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A hang-glider or a gyro-glider would suffice also, with the purpose of actually working.

I was hoping it wouldn't require a motor, because I doubt a motor could be built in medieval times.

If it could be built, how much manpower and resources would go into one single one? Would it be viable to mass produce in military applications (surprise attack on lower altitude enemies)? How reliable would the thing(s) work?

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    $\begingroup$ For gyro-plane you need motor, if your heroes are not super-humans... not viable for comparable to us. Ability to build motor electrical or combustion means you are not in medieval for sure... With this level of science and production you may as well build machine-guns. $\endgroup$ – Artemijs Danilovs Mar 17 at 19:55
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    $\begingroup$ Thanks for the upvote, but it is usual to wait a bit with accepting to see if better answers come around. So you should take the acceptance back. I'd be happy to get it again, tomorrow or the day after ... $\endgroup$ – o.m. Mar 17 at 20:01
  • $\begingroup$ In the Middle Ages they did not have the ability to mass produce anything. They didn't even have the notion of mass production. Even introduciung the mere idea of mass production, for example of uniforms, pikes, and arquebus, would give a tremendous military edge; in real history, standardized pike-and-shot formations became possible only well after the end of the Middle Ages. $\endgroup$ – AlexP Mar 17 at 20:38
  • $\begingroup$ @AlexP - Nope, there are examples of mass production in medieval age. Venice's Arsenal is a good example. But at large you are right... $\endgroup$ – Artemijs Danilovs Mar 17 at 21:20
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Gyroglider

I would say no. It will be impossible to get bearings for the rotor that can turn easy enough and avoid running hot or seizing up. Plus the problems with the glider.

Fixed-Wing Glider

It will be problematic to get the structure strong enough and light enough at the same time. Getting materials for the wings will difficult, too. Imported bamboo and silk?

The next problem are the control surfaces. That could be overcome with a basic hang glider, but for anything larger than that you probably need steel wires (and bearings, again).

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  • $\begingroup$ Spruce was the go-to material for early aircraft. $\endgroup$ – WhatRoughBeast Mar 18 at 1:18
  • $\begingroup$ On the silk : en.wikipedia.org/wiki/Byzantine_silk $\endgroup$ – Ville Niemi Mar 18 at 1:43
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    $\begingroup$ You don't need silk and bamboo. Otto Lilienthal built perfectly good gliders using ordinary wood (probably spruce -- airplane makers tend to favor that) and fabric. $\endgroup$ – Mark Mar 18 at 5:03
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    $\begingroup$ @Mark "Perfectly good" insofar as they did sustain flight, briefly. Less perfect in that they were extremely hard to control, had fatal stall characteristics, and did in fact kill him. So much less than perfect that no-one ever considered repeating his experiments. Modern hang gliders came from Rogallo's work on semi-structured wings, not Lilienthal. $\endgroup$ – Graham Mar 18 at 8:59
  • $\begingroup$ Re "bearings for the motor", it's actually the entire motor. Even a high-pressure steam engine (which is about 500 years too late for the mediaeval period) didn't have the power to weight ratio. Only an internal combustion engine can do it. $\endgroup$ – Graham Mar 18 at 9:04
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A hang-glider could certainly be built. Back in the 1970s, people made their own out of bamboo and canvas. Otto Lilienthal did too.

And they all died with alarming regularity too. It turns out that designing the right stall characteristics is not so straightforward, and if you get it wrong then you simply fall out of the sky and die. Even with 1970s knowledge of aeronautics, it still took a decade to get reasonably safe hang-gliders. So building the hang-glider, yes. Knowing what dimensions to build a working hang-glider, probably not.

As for engines, absolutely not. Nothing before the internal combustion engine had the power-to-weight ratio to let an aircraft sustain flight. So they aren't going to be flying around and dropping bombs. Steam engines were used for propelling airships in the 1800s, and the development of the ICE alongside improvements in steam power for heavy transport allowed further development of ultra-lightweight steam engines which made steam-powered aeroplanes technically possible (although only after the ICE was already a better solution). But medieval technology would have had problems even constructing a beam pumping engine and certainly could not have allowed the construction of steam vehicles, never mind steam aircraft. So no powered aircraft would be possible with pre-1800's technology.

If we assume for the sake of plot that someone managed to build a working hang-glider though, there is another use for it, which is reconnaissance. With a carriage fitted with a winch and several fast horses it would be possible to get a hang-glider to a reasonable altitude from which you could see the enemy's army. A Montgolfier balloon would be a much easier solution though - still an anachronism, but less so, and much easier to launch too.

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  • $\begingroup$ 1970s is quite late. There was already a very active and professional gliding community even in the late 40s. $\endgroup$ – vsz Mar 18 at 5:28
  • $\begingroup$ @vsz For sailplanes, yes. The OP asked about hang-gliders though. $\endgroup$ – Graham Mar 18 at 8:54
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    $\begingroup$ The main differences between a 1920s vintage German "primary glider" and a 1970s hang glider (or Lillienthal's versions, for that matter) is that the early hang gliders used weight shift for control, while primary gliders, built to train pilots for power airplanes, used conventional control surfaces. Of course, hang gliders used those too, after they'd advanced a little. $\endgroup$ – Zeiss Ikon Mar 18 at 11:40
  • $\begingroup$ Very interesting idea with the fast horses replacing a car for the lift there. +1 for creativity. $\endgroup$ – Firemorfox Mar 18 at 23:25
  • $\begingroup$ @ZeissIkon That isn't really true. The difference is that hang-gliders are defined as being foot-launched, not something you sit in. Hang-gliders with control surfaces weren't widespread until the 1990s with the Swift. It took another 10 years before there were enough in the UK for there to be enough to consider including them in competitions. Weight shift hang-gliders are still very much the majority. $\endgroup$ – Graham Mar 19 at 0:20
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Since it's been determined that a motorised machine is out of the question, and also that even until recently, gliders were pretty much death traps, we might as well have fun answering the subquestion involving getting a flying weapon from a higher to a lower place with some stealth.

To which end,

allow me to introduce the Trebuchet Launched Warbird!

Ready for launch signal!

In this image from an ancient manuscript in the Puddlian Library, we can see the Warbird awaiting launch. The graceful and powerful descent of the trebuchet weight lifts the long arm thus yanking the Warbird by the short tow rope. The massive weight drives the light craft to an incredible upward velocity.

Up up and over the edge of high Fortress Rockberg! Her graceful arc will send the bird out over the jagged rocks and her silent downward glide will surely take those Foreign buggers down below by surprise!

There are, of course, a few ... ahem ... minor kinks to be worked out. What with the trip being one-way and all. But surely the lads of the Rockbergian Army shall be queuing up to do their bit for King and Country all the same!

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In a medieval world with current knowledge of aerodynamics, yes. Nature provides enough tough materials to build a structure that a single human could use to glide a bit.

Problems:

1) With current knowledge, a design could, within a few months and with small loss of life and limb, be brought to perfection, but with then contemporary knowledge, it would be very hard, and could only be bought by many years of experimenting, and a host of lost pilots. You'd need to get medieval to find more testpilots. Hey...

2) This is about a glider. Not a good one, either. Optimistically a glide ratio of 3:1? (Every 3 meters you go forward are bought with one meter height loss (https://www.britannica.com/sports/hang-gliding)). High ground was coveted even then, So having to find an accessible yet steep hill overlooking your target, undefended, and then schlepping your gear up there, to surprise the enemy below? Not that many chances for that.

3) Using mechanisms to gain height, like winches, counterweights or mooring in a stiff breeze would add many more years of testing, invalidating many of the pure glider designs because they now also be able to survive these forces.

4) Birds, stones, arrows, and many other flying things were known in medieval times, so a commander getting credible info about the enemy being able to glide 'like a chicken with clipped wings' (or some such) could identify possible ambush-places that were made viable by such technology. And you have just been chucking people from your castle walls tied to tents for years now. This will not be a secret. People will be somewhat prepared.

5) Whether by time travelling aeronautics engineer (cum carpentry enthusiast (with a pinch of not getting burned as a witch)), or pure aristocratic bull-headedness, you now have gliders that can be packed like tents, a mobile launch system, fighter-pilots, and a bird-related nickname. Whence now?

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  • $\begingroup$ Re 2), you could fairly easily get 5:1 glide with basic hardware. Hang-gliders aren't that light - it's more about the aerodynamics. Precision measurement and assembly is going to be the biggest obstacle. Re 4), shooting any distance upwards with arrows is pretty inaccurate - and you have to be careful where they come down. Hawks could be a practical anti-aviator weapon though. $\endgroup$ – Graham Mar 19 at 12:23
  • $\begingroup$ @Graham rere2) I was going from the idea that they would not top the first current Hangliders in terms of glide ratio britannica.com/sports/hang-gliding --- rere4) I wanted to convey that medieval people were aware that things could approach via airtravel, and therefore would not be on completely unknown territory if faced by gliding foes. -Edited my answer. $\endgroup$ – bukwyrm Mar 19 at 13:35
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I have a question: What counts as a "motor" for the purpose of this topic? A world record for human powered flight was awarded 30 years ago to a plane called Daedalus, which was flown by a super-fit Greek cyclist. I realize this isn't the same as a gyroplane, but it would have been possible to build during medieval time, assuming you had a King's budget.

Before you posted the illustration, I was picturing a small glider of some kind being deployed by hot-air balloon. While I could find no evidence of thermodynamic knowledge in medieval Europe, paper hot-air balloons existed in China pre- Marco Polo. (I believe they were used in funeral ceremony.)

Depending on how much of a stretch you're willing to accept, a combination of these ideas would theoretically make it "possible." I hope my answer is acceptable. I've never responded to a question on Stack Exchange before.

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  • $\begingroup$ Welcome to Worldbuilding.SE! We're glad you could join us! When you have a moment, please click here to learn more about our culture and take our tour. Normally this would be posted as a comment to the Q for clarification, but you need a couple of more rep points to do that. No problem! Thanks for joining us and we hope you have fun building worlds! $\endgroup$ – JBH Mar 19 at 22:40

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