I am test running my PST J600R on the bench. (+UAT) The turbine runs out of fuel. There was some fuel left in the tank (50oz Dubro) about 1-2 oz and also about 2 oz left in the UAT. (the UAT in almost empty) Is this normal? Shouldn't there NOT be any fuel left in the main fuel tank (maby alittle) and the UAT full?
Mario

That's probably about normal. How much fuel you have left depends on how good a job you did plumbing your tank and what type of clunk you have. If you want to suck your tank dry make a pleated paper filter clunk. Do an RCU search in the Jets Forum to find out how to make one.

Joe

Here's a short tip about the UAT.
Make darned sure that the UAT filler line doesn't leak any air at the fitting or the plug. If it does, the engine will drain the UAT , then flame out. No fuel will be used from the mains or header.
The UAT must remain totally sealed in order to draw fuel because it is on the SUCTION side of the fuel system.
Some years ago, I witnessed a flameout that occured while taxiing to the runway for takeoff. The owner had inserted an allen capscrew into the UAT filler line. When I asked him where the plug went, he said he left it on the workbench at home. Air was leaking past the threads of the bolt, and the engine simply drained the UAT.
Didn't matter. After he sealed the line with a loaner plug and took off, the stab blew off and the airplane, engine, and radio were totally destroyed in the fiery crash.


Harley Condra
BVM REP
JetCat REP

Or even better, don't use the UAT at all because it is giving you NO extra benefit and only trouble. Here in germany most pilots are not using the UAT at all and the ones I know only had it for some flights because it causes trouble (bleed air, leaks's)

Use a standard Hopper tank, and felt clunks in your main tanks. This is more safe. All european manufacturers don't recommend the UAT.

This is just my experience and not mandatory!

Andreas nows best

we have build over 50 models incl a uat never had any issues.
we have sold a few more even last year can tell how many
if you have no idea in how to make a fuel system then this answer is a perfect one.
i now of many cases where the uat saved the flight.
however i DO see a lot of festo connections that have not been cut properly , they need to be cut abolutely strait!
otherwise they will leak!.
andreas you have no idea what you are on about.
i give UAT standard with our turbines.
infact these are the best fuel filters in the world , i dont even use fuelfilters anymore after the uat no need for them.

Well I re-plummed everything and my UAT is going almost all the way down until my turbine runs out of fuel. I have about 2-4 oz left in the main tank.... Its in my boomerang now. Shouldn't the UAT always be full? Of course until you run out of fuel in the main tank then it starts to get into the UAT.

Why would you want to drain the UAT on a test stand?? Once is is full, and all the bubbles are removed, you should leave it full of fuel. Once you see bubbles coming from the main tank, that is the end of your useable fuel, and you should shut down....

A couple of ounces left in the main tank is not bad..it depends how effective your main clunk is in picking up that last bit of fuel off the bottom of the tank.....

I'm NOT draining my UAT.. the turbine is.. the turbine runs on the main tank for a bit then it starts pulling fuel from the UAT until the turbine runs out.

If the UAT is draining before your fuel tank, you must have an air leak or incorrect plumbing. Any air leak, the uat will drain instead of pulling fuel from the tank. Like it has been said above, ensure you are using the proper plug for the fill line. Then move along the fuel system looking for bubbles.

Did you replumb everything? Even the line and clunk in the main tank?

The uat should remain completely full until the main tank is empty. If it runs out before the main tank, there is a problem. Usually at the filler plug, sometimes at the cap. I only had one problem with my uat. Some dummy didn't properly shut off the valve on the filler line. Luckily it died just when I started to taxi out. ..... Yep, I'm the dummy.

Thanks guys. I will look over again.

I'd like to re-phrase what Randy just said. If everything is working normally: The UAT should remain completely full until the main tank no longer draws fuel.

As I said above: how much fuel you have left in your main tank when it stops drawing fuel depends on how good a job you did plumbing your tank and what type of clunk you have. Also the shape of the tank can have an effect.

The bottom line is that a couple of ounces isn't bad. If you have much more than that you should fix it. Does your clunk reach almost to the bottom of the main tank?

Joe

Yes my clunck reaches the bottom of the main tank. Funny thing. I went to pull all the tubing off my UAT and when I cut the fill line on the UAT, the UAT filled up with fuel. (the UAT was still connected to the main tank and the main tank had some fuel in it) The fuel from the main tank filled up the UAT... Its was like when I cut a slit in the fill line in the it started filling up with fuel from the main tank...

If the main tank is higher than the UAT it will siphon into it when you open (slit) the fill line, which now acts as a vent.

Hey, thanks for calling me an idiot. If this your personal behavior then I never would like to be in the situation to ask support from you............ Why are you so priggish and what of?

But to explain that even you understand what I want to say:


No major and important Turbine manufacturer in europe, ( and important means the ones who sell quantities and are not only cary their Turbines to test events) are recommending the UAT. I never have seen in any manual the hint to use a UAT (Nor AMT, Jetcat, Graupner, Wren). Reason for that?

My personal experience is (I am flying Turbines right from the beginning so now more than 9 years now) that a simple setup for the fuel system is the best. If possible never ever use more than two tanks. Use as less connectors as possible, use a good filter in the filling line and in the tank itself, so that will prevent to get dirt in! If u use a two tank system cut every fuel line perfectly the same langth, connect it with a "Y" type connector (also the Vent line!!!), then go to the pump. Keep the line from the suction side as short as possible to prevent micro bubbles. Take care that the fuel lines are minimum 4 mm inside on the suction side.

If you take care of all about this the UAT is waste of money. If you anyway get flameouts........ send your Turbine to service. If you just want to use it as a spare tank, uhhm think about it....


I use exactly this setup since 7 years now in my F-22 with different Turbines (AMT-Pegasus, Jetcat and now a new one) without any trouble. With more than 300 flights I never had a flameout
A hopper tank is a relict from the Impeller time where the fuel got shaked like hell from the vibrations. Do we have any vibrations with our turbines??

Have a nice christmas

Moe, do you have a picture of your setup?

What clunk do you have? I am running Jetcat/Orbit clunk and suffered a flameout a while back due to running out of fuel. The main tank was almost bone dry (just a few drops in the bottom). The UAT remains completely full until the main tank is completely empty.

I would double check that you have plumbed the UAT correctly, check any connections between the UAT and the tank and try an Orbit clunk (if it fits in the dubro tank).

I too didn´t use a UAT and have good results... however it must be mentioned that the UAT has two advantages over the header tank.

The first one is a screening tissue that acts as a filter, and it is better than because it is a lot less prone to get clogged due at it´s bigger area compared the the standard filters.

The second advantage is that the UAT still works even if a large bubble is developed inside it, acting as a warning that something is wrong in the plumbing or in the tank setup... instead of a large bubble on a header tank that means a instant turbine flameout.


Seems that it is not senseless at all to pay $65 for a plastic tank...

Enrique

open your vent, go fly it and show us the pictures.

As Cars implied your vent must have been plugged and some pressure had built up in the main tank.

Joe

Seems to me the key question is this - does the UAT gradually collect air throughout the draining of the tanks, or does it only start getting air near the end ?

If you are only seeing air once you get down to the last couple of ounces in the main tank, then it seems to me there is little to worry about. I don't know of anyone who relies on getting the last 10 second's worth of fuel out of their tanks !

I now use a uat didn't used to, had no problems before, though i do like the idea of the filter bag

the only difference i run my tanks in series, that has been beneficial

m

Do you have any check valves installed........
anywhere..... which would allow the tanks to fill but not vent?

vent lines restricted?


Bring it to woodland for hoppy to look at,
please don't burn up that nice pst engine.

What does everyone use to plug their fill lines for a leak free plug? Festo caps?

I've had one flameout on take-off due to an improper seal in the filler line, so I elected from then on to use a double-redundancy method.

I have a festo ball-cock on the fill-line, and a "stub" - a small (about 2 or 3") length of the 6mm tube plugs into that with a good quality fuel-dot in it.

To fuel the model, I remove the small length of line, and open the ballcock. When it's full, I close the ballcock first to prevent air getting in when I pull the filler line out, then I put the stub in place.

Sounds complicated, but it isn't really, and it has worked extremely well for me. If the stub isn't properly seated, the ballcock prevents leaks ; if the ballcock isn't properly closed, the stub prevents leaks.

Gordon