I was recently flying on an A380 and from my window seat, I could see the vast expanse of the wing. It was HUGE – you could play badminton (or cricket for those who are familiar) on it.
And I just couldn’t fathom how it holds up with most of its length having no support. It’s carrying the weight of thousands of litres of fuel and two large engines, while being subjected to all the forces there would be while taking off, landing, and in-flight banking, turbulence, etc.
What is the engineering that causes them to not break?
In: Engineering
First, the wings themselves are made of materials that are both very strong *and* very flexible, like aluminum alloys and/or various composite or carbon fiber materials. [You can see the internal structure of an airplane wing here](https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/854947b496763fb07fee4164cb986108/large.png). So the materials themselves are very strong, and [the wings themselves can also flex quite a lot](https://www.youtube.com/watch?v=–LTYRTKV_A) so they don’t snap under stress or force they’re expected to encounter.
>And I just couldn’t fathom how it holds up with most of its length having no support
They actually have *a ton* of support, you just don’t see it, much like how you don’t really see the steel and concrete support structure of a skyscraper. Aircraft wings aren’t just attached to the body of the plane on the outer skin. The internal support spars of the wings actually go all the way through the body of plane, which is called the [center wing box](https://www.researchgate.net/publication/355380957/figure/fig1/AS:1080311945396237@1634577847252/The-fitting-joint-between-the-center-wing-section-and-the-outer-wing-section-of-the.jpg). At the center wing box, the support structures of the wing are very securely attached to both each other and the internal structure of the plane, so all of the stress and forces from the wings are smoothly transferred across the entire body of the plane. It’s sort of like how the wheels on a car aren’t just attached to the outside of a car but instead are attached to axles that go across the width of the car.
So in short, strong yet flexible materials and also a ton of internal structure and support that you don’t see.
An a380’s maximum takeoff weight is 1.2 million pounds (545 thousand kilos). Sure, that’d be a heavy thing for you to carry around on your back, but compared to a non-airplane-object of similar size it is extremely light.
So, 1.2 million pounds. There are two wings, so each ~130′ wing carries 0.6 million pounds. 600,000lbs. Now that’s a lot of force, to be clear, but metal is absurdly strong. Treated 7075 aluminum has a tensile strength of 570 MPa. 82,700 psi. A single square inch of aluminum can survive 82,700 pounds of force pulling on it. You could hang the entire plane from a 4-inch aluminum cable.
The exact force required gets a little bit more complicated, since the wing acts as a lever, but the wings are something like a foot thick and several feet long. Not only is there plenty of room for the necessary aluminum – there’s so much room that the wing is largely hollow!
Mainly because they’re designed to take tremendously more stress than they’re currently under.
[Check out this wing flex test to see what the wing can really do](https://youtu.be/Ai2HmvAXcU0)
Actually in flight, it supports itself. The aerodynamic force on it is more than sufficient to hold it up.
The impressive part is that it’s capable of holding the rest of the plane up while in flight, and that on the ground, the rest of the plane can hold IT up. Most structures aren’t required to have to direction of load reverse itself like that. Wings are.
Fun fact: At 238ft long, the A380 is nearly twice as long as the Wright brothers first powered flight (120ft).
Another way to think about planes is – instead of a metal tube with two wings sticking out the sides, it’s a double wing with a metal tube attached to it. Seriously, wings are what flies, everything else is an augmentation.
This story hasn’t aged well because of all the grief Boeing is going through right now, but…there was a special years ago about the design of the 767, and one of the tests it had to pass was a wing stress test.
What this means is you take a wing, secure it at the root, then force the wingtip up, and up some more, and up some more. To pass the wing had to tolerate something like a 30 degree bend, which sounds outrageous, and it looks outrageous when you see it. You’d never imagine that something so massive could flex. Picture the wingtip being like (I’m trying not to exaggerate) 20 feet up from its starting position.
The wing on the show aced the test, got to the required number without any trouble (though it was sweat-inducing to look at) and this was a destruction test, so after passing they kept loading the wing, harder and harder, so they could find what its breaking point was. That wing was like 40-something degrees up before something inside finally let go and it sagged, and the design team cheered and celebrated because they had designed a wing that was tough as hell.
Engineer here. We use what’s called safety factor. We design the wing to be a minimum of 50% stronger than we ever need it to be.
Here’s more: we define “design loads” or forces that we expect the wings to carry throughout the flight envelope during its life. We multiple those loads by 1.5 and then design, build, and test the actual wings to ensure they won’t structurally fail.
Let us do some math…the max Takeoff weight of the A380 is 543000kg….the wings effectively have to produce an upward force greater than this to get it airborne….the wing area is 843sq metres or 8430000sq cm……so if upward pressure on wings is greater than 0.067 kg/sq cm or 0.9 PSI the aircraft will lift off…..compare this to the pressure on your car tyre 35 PSI…..so technically your car tyre has 35 times more stress than the wings of A380.
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