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Deino said:
"Not the blades again!"
;D
Chengdu J-20 pictures, analysis and speculation Part II
- Thread starter overscan (PaulMM)
- Start date
"Not the blades again!"
;D
FighterJock
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Deino said:
Not too sure if the weapon bays are longer than the early prototypes, it is difficult to judge with the black paint getting in the way, a side by side view of an early prototype with 2011 would be better, then we would know for sure.
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it's obvious that if you reduce the number of door blade seal chevrons with given angle at the top while keeping their baseline (rear wall of the weapon bay) at the place, you get them protruding further back.
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Playing in Photoshop I am 99% sure that the bay dimensions are unchanged, the doors are longer due to the larger zigzags like Grigori says.
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I know WantChinaTimes is a pretty garbage source, but what do you guys (especially Deino) make of this?
http://www.wantchinatimes.com/news-subclass-cnt.aspx?id=20140329000069&cid=1101
http://www.wantchinatimes.com/news-subclass-cnt.aspx?id=20140329000069&cid=1101
latenlazy
I really should change my personal text
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RadicalDisco said:
Duowei is decently reliable, which is where WantChinaTimes got the news from. That said, taking this news too far is making a mountain out of a mole hill. There's a reason why the plane is a prototype, and it's not like the thing ended up not flying at all.
RadicalDisco said:
Yeah it really is a bit of a non statement unless they have more details... "Problems" could refer to anything.
So overall, there is no reason to doubt or be surprised that issues are still being found, considering it is a prototype like latenlazy said, but there is also a degree of amusement that such news would be publishable.
There isn't much much more that any non-insider can shed on this, really.
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Basically this means nothing..
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Foxglove said:
Many stealth (VLO) aircraft have a conductive coating. This is especially important for aircraft that make liberal use of composite materials. This layer is often called "silver paint" or "silver coat", even though it may not be silver or metallic in appearance. The stack ends up looking something like this:
Skin
Primer
Silver Coat
MAGICAL RAM
IR suppression coating (Optional)
Ceno Technologies are the go-to guys for these kinds of things in the western world.
Based on the external appearance of 2011 - edge treatments, seams, lack of fuzzy dice - it would not be unreasonable to conclude that it does not currently have it's full stack of MAGICAL RAM coatings.
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Sundog said:
The IR suppression layer. For it to be most effective it has to be the layer on top. In modern applications the IR layer has the visual pigment. In some older applications the IR layer was over the pigment layer like a lacquer or varnish.
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That is CGI.
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Radical
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I noticed that the aft fuselage where the engines are housed is "waisted" near the wings. Perhaps better volume distribution and greater adherence to the area rule? Wonder how fast this thing can supercruise when the planned WS-15s arrive.
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RadicalDisco said:
It will probably be around M=1.8 max. Once you start supercruising for any period of time above that speed you have to start going to exotic materials to be able to handle the thermal loads. The important feature of the new engines may not be greater thrust, but greater mass flow at lower throttle settings, which leads to more efficient supercruise performance; i.e.-range.
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Sundog said:
Speaking of mass flow, do we know if the new intakes in bort 2011 have different capture area compared to 2001 and 2002? The shoulder drop should decrease it somewhat, unless the intake was also made wider.
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10 per cent mass flow is quite a lot in propulsion terms but only means a 5 per cent change in inlet height and width. Not too easy to measure off a photograph.
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Sundog said:
Pretty sure it's higher than that. From Jay Miller's B-58 book:
"Convair's engineering team succeeded admirably; the B-58, without modification, proved easily capable of a long service life while providing SAC with a Mach 2 capability. Additionally, though it was never utilized, the B-58 structure proved without modification to be capable of sustained speeds of Mach 2.4 at reduced gross weights.
The basic B-58 airframe and structure provided maneuver load factors of 2 g's at the takeoff gross weight of 163,000 Ibs. and 3 g's at the combat gross weight of 100,000 Ibs. Following completion of the fatigue certification program, total structural life was eventually determined to be 7,000 hours.
Basic structural materials consisted almost totally of aluminum alloys with steel used only in excessively high temperature areas. The wing covering structure, for instance, consisted of panels of chemically bonded 2024-T86 aluminum skins with phenolic-resin-fiberglass or aluminum cores. The fuselage had 2024-T80 beaded stiffeners filled with aluminum honeycomb and bonded to the 2024-T81 aluminum skin.
In the structural development program for the B-58, analyses and tests were based on a material temperature of 260°F., which was the calculated adiabatic wall temperature on an AF ambient hot day at 36,000'. Extensive analyses, design studies, and tests were conducted during the development program to obtain a reliable structure for high temperature service. Aluminum alloys, honeycomb sandwich cores, adhesives, plastic laminates, and other materials were screened and evaluated to assure the capability for supersonic flight. Composite structures of these elemental materials were subjected to demanding environments and tested for durability and structural integrity. The fiberglass honeycomb cores were fabricated of glass cloth impregnated with high temperature resin. When sandwiched between two sheets of aluminum, they were then cured at a pressure of 175 psi at 350° for two hours. This combination Gf materials retained high strength at temperatures beyond 325°F. and was not affected by prolonged exposure
at this temperature."
And there is some BMI out there capable of at least those kinds of temperatures.
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I haven't read that book in a while. I'll have to go back and read it again just because it's the B-58.
But I'm glad you had pointed that out, because I've seen many times where M=1.8 is listed as the approximate supercruise limit due to thermal loads for the materials used (keeping costs down), yet we know the YF-23, at least with the GE engines, easily surpassed M=1.8 in supercruise (I think it was M=2.2?). I wonder if the ATF's "active thermal management" to control IR signature also had something to do with that? In that context as well, there isn't any reason to think the J-20 wouldn't do the same thing.
But I'm glad you had pointed that out, because I've seen many times where M=1.8 is listed as the approximate supercruise limit due to thermal loads for the materials used (keeping costs down), yet we know the YF-23, at least with the GE engines, easily surpassed M=1.8 in supercruise (I think it was M=2.2?). I wonder if the ATF's "active thermal management" to control IR signature also had something to do with that? In that context as well, there isn't any reason to think the J-20 wouldn't do the same thing.
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Aluminum alloys can run reasonably well up to M=2.4 or so. Composites not so much, unless you go to the bismaleimides. The real limfac on fighter supercruise is a high T/W, efficient engine (which means a high overall pressure ratio) that can run to high Mach without throttling back.
More Mach equals hotter air at the inlet. Multiply (effectively) by OPR and you have very hot air at the compressor exit. That's the difference between the F119 and anything else.
More Mach equals hotter air at the inlet. Multiply (effectively) by OPR and you have very hot air at the compressor exit. That's the difference between the F119 and anything else.
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Radical
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I'm wondering why the outboard edge of the LE flaps aren't planform aligned with the rest of the aircraft. In fact, it seems to make a 90 degree angle with the leading edge.
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