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My experience running a tank dry.

I may be interpreting what was written, but it sounds like the water froze in the tank, so testing the fuel might not have picked this up. I could be wrong of course. It's something that I don't believe I've ever experienced, but will keep an eye out for.

Sticking a fuel testing cup pin into the fuel sump drain port and NOT getting anything out of it would be a no-fly condition as well.
 
Another suggestions...make sure fuel flow from both tanks is good and the engine runs for a reasonable length of time on each *while on the ground*. In an RV, this is pretty easy...my checklist is to start up and taxi to the run-up area on one tank, then switch tanks and do the run-up and take-off.

That way, I'm reasonably assured that I have good flow from both tanks prior to departure.
 
You know your mission better than I do, but don't you want to balance the load a bit by changing tanks every 30/45/60 minutes or something like that? What I do is fly on the right tank while the minute hand is on the right side of my watch (minutes 0-29) and on the left tank when minute hand is on the left side (minutes 30-59). Seems that there is some additional (unnecessary?) risk in staying on one tank until it's dry, then changing tanks. Just my 0.000003 BTC.
My usual methodology is to takeoff and climb on one tank, using 10.5L, change to the other tank until fuel exhaustion, then switch back to the original tank. This proves I can feed fuel from both tanks early enough to discover a problem and allow an safe return, while at the same time giving me a known 'time-to-empty' from the second tank once stable at cruise power.
 
Here's an update on this thread, at least the core issue with it.

My 9A has an IO360 with Bendix injection and no engine-driven fuel pump, using the SDS dual electric fuel pump module through an Andair duplex fuel valve. Previously I had Airflow Performance fuel pumps and practiced running a tank dry a few times during Phase I, and it recovered just fine.

Recently I changed the fuel pumps from the AFP to the SDS module, including the Borla fuel pressure regulator for return back to the tanks, and today was a good day to repeat the test for actually running the tank dry. I climbed to 9,000 above a local airport with very little traffic and an 8800' runway (KBPG) and ran my left tank dry with 10 gallons still in the right tank, remaining within easy glide range of the airport. I saw the fuel pressure start to wobble from it's normal 40 psi and got the Dynon "low fuel pressure" warning at 25 and kept going - fuel pressure would wobble up and down as it caught slugs of liquid and vapor, and then about 25-30 seconds into it the pressure dropped below 15 and the engine surged for a few seconds as pressure fell through 5-6 psi, and the engine went cold. I left it as it was for another 15-20 seconds to make sure I was pulling a good slug of air into the system (since that seems to be the failure mode everyone is afraid of) and then switched tanks. Nothing at all on the fuel pressure for a good two-count, then at 3 seconds suddenly full pressure and full engine power was restored, zero hiccups past that point. This was all done using one single pump with the other pump in reserve. I do have an AFP purge valve installed at the injector divider, but did not touch it for this test.

A couple things out of this test - even if you've got your head up and locked, and accidentally arrive at an empty tank, you've got 20-ish seconds after the low-fuel-pressure warning with this setup to change tanks before the pressure drops enough to notice any difference in the engine. Second, recovery with the fuel pumps, even if they are slugged with vapor, occurs very rapidly and should not be feared. With that in mind I will not be shy about running one tank completely dry in order to maximize range if the situation called for it.
 
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Good data, but... It may be an important detail that your system's regulator bypasses to the tank, vs the typical boost pump>engine-driven pump that most users have installed. I suspect that the 'no empty tanks' caution from the current crop of pump vendors is driven by the fact that bypass on those pumps (which have built-in regulators) is back to the pump input. They probably fear that if the engine has stopped and isn't consuming fuel, then the pump will recirculate air instead of drawing new fuel.

The core pump is a positive displacement pump, and will pump air (self prime) pretty well, as long as the output is going somewhere.

Just my thoughts; worth what you paid...

Charlie
 
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