Fuel Return Lines?

Yes it would be prudent to install a fuel return line during your build as Rotax requires a return line for both the carburetor and injected versions of their 912. I recommend you download the installation manuals for the versions you are considering.

The return line is NOT an Arguable Option Option for the Fuel-injected engines.

If you Plumb your wing tanks as a single tank (ON-OFF Fuel Selector Valve) with a generous (3/4") crossflow, you can return the fuel to either side without issue. 

If the tanks are plumbed as two separate selectable tanks, (Off-Left-Right-Both Fuel Valve) the return line will need to switch in unison with the selected supply tank or the unselected tank will overflow in short order. 

A Dual Off-Left-Right-Both Fuel Valve will be required.  $$$

The return line has a 20-30 gallon per hour flow rate. (20-30gph is NOT a typo.)

It is not uncommon for 100% of your fuel to pass through the engine multiple times during a flight.

If the Rans has a header tank, you can return to the header tank rather than the wing tanks.

Ken Ryan wrote:

If the Rans has a header tank, you can return to the header tank rather than the wing tanks.

Good point, Ken.

As long as the header tank is vented, it will work.

Some installation return to the unvented Gascolator.

This is a bad idea as there are a lot of vapor bubbles generated by the pressure regulator that need to be vented.

Hi Bill, thanks very much for your reply.  Is your comment about returning the fuel line to the gascolator for the 912 ULS or the 912 iS (or both)?  My RANS S19 kit uses the 912 ULS and the return fuel line goes to the gascolator.

Mike