J-20... The New Generation Fighter II

rhino123 said:

Learning from past experience and taking these experiences seriously is one thing that all nations would have to do. When China and Russia (Soviet Union) turned for the worst, Soviet Union had pulled back all her engineers and technical assistance from China, thus the Chinese were left alone to figure out many (at that time) high technology system herself.

This should already be a wake up call for China, and there is no one except one own self to depend on when it come to national interest and defence.

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realism ftw. it's everywhere, regardless of IR, business, whicheverwise. plus, i'd think china sees an indigenous aircraft more valuable

I doubt the Russians would be this dumb showing off a 5th generation plane less stealthy than the Rafale.

cn_habs said:

I doubt the Russians would be this dumb showing off a 5th generation plane less stealthy than the Rafale.

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It is possible that a bare Rafale has lower RCS than a bare T-50.

Of course, in reality, Rafale has to carry weapons externally, so the RCS would be easily 5sqm or 20sqm.

The calculation is off anyway, because all the data (assumption) is for frontal RCS. Underside RCS can be very different, usually much larger. F-15SE claims low frontal RCS similar to F-35, but Boeing is frank that the underside is not stealthy.

Saw-toothed doors don't matter if engine compressor blades are exposed

Saw-toothed doors don't matter if the engine compressor blades are exposed and returning a massive radar signature. However, for the J-20 and F-22, the serpentine air-inlets (and DSI on the J-20) hide the engine compressor blades. Once the major factors for RCS have been hidden or dramatically reduced then the little details like saw-toothed doors matter if you want to achieve a RCS of 0.0001 m2.

The Russians are logical. Since the T-50's engine blades are exposed, why bother with extensive saw-toothed doors, frameless cockpit canopy, RAM-coated cockpit glass, removing exposed rivets, removing all those gaps, vents, and protrusions from the underside of the T-50, etc.?


Russian T-50 underside is a messy design. Vents, gaps, stuff jutting out, etc. This is not stealthy.


J-20 has a very clean and smooth underside. Once the wheels are retracted, this is a very smooth, RAM-coated, and stealthy design.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

Martian said:

Saw-toothed doors don't matter if the engine compressor blades are exposed and returning a massive radar signature. However, for the J-20 and F-22, the serpentine air-inlets (and DSI on the J-20) hide the engine compressor blades. Once the major factors for RCS have been hidden or dramatically reduced then the little details like saw-toothed doors matter if you want to achieve a RCS of 0.0001 m2.

The Russians are logical. Since the T-50's engine blades are exposed, why bother with extensive saw-toothed doors, frameless cockpit canopy, RAM-coated cockpit glass, removing exposed rivets, removing all those gaps, vents, and protrusions from the underside of the T-50, etc.?

Russian T-50 underside is a messy design. Vents, gaps, stuff jutting out, etc. This is not stealthy.

J-20 has a very clean and smooth underside. Once the wheels are retracted, this is a very smooth, RAM-coated, and stealthy design.

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Keep in mind what we see is still the prototype of the T-50, I'm sure later prototypes and production models will shield the blades in some form either with an S inlet or a radar blocker. I can't imagine Sukhoi will go and take notice of all the other aspects of the T-50's VLO (planform alignment etc), only to screw it over with exposed engine blades.

And the details like frameless cockpit, saw tooth edging etc could all be added in due course -- I won't count the Russians out on such areas though the carrying on of the Flankers distinctive engine "pod" design won't help VLO very much.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

Bltizo said:

Keep in mind what we see is still the prototype of the T-50, I'm sure later prototypes and production models will shield the blades in some form either with an S inlet or a radar blocker. I can't imagine Sukhoi will go and take notice of all the other aspects of the T-50's VLO (planform alignment etc), only to screw it over with exposed engine blades.

And the details like frameless cockpit, saw tooth edging etc could all be added in due course -- I won't count the Russians out on such areas though the carrying on of the Flankers distinctive engine "pod" design won't help VLO very much.

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I would agree to a point. Saw tooth edging and frameless canopies can be added later. But I don't know that an S-inlet can be put in now....seems too late for that.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

Bltizo said:

Keep in mind what we see is still the prototype of the T-50, I'm sure later prototypes and production models will shield the blades in some form either with an S inlet or a radar blocker. I can't imagine Sukhoi will go and take notice of all the other aspects of the T-50's VLO (planform alignment etc), only to screw it over with exposed engine blades.

And the details like frameless cockpit, saw tooth edging etc could all be added in due course -- I won't count the Russians out on such areas though the carrying on of the Flankers distinctive engine "pod" design won't help VLO very much.

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Platform alignment? J-20 has lines in 3 directions. F-22 in 5 directions. T-50 in 7 directions.

Frameless cockpit is technically difficult, and very expensive. Saw tooth edging should be easily doable though.

The strangest part is the engine vents. No, they are not like the F-117 style grids, and they appear on all three sides of the engine intake. Why are they there? There must be a reason.

Another issue is the weapon bay. The center bays seems to be long and thin, should carry no more than four mid-range missiles. There are two under-wing bumps which would be carrying two additional short-range missiles, at the expense of stealth. If you get rid of those two bumps to improve stealth, you also loses the additional missiles.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

Bltizo said:

Keep in mind what we see is still the prototype of the T-50, I'm sure later prototypes and production models will shield the blades in some form either with an S inlet or a radar blocker. I can't imagine Sukhoi will go and take notice of all the other aspects of the T-50's VLO (planform alignment etc), only to screw it over with exposed engine blades.

And the details like frameless cockpit, saw tooth edging etc could all be added in due course -- I won't count the Russians out on such areas though the carrying on of the Flankers distinctive engine "pod" design won't help VLO very much.

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The J-20 is also a prototype but the primary LO aspects are already completed. There would be no major restructuring of the plane for production. Little details like the ventral fins can be removed easily as they are not necessary for the plane to fly.

The T 50 prototype we see today would require extensive redesign and testing for it to be truly LO. Designing and implementing serpentine inlets are not easy as they require a complete overhaul of the airplane. I'm sure the Russians can fix small details easily but the engine inlets are currently a huge problem that would take a lot of time and money to fix. Before the Russians fix this fixing the small details would be pointless.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

tanlixiang28776 said:

The J-20 is also a prototype but the primary LO aspects are already completed. There would be no major restructuring of the plane for production. Little details like the ventral fins can be removed easily as they are not necessary for the plane to fly.

The T 50 prototype we see today would require extensive redesign and testing for it to be truly LO. Designing and implementing serpentine inlets are not easy as they require a complete overhaul of the airplane. I'm sure the Russians can fix small details easily but the engine inlets are currently a huge problem that would take a lot of time and money to fix. Before the Russians fix this fixing the small details would be pointless.

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I have to wonder whether J-20 has entered late stage of flight testing.

For example, pay attention to the the "strips" - two on vertical stabilizer, two under the cockpit (under the fold line), and two under the wing close to the wing tip. Those are the same strips as J-10B (not on J-10A). J-10B has four, two under the cockpit (same as J-20) and two close to the engine nozzle. Some suspect that they are ECM antennas.

If that are indeed ECM antennas, it means the J-20 prototype is quite complete, possibly with the complete avionics.

Another evidence is the air speed probe. One improvement Pakistan did on JF-17 is to use French sensor for air speed to replace the long air speed probe. On J-20, you can see the probe is off center. But if you saw one of the older photos, you will also see a light patch on the tip of the radar radome. I believe that light patch is the Chinese version of the air speed sensor to replace the long probe (and the probe is there to test the accuracy of the new sensor).

All the detail shows that the advanced stage of varies sub-systems, way beyond what maiden flight indicates.

A lot of people have suspected that was not the first flight. The "Project 718 first flight" might refer to the engine instead of airframe.

Re: Saw-toothed doors don't matter if engine compressor blades are exposed

johnqh said:

I have to wonder whether J-20 has entered late stage of flight testing.

For example, pay attention to the the "strips" - two on vertical stabilizer, two under the cockpit (under the fold line), and two under the wing close to the wing tip. Those are the same strips as J-10B (not on J-10A). J-10B has four, two under the cockpit (same as J-20) and two close to the engine nozzle. Some suspect that they are ECM antennas.

If that are indeed ECM antennas, it means the J-20 prototype is quite complete, possibly with the complete avionics.

Another evidence is the air speed probe. One improvement Pakistan did on JF-17 is to use French sensor for air speed to replace the long air speed probe. On J-20, you can see the probe is off center. But if you saw one of the older photos, you will also see a light patch on the tip of the radar radome. I believe that light patch is the Chinese version of the air speed sensor to replace the long probe (and the probe is there to test the accuracy of the new sensor).

All the detail shows that the advanced stage of varies sub-systems, way beyond what maiden flight indicates.

A lot of people have suspected that was not the first flight. The "Project 718 first flight" might refer to the engine instead of airframe.

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That is an interesting theory, but it doesn't jive with the prototype numbers nor does it seem possible that no one saw it until now.

That said, you're right, the J-20 seems like a pretty mature design for a first flight prototype.

On another note: Anyone know how to create a signature on this forum? I cannot find it for the life of me.