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Old Nov 15, 2004, 10:15 AM
never fast enough !!!
wojtek's Avatar
old bridge, nj
Joined Nov 2004
258 Posts
UAT positioning ???

I know there has been some discussion about this throughout several forums, but there still is no clear answer ..... can a UAT be positioned over on its side ??? i know vertically or at an angle is optimal, but why not on the side (with the nipples on the top) ....
Im getting a lot of air in MY UAT in my KingCat, and can't tell where its coming from .... the vent line that atatches to the center header has no bubbles in it, but when draining the UAT, the air seems to be of unlimited suply .... i cant tell where its coming from ?? I though maybe it might have been a leak in the lines somewhere or at a fitting, but then again if it was I would have been getting fuel leaking out durring fill .....

I don't have much space left to position UAT vetically without binding up any lines or getting in the way of anything ...

There is enough air in my system that when throttled down quickly my AT400 would quit with a "low RPM : error (which per manual is a air problem in the lines) .....

On my Gripen, i also have the UAT sideways, and did have a flame out when slaming the throttle from full to idle. In the gripen however i did not note any air in the system .... Bob Wilcox had told me that it was a issue in my version of the ECU where the pump voltage was being dropped to rapidly causing a flame out , and i needed a ECU update (i have v4.h ) ... now im again thinking maybe this has to do with the UAT position ????


Wojtek
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Old Nov 15, 2004, 10:37 PM
FMC
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Wojtek
The reason for the positioning of the UAT as explained (at an angle) in the BVM instructions is to keep the air trapped in the corner, as more air bleeds into the system, of course this bubble will grow bigger but it will remain pushed in that area since air is lighter of course than fuel.

If you put the tank flat, the bubble will settle somehwere on the top surface and travel back and forth as the plane moves and some air might escape (unlikely but might) into the inside liner and find its way into the fuel line.

The chances of a flameout due to air bubble with UAT is extremely slim though even with the tank level, UNLESS you have a small air leak somwhere.

I cannot comment on the ECU update, perhaps it is worth sending to Jetcat for the update.

Regards
Peter
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Last edited by FMC; Nov 15, 2004 at 10:39 PM.
Old Nov 15, 2004, 11:00 PM
never fast enough !!!
wojtek's Avatar
old bridge, nj
Joined Nov 2004
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well, i might be having 2 separate and independednt issues between the 2 planes ... on the King Cat i noticed today that the big festo fuel filter that comes with the AT400 has a big air bubble in it .. it took some flicking around durring a run to get it out .... I also fully purged the UAT and now dont think i am getting as much of a air bubble in the UAT ,., i will check further tomorrow .... i will keep the UAT on its side, as i think that even with the little bit more air stuck up top, it should still suck fuel and no air ...



thanks ,

Wojtek
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Old Nov 15, 2004, 11:21 PM
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Daytona Beach
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Woj,
Make sure you have silicone thread tape on the UAT cap threads, sounds like you may be leaking from the cap when the system is under vacuume. I have successfully used the UAT on it's side for over 550 flights on my Euro without one flameout....!

Regards,
Todd
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Old Nov 16, 2004, 01:20 AM
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Cordova, TN
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Speaking of Festo fuel filters, where can I get them? I used them in my Avonds and I like them because you can see if there's air or junk in them.



Anyone?
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Old Nov 16, 2004, 02:28 AM
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Maastricht, Netherlands
Joined Aug 2004
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Quote:
Originally Posted by wojtek
well, i might be having 2 separate and independednt issues between the 2 planes ... on the King Cat i noticed today that the big festo fuel filter that comes with the AT400 has a big air bubble in it .. it took some flicking around durring a run to get it out .... I also fully purged the UAT and now dont think i am getting as much of a air bubble in the UAT ,., i will check further tomorrow .... i will keep the UAT on its side, as i think that even with the little bit more air stuck up top, it should still suck fuel and no air ...



thanks ,

Wojtek
also to consider:

i see a lot of manual stop valves there
and filters on the pictures

basicly and this is my opinion
all valves and filters need to be mounted AFTER
the fuel pump.
i asume you are using eather a jetcat fuel clunck in the tanks? or a felt clunck?
the jetcat type clunck have a history of getting clogged up with fuel residence fast
also these are basicly your filters for the pump
the rest is for the turbine only so therefor i always mount my filters and fuel stoppers and electronic valves AFTER the pump
if there is to much drain you will get a cavitation somewhere in your system
for testing your system make sure you do it "real time" so not more then a 700 ML a minute otherwise if you test with a refill station that can do
1200 ml a minute you will also get cavitation
remeber most of the festo parts are made for pressure and not vacuum!

for best results and flowrate i use

from both tanks 6MM (5MM inside) festo hose to the UAT
then from uat to pump 6MM festo
after the pump i go back to 4mm festo tubing
never have been a problem
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Old Nov 16, 2004, 10:42 AM
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under a rock
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Welcome RCU rejects. I can sure see where air could enter the system as very few ties are used on the lines, or is this sop.
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Old Nov 16, 2004, 02:40 PM
kgb
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Quote:
Originally Posted by Enriki
Welcome RCU rejects. I can sure see where air could enter the system as very few ties are used on the lines, or is this sop.
lol. it might be bvm's fault
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Old Nov 16, 2004, 03:13 PM
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Cordova, TN
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Quote:
Originally Posted by Enriki
Welcome RCU rejects. I can sure see where air could enter the system as very few ties are used on the lines, or is this sop.
Rejects? You stumbled into the jet forum to share this useful piece of knowledge?

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Old Nov 16, 2004, 03:15 PM
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Quote:
Originally Posted by Lt. Dan
Speaking of Festo fuel filters, where can I get them?
Just buy 'em from Festo.
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Old Nov 16, 2004, 03:24 PM
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Cordova, TN
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Quote:
Originally Posted by Fred Arque
Just buy 'em from Festo.
I went to their website but didn't see any prices. It looks like they only sell in bulk.
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Old Nov 16, 2004, 03:32 PM
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Quote:
Originally Posted by Lt. Dan
I went to their website but didn't see any prices. It looks like they only sell in bulk.
Just call 'em up and ask the prices.

Many items they sell individually, others (typically the cheaper & more common stuff) they sell by the pack - e.g. 10 x 6mm connectors in a pack.
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Old Nov 16, 2004, 04:57 PM
kgb
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Here is your problem Lt. Dan
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Old Nov 16, 2004, 05:09 PM
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Cordova, TN
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Quote:
Originally Posted by kgb
Here is your problem Lt. Dan
I'm not the one with the air problem. (This is Wojtek's post, I'm just looking for more of these filters)

I've never had a problem with the festo fuel filters, ever. Further more, I didn't build that jet, I bought it that way, and I wouldn't be caught dead with a mess like that inside of one of my planes.
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Last edited by Lt. Dan; Nov 16, 2004 at 05:12 PM.
Old Nov 16, 2004, 07:00 PM
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under a rock
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No sence of humor, or being a a$$, I just ask a question trying to learn. Maybe it was not ask in a manner you liked but it was a legitmate question. As to stumbleing in to the jet forum, nope came in the same way you all did. The question still stands.
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