Alon A2 unusable fuel?

I gave E.I. 24 gallons for my useable fuel. That seems to work will with the fuel remaining on their CGR-30 display.

With the 415s and Forney mains draining so low a point and being sucked by the fuel pump I would think your very close to being right on for the mains. I have never tried to run a header tank dry, but I sure don't want to try while flying...

Wow!  That’s very interesting. Did you sump the tanks after it quit?  More modern POH’s will have an actual ‘unusable fuel’ listed to be used as part of the weight and balance. 

I have been an A&P mechanic for over 25 years.  Doing maintenance on a 767, the aircraft fuel pumps were used to pump the fuel into the fuel truck. Then the drain sumps were removed and the tanks were drained. Then another 50 gallons were vacuumed out by hand from inside the tanks.  (Talk about unusable fuel!)

I have no idea where the pickup on the Aircoupe wing tanks are, but they are typically designed to be slightly above the sump to leave some room for the inevitable water due to condensation.  The header tank gravity feeds the carburetor.   At some point the fuel in the system will be so low that the carburetor is going to be above the fuel in the lowest point in the system.  

I would expect something (a few ounces?) left in the wing tanks after they are pumped dry, and the remainder in the lines and gascolator below the level of the carburetor.  

I have ordered an Electronics International engine monitor and they are asking for unusable fuel.  Is it safe to say 1/10 of a gallon?   


 

As long as the fuel pump is working it's all "useable" unless Service Bulletin19 has been accomplished. SB-19 reduces the useable fuel in the fuselage tank by roughly 2 1/2 gallons, or 15.5 pounds as mentioned above. If the fuel pump is not working, none of the wing tank fuel is useable. If you're setting up an EFB weight and balance program, you need to burn the wing down tanks first before the fuselage tank.