanks (and the header tank is therefore free to fill to it's heart's content), and the wing tanks then separately vent through the filler caps.

 

Regards Geoff

 

 

[jetjr]

Mine leaks around O ring when full and on a slope (or a flat tyre)

 

Replaced O rings, became stiff and leaked a few weeks later, so no it doesnt help much

 

 

[Guest Decca]

On that note, David & all other contributors, the consensus appears to be wing fuel tank imbalance created by (inadvertent) pilot input.

 

As per Post 2, then, there’s no point me starting any research into imbalance created by any other means as the response here has been conclusive.

 

Unless anyone’s got anything more sinister to add…………?

 

Regards all, Decca.

 

 

[blueline]

Cessna just the same!

 

2008 model cessna 172's all draw more fuel from the L/H tank - seems to vary a little but about 30 litres is not uncommon.

 

Old 182 (with bladder tanks) seem about the same.

 

Jabiru don't have a monopoly on this issue!

 

 

[jetjr]

Just reinforcing the issue, I recently fitted a roll Autopilot servo, now I know its flying level but I feel like its LHS down quite noticiably, to the point I keep trying to correct it, finally I gave up and this flight let it do its thing

 

Guess what, over three hour flight, tanks fed perfectly level. First time ever. It was also perfectly on track too.

 

JR