How does an upside down airplane's engine get fuel?

Airplanes rely on gravity to disperse fuel to the engine, but what happens when the plane is flying upside down? Tune in to this podcast from HowStuffWorks.com to discover ways that acrobatic planes fly upside down without crashing.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how stuff works dot com
where smart Happens. Hi. I'm Marshall Brain with today's question.
When an acrobatic airplane flies upside down, how does the
fuel get to the engine? Gravity is one of those

(00:23):
amazing things. It's constant and we take it completely for granted.
For example, the fuel system in any normal car or
airplane depends on gravity to position and move the fuel
in the fuel tank. A high wing monoplane would stall
almost immediately if you tried to fly it upside down.
Gravity draws the fuel from the fuel tanks in the

(00:45):
wings down to the engine. So how does an aerobatic
plane fly upside down and get fuel from the gas
tank to the engine. One technique is called a flop tube.
It's a tube with a weight on it that literally
flops around inside the fuel tank. When you fly upside
down or sideways, the fuel and the tank shifts, but
the tube follows the fuel and flops into position. There's

(01:08):
one other technique that's used on some airplanes. It's a
small extra fuel tank located near the pilot's feet. When
the plane is right side up, fuel flows down into
this tank. Then, when the plane flies upside down. This
tank is above the engine and it provides the fuel
by gravity. Be sure to check out our new video podcast,

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