wrote:

...

You could still get
uneven flow if you flew with one wing a bit low; remember that the
tanks are well apart and a slight bank will raise one above the other
to cause crossflow. Check valves could stop that, but they'd have to be
installed as low as possible so that the small amount of head pressure
will open them, and their springs would have to be very weak. My old
Auster had such check valves but still used two shutoffs because the
tanks were separately vented at the caps.

I'll add that check valves present an unwanted resistance to flow in
the intended direction, minimization of that effect tends to go
hand-in-hand with reduce reliably and completeness of closure when
the pressure is reversed.

If I was to build another airplane I'd have shutoffs right at the
tank outlets; maintenance on the system is a pain if you have to drain
the tanks every time you want to fix something, and it would be nice to
have them there in case of a leak lower down in the system while in
flight.


For that application, would not full-aperture ball valves be
appropriate?

--

FF