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I became curious about origami and its application to aeroplanes and was wondering if there were aircraft that either fold and/or employ folding in their design in interesting ways.

Let's limit this to mechanisms requiring two or more creases/folds/axes/pivots that alter the geometry of something in a significant way. This should cut out most of the the obvious things e.g. fixtures (doors, food trays, landing gear and stair cases), control surfaces that act alone (canards, rudders, ailerons and flaps) etc. I wouldn't want to rule out any interesting applications however e.g. the use of leading and trailing edge flaps together (2 axes) or swept wings (2 pivots) is certainly acceptable. Finally, anything that is bizarre, curious or weirdly obvious is happily accepted !

Paper aeroplanes should be excluded unless there was some real world application thereof. Space stuff is also out.

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    $\begingroup$ Sorry, I don’t mean to rain on your parade, but there’s really no connection between oragami and aircraft construction other than the word “folding”. The mechanisms involved in folding aircraft wings are not similar in any manner to creases in paper. You are stretching to establish some commonality that really isn’t there. Downvoting the question unless you can make a better case for a possible relationship. $\endgroup$ – Michael Hall Aug 15 at 1:38
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    $\begingroup$ No problems, I packed an umbrella ;) It was a bit of a loosey goosey question. I saw an article on a wing design where the wing comprised of two smaller wings placed in "series" and a third extending out from the fuselage would stretch out and join them to form a larger wing with a longer chord. It got me wondering if there were other curious designs. One thought was that one might fold a wing in against the fuselage to form a lifting body. The other was that a wing might be curled up to form a channel wing. I was curious to know if other odd designs had been tried. $\endgroup$ – Carel Aug 15 at 2:23
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    $\begingroup$ Related question about variable geometries, some examples of which include folding like you describe: aviation.stackexchange.com/q/66896/22400 $\endgroup$ – Adam Aug 17 at 0:49
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    $\begingroup$ Applying origami is actually a thing in engineering: look at those applications for example. If you are looking for more origami-esque contraptions, you might want to broaden your question to include spacecraft design as well, for which unfolding things is a common design problem. $\endgroup$ – null Aug 17 at 16:10
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    $\begingroup$ @null I expressly excluded the space stuff since this is not the site for that and there is a difference between unfurling ones tinfoil device in the vacuum of space versus a "hefty"atmosphere. $\endgroup$ – Carel Aug 17 at 22:59
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My favourite is probably the Nikitin-Shevchenko IS which could morph between biplane and monoplane by folding its lower wing up into the upper one. The lower wing had two hinges on each side, one at the root and the other at about one-third span, so its outer section was indeed double-hinged. Nikitin-Shevchenko IS-1

Does it count to do something similar but cruder and simply let the upper wing go once you have taken off? This slip-wing was trialled on the Hillson Bi-mono before being fitted to a Hurricane.

The Tu-144 airliner and Dassault Mirage "Milan" had retractable "moustache" canard foreplanes which they deployed to improve takeoff and landing performance. Being tailless deltas, they had limited scope for conventional flaps, so put moustaches at the front instead. The moustache of the TU-144 was quite complex, having full-span flaps which amounted to a variable-camber aerofoil, so their trailing sections provide another rare example of genuine double-movement. Tu-144 twirling its moustache

The XB-70 Valkyrie folded its wing tips down during Mach 3 cruise, to improve stability and waverider lift. The A-12 variant of the Blackbird was one of a small handful of types to have had a more prosaic ventral fin which folded up for landing and takeoff.

The Wild Goose and Swallow projects of Barnes Wallis at Vickers deserve mention, although they only flew as sub-scale test RPVs. They were examples of what he called the "wing-controlled aerodyne", having swing-wings in place of conventional control and tail surfaces. Not so much a double-action as eliminating the double-action of control surfaces on a swing-wing by using the whole fuselage as one giant multi-functional control surface (a tip he picked up from his work on airships such as the R100).

Does sliding count? The Akaflieg Stuttgart fs29 sailplane has telescoping wings which can pull in to increase cross-country speed. A few other experimental types had them too, such as the Makhonine Mak-10. The Gérin Varivol had a more complex variation on the theme, with a full-span high-aspect-ratio fixed section, which supported leading- and trailing-edge sections that were stowed in the fuselage and scrolled out along the wing like lowering a Venetian blind.

Polyhedra are solids with flat surfaces. Folding them using origami techniques is quite an art form, so I make no apology for the next example. Most polyhedra assemble rigidly but some, known as "breathing" polyhedra, can flex to a limited extent. An example from aviation is the variable-thickness wing experimented with by Rocheville among others, which bulges its top surface upwards to provide high lift for takeoff and landing, then draws it back down to create a thin wing for high-speed flight.

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  • $\begingroup$ Sure single hinged mechanisms are acceptable as are telescoping wings. Thanks for the interesting examples. $\endgroup$ – Carel Aug 15 at 11:14
  • $\begingroup$ Is there more than one sailplane with telescopic wings? I thought that only the fs29 used those successfully. The SB-11 could slide a wing extension out backwards to increase wing surface area. And if you need more folding vertical surfaces: The MiG-23 and the SAAB 37 Viggen had those, too. $\endgroup$ – Peter Kämpf Aug 15 at 18:53
  • $\begingroup$ @PeterKämpf Thanks, answer updated accordingly. However I never saw anything fold on a Viggen in flight and I have not discussed folding for ground storage. $\endgroup$ – Guy Inchbald Aug 15 at 20:32
  • $\begingroup$ [www.festo.com](Festo) has a curious selection of creatures including an Air ray, Flying Fox, Jelly Fish, Air Penguins and a rotating origami ring structure (At least I've seen this folded elsewhere) $\endgroup$ – Carel Aug 15 at 22:49
  • $\begingroup$ @GuyInchbald: Admitted, the Viggen would only fold the vertical during taxi, not flight. If you need more in-flight-folding: There were some involuntary cases, too. $\endgroup$ – Peter Kämpf Aug 16 at 1:52
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There are many, many examples of folding wing planes. Most, like this Vought F4u Corsair, were designed to take up less space in the tight confines of aircraft carriers or small hangars.

Voght F4u Corsair

Some planes even fold their wings in more than one place, like this Supermarine Seafire.

Supermarine Seafire

Swing wing aircraft like this F-14 Tomcat can sweep forward for slow flight maeuverability and sweep rearward for high-speed flight and stowing.

F-14 Tomcat

F-14 Tomcat swept

V-22 Ospreys can even rotate their entire wing and engine assemblies 90 degrees to bring them in line with the body of of the aircraft.

V-22 Osprey

You really should check out this wikipedia link for plenty more examples.

https://en.m.wikipedia.org/wiki/Folding_wing

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    $\begingroup$ Note how the F-14 pops out little epaulette-like leading-edge root extensions when swept back. $\endgroup$ – Guy Inchbald Aug 15 at 6:49
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    $\begingroup$ @GuyInchbald: I’ve never noticed that before. That’s a great mention. $\endgroup$ – Aaron Holmes Aug 15 at 12:54
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    $\begingroup$ Also the B-70 Valkyrie, which had large wing area that folded down for high-speed flight: en.wikipedia.org/wiki/North_American_XB-70_Valkyrie And Boeing's newe 777Xr airliner has folding wingtips. $\endgroup$ – jamesqf Aug 16 at 16:48
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    $\begingroup$ The Fairey Gannet has a much more obvious Z-fold mechanism than the Seafire. $\endgroup$ – Roger Lipscombe Aug 17 at 8:55
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    $\begingroup$ @GuyInchbald These only exist on the F-14A and only extract at supersonic speeds anft.net/f-14/f14-detail-glovevane.htm $\endgroup$ – DeepSpace Aug 17 at 18:10
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Since

Finally, anything that is bizarre or weirdly obvious is certainly encouraged !

There's the NASA AD-1 with its center-pivot,

enter image description here

its RPV predecessor the Oblique Wing Research Aircraft

enter image description here

and the original Blohm & Voss P 202 WWII design study. Both the Chief Designer Richard Vogt and his Head of Preliminary Design Hans Amtmann were hoovered up by Operation Paperclip and went to work in the US after the war (apologies for the poor image but good, authentic ones are hard to find free of copyright).

Blohm & Voss P 202

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    $\begingroup$ Apologies but I added the original design study to your answer. $\endgroup$ – Guy Inchbald Aug 15 at 18:11
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    $\begingroup$ That long-exposure photo is gorgeous. Excellent find! $\endgroup$ – Criggie Aug 15 at 22:42
  • $\begingroup$ Does anyone know if the handling was adversely affected when the wing is pivoted ? $\endgroup$ – Carel Aug 15 at 22:54
  • $\begingroup$ @Carel there's a flight test results paper here: ntrs.nasa.gov/… $\endgroup$ – Organic Marble Aug 16 at 0:39
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    $\begingroup$ @OrganicMarble Thanks for the article made for an interesting coffee break :D $\endgroup$ – Carel Aug 17 at 23:01
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When building a lead ballon, the mythbusters employed a origami-inspired folding technique to ensure that the thin material unfolds slowly and without tearing during inflation.

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    $\begingroup$ If you're gonna include inflatables, you could say that regular hot air balloons and even blimps employ folding techniques as well. Perhaps it's less critical when the balloon isn't made from easily-tearable lead foil. $\endgroup$ – Darrel Hoffman Aug 17 at 16:06
  • $\begingroup$ @Darrel Hoffman: Then that gets us into parachutes & parafoils... $\endgroup$ – jamesqf Aug 17 at 18:20
  • $\begingroup$ @jamesqf I thought about that too, but I'm not sure if a parachute qualifies as an aircraft so much as a landing softener. Parafoils might qualify, bit of a grey area there. $\endgroup$ – Darrel Hoffman Aug 17 at 18:30
  • $\begingroup$ @DarrelHoffman and jamesqf folding sails, foils and balloons should be acceptable in my view, especially if there are any interesting ones e.g. The origamist (?) Robert Lang worked upon an airbag design; it seems they used the mesh of the 3D model as the basis to fold the bag into the compartment. $\endgroup$ – Carel Aug 17 at 23:11

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