[sathackr]

How does the fuel get from the tank to the jet or fuel injected engine when the pickup is on the bottom of the now upside-down tank?

There are ways to ensure fuel delivery, but the problem certainly isn't unique to carbureted engines, only the particular issue of managing the fuel in the carburetor bowl.

[bigiain]

In "toy planes" we (used to) use "clunk tanks", where the fuel pickup is a piece of flexible tube with a weight on the end, so no matter what orientation the airframe is in, the "sloshed fuel" and the fuel pickup end up in the same place (near enough). For aggressively aerobatic model planes (like control line combat wings) a pressurised fuel bladder was sometimes used (made, back in my childhood, we made these from baby pacifiers!)

Note: this is a couple or more decades old knowledge... Modern electric powered rc planes and builders don't have this problem to deal with.

[Neliquat]

The issue is a non issue. For ages in planes, race cars, etc we have had fuel cells. A few types exist, from just adding more baffles and pickups with vapor locks, to fuel bags (no air to make it to pickup) or the more modern foam matrices that use capilary effect.

[sathackr]

As I said. There are ways to combat the problem, but the above comment that it did not apply to jet engines or fuel injected engines did not take into consideration the requirement that the entire fuel system be able to operate at low or negative G's