Jason, one of the issues was at Mississippi Afterburner circa 2001 (I think, could be a year off). It was in Dennis Lott's BVM F-4 (awesome aircraft!). Dennis would have to address this to be certain, but from the way I understood it it appeared that the UAT started leaking around one of the fittings. It was one of the planes first flights (I think) and it ended in a dead stick that was a close call. The other failure was at that same jet meet, but to tell you the truth I don't remember any details about that one so lets just wipe that one out (all I remember was that there was another problem, possibly related to the same failure mose).

You said "but with the uat you can almost empty it". ANOTHER reason to use the pleated paper instead! With he pleated paper, you CAN empty it! I once flew the original Isobar dry just to test the pleated paper technique when it was new to me (I guess around 2000 - 2001). I dead sticked her in and looked at both the main tank and the header tank. The main had a tiny bit of residue in it that could be seen only if you tilted the plane so that anything left would gather in one corner. Same thing for the header with [erhaps 2 or 3 drops remaining. I was truly amazed. The surface tension phenomenon (the same reason that a UAT does its job) keeps the pleated paper pick-up sucking fuel even when 95% of its surface area is exposed to air (that's what Steve Ellzey told me they had shown in the Lockheed Martin lab in Texas where he works on small turbine powered cruise missiles back in the 2000 time frame, which is why I tried the pleated paper).