flycatch

My Feedback: (26)

Calil, go with a hopper tank.

AndyAndrews

Sometimes the caps can crack if they are tightened too tight. You will see a very fine crack along the top corner of the cap. It's not very noticable unless you look close. Also, get rid of the festos and use a plug like shown in the other setup (silver plug). I don't like where your ECU is so close to those magnets. Are you sure it's bubble causing this? What does the EDT say after the flameout? One other thing to look for is a faulty throttle wire from the ECU to the RX. Lastly check the connectors to the ECU batter to make sure there is no corrosion. The slightest little corrosion can cause arcing which will shut down the ECU.

One other thing. You can get a felt clunk for your main fuel tank that basically does the same thing as a UAT. I know a lot of the European guys use those instead of UAT's all together.

Andy

ravill

My Feedback: (11)

Airbubbles causing flame outs is the very bane of our existence.

What Andy suggests here cured my problems that I could reproduce on the ground. And always, always test your system on the ground to see if you can reproduce any symptoms.

basimpsn

My Feedback: (5)

"I know it's air bubbles because I saw a lot of bubble and a big bubble on the UAT. I flew a lot without the last flameout saturday. But I understand that even if bubbles come to the UAT it shouldn't allow bubbles to the fuel pump. It happened after a quick rudder turn around."


Lot's of good idea about your fuel system. But remember if there is one big air bubble inside a (FULL) UAT bottle..that's normal because of the main tank air gap. But If air bubbles is in the fuel line going into the engine then it a air leak between, engine and fuel solenoid, or UAT to fuel solenoid. If not then it's something electrical. I would also check the fuel solenoid valve connection to the ECU. Was there any white smoke when it flame out? or any error messages from the data box.

P.S a quick test is to remove the fuel line from the engine and clamp it tight, then do a brief pump prime test and look for leaks.

Just my opinion.

stevekott

What I've done with a pesky fuel system is a pressure test.

You need a gauge that reads low pressure. The one I use I bought at an auto parts store it reads up to +10 Psi and down to 25mm Vacuum. They are used for checking fuel pumps and manifold pressure, not that expensive.

I drain the fuel system and connect the gauge to the fuel tank vent tube using Tygon fuel line. I put a Jetcat shutoff valve in the fill line an start putting fuel into the system as normal.

Build up about 3psi and than shut the Jetcat valve. Now you have trapped the pressure in the fuel system. If you have a leak you will see the pressure dropping on the gauge. You should be able to hold the 3psi overnight.

If you are concerned about the Festos leaking under suction you can partially fill the system with fuel. Then put the Vacuum gauge on the vent line. De-fuel the tank until you show about 5mm (about -3psi) on the vacuum gauge. Again you will see results relatively soon if there is a leak.

You can use a little higher or lower pressure BUT BE VERY CAREFUL. You don't want to implode or rupture your fuel tank which can easily happen. I would recommend not exceeding the 3psi/5mm pressure.

Good Luck, Happy Flying!

Vettster

I eliminated all the possible leaks with my UAT. I did this by eliminating the UAT all together! I now only use a filter clunk in the main tank, like the one seen in the post above. The engine never misses a beat and I even landed once with less than a 1/4"of fuel and the engine never shut down.

7 points of leaks eliminated. Weight savings of over 250 grams

Calil

I liked the idea for the filter clunk. However the wren 44 is such a small turbine that any bubble can really shut it off in high demand.

I'll get more fotos from my complete fuel setup and post here later. I don't see anything wrong but may be with everybody eyes here we can get a solution

On the other hand, here we see that big turbines don't care much for bubbles:
https://www.youtube.com/watch?v=riRMJhZy2pI After seeing this video I think if UAT works flawlessly or big turbines have much bigger tolerance than small ones.

erbroens

Turbinen + Luft in the lines = Kaput! The bigger the turbine, the more tolerant is to bubbles the same size.

Have you tried my suggestion yet Calil? also about the CG in the T-Rex?

abc, Enrique.

darryltarr

My Feedback: (2)

Calil, please check my Last Post on the other forum.

http://rc.runryder.com/helicopter/t784457p1/

mr_matt

My Feedback: (10)

A lot of good feedback here, to amplify what I think Vincent first said, you have to really check that output nipple on the UAT and especially how you have the 6mm to 4mm tubining transition set up.

There is a lot of suction there and you can get a lot of air there, especially if there is a tight bend and when the polyurethane line gets old it just gets worse

Vettster

When I mentioned that I landed with just 1/4" of fuel... That was on my P-60. So thats pretty small too.