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So, dragons, gryphons, what have you. They're usually (before Skyrim and Game of Thrones in the dragons' case) depicted as six-limbed, quadrupedal creatures. Now, the thing is, staying aloft is much easier than getting into the air. If I could cheese the takeoff, I could basically cheese flying.

According to a 2013 paper from Michael Habib, evolution often constrains the maximum size of flying creatures based on how they take off. Birds, for example, have a mass-inefficient launch scheme, as they use their legs to get the ground clearance for their wings. Those legs become dead weight during flight.

https://www.academia.edu/12192191/Constraining_the_air_giants_limits_on_size_in_flying_animals_as_an_example_of_constraint_based_biomechanical_theories_of_form

Bats and giant pterosaurs, however, can take off using their flight muscles and wings to pole-vault into the air. This works for about wingspans of 11 meters, the predicted wingspan of giant pterosaurs.

For heavier dragons, we could alter the wing's shape to have a higher surface area at the expense of aspect-ratio, which might not be a big problem.

The aspect ratio determines aerodynamic efficiency, as a high-aspect-ratio (read: very long and narrow) wing can generate more lift at lower speeds by separating a longer tube of air around it. However, due to how long it is, this wing-type requires lots of muscle to move because of leverage, and ridiculous ground clearance, forcing the bird to taxi, and get to sufficient speeds that way.

We are looking for a middle ground here, which comes on the wings of eagles, pelicans, and stonks.

Slotted, lower-aspect-ratio wings with a big area are preferred. While they require some speed, they don't suck at gliding, require less ground clearance, and the slots can enslave harness the wingtip vortices.

But, here's the thing, assume we made the wings, they span about 11 meters and have a realistic wing loading (25> kg/m^2). Got all that? Well, we still have the issue that launch strategies are morphology-specific, and my dragons and gryphons have a lower profile than the quetzalcoatlus (i.e: they aren't as tall as a giraffe), plus an extra pair of lighter limbs, optimized for burst-speed.

So, now I'm here, thinking if there's a way to come up with a sensible launch strategy that can work with a creature that's less vertical than a giant pterosaur, and has six limbs. It's supposed to either exploit the creature's body plan, work in spite of, or regardless of it.

What should that launch strategy be?

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  • $\begingroup$ worth noting bird take off is so weird because birds evolved flight weird, they evolved into flyers WHILE having to maintain good running thus they have two decoupled motor systems. It is also why they evolved flightless ness again and again. so if your creatures do not use their other limbs in flight expect bird like inefficiency. expect big hind legs like cats to get a good jumping height. $\endgroup$ – John Dec 7 '20 at 2:32
  • $\begingroup$ Science based: There are constarints. Maintaining such a heavy undercarriage with muscles and drive trains would most surely make a vertebrate creature prohibitively heavy for flying on its own. Insects, ok ... $\endgroup$ – a_donda Dec 8 '20 at 11:55
  • $\begingroup$ Note one problem with high aspect ratio wings is they are heavier, becasue longer wings ae subject to greater stresses due to having longer levers. they are also worse at takeoffs because the take off flight stroke is smaller (otherwise they hit the ground) $\endgroup$ – John Jan 8 at 6:34
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Hm... I am not a expert on aerodynamics of the biology of flight, but such a creature might fly using a couple methods. It may:

  • Have a sort of sac on itself that stores pressurized air, and that gives the organism the punch it needs to launch into the air, and it would continually fire bursts of air to keep itself afloat-the sacs could be located on the 6 arms, then the creature would be able to control it's flight much better. Sort of similar to how an octopus 'flies' in water.
  • You could have a creature that has 6 legs that are also wings, although then the body plan of the creature would be a mess and idk whether it would be able to fly or move at all.

Overall the sac method is the best, as it's been used by organisms here on earth already. Honestly the biggest issues here are aerodynamics and weight.

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Why would the pterosaur and bat approach not work just because you added two more limbs? If you have any decent-sized dragon actually rear up on its hind limbs, it's going to look very tall: that isn't any reflection on its typical posture when you're talking of a six-limbed dragon.

If the wings are sturdy enough, they can be used to push off the ground together with the four legs (or two legs and two arms, however those are defined for this creature). If there's enough muscle in the wings for true flight (not just gliding), there's enough muscle in them to provide a lot of lifting force when taking off, presumably enough to gain the necessary clearance to flap the wings; otherwise, this creature probably wasn't able to fly properly in the first place. Your solution is actually very simple: the wings don't need clearance for taking off when pushing them against the ground is what gets you that clearance.

Of course, there's still the problem of cramming in sufficient musculature for six limbs in a dragon-sized flying creature (not to mention the vital internal organs and arteries and so on) without making it too heavy to take off, but that isn't in the scope of your actual question.

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Running jump

I would have posted this sooner, but I was mesmerized by my source material.

In the linked gif, notice the Malinois' form: after a running start it plants its front paws, plants its back paws immediately behind its front paws, then leaps again off its back paws. Though I wouldn't want it to jump off my back, the same principal could work for a dragon, depending on size.

If you want your dragon to be able to run at speed, consider limb structure on four-legged animals. With a few exceptions, most of use "rear-wheel drive", which requires stronger back legs than front and lends itself well to jumping under speed

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make it go to its hind legs, here, you start flapping a bit, then you get a bit of a jump, synchronized with the flapping, and if you get enough thrust, you could get of the ground,

but what you really want is this, a launch that uses all 4 legs foreward, and the wings to get a bit of upthrust here, otherwise,

running, to flight is not very good, but it is what some birds, and in most stories, gryphons, even if this is technically worse than birds, and better, as it tells you they can run fast, but it is more flight drag,

after that i can not really see it work, apart from insect takeoff

and one that is a mix of some i said, as well as others

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