J-20 5th Gen Fighter Thread V


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TerraN_EmpirE

Tyrant King
Okay so why mount a fighter like this?
Answer RCS.
Explanation. Although Radar testing is common for models there is still nothing like the real thing. The mount is itself typically stealthy The jet is mounted and the mounting can move the aircraft along a number of angles. as a number of ground mounted radars are pointed at it. the jet will be moved in a set number of angles. This kind of testing it not unique to Stealthy types they also test conventional aircraft.
The first picture shows only the pole stand.
The second picture has a J-20 full scale mock up mounted on the pole for testing purposes.

In other words the pole stand is fixed, but the J-20 mock up is removable.


Many aircraft, and stealth aircraft in particular undergo this type of testing.



If you look at the upper photo you should see that the base of that test stand is inside a open space. this is so that the stand can move.
note both these stands are angular as they are both stealthy themselves.

Story is when they did this type of testing on the F117 they aimed the radar and got a return. They felt they had failed until someone looked out a window and saw that a bird had landed and was standing on the testing model giving them a larger return then the actual return.
testing is doen typically with models that can be to 1:1 scale and often on projected Aircraft.
 

plawolf

Brigadier
Possibly, but from what I understand, dedicated RCS airframes are made for these purposes instead of static test fatigue airframes.

It makes sense to have dedicated RCS representative airframes instead of fully representative static test airframes, I think, given static test airframes will be much heavier and feature many internal structures which may not be required for RCS testing. And of course a static test airframe would be much heavier than a dedicated RCS representative airframe.
Perhaps, but we are, after all, talking of full blooded 5th gen fighters here, so the degree of precision for RCS testing would be significantly higher than for conventional aircraft.

For stealth fighters, it's not just the external shaping that is crutical to their stealth characteristics, the internal structures are also heavily influenced by the need to minimise RCS.

For a conventional fighter, the extra RCS from radar reflection off of internal structures is unlikely to make a meaningful enough different to warrant much more than a dedicated RCS testing shell.

For a full blooded 5th gen, the external RCS should be so reduced by shaping, that the small RCS from internal structures matter.

That's why I think it would be worth while to test how the RCS of the entire package is, rather than just how well the shaping worked.

I would imagine they would do many sets of tests, ranging from RCS of the bare airframe with no RAM coatings, to RCS of the intended final package with full coating and everything in between.

Using the static test airframe has a good economy of effort to it by recycling an otherwise useless airframe without negatively impacting the testing timetable as would happen if you pulled a flying prototype for the tests or waste the resource of building a dedicate RCS testing airframe.

Timetable wise, the static test airframe would also represent the first version of the design, and you can get RCS results back early enough to make any necessary tweaks and changes feasible in time for it to make it onto future test airframes and LRIP birds.

You could then use the second static test airframe of the LRIP version to verify the effectiveness of any modifications prior to final certification and production.
 

Bltizo

Lieutenant General
Staff member
Super Moderator
Perhaps, but we are, after all, talking of full blooded 5th gen fighters here, so the degree of precision for RCS testing would be significantly higher than for conventional aircraft.

For stealth fighters, it's not just the external shaping that is crutical to their stealth characteristics, the internal structures are also heavily influenced by the need to minimise RCS.

For a conventional fighter, the extra RCS from radar reflection off of internal structures is unlikely to make a meaningful enough different to warrant much more than a dedicated RCS testing shell.

For a full blooded 5th gen, the external RCS should be so reduced by shaping, that the small RCS from internal structures matter.

That's why I think it would be worth while to test how the RCS of the entire package is, rather than just how well the shaping worked.

I would imagine they would do many sets of tests, ranging from RCS of the bare airframe with no RAM coatings, to RCS of the intended final package with full coating and everything in between.

Using the static test airframe has a good economy of effort to it by recycling an otherwise useless airframe without negatively impacting the testing timetable as would happen if you pulled a flying prototype for the tests or waste the resource of building a dedicate RCS testing airframe.

Timetable wise, the static test airframe would also represent the first version of the design, and you can get RCS results back early enough to make any necessary tweaks and changes feasible in time for it to make it onto future test airframes and LRIP birds.

You could then use the second static test airframe of the LRIP version to verify the effectiveness of any modifications prior to final certification and production.

I do agree with you, and I believe they would definitely be interested in developing an accurate and representative RCS mock up of the real thing with representative internal structures that may possibly influence RCS.

But I do not think they would necessarily use a static test airframe for pole mounted RCS tests, and would instead develop dedicated mock ups designed specifically to replicate as many of the aircraft's RCS characteristics that may be influenced by internal structures as possible, while also substantially reducing the weight of the internal structure to allow it to actually be fit upon the pole.

A static test airframe (or better yet, an actual real aircraft with working subsystems and everything else) would be more suited for anechoic chamber RCS and EM testing, which is one step up from pole mounted RCS testing, and more importantly they can put the entire full scale article inside without having to make it light enough to fit on the top of a pole.

f22_anecho_test_79.jpg
 

GreenestGDP

Junior Member
We all know from 2014 Zhuhai show, PRC is offering at least
3 different kind of Anti-Stealth Radar devices, each using different
technology for sale to the global market.

I am thinking ... ...

Because PLA AESA and Anti--Stealth Radar technology and Stealth Coating Materials are advancing so quickly, new tech breakthrough,
after breakthrough keep flowing out from the Radar Labs across the nation ... ...

Chengdu is using a permanent RCS Testing facilities to test the RCS of
the latest J-20 Stealth coating iteration, against all the latest Anti--Stealth Radar devices coming online from the Labs.


This Martin Su ( top notch expert ) link below has fantastic write up on
PLA radar development and it has many pictures:

Please, Log in or Register to view URLs content!



JY-26 Anti--Stealth Radar for sale to the global market
JY-26--anti Stealth--RADAR--1a.jpg
 
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