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I take no credit for the image below. All artwork and information belongs to Blue-Hearts on DeviantArt:

(click on image for a higher resolution)

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I'm personally very impressed at her level of detail and how she managed to make a (feathered) winged human/ angel build seem at least believable. Then again, I'm not a biologist.

edit: this is only muscle structure, she has posted a bone structure one on her DeviantArt as well (as well as a few more, maybe).

edit 2: (sorry I keep editing!) let's say the bones are hollow, as user Shadowzee mentioned in a comment, otherwise they'd be too heavy to fly.

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    $\begingroup$ While interesting and detailed, a winged human is too heavy to fly. Without major changes to our Bone structure and muscles it would be impossible to fly. Or you can always add a touch of make believe or magic. $\endgroup$ – Shadowzee Aug 5 at 5:30
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    $\begingroup$ Hi pumkin, and welcome to Worldbuilding! I agree - this is an amazing piece of artwork. However, your question could use a little more work to explain what research you've already done and why/why not you think it's feasible. We have several questions on this site already about winged humans - did you get a chance to look around, and maybe take the tour or visit the help center? I've voted to place your question on hold until you get a chance to add some more information so you don't get swamped with unhelpful answers. $\endgroup$ – Dubukay Aug 5 at 5:43
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    $\begingroup$ As you edit it, it looks nice to just build the additional information into the body of the question rather than adding them as a list of edits at the bottom. StackExchange is nice because it automatically tracks edit history and other users can click on the edit history to see how the question has improved over time, if they're curious! $\endgroup$ – Dubukay Aug 5 at 5:44
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    $\begingroup$ Are we assuming that this winged person lives on a world of Earth-normal gravity? I suspect most of the "just too heavy" answers wouldn't apply on a smaller world, like Mars. $\endgroup$ – Shawn V. Wilson Aug 5 at 15:55
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    $\begingroup$ You can increase the air pressure on your world. With a high enough air pressure a human would be able to fly with a smaller sized wing (although you'd still need beefy muscles). $\endgroup$ – Ariel Aug 5 at 16:20
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Probably not

I agree that the work is incredible, but ultimately the problem with the design is always going to be the downstroke of the wing.

Birds have massively well developed pectoral muscles. In chickens, this is what we mean when we describe the breast meat. It's the largest single muscle group on a chicken and most other birds because of the sheer force required to pull the wing down and lift the bird up via the air underneath that wing.

The design in the picture has two critical faults; the first is that on a bird, the wing is in fact an evolved arm and therefore is connected directly to the pectoral muscle. These wings are behind the arms, with no clear muscle group in play for pulling them down.

The second is that the pectorals are nowhere near as well developed as they would need to be in order to support the body of the human in flight.

Even if we connect the pectoral muscles directly to the wings on the back, more or less rendering the arms useless, you would need pectoral muscles of a much larger size to generate the power needed to flap those wings. Remember, that humans are much larger creatures to most birds and therefore suffer the setbacks of the square cube law, which basically says that volume increases exponentially to length, surface area, etc. meaning that you need much larger wings and much larger muscles to drive them by proportion to a smaller bird.

If you're in doubt about that, check out the size of a hang glider. That gives you some idea of what size a wingspan a human may need to get controlled flight.

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    $\begingroup$ A great answer. However, a nitpick - volume does not increase "exponentially" relative to length or surface area. It increases linearly relative to surface area (x^3/x^2) and quadratically relative to length (x^3/x). It is sufficient for your answer to say that it increases. $\endgroup$ – Dast Aug 5 at 15:05
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    $\begingroup$ To be precise, volume increases cubically with length, and it increases as the surface area to the power of 3/2. $\endgroup$ – Tanner Swett Aug 5 at 15:59
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    $\begingroup$ Chicken is probably a poor example given that they have been bred to maximize meat and they also can't really fly. $\endgroup$ – Brad Aug 5 at 17:30
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    $\begingroup$ Not to mention that most (all?) birds have hollow bones, trading durability against weight... $\endgroup$ – Jared Smith Aug 5 at 20:40
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    $\begingroup$ @JaredSmith Well, we also have more air (and marrow, which birds have very little of) in our bones than actual bone mass. The main adaptations of bird bones are 1) the hollow insides are connected to the respiratory system, 2) the bones are very thin. Needless to say, neither would work for a "humanoid angel". $\endgroup$ – Luaan Aug 6 at 6:58
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Someone else used this exact picture and asked the same question. The picture is detailed but misses several important elements.

https://images.app.goo.gl/k3oPSuLqVxpikx967

This is a bird's anatomy, if you look at the bird you can see a massive pectoralis major (chest muscle).

https://images.app.goo.gl/v6QYooyoSV5SNguJ7

Looking at the skeleton that pectoralis major needs a massive potruding chestbone to attach itself too, and it needs to extend far out so that the forces the muscle creates are more aimed in a downwards direction. The picture above misses this because it would lose the human aestetic.

Besides the small pectoralis major the humerus of the wing is simply attached to the scapula (shoulderblade). The normal humerus is attached to the most complex kinematic chain in the body consisting out of the scapula, clavicula, costa (ribs), sternum (chestbone) and a long range of muscles. This humerus is just attached to the scapula, meaning it has the Range Of Motion (ROM) of the scapula as well. This means that most of the power generation for downwards movement has to happen with the protraction of the scapula, especially since the wings themselves have a small amount of muscle attachments (mostly the wing-triceps) that are able to pull it downwards. Unfortunately much of the power generation of the triceps is lost somewhere else as the triceps take up surface area where the supraspinatus normally attaches, which partially helps with protraction, elevation and upwards rotation. The placement of the triceps, which is almost on top of the win, also limits the downwards ROM as the muscle simply cant contract that far. For an easier reference of the ROM this woulf give, try moving your humerus (upper arm) forwards with your biceps (funnily enough the biceps are better at representing this than the triceps due to the construction of the wing-humerus). You'll notice it mostly does your lower arm and when you move your upper arm the biceps do little, but your pectoralis major+minor and serratus anterior do most of the work. But aside from the triceps theres barely any muscles that directly help the wings move downwards, so almost all flight movement has to happen with the scapula protraction on a very tiny ROM with relatively speaking very tiny muscles.

Just how big do these muscles need to be? Meet the Illiopsoas, two muscles often referred as a single muscle and while it might not look it in the picture they are the most massive and powerful muscle in your body:

https://images.app.goo.gl/9r34Y7kjyypBbKmDA

These muscles lift either your legs, or your entire upper body. They allow you to lean backwards and look up without falling over and when doing belly crunches they are secretly doing 95% of all the movement of lifting the torso&legs rather than your abdominus muscles. And this is the absolute minimum size that you would need to glide, not fly, glide. Just imagine having to jump, and the floor moves up for you to jump again faster. That is basically what flying would be like, one continuous jump with very little time inbetween. Try it now, jump as high as you can for half an hour and realize that you would somehow need to jump EVEN FASTER to "fly".

TL: Dr: no you wont be able to fly with the setup in the picture, although it is a very well done picture.

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    $\begingroup$ J.B.S. Haldane calculated that an angel would need a chest-bone that sticks out by about four feet. On Being the Right Size $\endgroup$ – Martin Bonner Aug 5 at 16:11
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In addition to the problems already mentioned, the wings are too high on the body. You need equal weight infront of and behind the wings. Having the wings attach on the shoulders, the legs would fall. It's not balanced.

Gliding animals, such as the pterodactyl, may have gotten aloft by running very very fast due to powerful legs, and as a result, needed smaller wings. The wing size could work if the body was sufficiently strong and sufficiently light and if the flight was primarily gliding not powered and extended flying.

But the wings would need to be attached on the sides down at least to the hips or top of the legs, not just attacked on the back down to the ribs. That extra extension would create balance for possible gliding - that is, if humans could run 45 or 50 mph to take off.

http://dinosaurpictures.org/Pterodactyl-pictures

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    $\begingroup$ The flying pose depicted won't work, but if you tuck the legs forward and extend the arms, that should take care of the balance issue. $\endgroup$ – Mark Aug 5 at 20:53
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    $\begingroup$ No, tucking will not work. The center of gravity (C.G.) for humans is located around the lower abdomin. To fly, the C.G. has to be towards the forward part of the mean aerodynamic chord of the wing, which is clearly at shoulder level. No matter how tighly you tuck, by the time the CG is under the appropriate part of the wing, the angle of attack is into the stall range. $\endgroup$ – Paul Sinclair Aug 5 at 22:07
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This is a very nicely detailed piece of anatomical speculation. However, at normal human scale, such a being would be unable to fly on Earth unless their muscles had a much higher force to volume ratio. A human sized winged being would require prohibitively large wings, and the volume of their muscles would contribute to them looking rather alien to us.

However, there are two circumstances under which having this anatomy could result in a being capable of powered, independent flight: The first is by reducing the scale of the winged humanoid, the second is by reducing the gravity of the environment in which they might fly.

By reducing the being in size to around that of a sparrow, this being may be able to fly on Earth. Of course, at that size, the being would not possess enough neurons in their brains to have anything near human-level intelligence.

On the other hand, reducing gravity would allow a human-sized flier. At approximately 0.1g and normal Earth sea-level atmospheric pressure, flight may become possible. Such an environment is most likely to be something like a large orbital habitat, where gravity is a function of speed of rotation rather than mass.

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A being with a non-birdlike (such as the winged humans shown) anatomy can fly, if the planet in question is more forgiving. Specifically, if gravity is less, and air is denser, less lift is necessary to fly with equivalent mass. Credit goes to Randall Munroe for the idea: https://xkcd.com/620/. See https://www.explainxkcd.com/wiki/index.php/620:_Wings for a discussion of the math.

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    $\begingroup$ Also higher oxygen content in the atmosphere so the lungs can stay... not so big $\endgroup$ – Richie Frame Aug 6 at 0:24
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    $\begingroup$ At some point, the distinction between flying and swimming gets a bit blurred... $\endgroup$ – Robin Bennett Aug 6 at 9:11
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    $\begingroup$ @RobinBennett On this theme, I've heard (Citation needed) that bugs don't fly, they swim in the air. $\endgroup$ – Matthew Grivich Aug 6 at 18:07
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Everyone is talking about the biology involved.

Let me approach this by the engineering angle. Humans already fly with wings. It's called gliding and these people do it:

Hang gliding

Flying squirrel suit gliding

And here is a video of a group of airbenders using wingsuits to glide pretty close to the ground, because some people are that crazy.

People in flying squirrel costumes can only glide down, generally speaking. People in hang gliders can gain altitude if they pass over an upwards stream.

The point here is that the lift you can get - from speed, from wing beats, or from streams - is proportional to the area of the wings.

If your angel creatures can hold their wings open, they will at the very least be able to glide somewhat - they seem to have more wing area than the people in wingsuits.

But in order to lift themselves... That's a no.

Look at the blue critter at the bottom right corner of the image below:

Quetzalcoatlus

Conservative estimates have its weight at around 75kg, which is about the average adult human male. It was much more aerodynamic than your angels, and seems like it had much more wing area.

Even if your angels weight, say, only 40 or 50 kg due to lighter bones, their shape still makes flying awkward. Their center of lift is not aligned with their center of mass, for example. That could be fixed with a bird-like tail, but I don't see that in the DeviantArt image.

So in all likehood your angels would be pretty good at base jumping. But they would have to land on water in order to not break any bones. To land on land they will need a parachute.

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    $\begingroup$ Note that Quetzalcoatlus used its forelimbs as its primary locomotion limbs when on the ground. It's hind limbs were essentially just for balance. That is how it could be so big - big birds need to run to take off, and that means they need big (heavy) legs which are just dead weight. Quetzalcoatlus could run and then take off by jumping - and use the same muscles for running as for flying. $\endgroup$ – Martin Bonner Aug 5 at 16:08
  • $\begingroup$ The flag/logo on the back of the suit glider's helmet looked rather like an "L" plate at first glance. :-) $\endgroup$ – StephenG Aug 5 at 22:33
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    $\begingroup$ It's worth adding that this is just for gliding. Even the lightest paraglider needs a 20hp motor to take off from level ground and climb. I'd love to know how the Quetzalcoatlus hunted if it was limited to landing at the top of steep hills that faced the wind. $\endgroup$ – Robin Bennett Aug 6 at 9:10
  • $\begingroup$ @RobinBennett it probably lived in very windy places. $\endgroup$ – Renan Aug 6 at 9:15
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I don't think that's going to work: in our body the pectorals are good at moving our arms because of their location and the interaction with the shoulder articulation.

In this design the pectorals still look better suited for providing strength to the arms, not to the wings: even with tendons transmitting the needed force, having them go around the torso to reach up the wing seems rather ineffective.

detail of muscle disposition

It would probably work better to have the wings as in normal birds, and some sort of tentacles on the back for manipulatory purposes.

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There needs to be a connection through to the sternum via very large pectoral muscles to the chest/front of ribcage. Large means like a pigeon's vs the size of it's body, with a protruding sternum. A human skeleton would be torn apart by such muscles, the bones that make up our skeletons are wrong also. The wings would have to be very large vs body size. The scheme would probably need to go towards large bat rather than large reptile. Reptiles have a single attachment point for each wing whereas mammals have a long web of skin all the way along the side of their body.

Maximum size of a flying animal is limited by % atmospheric oxygen, earths' gravity, strength of materials that cells can build.

The biggest mammalian scheme viable at the moment are bats like the big fruit bats in Australia

Back in pre history.... late Cretaceous, Carboniferous..... larger flying animals would have been viable, when higher CO2 levels would have supported thicker forests + marine algae to produce higher Oxygen levels, then it would be possible to get away with smaller wings and larger body size by flapping more rapidly, which needs a higher metabolic rate.

High CO2 allows the plants and algae to grow faster, so long as there aren't too many humans around.

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