Splitting the Glasair Main Fuel Tanks


DO NOT split your main fuel tank. We split ours and I don’t think is was worth it. Use the check valves to prevent fuel siphoning out the vents.

Glasair fuel tank flapper valve
Fuel tank flapper valve.

If you are concerned about fuel movement and imbalance conditions, add some additional flapper valves in the fuel baffles to minimize (slow down) the rate of fuel transfer from one wing to the other in uncoordinated conditions or sloped taxiways/ramps etc.


Splitting the tanks requires additional plumbing, a second sump and pickup through the spar plumbed to the valve through the A rib, a second fuel probe and associated wiring, a second inspection/access cover in the center of the wing (under your inboard leg), a center tank dividing rib, additional fuel baffle ribs and flapper valves just outboard of the pickups, and a new fuel selector valve. The lower center panel at the bottom where it attaches to the wing also needs to be modified.

Adding all this is not that much work, but it will add time, complexity and expense.

You will then have to switch tanks in flight, again, not a big deal (we do it in pipers and other low wings all the time). Not a problem unless you forget or have fuel selector problems that is.

Our fuel selector would get stiff after a few months and need to be removed, cleaned and re-lubricated. A BIG pain. If it wasn’t done, it would get so stiff, I wouldn’t switch tanks unless I was over or near an airport in case the handle broke off!

Switched to a better valve and so far so good.

The check valves were not available when we built the wing so we split the tank. Next time, I’d use the check valves.

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Neal Garvin
Glasair SIIS-RG, N15F