Wing Fold & Locking Mechanism
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Wing Fold & Locking Mechanism
Looking at a typical aircraft with folding wings such as the Skyraider.
When the wings are unfolded, how is the stress from airloads on the outer wing panel transmitted through the join in the spar. Logic would suggest that some locking pin is used, but the pin is smaller than the spar, so how does the pin not that is much smaller than the spar carry the loads. Is it as simple as a bloody strong pin?
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Join Date: Mar 2001
Location: I wouldn't know.
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I would suggest going to the next glider field and checking out how the wings are secured there, after all they are built to be taken apart easily (folding the wings, often at several points along the wingspan), also to carry the loads once everything is back in place. And they have design at least +5.3g/-2.65g in normal operation (yes, every glider is according to EASA at least an utility category plane). From my experience, and that is a bit out of date, it is usually one or two bolts for the central point, and quite small pins for mid to outer span points.
On the Buccaneer it pretty much was a bloody great pin.
On this picture, about 1/3 of the way from the left hand edge of the wing there is a pale grey ‘spade’ shaped thing with a hole in. When the wing was unfolded, that would engage with the sloped bit on the inboard section of the wing and then the big pin would sequence down through the hole.
HtH
On this picture, about 1/3 of the way from the left hand edge of the wing there is a pale grey ‘spade’ shaped thing with a hole in. When the wing was unfolded, that would engage with the sloped bit on the inboard section of the wing and then the big pin would sequence down through the hole.
HtH
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@ the original poster:
One can also have a steel pin in steel fittings, attached to aluminum spars.
Google something like 'Corsair wing fold mechanism'. I'm not sure but there seems to be just a main spar pin to take mainly bending forces (rotating around a top one, pinned at the bottom), and some mechanism near the leading edge to take torque forces.
Bigger faster aircraft may use a bunch of pins. (Newer ones will also be certified under 'fail safe' rules requiring more damage tolerance, designs where even for the wing in general, there isn't just 1 critical spar, but a bunch of spar webs in the wing.)
One can also have a steel pin in steel fittings, attached to aluminum spars.
Google something like 'Corsair wing fold mechanism'. I'm not sure but there seems to be just a main spar pin to take mainly bending forces (rotating around a top one, pinned at the bottom), and some mechanism near the leading edge to take torque forces.
Bigger faster aircraft may use a bunch of pins. (Newer ones will also be certified under 'fail safe' rules requiring more damage tolerance, designs where even for the wing in general, there isn't just 1 critical spar, but a bunch of spar webs in the wing.)
No question about the "bloody great pin" a third of the way down from the left-hand side of the pic, in fact the top of that pin is visible. It works vertically. However, the red locking fork on the right is surely a transit securing piece that's removed prior to flight? It too has a pin that operates horizontally and it is more clearly visible.
I think.
I think.
IMHO it's very clever engineering, not just the hinge and locking mechanism, but also pivoting fuel and hydraulic lines, control runs, electrical feeds, and in the case of the Buccaneer, ducting for the 'blown lift'.
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Re the bloody great pin that some steel alloys are rated at 100 tons per square inch in tension. So not too many pins are needed to support the air loads. Probably more for redundancy in multiple load paths
https://www.youtube.com/watch?v=1F23RciUwDE
Looking at a typical aircraft with folding wings such as the Skyraider.
When the wings are unfolded, how is the stress from airloads on the outer wing panel transmitted through the join in the spar. Logic would suggest that some locking pin is used, but the pin is smaller than the spar, so how does the pin not that is much smaller than the spar carry the loads. Is it as simple as a bloody strong pin?
Looking at a typical aircraft with folding wings such as the Skyraider.
When the wings are unfolded, how is the stress from airloads on the outer wing panel transmitted through the join in the spar. Logic would suggest that some locking pin is used, but the pin is smaller than the spar, so how does the pin not that is much smaller than the spar carry the loads. Is it as simple as a bloody strong pin?
Does a piston engine have a choke for a cold start? Or is there another arrangement like the fifth injector on my car?
Does a piston engine have a choke for a cold start? Or is there another arrangement like the fifth injector on my car?
so how does the pin.......that is much smaller than the spar carry the loads. Is it as simple as a bloody strong pin?
The 737NG, for example, uses eight bolts and three shear pins:
Thank you both, I stand corrected, (and am slightly relieved, to be honest) 
Last edited by Uplinker; 19th Apr 2020 at 10:47.
