ORIGINAL: marc s
Andre, whilst clunks in tanks often provide a reliable bubble free fuel flow to state that UAT's probably induce more problems is a tad rich.
In a tank you have a large mass of fuel flying around (even small movement makes one hell of a swirl - try holding a shallow tray of water and walking about ;-)) so yes a good clunk will follow the fuel within reason but as the fuel draws down the time the clunk spends in air increases and this will result in a greater chance of air being drawn in.
In a well made and properly plumbed UAT product the volume of fuel is small in comparison to the main tanks and the filter/pickup is fixed and not whooshing about, this as a device is going to provide a better chance of not drawing air in with fuel.
There will always be those who use UAT's and those who don't, choice is great.
Just one small note, I was asked to make 4 large custom CAT products for a very well known American aerospace company to use in a large three turbine powered experimental aircraft, the turbines are 400N units and the fuel system has worked flawlessly, so if at the cutting edge of technology the use of UAT type products is considered important then I would suspect they have done some homework
marcs
Marcs,
I am sure that for some type of installs a UAT would help, especially if the rest of the system is not up to the job. Problem I have with UAT 's( I used them as far back as 1980's in Pulse jets) is that during maneuvers the fuel is always going to go to the outside perimeter of the tank and the centre will be just air if the tank becomes too much of an airtrap. On pulsejets this was an instant flameout if you made any roll with some negative G's. This is where bladder tanks came in. A moving felt type clunk as described by John in the final tank is thus preferred. On my UAV systems we had 8 wing tanks feeding a 1 litre tank with felt clunk. I managed to get it certified as an airworthy military craft authorized to fly in mil airspace.
That said if someone thinks they need a UAT for a given install they probably do.....
What could be really usefull is a UAT that would constantly purge itself from air.
I would buy one....
Andre