Hi Anurag:

That is scary!

I am suspicious that you might have had trapped air in the ACCU sack from the start due to incomplete purging, and then with each flight you may have added a small amount of additional air until you reached the sucking air and not fuel limit. I have used Tom's ACCU before, but don't like the fact that you can't see what is going on inside. It is very similar to a BVM UAT with the semipermeable sack inside.....just has the non-collapsible alu housing. I no longer use them and am back to a BVM UAT in my UB.......I am well aware of all the posts about UAT and P-200, but in my case, I have had zero problems over about 57 flights. Zero flameouts with lots of full throttle hill climbs. I occasionally see a small amount of fine bubbles of cavitation forming at full throttle in hot weather over 90F, but the quantity of air at the end of the flight is no more than a few mm from the top of the UAT. I use all 6mm OD clear P.E tubing up to the pump. I only use Tygon on my fill line.

I would first purge the ACCU. What I do is loosen all the fittings holding it in place. Then fire up the turbine, put on your ear protection and run up to at least 1/2 throttle....then shake and rotate the ACCU thru a full 360 degree, holding it top end up and then bottom end up. That way you don't have to shake and roll the whole airplane.

When all bubble appear to be out, then run the turbine at 3/4 throttle until the mains are empty and about 3/4 fuel remains in the hopper, carefully checking for any bubbles......finally briefly run up to full throttle for 8-10 seconds before shutting down. Then refuel, carefully observing how much, if any air, escapes back to the hopper tank during the initial re-filling. Should be only a few bubble, no more......

The only other way to get air into the ACCU and the line from the hopper to the ACCU would be a leak between the two, but it sounds like you have definitely ruled that out.

Tom