UAT problems
 

Hi guys is anyone else having problems with UATs loosening the main cap?
We had already three diferent jets with the same problem. When you check the cap it is loose. Two of the jets had flameouts and one was lost.

Anyone else having this problem?

Michel

RE: UAT problems
 

I think the solution for this was to wrap teflon plumbing tape around the threads.
Bob

RE: UAT problems
 

Teflon Tape!

RE: UAT problems
 

Never had that problem.

Which brand of UAT are you using ? BVM, or Hansen or any of the ohter knock-offs ?

RE: UAT problems
 

All UATs installed on these jets are BVM... The bad thing is that the manual say that the cap must not be touch at all...[:o]

RE: UAT problems
 

Never had the problem.

RE: UAT problems
 

Well, instructions or not, if the cap has come loose enough to drip fuel or suck air, then unscrew it from the bottle, pull it apart, wrap the threads with teflon tape and reassemble. Good as new. Do a leak check in a pan of water just like you would any other fuel tank. I've rebuilt over a dozen UAT's and they're not fragile. I've also seen a few leak, both at the fittings and at the cap. Doesn't hurt to occasionally see if the cap can be snugged up.

RE: UAT problems
 

I agree 100% with Mr: Thud D, I have also rebuild a few. We have a Kingcat that is about 6 to 7 years old and so was the UAT, it was leaking through the cap and nothing could fix it, so we change it.

The plastic bottles have a certian amount of life ( cycles ) and when they get to it they have to go, they are about $ 1.50 a piece.

RE: UAT problems
 

nary a problem. I make sure the caps are snug and have teflon taped a few of them, and rebuild a 5 year old one...but never any leaks....

RE: UAT problems
 

Hey Michel,

I did the test flight for a friend of mine and had the same problem. I let him fly a little bit and as soon as I got it back the turbine shut down. I got the plane down in one piece when we looked the BVM UAT was empty and the cap was loose... This happend this week...

David

RE: UAT problems
 

Guys,
Sorry, no flames intended, but the above statement is incorrect and should be disregarded.

The UAT instructions are very specific regarding the cap.

Quoting paragraph two on the face of the BVM instruction sheet that included in every UAT packed and ahipped by BVM:
"Apply a wrap of safety wire to the 6mm tubing on the brass fittings. Periodically check that the plastic cap is hand tight on the bottle neck."

The photograph on the front face of the instruction sheet also shows that the threaded bottle neck comes with a teflon tape wrap to help seal the bottle. Quote; "This shows the proper orientation of the sack in the tank. It is best not to open the tank unnecessarily so as not to disturb this setting. Note the teflon seal on the bottle cap threads."

If you mount the UAT in the position indicated on the instruction sheet, visible in your installation, and at the suggested 20 degree angle with the brass fittings up, it should not be much of a problem for you to occasionally check the cap for tightness, like at the first flight of the day) and the UAT for security of mounting.
Preventative mainenance checks sometimes prevent inflight problems.

These quotes are supplied for those among us that don't read the instructions.

RE: UAT problems
 

There you go again Harley, ruining a thread with clear, concise, factual information. Where's the drama?

Craig

RE: UAT problems
 

I had a UAT leak from the aluminum fitting inside the center cap, only after refueling and only after the nose of the aircraft elevated over 20 degrees. My first occult UAT leak in over 30 UAT's I've owned.

I found this after 2 consecutive flame outs. This ultimately cost me my airplane. [:@]

Harley, I helped a local guy install his brand new UAT that he got from Tam and the instructions actually said it was ok to mount it vertically??? [X(]

I know many, MANY people have had success with a vertically mounted UAT, but the instructions CLEARLY stated the slant in the UAT was the preferable method.

Raf

RE: UAT problems
 

Nope ... some companies who have copied the idea also call their tanks a UAT.

See e.g.
[ul][*] http://shop.digitech-turbines.com/in...5i5oplue80e7r7[*] http://www.worldhobby.eu/katalog/e41.pdf has a BVM UAT but also several other UATS that are their own.
[/ul]
and then try to tell me that these UATs are ALL from BVM !

RE: UAT problems
 

Rav,
In the KingCat, the UAT is mounted vertically, and secured by a laser cut plywood mounting plate.

The UAT seems to be fairly tolerant of the mounting angle. When they were first produced, I retrofitted my Classic Bandit with one but had to mount it horizontally (brass fittings at the top), and it worked just as advertised for many flights.

Just be sure to keep the cap tight!

RE: UAT problems
 

I think he meant that all the UATs they are having trouble with are BVM...

RE: UAT problems
 

The only UAT problem I have ever had was with the one that has a Festo fitting on top. I prefer the barbed end type like BVM provides. The "other" guys are now offering that type on Dreamworks for 1/2 the price of the BVM.

Andy

RE: UAT problems
 

Ah ... OK - although that's not what was written, it does make more sense than what was. Can't fault someone in Chile for not having absolutely perfect English, so thanks for the interpretation ! [8D]

RE: UAT problems
 

You good know now. Thank taking for your time to discuss.

Andy

RE: UAT problems
 

I meant that the UAT in those jets where BVM as every single UAT we have in the jets on our club. I modified the post above...:D
The weird thing is that these three UATs where installed a completelly diferent times.
The one in my Rafale had 1.5 years.
The one in the F-16 1/6 has about 3 months
The one on the L-39 had a little less than a year
Only thing in common is season change from summer to winter... passing through autum of course.;)

Harley sorry for the bad info about the manual it has been a long time since I read it so I guess I must forgot what it said exactly, I will read it again...[:o]
Anyway I thing BVM UATs are of great quality and work great, I will continue using them in all my jets.:D

Michel

RE: UAT problems
 

Cycles of heating and cooling are quite infamous for loosening anything that can expand & contract – so maybe that could actually be the source of the problem.

One other thing to beware of for loosening the cap, is if you ever remove the fuel line that goes into the cap – the act of turning the metal screw that holds the fuel line in place can also loosen the whole top, since its rotation is in the exact same plane. If you ever loosen or remove that metal part, hold the cap firmly to prevent it moving, and then double check the cap snuggness when you are done.

Gordon

RE: UAT problems
 

hola Michel!!! que tal ???

we are worried, I go to verify frequent before the flight, until the moment we did not have problems.

abrazos

jose [8D]

RE: UAT problems
 

I have only used the BV UAT in the past, but have several of the Hansen UAT's at home. They seem to be the same thing, does anyone have any comments on the Hansen one...

RE: UAT problems
 

I am using the Hanson UAT..it works perfectly....got the one with the bvm style fittings...not the festo type

RE: UAT problems
 

Regular push-in Festo style fittings can display a problem that could cost you an airplane.

The bend radius needs to be large enough to prevent the fitting from sucking air. Bend the line in too tight a radius, and the tubing on the outside of the bend will migrate away from the conical seal, and you will get an air leak. One big air bubble too large for the pump to process, and you have a flame-out.
Proper routing of the lines will prevent this. It is not a sin to have large bend radii in your fuel system.

Conversely, barbed fittings, like supplied on the BVM UAT, won't leak at small bend radiuses.
I've been there, and done that.

A word to the wise...........

RE: UAT problems
 

Thanks

RE: UAT problems
 

Had mine come loose, but now I check it before first flight. No problem since

RE: UAT problems
 

Hi Guys

I have used the BVM UAT and other similar " air trap " devises for years now and here are a few tips to problem free fuel delivery.

- NEW - I take apart each and every unit and wrap one wind of YELLOW ( oil / gas compatible ) teflon tape. DO NOT USE THE WHITE
TEFLON PLUMBERS TAPE. It will deteriorate over time.

- At the beginning of every flight season I empty the UAT of the old fuel, reseal the cap and refill the unit with fresh fuel. I then allow it
to sit for a while prior to the first flying session. First engine run of the season I give the plane a shake and do several full throttle run
ups followed by a taxi test. I then refill and commence a full flight.

- Make a reference mark on the cap to tank body as a visual check to ensure the cap has not " wandered "

- Lastly - USE 8 volts or less on filling. The guys that use 12volts on filling pumps put expansion / contraction strain on the tank and cap. That's a good way to burst a seam.

As for orientation - once the UAT sack is saturated / primed ( whatever you want to call it ) it does not matter how you position the tank. For peace of mind, most guys place it in a position that creates the least amount of free air space ( ie nipples up and at a slight angle )

Dean W.

RE: UAT problems
 

I think any of the Nalgene or similar tanks we use in the jets - its always a good idea to check the cap every once in a while, to make sure they are still snug. Thats really just simple maintenance. I've noticed my Topcat tank on occasion needs to be snugged up a bit, along with a pleated filter Nalgene hopper tank I made 6 years ago for another model. [8D]