I don’t understand all the internet explanations using terms like “Range of attack” “Stall speed”
I’m trying to understand why it matters that the wing has a blunt front, if just angling a flat sheet slightly upwards should in my theory still lift it up at speed.
Although those round edges intuitively make sense somehow, i just want to understand why they work.
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As I understand it, the sharp edge would require a near perfect wind angle/airflow. The blunt rounded one allows for more play withe the angles, hence “range of attack”. Essentially it makes it more stable and easier no use
Take a butter knife (to be safe) and “slice” the air. Now try the same with a piece of paper.
Airplane wings are not made of heavy material like solid metal the way the knife is, it’s made of composites and a round shape in the front gives the wing more stability no matter whether the plane is ascending, descending, or turning.
1. It’s not all about minimizing parasitic drag. You also have to maximize *lift*, and thicker wings make more lift at lower angles of attack. There’s a reason you only see thin leading edges on old super-sonic fighters.
2. The wings have a lot inside them like fuel and mechanical components so they can’t be thin like you describe. Given how thick they *need* to be, the size of the wing required to give that sharp taper you describe would be prohibitively large.
Gusts and maneuvering and stuff change the angle at which air hits the leading edge. If the leading edge is sharp its response to those varying conditions isn’t as smooth.
And because it’s the leading edge you get a stagnation line anyway. There’s a line where the air has to choose between going over the top or the bottom. Air that can’t pick one or the other builds up and creates a slippery ridge of pressure that splits other flow-lines. So a blunt leading edge doesn’t make much more drag than a sharp one. It just behaves better.
That’s the explanation for old-school airfoils. There are wing designs from the mid 20th century to now that use sharp leading edges, slotted edges, all kinds of weird stuff. The details of aerodynamics are complicated enough that you really need wind-tunnel and flight testing. (Computers help you get close but they’re still not good enough to trust.)
Well, I just realized this is true for the U2 spy plane AND the smash hit band U2. Mind blown.
One reason is it buffers extreme “cutting” through the air. If it was more like a blade it would violently scoop air above or under the wing and be uncontrollable.
The goal basically is to split the airflow so that the air goes away from the top of the wing, but still close to the bottom.
This produces an area of low pressure above the wing, and the normal pressure underneath lifts the wing up into that.
The rounded shape affects how the air moves, and the width of the wing provides surface for the air below to press upwards on.
Submarines do something similar. The round front guides the water away from the hull, which reduces friction and helps the boat move faster.
Your second paragraph makes me think you have a fundamental misunderstanding of how a wing works. Wings don’t lift by changing their angle. They are shaped such that the air traveling above the wing has further to travel than the air below the wing. This means the air above is traveling faster and creating a low pressure zone above the wing. This is how lift is created. The best way to create lift like this is a sort of teardrop shape that is wide at the front. The control surfaces do change shape to turn or like flaps to allow the plane to fly slower while still creating enough lift.
Air doesn’t go fast around sharp corners very well. When you force air around a sharp corner, right behind the corner is a sort of swirly area where the airflow kinda loops back around on itself instead of just continuing on its way, while the main air flow goes around the outside of the swirly part. This is called ‘flow separation’ and it screws up the aerodynamics of a wing. The swirly part doesn’t have the same low pressure you would find if the air was flowing along the surface of the wing, and there’s lots of extra drag because it still takes energy to make the swirly part swirl, but that energy isn’t doing anything useful for your airplane.
So if your flat plate, sharp wing is curved a little, you could line the front of it up with the direction the air is going and it would work ok; there would be no sharp turn in the air flow and the air would follow the curve around and be going down a little bit at the end. But it would pretty much only work well at that specific angle. If you changed the angle very much, you’d suddenly have a sharp corner in the flow. For airplane wings, it’s important that you can change the angle, because generally flying slow requires a higher angle than flying fast, and it’s good to fly slow when you land.
> if just angling a flat sheet slightly upwards should in my theory still lift it up at speed.
It will, but it doesn’t do so very efficiently. With sufficient thrust, almost anything can be made to fly, but when you design an airplane; and especially a long distance transport plane, you want to minimize drag as much as possible. The more drag your wing creates, the more thrust you need to overcome that drag, which translates into more fuel burned. And fuel costs money, and airlines operate on thin profit margins.
To minimize drag you want the air to flow smoothly over the wing. The reason you don’t want a sharp leading edge is because the air can’t “turn the corner” fast enough, and so instead of flowing smoothly over the wing, the airflow will “separate” and create a large region of turbulent flow over the upper surface of the wing. To avoid going into the math, think of it a bit like driving a car – if you try to turn too fast, your car might go off the road. [Here is a picture of a flat plate wing in a wind tunnel](https://i.stack.imgur.com/kHr6r.jpg). You can see that the air flowing over the top surface doesn’t follow the shape of the wing, and lot of turbulence is generated as a result.
This condition is known as “stall”, and it results in such a large increase in drag and decrease in lift that most planes cannot generate enough lift to fly in this condition (some fighter aircraft have such powerful engines that they can). Any wing has an critical angle of attack at which it will stall, but for a flat plate wing this angle is very small, such that it is hard to generate much lift at all without stalling.
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