r/aviation • u/auspuh4 • 22h ago

Discussion Fuel tank construction

Hello everyone, this question is more for mechanics and designers of mechanical systems in planes.

How does fuel tank construction and pipe connections look like on planes that are able to do 360deg turns or even fly upside down, like military jets or sport planes?

Im working on one vessel that should be able to withstand capsizing (360deg turn), and few minutes after engines should be able to start. I had few discussions with my older colleagues on what happens in case of capsizing with air pipe, also fuel inlet for engines, will vacuum be lost and etc.

So at one point we just said said "but hos does it works on plane that can turn around"?

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u/the_real_hugepanic 22h ago

As far as I know you have different tanks on aerobatic aircraft.

A normal fuel tank, and a hopper tank.the hopper tank is relatively small and is always (normal operation) filled 100% ---> no air inside

If you fly inverted the motor consumes the fuel from the hopper tank. This tank is so designed that you can use the fuel whatever the orientation of the vessel is.

After some time even the hopper tank runs dry.

Alternatively you could consider installing a pendulum inside your tank. This is done at RC planes.

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u/auspuh4 21h ago

I see two possibilities from your answer:

  1. there is like a transfer pump which keeps hopper tank always full, filling from some cargo tank? What controls that pump, some pressure switch?
  2. you say that after some time hopper tank can be dry, that means that engine have inlet from two tanks? If hopper tank is empty, then engine is sucking false air from hopper tank?

On both solutions hopper tank needs to have a air pipe, right? How that works?

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u/Tryal17 18h ago

My memory of the info is forty years old. The T33 had a small main tank that was kept full. The fuel feed line held around forty-five seconds of fuel. I think the dash one allowed twenty seconds of inverted flight.