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  • If airplanes are so heavy, how is it that they can fly?

  • Hello flyers, Lissette here for DNews. Flying scares the bejesus out of some people but

  • it’s actually one of the safest ways to travel. That’s because along with the regular

  • aircraft inspections, strict regulations, and thousands of hours of training pilots undergo

  • the aircrafts themselves are made to withstand some pretty incredible challenges.

  • The wings of the Boeing 787, for example, are engineered to withstand one and a half

  • times the most extreme forces it would ever meet in flight.

  • There are a lot of things that go into making the wing that strong, like its design and

  • construction. But the most important factor is the materials used. Materials are where

  • everything starts and they determine how easy a part is to machine or weld, how strong it

  • is, how flexible it is, how it behaves at different temperatures, how it stands up to

  • corrosion, and how much it weighs. These are all factors aeronautical engineers have to

  • consider when theyre designing different parts. And for decades,

  • aluminum was the go-to material.

  • Forty years ago, aluminum could make up as much as 70% of an aircraft. Aluminum, though

  • half as strong as titanium, is lighter and, more importantly, much cheaper. It gets stronger

  • at colder temperature but stays ductile, and has it’s own anti-corrosion mechanism. Today’s

  • jets are only 20% pure aluminum, but the metal is still present in abundance, it’s just

  • mixed with other metals to form alloys. Aluminum has so many alloys it’s hard to keep track

  • of all of them even though theyre numbered. The most common one used for airplanes is

  • 7075, which uses a little zinc, magnesium, and copper as well as trace amounts of manganese,

  • silicon, iron, titanium, and other metals. The result is an alloy that’s as strong

  • as steel, but isn’t too difficult to shape, drill, or weld.

  • Techniques and technology for machining metals is improving - making other alloys available,

  • that were previously too hard to work with. New alloys like titanium aluminide are replacing

  • older nickel based alloys that were twice as heavy but just as heat resistant. In some

  • parts of the engine metals are being replaced altogether by parts that use ceramics reinforced

  • with silicon-carbides. The benefit of these lightweight parts is that engines can operate

  • at higher temperatures and run more efficiently. Reducing weight anywhere in the aircraft is

  • always a goal because it means the jet has to use less power to move - saving fuel. In the last decade, aircraft

  • makers have gotten even more clever with their materials in the pursuit of lightness.

  • Composite materials were first used for light structural or cabin

  • components, but more recently, theyve taken over metal for some serious structural parts, too.

  • Composites are incredibly light and strong, and can be molded into complex shapes. This

  • reduces the need for heavy fasteners or joints, which are potential failure points. Boeing’s

  • 787 dreamliner was the first commercial aircraft to use composites extensively. It has kevlar

  • honeycombs in the wings to make them light, flexible, and strong. The 787 also used carbon

  • fiber to strengthen the fuselage. This saves weight, and as a bonus, the cabin can be pressurized

  • more than previous aircraft, and composites can tolerate higher humidities without corroding

  • making the ride more comfortable. Carbon fiber was also used in the engine housing to trap

  • sound and make aircraft quieter.

  • But engineers are never satisfied. Theyre are constantly coming up with new alloys,

  • designs, and construction techniques to make aircrafter harder, better, faster, stronger.

  • HRL laboratories, in a joint venture with Boeing, recently developed the lightest metal ever.

  • The metal is arranged in a microlattice structure which means it’s about 99.99%

  • air. A light flexible material like this could be used inside the cabin and save even more

  • weight on future aircraft.

  • So that’s the technology making modern aircraft awesome. But what about future spacecraft?

  • What do we need to develop before we can rule the galaxy? Julian talks about that here.

  • Now that you know what planes are made of, does that make you more confident in flying,

  • or do you still get the shakes?

If airplanes are so heavy, how is it that they can fly?

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What Makes Airplanes Light Enough To Fly?

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    羅紹桀 posted on 2016/07/27
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