J-20 goes operational again

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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sferrin

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Unread post04 Oct 2019, 11:04

mixelflick wrote:
sferrin wrote:
mixelflick wrote:Pretty shameless knock off of the F-22 wing/fuselage/canopy, coupled with inlets from the F-35. I have a lot more respect for the J-20's design, albeit you could argue that too was inspired by the Mig I.44.


Ahem:
The attachment ce_002.jpg is no longer available



And this is who's concept art?

Tough to say based on the illustration.


It's LM. And more than concept art. There are pics around of a wind tunnel model.

calf_lockheed_01.jpg

"Lockheed stealthy, supersonic fighter suitable for conventional and STOVL applications looking much like the eventual F-35 with canards " (CALF phase.)
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Unread post04 Oct 2019, 19:17

mixelflick wrote:
weasel1962 wrote:Neither J-20 or J-31 is an exact copy of any aircraft. The general shape may be there but the reality is aeronautical design is designed around the engines. Simplistically, the engines being different will result in a different aircraft. The size of the wings will then be dependent on the fuselage, weight etc. No doubt the shape of the wings could have relied upon F-35/F-22 as a basis but that's just incorporating what others have learnt.

If one takes the definition that if it looks roughly alike then its a copy then every fighter designed to date is a copy. Example, in order to break the sound barrier, designers realized that the shape of the plane had to take into account both wings and fuselage together (previously designed separately). Today, everyone applies the same principle, otherwise one can't break the sound barrier. One might argue everyone is a copy but imho, that's too broad a definition.

Today's fighter shape is such that in order to achieve stealth, that's the optimal design for stealth. If designers can find something better, they would but logically, fighters that want to achieve the level of stealth would have to adopt something like a flying wing design. You can't achieve stealth otherwise (unless a breakthrough happens - which may happen with the PCA/NGAD). The J-20 is slightly different in view the Chinese incorporated canards into the design. I originally thought it would render the design less stealthy but clearly they incorporated the canards as a necessity for the performance of the aircraft.

There are so many basic design differences to the mig 1.44 that only a lay person would suggests its the same. Its like saying airbus copied boeing for all their airliners because both have 2 wings and a tail and look alike. Just a simple basic feature difference is the location of the intakes. Whilst China has a well earned reputation for a copy nation, I think objectively, both J-20 and J-31 designs are really local designs. Another person who has the same mig 1.44 blueprints would not have come up with a J-20 design.


That's why I used the word inspired, not copied when referring to the J-20 and its likeness to the Mig I.44. Regardless of design input, inspiration etc. I think we can all agree it's going to be limited by its motors. By the time China develops engines with adequate reliability/thrust etc., the basic airframe is going to be dated. I think there's a reason we don't see hundreds in service already (according to most estimates). The engine/airframe is a total mis-match, worse than the F-14/early TF-30's. They're only going to glean so much from the SU-35's engine, and it isn't designed to super-cruise, be stealthy in the RF/IR spectrum etc..


Partially correct. Remember that the DoD was claiming the J-20 would be IOC in the 2020-2022 timeframe, but I think they were looking at the engines as the chief limitation. What the Chinese ended up doing was rushing the airframe in with make-do engines, and it's possible the Chinese may not fully certify the WS-15 by 2022 (rumor in early 2019 was that we'd not see it before 2022).

On the other hand, leaked documents from the Chinese claim they knew this was going to happen and tried to compensate for it. The LERX canard delta they chose was to guarantee supermaneuverability (which strictly refers to post-stall or ITR maneuverability), supercruise, and some level of stealth even with bad engines.

As to whether the J-20 CAN supercruise, most people think it can't, but it's a low-drag airframe that likely weighs in the 18,000-19,000 kg range. Rumors suggest the J-20 already reached Mach 2.4 in test flights, suggesting it can supercruise already with WS-10 / AL-31.

One thing to note between the J-20 and the J-31 is that the J-31 seems to be designed for WS-18/19 or whatever they call their upgraded RD-33 derivatives. I.e, the J-31 has no bells and whistles to counter the engine weakness, and they'd rather delay it until the engines are fully upgraded. That's to say, the J-31 can be late, and the Chinese wouldn't care. The J-31 can be cancelled, and the Chinese wouldn't care that much. The J-20, on the other hand, has been in some form of IOC since 2017 with underpowered engines.
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wrightwing

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Unread post04 Oct 2019, 21:07

Hitting M2.4 with afterburners doesn't suggest the ability to supercruise. Plenty of 3rd and 4th gen fighters could exceed M2 with AB, but couldn't operationally supercruise.
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Unread post05 Oct 2019, 00:21

Su-27 can't supercruise with 2 AL-31Fs. Why would the J-20?
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Unread post05 Oct 2019, 13:26

It's LM. And more than concept art. There are pics around of a wind tunnel model.

calf_lockheed_01.jpg

"Lockheed stealthy, supersonic fighter suitable for conventional and STOVL applications looking much like the eventual F-35 with canards " (CALF phase.)[/quote]

Sounds as if LM is going down this road for a "Super F-35", if I'm reading you correctly?

First I've heard of it, and nowhere can I think of seeing them using canards. But hey, maybe so. If it gets performance levels up substantially and makes it that much better (and we have the $), why not? If this really is the case, LM should consult Boeing on how to sell it to Congress. Hell, that's what Boeing did (masterfully, I might add) with the legacy to Super Hornet. And even today, they've sold the Navy on the Super Duper/block III or whatever they're calling it.

I'm all for this Super F-35. Hopefully, it can finally silence the critics who want an off the charts STR, thrust to weight ratio and all of the "old school" metrics that matter less. The question I'd have of LM if they do it would be this: Why add those new capabilities, knowing that superior SA, sensors and stealth (which it already has) are more important?

If they build this thing right, would we then need F/A-XX??

EDIT: I see now, its LM concept art for the Common Affordable Lightweight Fighter. My bad. Won't be a replacement for the F/A-XX as that's a heavyweight platform. Might be an interesting final iteration of the F-35 though..
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Unread post05 Oct 2019, 14:53

weasel1962 wrote:Su-27 can't supercruise with 2 AL-31Fs. Why would the J-20?


Not same engines. J-20 use AL-31F M2 (Salyut deep modification of AL-31F):

https://en.wikipedia.org/wiki/Saturn_AL ... ns_(AL-31F)


There are noticeable changes compare to AL-31F:
AL-31FM2 and 31FM3. The AL-31FM2 (Item 99M2, or AL-31FSM (M1S)) has a low-pressure compressor KND-924-4, but with some adjustments in aerodynamics over the previous engine, so that pressure ratio increased to 4.0. Also, low pressure turbine has a new 3D aerodynamics, its input can operate at temperatures 1467-1507 ° C. Further cooling system was modernized and the control system optimized. In the summer of 2007 the engine underwent a series of ground tests. The M2 engine has had further increasments of thrust and life time. Thrust is demonstrably 14,200 kp (information from January 2007), with an increase to 14,500 kp or even slightly more likely. Time between overhault rose to 1000 or more hours.

http://www.leteckemotory.cz/motory/al-31/index.php?en

Wiki info about thust is 145kN which is 14.700kp so it is right data. Russians install AL-31F M2 in Su-34.

Su-35 with similar powered engine (117S) can super cruise without weapon load, +1.3 Mach confirmed by test pilot.

So J-20 can achieve similar speed with similar engine and probable higher super cruise speed because it is designed for super cruise while super cruise wasn't requirement for Su-27.

Chinese wouldn't start serial production of J-20 (they are finishing three production lines at least 36plane per year will be build) if J-20 interceptor can't achieve primary requirement and that is super cruising.
Last edited by milosh on 05 Oct 2019, 17:14, edited 1 time in total.
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Unread post05 Oct 2019, 15:42

mixelflick wrote:Sounds as if LM is going down this road for a "Super F-35", if I'm reading you correctly?

First I've heard of it, and nowhere can I think of seeing them using canards. But hey, maybe so. If it gets performance levels up substantially and makes it that much better (and we have the $), why not? If this really is the case, LM should consult Boeing on how to sell it to Congress. Hell, that's what Boeing did (masterfully, I might add) with the legacy to Super Hornet. And even today, they've sold the Navy on the Super Duper/block III or whatever they're calling it.

I'm all for this Super F-35. Hopefully, it can finally silence the critics who want an off the charts STR, thrust to weight ratio and all of the "old school" metrics that matter less. The question I'd have of LM if they do it would be this: Why add those new capabilities, knowing that superior SA, sensors and stealth (which it already has) are more important?

If they build this thing right, would we then need F/A-XX??

EDIT: I see now, its LM concept art for the Common Affordable Lightweight Fighter. My bad. Won't be a replacement for the F/A-XX as that's a heavyweight platform. Might be an interesting final iteration of the F-35 though..


The original Lockheed Skunk Works CALF/JAST was supposed to be canard delta, but they couldn't get that arrangement to work on a normal aircraft carrier, so they went to a tailed design. The issue was something about the canard not working with a larger wing needed for carrier landings. Wonder if F-35 was just USAF and USMC, it might have been a canard delta.
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Unread post05 Oct 2019, 15:49

That concept art is circa CALF/JAST days...(ie 25+years ago).

:whistle:
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Unread post06 Oct 2019, 14:44

disconnectedradical wrote:
mixelflick wrote:Sounds as if LM is going down this road for a "Super F-35", if I'm reading you correctly?

First I've heard of it, and nowhere can I think of seeing them using canards. But hey, maybe so. If it gets performance levels up substantially and makes it that much better (and we have the $), why not? If this really is the case, LM should consult Boeing on how to sell it to Congress. Hell, that's what Boeing did (masterfully, I might add) with the legacy to Super Hornet. And even today, they've sold the Navy on the Super Duper/block III or whatever they're calling it.

I'm all for this Super F-35. Hopefully, it can finally silence the critics who want an off the charts STR, thrust to weight ratio and all of the "old school" metrics that matter less. The question I'd have of LM if they do it would be this: Why add those new capabilities, knowing that superior SA, sensors and stealth (which it already has) are more important?

If they build this thing right, would we then need F/A-XX??

EDIT: I see now, its LM concept art for the Common Affordable Lightweight Fighter. My bad. Won't be a replacement for the F/A-XX as that's a heavyweight platform. Might be an interesting final iteration of the F-35 though..


The original Lockheed Skunk Works CALF/JAST was supposed to be canard delta, but they couldn't get that arrangement to work on a normal aircraft carrier, so they went to a tailed design. The issue was something about the canard not working with a larger wing needed for carrier landings. Wonder if F-35 was just USAF and USMC, it might have been a canard delta.


If canards were an issue, why not make them retractable? Something like the glove vanes the F-14 sported for while, until I think they dropped them. Would seem to give you the best of both worlds...
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sferrin

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Unread post06 Oct 2019, 16:16

quicksilver wrote:That concept art is circa CALF/JAST days...(ie 25+years ago).

:whistle:


Yep. :wink:
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Unread post07 Oct 2019, 14:16

mixelflick wrote:If canards were an issue, why not make them retractable? Something like the glove vanes the F-14 sported for while, until I think they dropped them. Would seem to give you the best of both worlds...


No the problem wasn't canards themselves. For Navy variant you need a larger wing to reduce landing speed for carrier landings, and that increased the root chord so there wasn't enough space for a canard since the fuselage length is supposed to be same for all variants. That was part of why Lockheed went from canard delta to normal tail configuration for CALF/JAST/JSF.
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Unread post08 Oct 2019, 16:05

disconnectedradical wrote:
mixelflick wrote:If canards were an issue, why not make them retractable? Something like the glove vanes the F-14 sported for while, until I think they dropped them. Would seem to give you the best of both worlds...


No the problem wasn't canards themselves. For Navy variant you need a larger wing to reduce landing speed for carrier landings, and that increased the root chord so there wasn't enough space for a canard since the fuselage length is supposed to be same for all variants. That was part of why Lockheed went from canard delta to normal tail configuration for CALF/JAST/JSF.


Given all these conflicting requirements, I'd say it's a miracle LM did as well as they did with the F-35. It makes what was asked of the F-111 look rudimentary.
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Unread post08 Oct 2019, 16:50

mixelflick wrote:
disconnectedradical wrote:
mixelflick wrote:If canards were an issue, why not make them retractable? Something like the glove vanes the F-14 sported for while, until I think they dropped them. Would seem to give you the best of both worlds...


No the problem wasn't canards themselves. For Navy variant you need a larger wing to reduce landing speed for carrier landings, and that increased the root chord so there wasn't enough space for a canard since the fuselage length is supposed to be same for all variants. That was part of why Lockheed went from canard delta to normal tail configuration for CALF/JAST/JSF.


Given all these conflicting requirements, I'd say it's a miracle LM did as well as they did with the F-35. It makes what was asked of the F-111 look rudimentary.


JSF was designed from the start for commonality in all 3 variants, while F-111 was not and only later tried to have it land on a carrier so the situation wasn't quite the same.
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Unread post09 Oct 2019, 09:12

The tomcats may have benefited from the F-111 experience.
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Unread post09 Oct 2019, 16:23

weasel1962 wrote:The tomcats may have benefited from the F-111 experience.


I would say most certainly. It was still a big machine, but more reasonably sized/weighted such that even with the same engines, it was far more agile. It was and still is an incredible airframe. A masterpiece of aeronautical engineering IMO...
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