It is little wonder that the quality is not high, because most of the good moves of j20 are not filmed by the official photographers. Lots of Chinese complained about that.
J-20 5th Generation Fighter VII
- Thread starter siegecrossbow
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If this is a production J-20, which we know it is because it was practicing for the airshow (test planes don’t fly in pairs), then we know the J-20 doing the display doesn’t have TVC. Is this kind of maneuver at very low speed almost stall or post stall conditions possible? In theory, yes. This was written about in the original design paper for the J-20, in the section discussing the canards as positively loaded control surfaces. The main takeaway here is that even if the wings are stalled out the canards can maintain lift and thus control authority. In the video you can see the canards remaining parallel to the free stream until the J-20 executes the roll to level flight. What’s likely happening is that because the canards are able to generate positive lift, as the nose of the plane wants to dip at stall angles the canards can generate torque to rotate the body of the plane. Technically the canards only need to generate enough torque to push the plane back into a state where the wings can generate lift, so it doesn’t need to have the control authority to execute the whole maneuver, just to initiate it. While the idea of a plane executing this kind of maneuver without TVC sounds astonishing, in practice it’s not that unrealistic so long as some control device is able to generate a sufficient force vector to push the rest of the plane back into a controllable state, regardless of whether that’s TVC or a surface that can still generate lifting force while the rest of the plane is stalled out. So what this maneuver demonstrates above all else is the impressive amount of control authority the J-20’s canards possess.
In some ways this maneuver is more impressive than the tumble roll the J-20 initiated for its actual flight performance. I reckon they did this lower speed lower energy maneuver during their practice runs because if the FCS can demonstrate controllability when the plane is already in such a low energy state it should have absolutely no problem maintaining control at a higher energy state. My understanding is that this maneuver was basically the low energy version of the tumble roll we got at the actual show in terms of the basic control laws at work.
Absolutely this maneuver is more impressive than the high alpha roll of the actual flight display. That maneuver is already right at the top in terms of impressive.
I'm unconvinced at your explanation but I'm also no aerodynamicist... how do the canards generate lift in a near vertical position with next to zero airspeed moving over those surfaces. I forget my fluid dynamics classes but where there's no pressure difference because there's no speed, how can we have lift in this vertical position?
Anyway my suggestion that it could be TVC is based on the obvious implication that they have fitted TVC on J-20. Because we don't see pictures of production J-20 with TVC does not mean they aren't being inducted into service already etc etc I know I know I'm talking theoretically. It is fallacious to assume that production and operational TVC equipped J-20 can only exist when SDF unanimously agree they do because we have photos and have known bases stationing J-20 TVC.
We already found out… it’s from the recent airshow and those J-20s were using regular AL-31 engines
If you pay attention to the video you’ll note the canards are not at a near vertical position. The canards are horizontal to the free stream while the rest of the plane’s body is at a near vertical position. In other words they are not stalled while the rest of the plane might be. While it doesn’t look like it from the video angle there *is* likely still a forward movement vector as the plane executes the roll. It’s also not rolling vertically but in fact is doing so horizontally, so by the time the roll is initiated the engine *is* pushing with a forward vector because to execute the horizontal roll the plane’s angle of attack needs to dip.
If TVC were in production for the J-20 the Chinese internet would be ablaze right now and there wouldn’t be any way to hide that information. It would show up in pictures and or in commentary since there would be production planes that would be visible to the general public.
Oh come on! No-one here claims anything can only exist, when the SDF community agreed it is real.
But how could an operational J-20 that is known from several close-up images from that Airshow clearly showing it uses regular AL-31 engines miraculously have TVC fitted to fly this maneuver?
And even more, I know most recent images showing J-20As from the 8th Air Brigade having fitted with the regular WS-10C engines.
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