What's new

Chengdu J-20 5th Generation Aircraft News & Discussions

Har...More like the pace and validity of my challenges to Chinese claims in military issues in general, and aviation in particular, is not good for YOUR health.
Maybe we can call it a end of today, and Chinese New Year is coming! I know you get quite some knowledge, but you have to admit smart DSI is not a bad idea at all.
 
.
Maybe we can call it a end of today, and Chinese New Year is coming! I know you get quite some knowledge, but you have to admit smart DSI is not a bad idea at all.
Explain to me this statement by your friend...

Changing the shape of the Bump could deliver smooth air flow into the engine at wide ranging, various conditions, without the use of cumbersome machinery and diverters.

Source: https://defence.pk/threads/chengdu-...ews-discussions.111471/page-508#ixzz4WkGmVvxh
How can you alter something's shape and dimensions WITHOUT machinery ? Whether the machinery is 'cumbersome' or not is a matter of opinion.

Let us take what I posted back earlier...

https://defence.pk/threads/chengdu-...news-discussions.111471/page-508#post-9108882

Here is an excellent technical and ENGLISH source I provided...

http://f-111.net/models/inlets/index.htm

In order for the F-111's inlets to alter the shape of the inlet spike, local air data conditions must be determined, hence the local Mach probes that are positioned in front of the inlets.

Does the J-20, with its claims of a variable DSI system, have local air data sources for such control ?

Getting a little bit deeper, does it NEED local air data at all ?

Why separate local air data sources ? Maybe disparate air flow due to maneuvering situations ?

Every aircraft have a Central Air Data Computer (CADC) that performs complex pitot/static air data calculations to display raw and refined air data information such as airspeed and altitude. Does this necessitate separate air data computers for each variable DSI bumps ?

These FOUNDATIONAL issues/questions never comes from you guys. Note that none of them challenges the idea that there can be a variable DSI bump, only that it challenges the argument that somehow a variable DSI bump can be done without 'cumbersome machinery'.

It is questions like these that pisses you guys off because it exposes you guys' ignorance at the core technical issues and that it induces doubts into Chinese claims.

I can tell you this right now...That I have looked at the images of the J-20 and can give a technically credible opinion on whether or not there is a variable DSI bump system. :azn:
 
.
Just in case the F-111 source is insufficient about the need for local air data information in order to have local air flow inlet control, here is a credible source about the F-15 which have inlet air ramp to have that local air flow control.

https://archive.org/stream/nasa_techdoc_19980218785/19980218785_djvu.txt
A description of the airdata system is worthwhile, considering its importance to the DES algorithm. The aircraft is equipped with an airdata computer to execute computations and furnish parameters required to aircraft systems and cockpit displays. The ADC receives inputs from a pitot- static system, AOA probes, and a total temperature probe. The ADC corrects these inputs for sensor error as required. The pitot-static system employs multiple pitot and static sources for redundancy, including left- and right-side of the forward fuselage and in each inlet duct. AOA probes are located on each side of the forward fuselage and measure local AOA. A single probe located on the left forward fuselage provides total temperature to the ADC.
Note the highlighted sentence that contains: 'in each inlet duct'

Nothing is made up. The F-15's overall engine control and performance throughout flight improves with local air data information, as in discrete air data PER INLET.

So if the J-20 is claimed to have a variable DSI system, the challenge for the Chinese claimants is to show the necessary components, not doctored up images that have no credible sourcing.

Finally, you guys can take what I posted, translate them to Chinese, then post on Chinese forums to make yourselves look smart. :enjoy:
 
.
That is a dumbass article.

The missile hanging on the outside for how long and its own body does not possibly compromise the aircraft's RCS ?
Yes it does, but for a much shorter time than when the doors are kept open to fire the missile
 
.
Guys ... calm down !! All of You.

If anyone argues in a kind manner even in critical tone, everyone is welcome to discuss. To take the nationality or "race" as some say here - as a sole reason to be allowed to discuss here is a very problematic point of view and will not be tolerated.



Deino
 
.
So if the J-20 is claimed to have a variable DSI system, the challenge for the Chinese claimants is to show the necessary components, not doctored up images that have no credible sourcing.

Finally, you guys can take what I posted, translate them to Chinese, then post on Chinese forums to make yourselves look smart. :enjoy:

China is never going to give such details. If they have a trick up their sleeve chances are they will try to withold it's information

Now some Chinese claim J20 has a variable DSI. Their claim is based on pictures. Lets just agree that their claim is not verfiable. Doesn't mean they are wrong but also doesn't mean they are credible .Lets agree to disagree :)
 
.
China is never going to give such details. If they have a trick up their sleeve chances are they will try to withold it's information

Now some Chinese claim J20 has a variable DSI. Their claim is based on pictures. Lets just agree that their claim is not verfiable. Doesn't mean they are wrong but also doesn't mean they are credible .Lets agree to disagree :)
We can do that. But that does not mean I am going to let the Chinese off the technical hook. We will let the silent readers decide who is the more credible.

Mr. Asok said that the J-20 have a variable DSI system. Nowhere have I said there are technical barriers to that. In fact, I provided my first jet, the F-111, as proof of that system.

Mr. Asok said that the variable DSI system would 'optimize' airflow into the engines. Never mind that the word 'optimize' have been abused to death by those who do not know what they are talking about but tries to portray themselves as knowledgeable.

Air is not uniform in density. Everyone who took basic science in high school know that. As altitude increases, air density decreases. This means airflow in aerodynamics forces and in jet engine operations will be negative affected. Negative as in decrease in efficiency and performance output. This is why rockets carries their own oxidizers -- oxygen -- in the fuel mixture.

http://www.braeunig.us/space/propel.htm
Liquid oxygen and liquid hydrogen are used as the propellant in the high efficiency main engines of the Space Shuttle.
As the rocket gains altitude, its flight will not be affected by the lack of oxygen to burn.

Going back to the J-20 and its claim to have a variable DSI system...

Q: As the jet fighter changes in altitudes, often unplanned, how would this variable DSI system know the available air density ?

A: Air data probes, specifically pitot and static.

https://www.grc.nasa.gov/www/k-12/airplane/pitot.html

Air data is needed for the flight control computer (FLCC) to calculate flight control surface displacement.

But the problem now is that because an aircraft is a complex body, airflow over its complex surfaces will be different in both velocity and pressure. Further, the physical structures themselves will create a variety of airflow behaviors. A jet engine inlet is a tunnel or tube, essentially trapping airflow, whereas the wing will simply let airflow travels over its surface.

So if this variable DSI bump is supposed to change its shape and dimension to optimize airflow into the engine, the system MUST have localize pitot/static air sensors. That pitot/static probe in front or on the size of the radome is for airflow that is in first contact with the aircraft. This is for raw airspeed and altitude information. As airflow travels the fuselage, its velocity and pressure changes. This means the inlet cannot use air data information from the nose where airflow velocity and pressure are different.

Sure...This variable DSI system can use CALCULATED air data information from the nose air data, but this is a high risk proposition because of the need for maneuvers where airflow will be different in diverse areas of the aircraft.

Therefore, the best, safest, and most accurate air data information for this variable DSI system must be independent of what the main pitot/static probe in the forward fuselage area have. Each engine inlet must have its own independent pitot/static sensor as close to the inlet entrance as possible, and each inlet must have its own independent air data computer to alter the DSI bump. The F-111 have it. The F-15 have the same layout.

Assuming the J-20 do have this variable DSI bump system, I doubt that the J-20 engineers are that much of risk takers to use calculated air data from a different part of the jet.

So where are the components for this variable DSI bump system ?

What I wrote above is clear evidence that I do know what I am talking about. You will NEVER find comparable technical information on basic system configuration from the Chinese members here. They have neither the aviation experience nor even basic education in the aviation fields to inform the readers this way.

The Chinese claimants maybe correct, but that would be from luck, not from experience and/or education.
 
.
We can do that. But that does not mean I am going to let the Chinese off the technical hook. We will let the silent readers decide who is the more credible.

Mr. Asok said that the J-20 have a variable DSI system. Nowhere have I said there are technical barriers to that. In fact, I provided my first jet, the F-111, as proof of that system.

Mr. Asok said that the variable DSI system would 'optimize' airflow into the engines. Never mind that the word 'optimize' have been abused to death by those who do not know what they are talking about but tries to portray themselves as knowledgeable.

Air is not uniform in density. Everyone who took basic science in high school know that. As altitude increases, air density decreases. This means airflow in aerodynamics forces and in jet engine operations will be negative affected. Negative as in decrease in efficiency and performance output. This is why rockets carries their own oxidizers -- oxygen -- in the fuel mixture.

http://www.braeunig.us/space/propel.htm

As the rocket gains altitude, its flight will not be affected by the lack of oxygen to burn.

Going back to the J-20 and its claim to have a variable DSI system...

Q: As the jet fighter changes in altitudes, often unplanned, how would this variable DSI system know the available air density ?

A: Air data probes, specifically pitot and static.

https://www.grc.nasa.gov/www/k-12/airplane/pitot.html

Air data is needed for the flight control computer (FLCC) to calculate flight control surface displacement.

But the problem now is that because an aircraft is a complex body, airflow over its complex surfaces will be different in both velocity and pressure. Further, the physical structures themselves will create a variety of airflow behaviors. A jet engine inlet is a tunnel or tube, essentially trapping airflow, whereas the wing will simply let airflow travels over its surface.

So if this variable DSI bump is supposed to change its shape and dimension to optimize airflow into the engine, the system MUST have localize pitot/static air sensors. That pitot/static probe in front or on the size of the radome is for airflow that is in first contact with the aircraft. This is for raw airspeed and altitude information. As airflow travels the fuselage, its velocity and pressure changes. This means the inlet cannot use air data information from the nose where airflow velocity and pressure are different.

Sure...This variable DSI system can use CALCULATED air data information from the nose air data, but this is a high risk proposition because of the need for maneuvers where airflow will be different in diverse areas of the aircraft.

Therefore, the best, safest, and most accurate air data information for this variable DSI system must be independent of what the main pitot/static probe in the forward fuselage area have. Each engine inlet must have its own independent pitot/static sensor as close to the inlet entrance as possible, and each inlet must have its own independent air data computer to alter the DSI bump. The F-111 have it. The F-15 have the same layout.

Assuming the J-20 do have this variable DSI bump system, I doubt that the J-20 engineers are that much of risk takers to use calculated air data from a different part of the jet.

So where are the components for this variable DSI bump system ?

What I wrote above is clear evidence that I do know what I am talking about. You will NEVER find comparable technical information on basic system configuration from the Chinese members here. They have neither the aviation experience nor even basic education in the aviation fields to inform the readers this way.

The Chinese claimants maybe correct, but that would be from luck, not from experience and/or education.

As a Mechanical engineer and a lifelong Formula 1 fan I do have many questions regarding changing area of an Inlet of an engine (let alone a DSI one on a stealth aircraft where you require a very good engine efficiency to keep IR signature low too) and I enjoy your posts on these things too as they are very informative. Just saying we are never going to get the answers of all these questions

One thing more about variable DSI. What happens to RCS of J-20 as its DSI changes shape. I mean we talk all the time how RCS suddenly increases when the weapon bay is opened and Serbs even claim the change in RCS was just what they needed to bring F-111 down. Can similar thing happens with a variable DSI ??
 
.
Thanks for let him have it, Giant Panda. Although, I have doubt he is a Vietnamese, at all.

View attachment 371700
Hey, bro. I agree with your many points though not every points. Keep your fact based arguments and calculations pls. It's more rational than any other talking.

I support you and also I hope you keep your stay at PDF and you must slap faces one by one when the official information releases out OK?

:D
 
.
A fan art depicting a J-20 carrying a full load of missiles. This might be useful in a situation when you are defending a high value target, like an AWAC, where run away, after you shoot your internally stored 8 missiles is not a very good option.

Screen Shot 2017-01-25 at 5.52.37 AM.png


Hey, bro. I agree with your many points though not every points. Keep your fact based arguments and calculations pls. It's more rational than any other talking.

I support you and also I hope you keep your stay at PDF and you must slap faces one by one when the official information releases out OK?

:D

Good idea, slap those doubters' face one by one, when official informations finally came out. I got a feeling, sometimes later this year, the WS-15 will be officially confirmed operational, after one or two regiments of J-20 are inducted into PLAAF.

The idea that PLAAF Commander, will allow J-20 go into production, without the Supersonic Cruise and Supersonic Maneuverability, first being tested thoroughly, with its WS-15 engine, is too outlandish.:mad:
 
.
The DSI was never designed for that purpose. If there is such a benefit, it is INCIDENTAL, never intentional.

But the real issue is somehow you can make the DSI variable in dimensions and yet gain no weight and complexity. Absurd.

Yes it is.

DSI is intended to move away complexity of heavy moving parts that is used in conventional inlets.

Long time ago the intention of DSI is to reduce a/c weight, and lowering maintenance cost. But of course another advantage of moving away the complexity of moving parts at inlet is reduce RCS.

We can do that. But that does not mean I am going to let the Chinese off the technical hook. We will let the silent readers decide who is the more credible.

Mr. Asok said that the J-20 have a variable DSI system. Nowhere have I said there are technical barriers to that. In fact, I provided my first jet, the F-111, as proof of that system.

Mr. Asok said that the variable DSI system would 'optimize' airflow into the engines. Never mind that the word 'optimize' have been abused to death by those who do not know what they are talking about but tries to portray themselves as knowledgeable.

Air is not uniform in density. Everyone who took basic science in high school know that. As altitude increases, air density decreases. This means airflow in aerodynamics forces and in jet engine operations will be negative affected. Negative as in decrease in efficiency and performance output. This is why rockets carries their own oxidizers -- oxygen -- in the fuel mixture.

http://www.braeunig.us/space/propel.htm

As the rocket gains altitude, its flight will not be affected by the lack of oxygen to burn.

Going back to the J-20 and its claim to have a variable DSI system...

Q: As the jet fighter changes in altitudes, often unplanned, how would this variable DSI system know the available air density ?

A: Air data probes, specifically pitot and static.

https://www.grc.nasa.gov/www/k-12/airplane/pitot.html

Air data is needed for the flight control computer (FLCC) to calculate flight control surface displacement.

But the problem now is that because an aircraft is a complex body, airflow over its complex surfaces will be different in both velocity and pressure. Further, the physical structures themselves will create a variety of airflow behaviors. A jet engine inlet is a tunnel or tube, essentially trapping airflow, whereas the wing will simply let airflow travels over its surface.

So if this variable DSI bump is supposed to change its shape and dimension to optimize airflow into the engine, the system MUST have localize pitot/static air sensors. That pitot/static probe in front or on the size of the radome is for airflow that is in first contact with the aircraft. This is for raw airspeed and altitude information. As airflow travels the fuselage, its velocity and pressure changes. This means the inlet cannot use air data information from the nose where airflow velocity and pressure are different.


Sure...This variable DSI system can use CALCULATED air data information from the nose air data, but this is a high risk proposition because of the need for maneuvers where airflow will be different in diverse areas of the aircraft.

Therefore, the best, safest, and most accurate air data information for this variable DSI system must be independent of what the main pitot/static probe in the forward fuselage area have. Each engine inlet must have its own independent pitot/static sensor as close to the inlet entrance as possible, and each inlet must have its own independent air data computer to alter the DSI bump. The F-111 have it. The F-15 have the same layout.

Assuming the J-20 do have this variable DSI bump system, I doubt that the J-20 engineers are that much of risk takers to use calculated air data from a different part of the jet.

So where are the components for this variable DSI bump system ?

What I wrote above is clear evidence that I do know what I am talking about. You will NEVER find comparable technical information on basic system configuration from the Chinese members here. They have neither the aviation experience nor even basic education in the aviation fields to inform the readers this way.

The Chinese claimants maybe correct, but that would be from luck, not from experience and/or education.


OK please help us to understand the way you think..

Please explain why variable DSI (if any) need pitot/static sensor while moveable cone or ramp does not?

Why variable DSI (if any) need such a complexed calculated air data while movable cone or ramp does not?
 
Last edited:
.
The idea that PLAAF Commander, will allow J-20 go into production, without the Supersonic Cruise and Supersonic Maneuverability, first being tested thoroughly, with its WS-15 engine, is too outlandish.:mad:
The logic is ok especially when you hear the sound generated by J20 in the Chengdu's sky.
 
.
The logic is ok especially when you hear the sound generated by J20 in the Chengdu's sky.

The distinctive sound of J-20's engine is very noticeable, the first time, I watched the maiden test flight video. I turned on my surround sounds speakers to just hear it. It's nothing like the WS-10 or AL-31FN.
 
.
The distinctive sound of J-20's engine is very noticeable, the first time, I watched the maiden test flight video. I turned on my surround sounds speakers to just hear it. It's nothing like the WS-10 or AL-31FN.

I think that you don't have to forcefully make Gambit and others believe that J-20 use a new mysterious engine. Let him believe what he believes. There is nothing that you can gain from your effort. Even if the J-20 is actually use WS-15, and has an advantage that unknown to everybody, let it be. I prefer that Gambit and others think that J-20 is inferior, with Russian engine AL-31FN, and less stealthy. Those believe will keep J-20 capability stay in the dark, and cause miss calculation on their part.
 
.
Never knew that being confident about the J-20's capabilities and backing up that standpoint with reasonable arguments makes you an inbred fanboy, mind. I also love it that attacking people using said insult when you disagree with them will likely earn you a free pass. :disagree:
 
Last edited:
.
Back
Top Bottom