Shenyang FC-31 / J-31 Fighter Demonstrator

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stannislas

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The FC-31 project is partially a demonstrator for new manufacturing and production techniques. One of the innovations is that the whole fuselage skeleton from wing to wing is one fused single piece. If I recall correctly this is supposed to help improve the strength to weight ratio of the airframe, allowing for it to be lighter. The first FC-31 airframe we saw, all the way back in 2013 was shipped as a whole single piece, for this reason, so it follows that an iteration on that design would be handled similarly. There have been various articles of evidence talking about how the FC-31 put together. It’s even been briefly touched on in a documentary that talked about production improvements at SAC. Unless someone has aggregated these sources or kindly chooses to do this for you though, you’re going to have to dig around the forum archives.
well, I do remember the news you mentioned about some advanced technology FC-31 used, but I think back then the picture came with that news is rather a very big picture of the fuselage mainframe, rather the whole thing.

But I could be wrong because something else I vaguely remember is that CAC used 3D print to build super-large titanium-alloy frame for J-20 or something...
 

stannislas

Junior Member
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One other thing to add is that static test airframes are not flyable lol.

That's why the J-20 and FC-31 static test airframes couldn't "fly" to Yanliang, because they literally are not designed to fly.

@stannislas
yes, I do understand that, and the static model was my original suspicion, but siege suggested it was a
It's not a static model. It is a flyable prototype.
so that makes me even more confused
 

latenlazy

Brigadier
well, I do remember the news you mentioned about some advanced technology FC-31 used, but I think back then the picture came with that news is rather a very big picture of the fuselage mainframe, rather the whole thing.

But I could be wrong because something else I vaguely remember is that CAC used 3D print to build super-large titanium-alloy frame for J-20 or something...
We know that SAC used 3D printed titanium bulkheads for the FC-31, and it was mentioned in some of the same sources that the J-20 also uses the same method for their bulkheads, but we only have good confirmation for the former. More importantly though, even if both use 3D printed bulkheads, the FC-31 is supposed to involve a lot more manufacturing innovations than just that single item.
 

Blitzo

Lieutenant General
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It's not a static model. It is a flyable prototype. The J-20 could be transported in pieces whereas the FC-31 (J-31/35 now?) cannot since the fuselage and wing are crafted in one piece.

Hold up, why do you think they're transporting a flyable prototype rather than a static test frame??
 

Richard Santos

Captain
Registered Member
Yes, actually. They need a full reproduction to study the strain on the entire frame.
having control surfaces attached in a static test frame does not reproduce the stress deflected control surfaces impose on a airframe in flight. if anything, attaching actual control surfaces probably hinder the attachment of actuators that would statically simulate the control surface load on the airframe, th
 
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latenlazy

Brigadier
having control surfaces attached in a static test frame does not reproduce the stress deflected control surfaces impose on a airframe in flight. if anything, attaching actually control surfaces probably hinder the attachment of actuators that would statically simulate the control surface load on the airframe, th
No. You don’t need to reproduce the exact strain conditions encountered in flight for a static test. You *do* however want to map what the strain looks like at various load conditions across a whole representative airframe. The load specific strain values, not the conditions under which you encounter them, tell you everything you need to know about whether that structure will hold up under your expected loads, especially over time. Remember, one of the central objectives of a static test frame is examine long term wear and tear. It doesn’t make sense to exclude control surfaces, which are some of the most crucial high wear structures of the frame, and even more so, are essential load bearing structures that will be on the receiving end of a lot of the forces acting on other parts of the frame. If you exclude the control surfaces you may not even get a representative picture of the rest of the frame, since the forces on the structures transmit across the whole body of a plane and you would be missing areas that forces would have otherwise transmitted to if they were present.

There are many ways to attach your strain gauges and measure strain. The idea that control surfaces would get in the way of getting a good read on loads for your wing is kind of preposterous.
 
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