N4S

Hi folks,

I have a T-One T-45 (mini Hawk). It is a PNP and came with a glass round UAT, I am assuming it is made by T-One, please see image. I have always used MAP or HSD UATs, both are plastic and never had any issues with air bubbles. I plan to maiden it tomorrow and run the engine today. Not being familiar with the glass UAT, I put the jet in different orientation, vertical with nose up and down. I noticed if air bubble enters the UAT while nose down, the bubble doesn't go away even after the jet is leveled. Every time I put the nose down, more bubble entered at it should and accumulated. I did this with engine at idle.

I checked the lines and my connections are correct with tank at the top, pump at the middle and feed/drain at the bottom. I am a bit concerned and thinking to put a MAP UAT in it. Any feedback is much appreciated.

FenderBean

Typically you will always have a small bubble, if the UAT is too small for the motor combo is when you run into issues.

jvaliensi

My Feedback: (1)

When you hold the model nose down, you are exposing the clunk to the air in the tank, so air will pulled into the trap. It seems the trap is working and catching the air.
The bubble will not go back into the tank with the pump running. The fuel flow is one way.
This condition will not be as severe when you are flying down-lines because the airplane will be accelerating which keeps the fuel at the back of the tank and the clunk is in fuel.

Good luck with your 1st flights.

Desertlakesflying

My Feedback: (28)

Lift the front of the tank with a couple of pieces of ply?

N4S

Thank you all for your response!

It is interesting that with the cheaper plastic UATs, no bubble accumulates. I always check my UATs after each flight and there are no bubbles. With MAP and HSD UATs, the feed/drain line and tank line are at the top of the UAT, I​​​​​​​ wonder if that has something to do with lack of bubble accumulation.

jesse2357

My Feedback: (2)

If the bubbles are coming from the main tank then it has nothing to do with the UAT. By what you described it sounds like what Jvallensi explained. Now why you don't have them in your other uat, could be the main tank has a felt clunk or no stiffener in the clunk line allowing it to stay in fuel. If your worried fly mostly level flight and mix in a few loops and check when you get on the ground. I suspect you'll be fine. I haven't used Pacific uat yet but run the clear uat on all my jets as being able to see the bubbles clearly gives me piece of mind. I also mount all my uat's vertical so ever fill up gets all air out.

Dansy

My Feedback: (53)

[QUOTE=N4S;12733180]Hi folks,

I have a T-One T-45 (mini Hawk). It is a PNP and came with a glass round UAT, I am assuming it is made by T-One, please see image. I have always used MAP or HSD UATs, both are plastic and never had any issues with air bubbles. I plan to maiden it tomorrow and run the engine today. Not being familiar with the glass UAT, I put the jet in different orientation, vertical with nose up and down. I noticed if air bubble enters the UAT while nose down, the bubble doesn't go away even after the jet is leveled. Every time I put the nose down, more bubble entered at it should and accumulated. I did this with engine at idle.

I checked the lines and my connections are correct with tank at the top, pump at the middle and feed/drain at the bottom. I am a bit concerned and thinking to put a MAP UAT in it. Any feedback is much appreciated.

She works great no worries……that style of UAT are the best

Auburn02

My Feedback: (1)

Having nothing to do with the original question, I hate that these style UATs have the fill/drain line at the bottom. I prefer to de-fuel my jets but I never want to drain my UAT. At least with the old school BVMs and such they're designed specifically to be able to run the pump in reverse until it stops pulling fuel, and be left with a nice full UAT. Of course you can watch it and stop it when it starts drawing from the UAT, or refill just the UAT, but I digress.

Mounting this style vertically would solve that at least, though the integrated mounts are usually not conducive to that.

Dansy

My Feedback: (53)

Humm I don’t understand your concern…..I never defuel my uat’s and either one the fuel go through the UAT…..I stop when I start seeing bubble and push just a tiny bit back into it…pretty easy to do…and she stay full…..

‘And to have air bubble when your flying nose down happen no matter what uat your using…..

Auburn02

My Feedback: (1)

Right, so you're doing exactly what I finished my comment with "of course you can...." There is no real concern, but I don't want to watch my tanks drain. I like setting my fueler to defuel, perform other tasks while this occurs, and when I hear the pump start sucking air I know I'm done and turn it off. Can't do that with this style because doing such would mean you just drained the UAT, then refill it. Yes it's easy, but it just seems so unnecessary to put the drain on the bottom for a unit that should essentially never be drained in practice. It's just a workflow issue is all.

jesse2357

My Feedback: (2)

I do the same, take the wings off and such. I've gotten spoiled with the digitech it doesn't empty the uat but with my intairco it empties. Of coarse it never fails when I haven't flown my T-1 in a while I empty the UAT

Dansy

My Feedback: (53)

As long as you push fuel back in that’s not a problem

highhorse

My Feedback: (2)

Sounds like a good question for mythbusters….but don’t forget that with constant thrust the acceleration on a down line is due to mother gravity, which exerts its influence on the fuel at exactly the same rate as the rest of the model. Hence, the fuel does not accelerate to the back of the tank. Neither will it flow to the front at first, but once the model’s acceleration begins to slow (increased speed = increased drag while gravitational pull remains constant) the fuel ABSOLUTELY WILL flow to the front of the tank. The good news of course is that our down lines are necessarily very short in duration :-)