Sunday, March 6, 2016

Matchdrilling the left wing tank (Again) Researching fuel return lines - 4 hours


Spent the morning working away on the left wing tank. The tanks is all cleco'd so I just need to match drill the holes and countersink the baffle rivet line.


I countersunk exactly the same as before.

I then drilled the drain flange. It took some time to figure out how to center the flange on the factory punched hole in the skin. After some trial and error. I found that the center punch worked perfect as its taper ensured the smaller drain flange hole sat perfectly in the middle of the larger factory hole.



P.S I know that the flange goes to the outside of the skin and not the inside as shown. Its just easier to work with it this way.


I spent the evening researching the details needed for the fuel tanks with respect to the flop tubes, fuel return lines, and fuel sender locations (with the flop tubes).

The burning question is do I need to install the fuel return line? The information is not exactly clear, and most build sites have the fuel return line. But the item that concerns me is what roadblocks will I run into placing the return line in through the root rib. Will I hit something?

So far, from what I can tell if I go Bendix or Precision fuel injection, no return line is needed. Since I plan on using an Aerosport Lycoming Clone (Which use the Precision FI) or a stock Lycoming (Which uses the Precision or Bendix). With the AFP system, a purge line/valve tees back into the flow line (before the selector valve), so you don't need return lines in the tanks.
 
ECI fuel injection uses the Return lines. Return lines if installed are typically placed away from the pickup to prevent 'frothing' in the tank which could get sucked up into the pickup and maybe introduce air into the line. Usually a couple bays over is fine.