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Since Tolkien put people riding on giant eagles in his books (or maybe even before that), the imaginarium of riding the winds on the back of magnificent birds has generated a plethora of images and other media.

Here is one such gallery

But one thing I see, is that the positioning of the rider atop the bird changes a lot. Sometimes it is over the wings, sometimes it is over the neck, sometimes even behind the wing articulations.

Some of these are not ergonomic. Not for the rider, much less for the bird.

So, I have to ask:

  • If we have humanoids riding eagles, where would they sit? Would it even be on top of the bird?

  • What would be the saddle's designs? Where on the eagle would the straps go?

Tech level is what we have here for the early XXI century. Kevlar, Teflon, Nylon, 3D printing, carbon-fiber, plastics, whatever is required for making it work.

This is , but only for the ergonomics. The basic assumption that there are giant birds humans can ride on is presented as postulate.

Also, I'm not concerned about using them for war, so they do not have a use as cavalry. Just transportation / sport. It is a modern setting, people ride giant eagles for sport, not war. Versus smart drones and supersonic ammunition, it is no use to fly a giant bird into battle.

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    $\begingroup$ This looks like two questions in one. Bullet 1 and 4 are about bird's biology and flight physics, and bullets 2 and 3 would be great as a follow up question. $\endgroup$ – Mołot Oct 4 '17 at 6:31
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    $\begingroup$ I know at least 1 species of bald eagle don't regurgitate semi-digested food to feed their young however maybe your domesticated oversized eagle can temporarily hold the rider inside their throat holding onto a periscope with a tube for breathing... unharmed! somehow... hopefully $\endgroup$ – user6760 Oct 4 '17 at 7:16
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    $\begingroup$ The Crossroads book series by Kate Elliott had eagles carry humans via a harness where the human was positioned at the eagle's chest. $\endgroup$ – Frostfyre Oct 4 '17 at 12:22
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    $\begingroup$ Interesting how all the riders in your gallery are buxom, half-naked women. $\endgroup$ – RonJohn Oct 4 '17 at 12:55
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    $\begingroup$ "it is no use to fly a giant bird into battle" ...You tell that to Gandalf when he grins and tells feather-butt to 'Put you down'. $\endgroup$ – Brent Hackers Oct 4 '17 at 13:38
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They will not sit on the bird, for (at least) two reasons. First, sitting is going to create a lot of aerodynamic drag, resulting in a bird that tires quickly. Thats why jockeys and bike racers lean over their handlebars, and - to pick something closer - why people who fly hang gliders do so in a prone position: https://en.wikipedia.org/wiki/Hang_gliding

Second is the matter of weight & balance. Basically, the rider's weight has to be pretty close to centered over the wings, otherwise the bird becomes unstable and crashes. (When you fly small planes, the manual has diagrams showing just how far from the CG you can put weight. If you add accessories, you need to adjust the table.)

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    $\begingroup$ Are you suggesting that the eagle riders should be below the eagles and in a prone position like hang glider fliers? If so, that's a good idea! Guess eagle and rider would have to take-off in unison, sort of, like taking off with a hang glider. This made me rethink the whole people flying on giant birds concept. Plus one for a nifty idea. $\endgroup$ – a4android Oct 4 '17 at 5:46
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    $\begingroup$ I found this while looking through a gallery of "giant eagle riding fantasy" on google: goodreads.com/book/show/210197.Spirit_Gate (go over the photo and click on enlarge cover) $\endgroup$ – John Hamilton Oct 4 '17 at 10:42
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    $\begingroup$ @a4android: I would think the eagle riders would lay on top of the eagle, with their weight centered between the wings. $\endgroup$ – jamesqf Oct 4 '17 at 16:49
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    $\begingroup$ @Mooing Duck: Not that top heavy, since a prone rider would be very close to the eagle's midline. Also supported along the spine, instead of squashed against the ribs and abdomen, which must flex in order for the bird to breathe properly. And while my knowledge of avian anatomy doesn't extend much beyond roast chicken, I think the strong muscles are underneath, in the bird's breast. So they pull the wings down on the power stroke, air pressure and structural elasticity push them up again. $\endgroup$ – jamesqf Oct 5 '17 at 3:40
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    $\begingroup$ @brichins. Micro is the key here. There is a difference between a tiny shift to compensate for ruffled feathers and a load that amounts to 25% of your body mass shifting significantly. $\endgroup$ – Mad Physicist Oct 5 '17 at 13:58
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Eagles are already used to carrying a load during flight. It usually happens after they hunt and carry their prey to their nest. It also happens on relatively short routes.

Therefore you have two options:

  1. Short routes: a light weight vessel where the passenger(s) or the load is accommodated, which is then taken by the eagle with its claws and carried to destination.
  2. Long routes: the passenger(s) lay flat on the back of the eagle, where the load deals the least disturbance to the flight asset. A periscope can be used to look the path and steer the flight. No way to enjoy to panorama, though.
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    $\begingroup$ On the eagle's back will be a huge disturbance to the flight asset. Even if you were able to stay out of the way of the wings, you would make the bird top-heavy and therefore very unstable. At the very least, it would cause a huge amount of energy expenditure on constant fine balancing adjustments. $\endgroup$ – Mad Physicist Oct 4 '17 at 16:22
  • $\begingroup$ @MadPhysicist I'm not so sure. Eagle wings already have pretty good dihedral which leads to excellent stability. Also, an eagle is already making a hundred tiny course corrections at any time so the eagle should able to handle minor instability. $\endgroup$ – Green Oct 6 '17 at 18:15
  • $\begingroup$ The rider's drag will reduce the eagle's range, no doubt. If the rider isn't flying in the prone position to begin with, this whole arrangement is a non-starter for anything longer than trivially short flights. $\endgroup$ – Green Oct 6 '17 at 18:17
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One thing to consider here is the eagle's carrying capacity vs its weight. A 12lb (very large) bald eagle can carry ~4-5lbs (source). Let's pretend that this carrying capacity of 1:3 scales up with size. You are pretty much forced to suspend the cargo under the eagle at this point, because you are asking it to carry nearly a third of its weight. Even with a cargo representing a much smaller fraction of the eagle's weight, placing the weight anywhere above the center of gravity will make the bird extremely unstable, no matter how carefully you balance the cargo because the eagle is not stable in one dimension like ground-based beasts of burden. That also happens to be how real eagles carry the prey they capture in their talons.

While contradicting the way eagle riders are often portrayed, being suspended under the eagle would actually have a huge advantages over riding on top for recreational applications:

  1. You could see where you are going.
  2. You could observe the panorama below.
  3. You could hunt with ranged weapons from an eagle without much risk of killing it. Archery would almost certainly be fine in terms of not knocking your own bird from the sky. You'd have to do a bit more research to figure out if firearms would work. I certainly wouldn't recommend using a bazooka or rocket launcher, regardless of how fireproof these eagles are.
  4. You could jump off with little risk to yourself or the mount. If people could ride eagles, that someone would try parachuting off an eagle is pretty much a given.
  5. You could have eagle-based UFC with strictly the riders fighting each other. This would probably be much more acceptable from an animal rights perspective, as well as safer. You would not want the platform and the combatant to be one and the same when you are very high up.
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  • $\begingroup$ This is a very good point. Unfortunately the result is that a 150lb person needs a 450lb eagle. Add 50lb of equipment and you're talking a 600lb eagle. You're squarely in microlight territory there as far as weight goes, and animal-wise that's the weight of a small pony. Getting this off the ground would be rather difficult! $\endgroup$ – Graham Oct 4 '17 at 23:43
  • $\begingroup$ @Graham, which is why OP accepts it for a postulate in their world. There are a few reasons this scenario is impossible. $\endgroup$ – Mad Physicist Oct 5 '17 at 1:20
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    $\begingroup$ Additionally, from below the eagle you can use ranged weapons on targets on the ground without any risk of hitting your mount. $\endgroup$ – Greenstone Walker Oct 5 '17 at 1:28
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    $\begingroup$ So, you're saying it's a simple question of weight ratios :) $\endgroup$ – brichins Oct 5 '17 at 13:36
  • $\begingroup$ @GreenstoneWalker. Sure. While OP does not want to use the eagles for war, hunting is a legitimate sport that I hadn't considered. Kinda like sniping off a helicopter. $\endgroup$ – Mad Physicist Oct 5 '17 at 13:46
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I'd say that the eagle should have a saddle or perhaps not even that, which is flush along it's back in between the wings. Here, a rider would either lay in a prone position or perhaps be sitting on their knees. In the front of the saddle, towards the eagle's head, there could be a bar or something for the rider to grip and hold on to.

The "saddle" should be attached by two straps that wrap the eagle's body, one at the base of the neck, where it meets the body. (Think; Like a collar) This piece attaches to the front-most part of the saddle. The rear strap wraps the body behind the wings. This is to me, the most efficient way that does not weight down the bird too much and doesn't restrict movement all too much either.

Additionally, straps and harnesses that attach the rider to the bird could be used for security reasons. However, if combat situations arise (not in OP's case) then attachment to the bird might be unwise if the bird is shot and the rider is attached and could introduce difficulty of getting free.

Sitting on the back of an eagle between the wings centralizes the weight and although it introduces drag, an eagle can catch fish from the water and fly away with them with relative ease, so I doubt that a human torso or head in the slipstream will cripple a giant eagles ability to fly.

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    $\begingroup$ When eagles fly with fish they point them head forwards for streamlining, so it's still important $\endgroup$ – Separatrix Oct 4 '17 at 12:43
  • $\begingroup$ @dannyboy it is a modern setting, people ride giant eagles for sport, not war. With smart drones and supersonic ammunition, it is no use to fly a giant bird into battle. $\endgroup$ – Mindwin Oct 4 '17 at 13:09
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    $\begingroup$ When I google "Eagle Flying With Fish" Almost all pictures show an Eagle flying with a fish whose relative angle and rotation to the flight path are irrelevant. Although these are pictures and they have no indication of whether the eagle changes grip on the fish in flight to reduce drag. I do however doubt that they do this and are more simple in their reasoning. More like "I have fish in claw, don't drop." and not "I should readjust the position of the fish in my claws to reduce drag and improve my aerodynamics." $\endgroup$ – DannyBoy Oct 4 '17 at 13:14
  • $\begingroup$ @Mindwin Yes, I know, hence the "(not in OP's case)". It was just a reflection on possible reasons why being attached with a harness might be a bad idea. If not in war, maybe if the bird has a heart attack or loses consciousness for some reason. $\endgroup$ – DannyBoy Oct 4 '17 at 13:16
  • $\begingroup$ You need to consider the weight distribution of the eagle. A 12lb bald eagle can carry about 4lbs. Even if your uber-eagle is not maxed out, adding a rider on top is still making it very top-heavy. It's like carrying a 50lb backpack, but in the air instead of the ground. $\endgroup$ – Mad Physicist Oct 4 '17 at 15:52
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I'd have the rider lying face down on the back of the eagle with some kind of aero fairing. Look to modern Moto GP or Boardman/Obree era bicycle time trials for inspiration.

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    $\begingroup$ Problem with stability arises. You can make a reasonably top heavy bike on the ground, but you can't have a top-heavy hang glider. $\endgroup$ – Mad Physicist Oct 4 '17 at 16:19
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I propose a rider lie down on the back. Maybe have straps that go around the base of the wing. The saddle could have foot/ankle sockets and "Handle bars" or leather straps by the shoulder of the bird the rider can hold onto if he goes upside down. I feel like if the rider were to ride the bird by the shoulder/neck area, he would put to much strain on that region, and could crack the bird's neck or the bird could just shove him off the shoulders.

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