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 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 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 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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