Surge Tanks

[punkalouver]

Big planes have them, small planes don't. At what size does this become a necessity. What is the smallest aircraft type you know of with surge tanks?

[Sidestick_n_Rudder]

It’s not about size I think. More than I’ve seen fuel spilling through vents out of of a over fueled Cessna or some such...

I suspect surge tanks are required by CS25 specifications, that’s why big planes have them...

[punkalouver]

Originally Posted by Sidestick_n_Rudder

It’s not about size I think. More than I’ve seen fuel spilling through vents out of of a over fueled Cessna or some such...

I suspect surge tanks are required by CS25 specifications, that’s why big planes have them...

Thanks,

Maybe someone could let us know if there is a regulatory requirement.

[megan]

I would assume this be the regulatory requirement.

§25.969 Fuel tank expansion space.Each fuel tank must have an expansion space of not less than 2 percent of the tank capacity. It must be impossible to fill the expansion space inadvertently with the airplane in the normal ground attitude. For pressure fueling systems, compliance with this section may be shown with the means provided to comply with §25.979(b)

FAR 23 aircraft don't seem to have any explicit requirement. As SnR notes, you will see fuel coming from vents, usually after refuelling, the cold fuel expands under the influence of the sun on the wing warming. Have seen fuel venting in high wing Cessnas in flight in steep nose down conditions following refuelling.

[punkalouver]

Thanks,

So it looks like every FAR 25 aircraft is required to have surge tanks.

I see from the ATR-42 manual that they follow the regulation for 2%...."An additional volume in each tank allows a 2% thermal expansion of fuel without spillage."

It would be interesting to know if there are surge tanks on an of the non-FAR 23 aircraft. I wonder how it worked for the large piston airliners back in the day.