Chengdu J-20 5th Generation Aircraft News & Discussions

[LKJ86]

The high-resolution videos of J-20
November 10, 2018: https://www.bilibili.com/video/av35724051
November 11, 2018: https://www.bilibili.com/video/av35772600

 

[LKJ86]

 

[LKJ86]

 

[Beast]

 

[siegecrossbow]

Best video from the 11th.

 

[ozranger]

Sensational work by the legendary Tonkatsu298

 

[Silicon0000]

The computer will adjust that dynamically in flight time.


Obviously not.

Agreed ..... but I was thinking could this difference of thrust can be used to change the direction ? May be someone good in physics can tell it better

 

[gambit]

After looking at the high res, I think that it is possible that the missiles they carried are live rounds. Practice PL-10D usually don't have transparent apertures for the seeker.

There is a difference between a 'dummy' vs a 'training' ordnance.

A dummy round is completely inert. No warhead, propellant, avionics, and moving parts of any kind. It is literally just balanced mass/weight. The only semi-electrical item on a dummy round is a short that tells the aircraft's weapons management system that there is a missile or bomb at station.

A training round is slightly different. It contains the seeker/guidance section and functions exactly as a live round would.

Agreed ..... but I was thinking could this difference of thrust can be used to change the direction ? May be someone good in physics can tell it better

Asymmetric thrust in a multi-engine aircraft is never a good thing, even with modern flight control system. The wider the spacing between the engines, the higher the tendency to enter a spin and eventually departure from controlled flight.

 

[Silicon0000]

There is a difference between a 'dummy' vs a 'training' ordnance.

A dummy round is completely inert. No warhead, propellant, avionics, and moving parts of any kind. It is literally just balanced mass/weight. The only semi-electrical item on a dummy round is a short that tells the aircraft's weapons management system that there is a missile or bomb at station.

A training round is slightly different. It contains the seeker/guidance section and functions exactly as a live round would.


Asymmetric thrust in a multi-engine aircraft is never a good thing, even with modern flight control system. The wider the spacing between the engines, the higher the tendency to enter a spin and eventually departure from controlled flight.

Yes but can that spin be used to change the plane direction spontaneously if controlled properly. I know it's extremely difficult but is it possible?

PS: I am not an expert, just thinking of an idea.

 

[Cookie Monster]

Asymmetric thrust in a multi-engine aircraft is never a good thing, even with modern flight control system. The wider the spacing between the engines, the higher the tendency to enter a spin and eventually departure from controlled flight.

Can't that be used to gain more maneuverability in the yaw direction?...if the thrust output of each engine can be controlled on the fly then a quick turn(in yaw direction) in a controlled manner can be achieved after which both engines' thrust goes back to being equal.

It would be something like using negative stability for F16 for more maneuverability. Or using TVC(a departure from normal direction of thrust for a relatively short amount of time)...

It can come in really handy for jets using 2D TVC nozzles(like F22) which only gives super maneuverability in pitch and roll. For yaw, the F22 has to rely on its control surfaces.

 

[gambit]

Yes but can that spin be used to change the plane direction spontaneously if controlled properly. I know it's extremely difficult but is it possible?

PS: I am not an expert, just thinking of an idea.

If your wallet have no limits, then eventually you will overcome all technical hurdles.

But the real question is why would you want to use asymmetric thrust to affect a directional change? Under what tactical situation? When I used the word 'tactical', it is not restricted to military situations but also to civilian flying. In flying, you make many tactical decisions such as fuel mixture, trim, altitude, etc. So under what flying condition(s) would a pilot in a multi-engine aircraft use asymmetric thrust to change direction? Jet engines are more responsive than props, so this would force a difference in techniques.

So far, exploitation of aerodynamic forces via flight controls surfaces have proven to be the best method to flight.

Can't that be used to gain more maneuverability in the yaw direction?...if the thrust output of each engine can be controlled on the fly then a quick turn(in yaw direction) in a controlled manner can be achieved after which both engines' thrust goes back to being equal.

It would be something like using negative stability for F16 for more maneuverability. Or using TVC(a departure from normal direction of thrust for a relatively short amount of time)...
...just curious

You are talking about designing an entirely new flight controls system architecture.

Here is a high level explanation of 'flight control laws'...

http://www.airbusdriver.net/airbus_fltlaws.htm

This have nothing to do with legalism but about what an aircraft is allowed to do with certain factors.

For example, if I lower the landing gear handle, the flaps/slats systems will actuate. That is one set of flight controls laws. Once there is weight-on-wheels (WOW), spoilers on top of the wings will deploy to kill lift and produce drag. That is another set of flight controls laws.

Currently, we have just managed to deploy thrust vectoring after decades of R/D. The flight controls laws for that must be as transparent as possible to the pilot, meaning the pilot's interactions must be minimal, if not none at all. In this speculation, we need the next level of engine responsiveness and fine grain control before we incorporate asymmetric thrust into the flight controls laws. But yes, the concept is 'do-able'.

 

[SME11B]

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Those pl-10 hanging outside like that lessen j-20's stealth and produce drag. Is that design there because it's not a lock on after launch missile?

 

[siegecrossbow]

Those pl-10 hanging outside like that lessen j-20's stealth and produce drag. Is that design there because it's not a lock on after launch missile?

I don't think that stealth is much of an issue when the J-20 is ready to use the PL-10.

 

[ozranger]

Those pl-10 hanging outside like that lessen j-20's stealth and produce drag. Is that design there because it's not a lock on after launch missile?

The design is trying to avoid the problems F-22 is having, which is launching SRAAMs from inside the weapon bays.

 

[SME11B]

I don't think that stealth is much of an issue when the J-20 is ready to use the PL-10.

Perhaps not for who it's fighting in the merge but it's in trouble there because it doesn't have a lock on after launch missile and doens't appear to be very agile. Not sure if it has a gun but I'll assume it does. It relies on the traditional methods of dog fighting in that case. And any missile launched on it near of from afar will benefit form the extra signature of those missiles. Does J-20 incorporate any IR stealth? It's engines don't seem very far into the airframe and I haven't heard anything about that. Who knows when ws-15 will come out but it sounds like it's still delayed, I keep hearing mixed messages.

The design is trying to avoid the problems F-22 is having, which is launching SRAAMs from inside the weapon bays.

I wasn't aware there were problems with that.