Its very interesting this debate, especially as most of my 'modelling' focus and products have almost exclusively been around fuel delivery and air management.

Most UAT's can be mounted in any orientation, its good to have a UAT that can be emptied of air by a reverse pump action, however following a lot of research and testing my view is to focus the biggest effort at the 'source' i.e. in the tank where the air is first ingested.

On a precautionary note there are many materials used to 'separate' or 'prevent' air from entering the pump side of a fuel system, most are not designed nor intended to be used with fluids, in fact most are for pneumatic applications not fuel systems.

I'm happy to fully refund in full anyone who can prove my BULLET clunk products don't reduce dramatically the amount of air drawn into the UAT or pump regardless of your flying style

This might be of interest to those who perform aerobatics:

Natrix and Bullet - the basic facts were like following: after starting training for f3s schedule/maneuvres we faced Hoppertank about 2/3 empty after each flight as shown on the pic - no shutdown of turbine but not acceptable and dangerous - schedule/aresti attached. That never happend before performing showflights or flying just for fun, so it must have been caused by all the long downlines in the given schedule, placing kero in front of the tank and having clunk outside of fuel... and Turbine cutoff is nothing you'll face during competition...
Replacing Brassclunk by Bullet solves that issue immediately, we never experienced any airbubbles in the Cat again, not one single ml of air. We tested 220N Behotec at full throttle - 8mm Bullet buffers 8 seconds "airless" runtime after being moved out of kero level on testbench.

This is from Patrick Hofmaier who won the German F3S championships this year flying a Paritec Natrix.

marcs