912UL fuel line & fitting size clean up (video)

Hi John

On oil tank, oil cooler, fittings they are available in AN.  In the USA and all certified engines from Rotax the fuel system and oil lines are all AN (UNF is the term Rotax uses)  There is a slight difference in AN to UNF (or JIC is another term for the same type). The AN fittings have a superior thread peak and valley to the threads that leaves them with about a 20% stronger part.  The thread pitch and sealing surface, 37 degree face, is the same. You can see these fittings in the illustrated parts catalogue from Rotax. 

For homebuilders these are easy to source from automotive speed shop suppliers.  

The simple reason these are not used in the cooling system is the relatively low pressures and the size.  An AN fitting with a 25mm size would be extremely heavy.  This is why it was never a consideration for Rotax. 

Cheers