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

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<v Speaker 1>Welcome to brain Stuff from how stuff works dot com

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<v Speaker 1>where smart Happens. Hi. I'm Marshall Brain with today's question.

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<v Speaker 1>When an acrobatic airplane flies upside down, how does the

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<v Speaker 1>fuel get to the engine? Gravity is one of those

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<v Speaker 1>amazing things. It's constant and we take it completely for granted.

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<v Speaker 1>For example, the fuel system in any normal car or

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<v Speaker 1>airplane depends on gravity to position and move the fuel

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<v Speaker 1>in the fuel tank. A high wing monoplane would stall

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<v Speaker 1>almost immediately if you tried to fly it upside down.

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<v Speaker 1>Gravity draws the fuel from the fuel tanks in the

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<v Speaker 1>wings down to the engine. So how does an aerobatic

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<v Speaker 1>plane fly upside down and get fuel from the gas

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<v Speaker 1>tank to the engine. One technique is called a flop tube.

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<v Speaker 1>It's a tube with a weight on it that literally

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<v Speaker 1>flops around inside the fuel tank. When you fly upside

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<v Speaker 1>down or sideways, the fuel and the tank shifts, but

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<v Speaker 1>the tube follows the fuel and flops into position. There's

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<v Speaker 1>one other technique that's used on some airplanes. It's a

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<v Speaker 1>small extra fuel tank located near the pilot's feet. When

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<v Speaker 1>the plane is right side up, fuel flows down into

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<v Speaker 1>this tank. Then, when the plane flies upside down. This

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<v Speaker 1>tank is above the engine and it provides the fuel

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<v Speaker 1>by gravity. Be sure to check out our new video podcast,

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