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There exist several aircraft - especially carrier-based ones - that have folding wings, to save space.

How is this structure strong, taking into account the considerable amount of force on the hinge-based system (is it?) from the wing loading? How are they prevented from just snapping mid-air?

Super Hornet (from Wikpedia)
Photo by Petty Officer 3rd Class Jason Johnston, U.S. Navy: Public Domain

The same question regarding helicopter rotors too.

Osprey (from Wikpedia) Photo by Lt. Col. Kevin Gross: Public Domain

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    $\begingroup$ I'm not sure what answer you're expecting here. The hinges are made from strong materials, and/or reinforced to carry the extra load. If you want detail you'll have to specify precisely what detail you're after. $\endgroup$ – user11933 Oct 24 '15 at 23:17
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    $\begingroup$ Technically that's not a helicopter. $\endgroup$ – CGCampbell Oct 24 '15 at 23:37
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    $\begingroup$ @Airsick: The mechanism and the component material was what I was asking about. $\endgroup$ – Raj Oct 24 '15 at 23:46
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    $\begingroup$ @CGCambell: Hehe. That's right! But this is used on other carrier-based helicopters too. $\endgroup$ – Raj Oct 24 '15 at 23:49
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The wing folding mechanisms (in aircraft) and rotor folding mechanisms (in helicopters) are different. The V-22 Osprey falls somewhere in the middle.

  • In case of aircraft, the wing folding mechanism is usually made of high grade steel (or titanium in some cases) and actuated either hydraulically (or in recent cases) electrically. The outer wing rotates about a hinge, to which the two parts (inboard and outboard) of the wings are locked. For example, the F/A 18 wing folding mechanism looks something like this:

Wing folding mechanism

Image from US Patent Wing fold push-pin locking assembly US 5558299 A

In general, once the wings are either folded (or unfolded), they are locked using very hefty sliding pins which provide a secure mechanical connection once (they) slid into place in sockets in the outer wing.

However, incidents do happen, usually because the pins have not locked and not because of failure. A number of incidents have happened where aircraft have taken off with wings folded (and landed safely, surprisingly).

Flight with folded wings

Source : reddit.com/theaviationist.com

  • In case of helicopters, the blade folding method is more or less the same with some variations- pull the pin that holds the blade (on one side) and fold the blades, which is done manually for small helicopters and hydraulically for large ones.

Folded wings

Source: reddit.com

They are then held either by hydraulic pressure or mechanical attachments.

Blades in folded position

Source: adf-messageboard.com.au

At-least in helicopters, there is little chance of a takeoff with the wings folded.

The V-22 Osprey is a special case- The propellers (or rotors) is folded first, then the engines are rotated, followed by the wings themselves.

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    $\begingroup$ Awesome answer. $\endgroup$ – McGafter Feb 21 '18 at 15:02

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