37-06 Step 5

The question: Should the bottom of the fitting (AN837-6D) be cut off bellow the nut to reduce the chance of fuel being pushed up the vent by fuel/air expansion?

The thinking: If left unmodified, with a full tank of gas the bottom of the unmodified fitting will be below the top of the fuel. Then thermal expansion of the fuel or trapped air could push the fuel up the vent line. Cutting the bottom of the fitting off below the nut would raise the fitting' entrance and minimize the potential fuel loss.

Thanks, Dave

Short answer. No. The venting system is designed to vent fuel overboard in that scenario.

Think high wing Cessna vent lines that drip fuel every time they are topped off.

That being said, I have only witnessed fuel drips from the vent line once on our -12. And I filled it up into the filler neck.

Dave,

Ditto what Kyle said.

That said, on the surface of things I see no issues with cutting the fitting as you suggest based on the reason you describe. However, that could be seen as (and is) a modification to Van’s construction plans.

Remember… if you are building your RV-12 as E-LSA, you are REQUIRED to build a carbon copy of the Van’s factory airplane per the plans… so technically no deviations can be made from the construction plans without Van’s written approval. If you are building your RV-12 as E-AB … then slice and dice/modify to your hearts content, as I have during my RV-12 build.

DaveLS said:

The question: Should the bottom of the fitting (AN837-6D) be cut off bellow the nut to reduce the chance of fuel being pushed up the vent by fuel/air expansion?

Click to expand...

I installed a 1/4" NPT flange similar to the one on the outlet to pump. There is nothing penetrating below the tank face. Also, this eliminates any possibility of molesting the seal of the tank/fitting if removal is required.