Fuel Follies

“Here’s my builder’s log,” said Walt, pointing to the open notebook on the workbench.

“That will be a big help,” said Chris, the DAR.

“I’ve got everything open for you.”

“I’m smelling gasoline. Do you have it stored here somewhere?”

“Ah, no, but I have noticed the smell after the cockpit is closed and then opened up for some reason.”

Chris walked over to the cockpit and sniffed. “Yep, it’s gasoline. “I think you have either a fuel leak or the hoses are not the right material.” Chris peered inside. “Is this a header tank you added?”

“Yes, I thought it would be a good idea.”

“Can you show me a drawing with the fuel line routing?”

“Ah, no, I just winged it.”

“I’ll tell you what. I’m going to let you solve the leak before I inspect the airplane. Give me a call. Also, please document the addition of the tank for me to review.”

As a technical counselor, I see issues with fuel systems that cause trouble right from the beginning. Here are some tips to consider as you plan your build.

Adding stuff that’s not in the plans

Yes, our airplanes are experimental, but you also want your airplane to be safe. Adding things is fine; just make sure you’ve checked in with the manufacturer and the builders’ group to make sure you have it installed safely. Document any work that’s not already in the manuals. You’ll be glad you did later, and it will enhance the resale value if you ever sell.

Fuel valve selector

Managing fuel while in flight should be simple and straightforward. But on many of the aircraft I’ve inspected, it’s confusing and complex. There should be only one fuel selector in a single-engine aircraft. It should be in a visible, easy to reach location for the pilot when he or she is fully belted in. The selector markings should be clear. 

Fuel filters (Non-fuel injected systems)

Some builders decide that the more filters they have, the better. More filters mean more opportunities for fuel starvation and more maintenance. What recommendation has the designer provided? Is it easy to reach and change out?

Sump drains

As handy as the gascolator is, it doesn’t replace having sump drains at the lowest points in the system. If you have a gascolator it does not have to be at the lowest point as long as you have sump drains at the lowest points. 

Fuel vents

Sometimes seen as an afterthought by builders, fuel tank venting is critical. Using a vented fuel cap without tank vents may not provide the air exchange needed to keep fuel flowing from a tank. Check and verify the details.

Winging the design

Don’t decide to design a special fuel system for your homebuilt unless you’re an expert. On design issues, check with the aircraft designer and/or the manufacturer for the kit you are building. If there is a builder’s group, they can provide additional real-world experience. 

There are two things that you do not want when you start flying: to unexpectedly run out of fuel from a design or build error, and to have a leak from same. There are enough things that can go awry without an engine out or a fire. Stay safe.