Why is it so difficult for us to just replicate a bird instead of the kind of fixed wing aircraft we have?
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Flapping bird wings are kind of inefficient. They’re great for picking yourself off the ground, but require a lot of energy to keep going
Larger birds, which are still small and light compared to an airplane, achieve flight easier by riding updrafts in the air and gliding, with very little flapping at all.
This is what the fixed wing aircraft replicates. This has added benefits of less turbulence, with the plane not being pushed up by the periodic addition of lift.
Number one reason is there is no need to.
The mechanics and engineering behind a pivoting wing that is also supporting of the weight needed would be complex. Also, the thrust provided wouldn’t compare to that of modern engines.
So more complex with more things to go wrong for less benefit.
Actually, I know it may not be intuitive, but helicopters fly like birds. Unlike fixed wing aircraft, helicopters manage lift, direction and thrust with their blades, as birds do to their wings. While airplanes handle lift with their wings (and other lifting areas), thrust with the motor and direction with flight control surfaces (e.g. ailerons).
If your question is why don’t we have airplanes which flap their wings: basically we don’t have any kind of material which could handle that kind of forces. Additionally, as others have said, it would be very inefficient.
It’s not that it’s difficult. We realized early on that mimicking birds wasn’t the way to go. Continuous thrust and non-moving wings are more efficient and simpler.
The answer is because we can’t. It’s somewhere between incredibly difficult and impossible. If we just built a plane-sized bird it would never get up off the ground, or it would shatter itself into pieces.
There is a general principle in mechanics and bio-mechanics called the square-cubed law. It applies to a lot of things, but in this case we’re referring to muscles and bones. The strength of a rope or the power of a muscle are proportional to their cross-sectional area. Making them thicker makes them stronger, but making them longer doesn’t. Same thing goes for bone.
When you double a 3D object in size, you’re doubling each dimension: height, width, *and* length. That will make each part of the object 4x as thick, but 8x as voluminous… which also means 8x as heavy. The strength scales up with the square of the multiplier, while the weight scales up with the cube of the multiplier.
So if you scale something up in size, the relationship between an object’s mass and its strength-to-weight ratio will go down at roughly a linear rate. Scaling up a bird to something large enough to carry a human would be 10x too heavy to lift itself. You’d have to replace the bones with much thinner, lighter materials, and the ‘muscles’ with much more power-dense actuators. And while we have developed materials and engines that can do that are better than bone and muscle, we haven’t developed ones that are *ten times times* stronger than bone and *ten times times* more powerful than muscles. And that’s just for carrying one person – forget about a vehicle large enough to carry hundreds of people.
So, it’s just mechanically not possible with the materials we have and, above a certain size, not possible with materials likely to exist. We could make toy ornithopters similar in size to birds, but that wouldn’t carry people. And that’s easier said than done because biological muscles are actually very impressive and power dense, and have a very convenient form-factor. We haven’t really developed an artificial muscle that can compete, and electric motors of similar power density are going to be bulky blocks with pullys and cabels rather than a directly embedded elastic muscle.
The closest we have are gliders, which are somewhat similar to birds in flight. These are massive, fragile vehicles that only weigh a few hundred pounds despite having wingspans of over 40 feet. The pilot is easily a third of the weight, and these craft are little more than fiberglass shells and a few cables to control a few aluminum flaps, rudders, and elevators on single hinges. The complexity and weight of including the hinges and larger, sturdier wings for complex wing movements and motors to move them would easily double or triple the weight, and render them unable to fly at all. If we want to make gliders fly, we need to use very power-dense petrochemical fuel and small jet engines, and even then that’s just enough to sustain flight, not to let the glider take off under its own power.
One thing that hasn’t been mentioned either is that the wing shape of a plane (airfoil) does in fact replicate/is very similar to a birds wing in cross-section.
It’s not hard…. At the size of a bird. Beyond that, things start to fall apart
Birds wings cannot carry much. There’s this fact of the universe called “the square cube law”. Tldr: if you make something bigger, it’s weight will increase faster than its size. This law is why there aren’t many elephant sized birds. If they got too big, their bones would be too heavy.
We can technically make bird-sized machines, but bird-like wings don’t really scale up well. They get too big, they just can’t support their own weight. In fact, it’s why there aren’t many elephant-sized animals. Most could not handle the weight of being that big
Tldr: Birds just aren’t the best at flying. That goes to aero engineers.
We build with metal, it’s much easier to build static wings and spinning engines. Birds build with bone and muscle. For them it’s easier to build things that stretch and retract.
What we have is more energy efficient. Also we are heavy and fleshy and all of our stuff that we fly around with us is heavy and cumbersome hahah.
Bird wings are great for making a lot of constant adjustments and sharp turns, and quick ups/downs. Planes don’t really need that, and need efficiency and reliability more. Just like a bird that is gliding for a long distance won’t move its wings too much to maximize lift and reduce energy use, a plane’s straight wing design works well for our long-distance travel- and in fact looks quite similar to a bird’s straightened out wing.
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