Yesterday i was watching Wrath of Titans and my wife asked "did those exist?" off course not i told her... but then, i wanted to know how long the wingspan of those mythic animals would need to be for them to realistically be able to fly.

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Please, take this into consideration:

The pegasus is like a horse with wings.

The musculature needed to move the wings with the required force should not be taken into consideration (optional, consider them).

The wings should be bird like, not bat-like or fly-like.

Please, oh please, for the sake of sciencie and everything that's good, use metric system

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· 7y · edited 7y
I started with this DotPhysics post that does the calculation for humans by extrapolating from birds:

Eyeballing the graph, it looks like horses (which I assume are about 450 kg) will need a wingspan of 10-20 meters.

But then we need to wonder how the pegasus uses those wings to fly. You mention birdlike, but there is a large variety in bird-flight. On one end, there is hummingbird-style flight (allows for hovering, but requires large muscles and large wings). On the other end there is albatross flight (takes advantage of weather systems to minimize muscle usage).

This thread has a nice discussion from which I got more numbers:

In particular, we can probably rule out Hummingbird-style flight. The muscles would interfere with the horse's leg muscles and would end up being heavy compared to the horses body mass.

However, one commentor mentions the Piper J-3 Cub, an airplane with a mass similar to that of a horse and a wingspan of ~11 meters. It has a stall speed of 38 mph.

The 25 mph number is actually fortunate, because 25 mph is also the typical galloping speed for horses. So a horse with albatross style wings could run to achieve liftoff.

I can use the lift equation from this page on Wikipedia to calculate what the new wingspan would have to be, assuming the wings have a similar efficiency to the Piper J-3 Cub:

The lift is proportional to airspeed squared and the area. Thus, I can construct the following equation (Assuming the width and span scale together):

(25 mph)2 *(Horse Wingspan) *(Horse Wing Width) = (38 mph)2 * (Piper Wingspan) * (Piper Wing Width)

Thus, the new horse wingspan is 17 meters or 51 feet.

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As most horses are only 8 feet long, their wings would require at least 3 elbow joints in order to fold along their flank like Pegasus's wings are often shown to fold.