J-20 5th Gen Fighter Thread V

[manqiangrexue]

Just because J-20 was not built around TVC doesn't mean it can't benefit from TVC as Su-30SM/Su-35 do and Typhoon could've with more funding.
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I believe there is a point in maneuverability where if you surpass it, all that adding TVC will do is reduce your TWR and black out your pilot. I think they said J-10 is there and I believe Typhoon is there too. Is J-20 there? With WS-15? So, add things wisely; not every upgrade is suitable for every aircraft.

 

[Air Force Brat]

I believe there is a point in maneuverability where if you surpass it, all that adding TVC will do is black out your pilot. I think they said J-10 is there and I believe Typhoon is there too. Is J-20 there? With WS-15? So, add things wisely; not every upgrade is suitable for every aircraft.

That's absolutely correct, remember the F-22 was putting folks to sleep, the F-35A, AF-02 when flown without the FCS "pitch limiter" was flown to 9.9 Gs, so people yapping about the F-35 being a pooch are "nim-rods" and they would to a man prolly be asleep well before 8 Gs or so, the F-22 or PAK-FA, J-20 and F-35 are prolly on the same page.

From the looks PAK-FA would likely have the highest instantaneous pitch rate at a given airspeed, prolly why they found significant airframe cracking that actually grounded 51, they considered "scrapping it", but later after taking the fuselage of 056 to repair 055, decided to refurbish 051 as well.

So for J-20, its probably in a very happy place with those very "long throw" canards, the FCS likely dials the throw back as speed increases, but they are huge, and they have the longest control throws that I have personally observed, I believe likely 90 degrees positive or negative pitch. They appear to move through nearly 180 degrees of travel, and they are "distant coupled" so a very powerful lever to move the aircraft rapidly, particularly since they move in unison with the flaperons/elevons/ruddervators to rapidly pitch the aircraft,

I believe there is a point in maneuverability where if you surpass it, all that adding TVC will do is reduce your TWR and black out your pilot. I think they said J-10 is there and I believe Typhoon is there too. Is J-20 there? With WS-15? So, add things wisely; not every upgrade is suitable for every aircraft.

with controls on both ends of the aircraft.

So you are right, likely no need to consider OVT, the Eng says very clearly that they will NOT, and are not pursuing it. He is in a different loop, or on the "inside track" than most of us. so he has me convinced, as Jeff says, we will have to wait and see, but we've seen none of the prototypes sporting OVT, and to be honest, incorporating OVT would require re-writing most of the FCS in my personal opinion.

Not that they couldn't or wouldn't, but why, and then you would basically start flight test from scratch, I just don't see any logic there???

Plus, all those very high G maneuvers have a very negative effect on airframe life, not to mention cracking or possibly even braking something, look at the F-15 that broke in half just aft of the cockpit??? The fuselage longerons were improperly manufactured, but still??? and the F-15 is a very strong airframe.

 

[vincent]

Well Brat, I think you know I like the J-20 and I think it's a great accomplishment by the PRC. But, it's also important we hear from critics of the plane, especially experts and engineers from advanced defense industries, or from high-ranking military officers.

The very fact that the reporter provided zero fact on the LM guy/gal is rather suspicious. For all we know, he/she is a janitor at LM

 

[Lethe]

TVC isn't only about extreme maneuverability, it is also about minimising control surface deflections to maximise speed and minimise RCS. And if implemented like F-22 it can also be part of a solution to reduce rear-sector RCS and IR signatures.

EuroJet was pushing TVC for Typhoon and even tested a nozzle design for it (see YouTube). None of the partners picked it up, but given how starved the Eurofighter program has been I don't think you can conclude anything from that.

 

[Quickie]

I guess you can also say that the J-20 would not even fly if you take out its AL-31 engines. Thus, the J-20 is not even an airplane because it can't fly without its engines.

TVC is part of the F-22's complete package. You can't ignore it when considering its function.

IMO it is misguided to dismiss the F-22's TVC by pointing to extreme maneuvers and then concluding they are for show, therefore TVC is useless in actual combat. This is a non sequitur, and I have no doubt that both LM and the USAF do not consider TVC useless. You are right that nobody knows which is more maneuverable, but certainly the TVC on the F-22 and the lack of it on the J-20 does not help J-20's case in claiming greater maneuverability.

I wouldn't go that far Bub, that likely belongs to PAK-FA, which honestly is the least stealthy, but possibly the most agile! anyway the F-35 does not have OVT, and supermaneuverability is not the necessity that it used to be, as we are all moving to BVR engagement!

Trust me, the J-20 is a very maneuverable, very high performance aircraft, and will be even more so once equipped with the WS-15.

As the only active pilot here, I'm well versed in this aspect of aircraft development, and I do understand the physics, I can't do the math, but I can "see" LIFT, really its not that hard, well maybe for "ground pounders"? AFB says this is a very revolutionary airplane, and a very fine fighter aircraft, with plenty of fuel, and long range AAM it better be on your list of "things to watch out for", believe me, no ONE, here in the US who are conversant with this subject and in da bidnezz will disagree with that assessment!

Wait a minute. I never said TVC is useless on the F-22. As a matter of fact TVC helps to expand its flight regime towards higher AOAs, which otherwise wouldn't be advisable because of the risk of stalling, like the case of the horizontal stabilizers losing its pitch control authority but without TVC to put things in order. These things has been discussed to death years ago in the other thread. Let's not go there again.

Again, no need to be so serious, each of us can have the own opinion as to which is the most maneuverable one.

 

[delft]

TVC isn't only about extreme maneuverability, it is also about minimising control surface deflections to maximise speed and minimise RCS. And if implemented like F-22 it can also be part of a solution to reduce rear-sector RCS and IR signatures.

TVC also reduces thrust and increases weight, factors which reduce speed and range.

 

[Inst]

The J-20 is designed to work without TVC, but the J-20 would benefit from TVC as certain rear control surfaces could be eliminated, reducing RCS, weight, complexity, and drag.

@Blackstone: I think there's a bit of overoptimism among the Chinese regarding the J-20 as well, especially considering its capabilities without the engine. However, Western media is not necessarily impartial. There is a long stereotype of Chinese technological inferiority, and considering how compromised the F-35 project is, from security to budget to timetable, there is a strong incentive to downplay its competitors, up to the absurdity of insisting the F-35 is not a strike fighter.

Generally, US reviews of foreign defense technology comes in one of two ways. Either our technology is better than theirs, or their technology is better than ours. In the former case, either something has gone wrong, or their product is competing with ours on the export market. As I've mentioned before, the F-35 is an example of such a product; its problems and the apparent capability of the J-20 could cause government buyers to rethink the project. And the US defense establishment dropping the ball is not an impossibility; tanks before the M1A1 Abrams were inferior to their Soviet counterparts, and the F-111 project was a disaster. The other possibility is that foreign technology provides a panic; see the MiG-25 interceptor and how it spurred the development of the F-15.

 

[manqiangrexue]

The J-20 is designed to work without TVC, but the J-20 would benefit from TVC as certain rear control surfaces could be eliminated, reducing RCS, weight, complexity, and drag.

Uh... I don't think any of that is true about TVC, as a matter of fact, I would say the opposite is true for most of your assertions.
1. What rear control surfaces could you eliminate? The all-moving vertical stabilizers? Or the flaps/ailerons on the wing? When have you ever seen someone do this? Did the Russians reduce the Flanker's rear control surfaces when they added TVC to their Flankers?
2. TVC increases the weight and complexity of the engine, thus the aircraft, not the opposite.
3. Why would drag be affected?
4. You could possibly slightly reduce frontal RCS by reducing the intensity of control surface movement during non-aggressive flight.

 

[vesicles]

As many have mentioned, a TVC is very heavy and will change the center of gravity of the plane. So my understanding is that adding a TVC to the J-20 would literally mean that they will need to redesign the entire plane.

 

[Inst]

I'm referring to the removal of rear control surfaces; see the X-36. The J-20's rear layout is not optimized for TVC yaw control, given that the engines are relatively deep-set into the fuselage, and would end up hitting things at high deflection, but it would not be impossible.

If the AMT and ventrals are removed, you end up with an aircraft that has the same number of control surfaces as the F-22, and one with a slighter frontal cross section, because obtruding strakes and tailfins are gone. That would help improve stealth by removing edge emitters, and it would help improve drag through FCS reduction.