747drvr

My Feedback: (5)

If you start chewing into your header tank capacity you should rethink your flying time !! Consider the header tank to be unusable and you shouldn't run into problems.

MDEE

I have flown several hundred flights using a UAT in several different aircraft, I initially had problems with with flame outs on take off. I was using a catapult system to launch the aircraft, I would throttle to full power, release the catapult, watch it tear down the field, then cut out, very embarrassing, particularly because I could not stop it until the catapult tension ran out.
I assumed it must be a leak after the uat, but this was only happening on the first flight of the day, subsequent flights were fine. The UAT was mounted horizontally.
I mounted the UAT using flexible Tygon pipes, when I tipped the UAT vertically I was amazed to see a stream of bubbles but only on the first flight of the day.
Since then I have never had a flameout in hundreds of flights but I always tip the UAT to check on pre flight.
It is a good product but I think over time air leaks through the cap seal. If you mount it where you can see and tip it to check, you will not have a problem

Mark

Kevin Greene

My Feedback: (85)

C'mon guys---Use your heads!!! :bananahea Before installing the UAT in the model connect it up to your fueling can (I use the one from The Jersey Modeler) and pump fuel through it while shaking it. Run a BUNCH (highly technical term ) of fuel through it until you are satisfied. Of course the return line is connected to the fuel can. When done, plug or use hemostats to keep the fuel from leaking out and install the UAT at your convenience.

The purpose of the membrane is that even if you run the UAT to 1/2 empty the membrane is still saturated with fuel and will continue to provide bubbleless fuel to the engine.

After the UAT is in the model I have never had more than a small bubble in the tank. It is expelled when I refuel. If you have a large bubble or a significant amount of fuel missing in the UAT then there is a plumbing/pickup problem in your system. Are you guys completely defueling your jets after flying? My buddies and I don't and maybe that is why we have never had a flameout related to fuel.

Kevin

Woketman

My Feedback: (6)

Or simply build the pleated paper clunk and use a Dubro header and keep an extra $30 in your pocket towards digital servos!

garrett_mcdonal

Kevin,

I had done that to my UAT and I still got a flameout while taxing on one of the first runs with the UAT installed.

I had also shaken the UAT while the engine was running.

Next suggestion?

I haven't had a problem since, but it did leave me scratching my head as to what more I could have done.

Regards,
Garrett

Kevin Greene

My Feedback: (85)

Garrett,

The only thing that comes to mind is that perhaps you had a hidden bubble in a fuel filter? You can get a hidden bubble in the UAT if it is not mounted at least 15 to 20 degrees nose up or vertical. I use the clear fuel filters from Festo. I don't like the JetCat aluminum filters because you can't see into them and many of them are prone to leak. I use barbed adapters (4mm to 6mm) to utilize the clear Festo filters as these filters have barbs with screw on compression fittings for 6mm fuel line. I also use tie wraps on EVERY fuel connection where a barb is used. I have never seen a bubble in the clear Festo filter. The only expanation that I can think of is that you had one last hidden bubble in your system on that first run.

I edited my previous response and added more info.

PS----The Turbine Connection has the Festo fuel filters on sale.

Kevin

Tom Antlfinger

My Feedback: (24)

I built up a Kangaroo for my buddy Dave who flew the stink out of it this summer. Although he mainly flew his Blade at Superman, he did fly the Roo and did many vertical negative flicks, followed by chicken flops, and then inverted spins before recovery (ala Dennis Lott)---never has flamed out during these maneuvers. Guess what? I used a round 2 0z Sullivan for the hopper tank with the brass tube centered and no clunk.

In my HotSpot and Bandit, I have used UAT, mounted horizontally in the HS, and about 15 deg tip up in the Bandit. Same angle for the filters, horizontal in the HS, and 15 nose up in the Bandit.
Except for 1 unexplained flame-out after close to 150 flights between the 2 planes, all with vertical flicks, conventional and flat spins, and long vertical downlines with flicks and rolls, the P-120's have never blown cold air out the butt end.

The beauty of the UAT is that it does allow you to drain the very last drop out of your feeder tanks. More than once I have landed with my feeders dry, and my UAT down 50%. Bad flight planning yes, but things like that happen every so often when you try to squeeze every last minute out of good flight, or some bozo stalls his plane on the runway when you are fuel-critical, on short final.

So like someone famous once said "You pays yo' money and you makes yo' pick!"

Just remember that bubbles can miraculously appear out of fluid due to cavitation or overheating a line (vapor lock) and that these little bubble will migrate and appear at the most inoppurtune time and place---at least with my bad luck.

And the UAT won't really get you into the BVM Hall of Fame. It's the product of Jeff Seymour (SWB Turbines), of Mamba fame-to-be, about 40 miles north of here. Jeff says he developed them for his commercial/military installations. BV private brands them for resale. BV has no time for this kind of stuff. He's way too busy building up Super B's, BobCats, and JetCases for all my friends from the U.K that attended FIJR!!!

Tom

garrett_mcdonal

Kevin,

No worries. I'll angle up UAT up a bit further. I make a point of not de-fuelling the model when I am done for the day.

On future installations I plan on making sure the UAT is angled up at least 30-45 degrees.

I may also put a tee in the line between the UAT outlet and the servo-operated fuel-shutoff valve that is required under the Aust turbine regs. This way, I can always fuel the model by pumping through the membrane which should dislodge any bubbles.

On my engine, there are solenoids under the front cover that form a return loop from the engine to the tanks when the engine isn't running. Because of this there is no chance of flooding the engine by fueling it in this manner.

Regards,
Garrett

Tom Antlfinger

My Feedback: (24)

Another---

Tom Antlfinger

My Feedback: (24)

Another:

David Gladwin

If it is so important to have the UAT angled up why do the BVM drawings for the F16 and F86 turbine conversions., which are on my desk right now, both show the UAT horizontally mounted ?

The more you guys tell me how air bubble problems in UATs can be overcome (angling upwards, purging, shaking, refuelling through the membrane, never defuelling etc) the more you point me towards a simple header because that system requires NONE of those procedures to work perfectly, for me at least.

The UAT actually gives perhaps two ounces more useable fuel over a simple four ounce header. With a fuel load of around 100 ounces thats almost insignificant.

Any comment from BVM an SWB turbines ?

BRG,

David Gladwin

garrett_mcdonal

David,

Very good point.

Regards,
Garrett

DavidR

My Feedback: (1)

I have probably somewhere around 400 flights with UAT's and have YET to have a flameout with one installed......well actually I had a flameout in my Bobcat when I failed to charge the ECU battery. (Verified by the JetCat electronics) I have them installed in my Bandit, Bobcat, and F-4 and all done in different orientations. I am careful to purge them when first installing them and don't drain them unless I am stripping the model down. I also shake the model (YES David you can shake a BVM F-4 that is full of fuel!) I have also flown my Bobcat several times until I had less than a 1/3 of a UAT of fuel left. I won't fly without one. Of course I never flew a DF plane without a hopper tank either.


David Reid

Kevin Greene

My Feedback: (85)

David,

Whatever works for you then stick with it!!! I will continue to use a UAT for my own peace of mind because for me it works well. I have not had any of the problems that others seem to have with their UAT. I believe that if you call BVM they will tell you that the optimum position for the UAT is slightly nose up rather than totally flat. I also fuel through the UAT as per the BVM instructions.

I'm also very anal when it comes to filtering my fuel. I have two filters on my fueling can. Another from the main fuel supply in the model to the UAT and a final fuel filter between the pump and the turbine. I have no fancy solenoids or complicated fuel return systems. I want to keep it simple. My fuel overflow/vent line fills my ground run tank when I refuel. I have two fuel cutoffs in the model---one between the UAT and the turbine pump and another between the pump and the turbine. When refueling I close only the valve between the pump and the turbine to not only keep from filling the turbine with fuel but to keep the pump primed. When I'm done for the day I close both valves to keep the pump primed and I block off the vent line completely sealing the fuel system to keep it from "breathing" with changes in atmospheric pressure and temperature. My engine in this installation is an AMT Mercury HP.

Kevin

Tom Antlfinger

My Feedback: (24)

David, I have an even a simpler setup. No hopper, no UAT. I really do believe these are holdouts from the D/F, skinny-tanks-with-no-baffles days. Tad K. at GWM believes this as well, one of the senior turbine gurus in my opinion.

I bought my first HS from German Jet Team Member, Tom Singer.
He had about 50 flights on it when I bought it. No flameouts. I put on a total of 230 flights on it before losing it to control failure at Scottsdale last January. That's the bird in my Avatar, 2 flights before it's demise.

The fuel system--Coke bottle with Du-Bro clunk. No UAT, no Hopper, no Felt. I could look in the tank and see what the clunk tubing and clunk were up to before every flight, thru the speed brake hatch. That's it! No un-explained flameouts in those 230 flights.

Oh my, another myth exploded!


So save your money----Go Hopper Naked! Save money on the UAT and make a few bucks selling Hopper Naked tee-shirts. Wonder if BV would private brand them??


Enjoyed it------Tom

Woketman

My Feedback: (6)

Kevin, you can buy the Festo filters for 4mm connections too. And mine ALWAYS have a bubble in them, but the bubble won't move. I've tried at full throttle while shaking the hell out of the filter, and that bubble just will not go anywhere.

Kevin Greene

My Feedback: (85)

Woketman,

Thanks for the 4mm filter info---I assumed they only came in the 6mm size since that is all I've been able to find. ( I suppose that if I look at the 4mm line at The Turbine Connection I'll find them there.) Where do you purchase yours?

When I initially fuel the model for the first time I run fuel through the festo filters with the fuel pump connected directly to the ECU battery. I run the pump until no bubbles are present with the line that goes to the turbine dumping back into my fuel can. I just won't accept any bubbles. I crimp the line for a second or two on the outlet side to build up pressure in the filter and then let it go! The bubble just shoots right outta there...

Kevin

Woketman

My Feedback: (6)

OK Kevin, I never thought of the line pressure thing. Very ingeneous. I will look at the receipts I keep at work (away from prying wifey eyes) and post the place I get the Festos. I believe it is E. B. Atmus Co.

Kevin Greene

My Feedback: (85)

Woketman,

Thanks!!! I just looked at Turbine Central (Not Turbine Connection) and they don't sell the 4mm ones. I would like to know of a place where I can purchase all of the Festo fittings at a reasonable price.

Yeah, the pressure thing works---I remember something in my engineering classes about breaking the surface tension of a liquid or air. That's where I got the idea from. I guess all that schoolin' didn't go to waste?!? Pointing the filter upright while doing this will let the bubble escape easier.

Kevin

David Gladwin

Well I really seemed to have stirred things up but I will give the UAT another chance, but the simple hopper stays in the F4 and F15 because it does work so I'm not going to fix something that isnt broken.

My final question is if the UAT needs to be angled up to work properly what happens in extended inverted flight ?

David Reid: I have asked my wife for an increased supply of wheaties as I may soon have to shake a big jet ! Weight watchers will have to wait !

BRG, David Gladwin

Ehab

My Feedback: (44)

David;

The idea behind the UAT being upright at an angle is to reduce the amount of air inside it while filling and running on the ground. The internal bag/filter will do its job and break up any air bubbles while flying. You may also notice that the regular 2 oz hopper tank will almost always be less than 100% full....same idea!!!

Vincent

My Feedback: (61)

Hey guys,

I have just installed a UAT in a new project and have always used the simple Gladwin type header in the past with no problems?? You guys have me convinced to rip it out and go back to "old school" even before it gets "wet"??? more confused now than ever!!

Another thing, I have never paid attention to the orientation of the Jetcat filters?? never had a flameout that I can attribute to that?? once they are filled there is no way air is getting trapped in this tiny filter??

Vin...

Gordon Mc

My Feedback: (11)

That's easy ... buy them from Festo !!

I simply look the parts up on their website : http://www.festo-usa.com then call em up and place the order. Some of the cheaper stuff (like 4mm to 4mm connectors) you have to buy in packs of 10, but the filters, ballcock valves etc can be bought individually.

Gordon

P.S. For anything that I can't find on the website, I just ask when I phone the order in - they have always been extremely helpful.

JET FX

Ehab- check out http://www.pstjets.com for nearest rep locations. Canadian PST rep Kelly Williams is nearest to you in B.C.
Let me know if you need further info.

Cheers-

rhklenke

My Feedback: (24)

Marty,

Sort of off subject, but will there be a PST rep. at Florida Jets do you know, and if so, might they have J600's available for sale there? I'm leaning heavily towards one and may be able to pick it up then...

Thanks,
Bob