F-35 vs J-20

Unread postPosted: 22 Mar 2017, 10:44
by inst
Oh hey, since the F-22 vs J-20 thread is locked, I'm interested in seeing whether or not this would have better luck, since it's more a more realistic contest. The Chinese, according to this article (http://www.ainonline.com/aviation-news/ ... production ), are planning to put up 500-700 J-20s. Compared to a US deployment of about 2450 F-35s, it's a reasonable counter; the US splits its air fleet among several regions, and the J-20s are intended as an air superiority fighter (large canards, large wing area resulting in roughly 380 kg/m^2 wing loading), instead of a multi-role strike fighter. If the aircraft performs remotely close to as promised, it could counter US F-35 deployments in the Asia-Pacific region.

As an airframe, the J-20 has certain advantages; it is built for very long ranges, it has a larger radar aperture, and it is probably more maneuverable in sustained turns. On the other hand, the F-35 has different advantages; its stealth is likely more comprehensive, lacking the 0-degree zone of death on the J-20, its radar and EODAS are liekly more advanced, and it has superior WVR missiles; the latest PL-10 / PL-ASR is rated at about 22 km of range, whereas AIm-9X Block II has around 50 km of range.

Here's some interesting facts you might be interested in. The J-20 is capable of at least 50 degree AOA, due to the PLA requirements. Normally, a canard-delta layout should create more limited max AOA, but the complex lerx-canard-lerx lifting body delta set-up apparently bypasses that. A lot of this might also be accountable to simply the LERX; the Eurofighter team, for instance, found that by adding LERX to their airframe, they were able to increase max AOA by at least 10 degrees. The F-35, on the other hand, has achieved 110 degrees of AOA in testing, but its official max AOA is 50 degrees.

Of course, this entire thing could be moot. IIRC, someone from Lockmart mentioned a while back that "let the missiles do the turning"; i.e, WVR HOBS missiles are getting so good, any WVR engagements would essentially come down to the quality of the missiles or alternately turn into an attritional battle. The decisive factor in any real engagement might not even be combat training, but the software integration of system of systems. The Chinese have the large Divine Eagle anti-stealth drone, but the US has the E-2D Hawkeye, with detection ranges of over 250 km vs LO targets.

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 11:54
by popcorn

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 13:36
by wrightwing
The requirements could be as high as 500-700, though I'd be surprised if they end up with more than 200. As for superior turning capabilities, sustained/instantaneous, that hasn't been demonstrated, nor has 50 deg AoA, supercruise, distribute aperture systems, etc....

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 14:38
by bigjku
Whatever it has going on the J-20 has what amounts to a bad heart. Engines are really the critical piece for 5th generation aircraft. You need very high thrust and efficiency to overcome the other challenges that going all internal for gas and weapons can present. Talking about the rest of it prior to getting the engines right is doing it backwards.

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 15:45
by gta4
viewtopic.php?f=55&t=52510&start=75

All critics from pilots focus on F-35's transonic performance (sustained G, acceleration), but so far no complain is about F-35's subsonic performance. However, F-35's subsonic performance are widely praised (constant turn rate, acceleration, roll rate, nose-pointing rate, controllability...). I don't see any adversary could get a favorable exchange ratio against a F-35 WVR

All major aversaries are underperformed in certain aspects:

Su-27/30 (non-TVC version): does not have the subsobnic energy recovery like F-35 (20%+ gap); does not have any approach to counter F-35's pedal turn (28deg/sec sustained); does not have the high roll rate like F-35 (exceeding 300deg/sec).

Su-30 (with TVC): does not have the subsobnic energy recovery like F-35 (20%+ gap); may have approaches to counter F-35's pedal turn when TVC is engaged, but still could not acheive the nose-pointing rate in a controlled spin (F-35 could acheive 90+deg/sec in a controlled spin); does not have the high roll rate like F-35 (exceeding 300deg/sec).

Su-35 (with TVC): similar to the previous case, except that subsonic acceleration is closer to F-35.

T-50: similar to the Su-35 case, and bear in mind that T-50 is a prototype with insufficient avionics and structure strengh. T-50 may subject to weight increase and maneuverability reduction when in mass production.

J-31: the worst performer, needless to say.

J-20: similar to the Su-27/30 (non-TVC version) case.

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 16:04
by ricnunes
inst wrote:...and the J-20s are intended as an air superiority fighter (large canards, large wing area resulting in roughly 380 kg/m^2 wing loading), instead of a multi-role strike fighter. If the aircraft performs remotely close to as promised, it could counter US F-35 deployments in the Asia-Pacific region.


If you're right with what you say that "J-20s are intended as an air superiority fighter" than this only proves one thing, that the J-20 is even more limited (even in the air-to-air arena) compared to the F-35.
Nowadays all and every new fighter aircraft are designed as multi-role. Again if you're correct the J-20 would be an exception and that exception is more likely due to technological limitations rather than a "design option/optimization".
Even the Brits are changing their Eurofighter Typhoons role - an aircraft also designed as an air superiority fighter - to a multi-role fighter like for example the Typhoon FGR4 variant.

Moreover I still don't get why people trend to think that Canards are some sort of a "magical aeronautical solution" that makes fighter aircraft turn like hovering helicopters?? And speaking of Canards from what I've read, Canards seem to increase the aircraft's RCS which means that in terms of RCS the J-20 is even more at a disadvantage compared to the F-35.
Even without Canards I doubt that the J-20 RCS would be better or much better than the Russian T-50 RCS which by itself is far from being "stellar" (around 0.5 square meters according to the Russians themselves).


inst wrote:As an airframe, the J-20 has certain advantages; it is built for very long ranges,


So is the F-35 with it's long range on internal fuel only (and very large internal fuel tanks/capacity).


inst wrote:it has a larger radar aperture,


What do you mean with "larger radar aperture"? :?


inst wrote:and it is probably more maneuverable in sustained turns.
....
The J-20 is capable of at least 50 degree AOA, due to the PLA requirements.


Where did you get that?



inst wrote:Of course, this entire thing could be moot. IIRC, someone from Lockmart mentioned a while back that "let the missiles do the turning"; i.e, WVR HOBS missiles are getting so good, any WVR engagements would essentially come down to the quality of the missiles or alternately turn into an attritional battle. The decisive factor in any real engagement might not even be combat training, but the software integration of system of systems. The Chinese have the large Divine Eagle anti-stealth drone, but the US has the E-2D Hawkeye, with detection ranges of over 250 km vs LO targets.


Trying to reply to the thread's title-question "F-35 vs J-20", it would be something like this:
1- F-35 detects and "locks" the J-20 much sooner and at much longer ranges than vice-versa.
2- The J-20 still doesn't have a clue that it was detected and "locked" by the F-35.
3- F-35 shoots an AMRAAM (pick your variant)
4- The J-20 still doesn't have a clue that it was detected and "locked" much less that it was shot at by the F-35.
5- Booommm, the J-20 explodes, crashes and burns

This is not to say that the J-20 doesn't have its own merits. For example a force equipped with 4th and 4.5th generation fighter aircraft like the Super Hornet, Rafale, Typhoon, Gripen, etc... which would have to face the J-20s could be at serious disadvantage (this is for you CANADA!) so in these cases similar steps as the above 1- to -5 steps could be repeated but this time in the J-20's favour!
I guess that in my opinion a more "interesting thread" would be something like: "Super Hornet vs J-20"

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 20:14
by weasel1962
I would suggest the j-20 is more likely to have an interceptor role, more like the mig-31, rather than an air superiority fighter. With primary targets like aew or tanker aircraft as key targets, it will still have to cross the f-series fighters defending such aircraft.

imho, the weakest link for the f-35 (and f-22) in the a2a role is probably the amraam missile. With pakistan getting the c5 variant, it can be presumed that the missile characteristics are fully studied by the plaaf, notwithstanding the improvements of the d variant. The second the missile is launched, the j-20 probably knows its targeted. The usaf needs a new aam.

Re: F-35 vs J-20

Unread postPosted: 22 Mar 2017, 20:44
by ricnunes
weasel1962 wrote:I would suggest the j-20 is more likely to have an interceptor role, more like the mig-31, rather than an air superiority fighter. With primary targets like aew or tanker aircraft as key targets, it will still have to cross the f-series fighters defending such aircraft.


Yes, when I first saw the J-20 I though the same thing and I still do.
The J-20 certainly looks (to me) to be more like a "stealthy" Mig-31 with probably some air-to-ground capabilities to conduct deep strikes.


weasel1962 wrote:imho, the weakest link for the f-35 (and f-22) in the a2a role is probably the amraam missile. With pakistan getting the c5 variant, it can be presumed that the missile characteristics are fully studied by the plaaf, notwithstanding the improvements of the d variant. The second the missile is launched, the j-20 probably knows its targeted. The usaf needs a new aam.


Unless the J-20 carries an advanced Missile Warning System the only way for a J-20 RWR to detect an incoming AMRAAM is when the AMRAAM is already on the last stages (12Km or so) of the missile's flight profile, or resuming when the missile is already close to the targeted J-20 aircraft when the AMRAAM's turns its radar ON thus giving the J-20 little time to react.

So yes you're right that the J-20 will or could likely be able to detect an incoming AMRAAM but when it does it will probably be too late for the J-20.

Which prompts me the following question: Will future variants of the AMRAAM or even current ones be able to turn on the radar when closer to the targeted aircraft (for example 5 km away alternatively to 12km away) thru for example a pilot selectable option?

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:10
by inst
wrightwing wrote:The requirements could be as high as 500-700, though I'd be surprised if they end up with more than 200. As for superior turning capabilities, sustained/instantaneous, that hasn't been demonstrated, nor has 50 deg AoA, supercruise, distribute aperture systems, etc....


The Chinese want a large quantity because the J-20 is their first shot at having peer capabilities to the US in their region. If the J-20 performs as advertised (doubtful at the present rate, and mainly due to subsystems, such as engine, radar, eodas, maturity), it'd outclass the F-35 similarly to how a Flanker can outclass a late-model F-16 (different weight classes). Then if you have 700 J-20s vs 1400 F-35s in the region, you're at strategic parity. Likewise, facing the F-22, there's only 186 or so F-22s, minus training and parts models, so the J-20 has a significant numerical advantage.

As to turning capabilities, we've seen videos of the J-20 with 20 deg / sustained turn rate, which puts it higher than the F-35, which has around 10-15 degree STR.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:33
by inst
Here's a few misconceptions; first, the J-20 is not intended as an interceptor, although it might be interceptor-like, especially with the hobbled early engines. If it were an interceptor, why would it add canards, which increase drag and RCS, two factors contrary to what an interceptor wants? Second, canards, while not necessarily the be-all-end-all of maneuverability, see the XB-70 Valkyrie, when properly applied and implemented, can increase the maneuverability of aircraft to near-OVT levels, such as with the Eurofighter and Rafale. Nor is it unviable for 5th gens, the Northrop NATF proposal had canards, the KF-X had canards, and the proposed Boeing 6th gen F-XX is a finless-canard fighter. Third, the J-20 is not sensor dead; it has a visible EOTS and is reported to have an EODAS. It will likely track AMRAAM from medium ranges.

About combat ranges, the J-20 is reported to have 1500-2000 km internal fuel range. The F-35 is reported to have around 1250 km internal fuel range. That's a substantial range advantage. And about the engine figure; if you trust the Chinese to have gotten empty weight down to 17500 kg through extensive use of 3D titanium, then factor in 12500 kg of fuel and 1000 kg of weapons, you'd get about 31000 kg. Fully loaded, with 142 kn engines, you'd get .93 T/W, which is still better than the full F-35, with 1.14 T/W at 60% fuel, compared to the F-35A's 1.04 T/W at 60% and .87 T/W fully tanked.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:36
by citanon
I think the other posters are right about the J20 being an interceptor.

In fact I would say it's a node of the Chinese as/ad network. It's designed to complicate the combat picture for an atracker by disappearing into airspace using its long range, then threatening adversary tanker, early warning, and naval assets both with risk of direct attack and by collecting Intel.

The adversary force will have to commit large amounts of air assets to find or defend against attack, slowing down offensive air operations.

The numbers of J20 will probably be fairly small because this is a first gen aircraft that China will not want to over invest in and because of the aforementioned operations concept which emphasizes leveraging of a relatively small number of platforms to tie up a large enemy force.

Because of this, and the state of Chinese engine development, I doubt the J20's aerodynamic performance will be fantastic. More important to the Chinese is sensor fusion and network integration, just like the F35.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:42
by citanon
inst wrote:Here's a few misconceptions; first, the J-20 is not intended as an interceptor, although it might be interceptor-like, especially with the hobbled early engines. If it were an interceptor, why would it add canards, which increase drag and RCS, two factors contrary to what an interceptor wants? Second, canards, while not necessarily the be-all-end-all of maneuverability, see the XB-70 Valkyrie, when properly applied and implemented, can increase the maneuverability of aircraft to near-OVT levels, such as with the Eurofighter and Rafale. Nor is it unviable for 5th gens, the Northrop NATF proposal had canards, the KF-X had canards, and the proposed Boeing 6th gen F-XX is a finless-canard fighter. Third, the J-20 is not sensor dead; it has a visible EOTS and is reported to have an EODAS. It will likely track AMRAAM from medium ranges.

.


The canards are to help with takeoff and landing on improvised landing strips once the air bases are taken out. It helps make up for lack of good engines.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:42
by inst
About the J-20's high AOA, that was rumored on different websites, after going over the aerodynamic plans for the J-20, as well as reports of the J-20's rival, what was essentially a stealth Su-30 that was unfortunately unstable in the 50-60 AOA regime. As to the J-20's stealth and stealth performance, Kopp simulations show that the J-20 is capable of -30 to -40 dBsm depending on angle, although it also has frontal angles where it drops to -10 or -5 dBsm. The main game for J-20 vs F-35 is going to turn into a fight between the respective EODAS systems, and the F-35 likely has more mature coatings, while being smaller as well.

On the other hand, you ask me to specify radar aperture advantage. That's to say, since the J-20 is larger than the F-35, and you can measure it, it has a larger space for its radar antenna. From observations and measurements, the J-20 has a 1000 m^2 (same as Su-35) to 1100 m^2 radar aperture. Considering similar levels of radar stealth, as well as reported Chinese radar detection ranges vs 0 dBsm, the J-20 can radar-detect the F-35 between 42-75 km, allowing it to cue its EODAS.

Likewise, the networking advantage of the F-35 is overstated, considering the Chicoms managed to get their hands on the F-35's subsystems data, and have a notable IT industry themselves, see Huawei / Baidu / DJI. There's nothing stopping the Chinese from replicating the F-35's networking advantages into the J-20.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:50
by citanon
Kopp's anything on stealth is ignorant trash and should be disregarded completely. We have zero real info on their relative lo performance.

The AoA is just fanboy fanfiction and also give no real information.

The size of the apertures are only one of several equally important factors determining performance.

I do agree that Chinese electronic and networking capabilities are quite advanced, but they lack experience. This will be a learning generation for them.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 00:56
by inst
@citanon: first, long time no see! Second, the main problem with the J-20 is that its capabilities are seen as static, when, like the F-35 and Su-27, it has high development potential. Second-generation datalinks and avionics on the J-20 can end up being replaced by more modern types during its lifetime, and if we estimate the J-20's combat weight at 31000-32000 kg, it gets a .9-1.1 TWR at different fuel weights, which is comparable to that of the F-35, which we don't call an interceptor. More importantly, with later engine upgrades, it can begin to sport F-22-like 1.1 to 1.4 TWRs, and if TVC is added to later airframes, the tailfins and strakes could be potentially ditched, creating an aircraft that is stealthier than the F-35 at the least, and potentially stealthier than the F-22.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:01
by wrightwing
inst wrote:
wrightwing wrote:The requirements could be as high as 500-700, though I'd be surprised if they end up with more than 200. As for superior turning capabilities, sustained/instantaneous, that hasn't been demonstrated, nor has 50 deg AoA, supercruise, distribute aperture systems, etc....


The Chinese want a large quantity because the J-20 is their first shot at having peer capabilities to the US in their region. If the J-20 performs as advertised (doubtful at the present rate, and mainly due to subsystems, such as engine, radar, eodas, maturity), it'd outclass the F-35 similarly to how a Flanker can outclass a late-model F-16 (different weight classes). Then if you have 700 J-20s vs 1400 F-35s in the region, you're at strategic parity. Likewise, facing the F-22, there's only 186 or so F-22s, minus training and parts models, so the J-20 has a significant numerical advantage.

As to turning capabilities, we've seen videos of the J-20 with 20 deg / sustained turn rate, which puts it higher than the F-35, which has around 10-15 degree STR.


Again, you're confusing "want to acquire" with "will acquire." Secondly, the F-35 doesn't have a STR of 10-15 deg/sec, nor is it inferior to the J-20 in turn performance.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:03
by gta4
inst wrote:About the J-20's high AOA, that was rumored on different websites, after going over the aerodynamic plans for the J-20, as well as reports of the J-20's rival...

...if you trust the Chinese to have gotten empty weight down to 17500 kg...

We should remind Mr. inst a few things:

First, PLA never made any "advertisements" about the performance of J-20. What you said "advertised performance" are purely web rumors which indicated the hope of Chinese military fanbase. The "17500 kg" empty weight is from Chinese web encyclopedia which could be edited by anyone. Web encyclopedia always has wrong data, such as the empty weight of F-16C block 30 (which should be 8100kg instead of 8500kg. It confuses block 30 with block 40), and it even marks the rate of climb of F-16 to be only 254m/s (which should be superior than 300m/s).

Secondly, If you have any video showing J-20 has 20deg/sec sustained turn rate, please post the link. Remember F-35 could uses some unconventional turing technique to sustain 28deg/sec, which is never shown by J-20.

Last, no proof shows J-20 has EODAS. It has a diamond pod at the chin of its fuselage, but nothing could prove what's inside. Worse still, there is no clue that J-20's potential EODAS could cover its rear hemishpere. That is a decisive disadvantage once it gets into a merge with a F-35.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:06
by wrightwing
inst wrote:About the J-20's high AOA, that was rumored on different websites, after going over the aerodynamic plans for the J-20, as well as reports of the J-20's rival, what was essentially a stealth Su-30 that was unfortunately unstable in the 50-60 AOA regime. As to the J-20's stealth and stealth performance, Kopp simulations show that the J-20 is capable of -30 to -40 dBsm depending on angle, although it also has frontal angles where it drops to -10 or -5 dBsm. The main game for J-20 vs F-35 is going to turn into a fight between the respective EODAS systems, and the F-35 likely has more mature coatings, while being smaller as well.

On the other hand, you ask me to specify radar aperture advantage. That's to say, since the J-20 is larger than the F-35, and you can measure it, it has a larger space for its radar antenna. From observations and measurements, the J-20 has a 1000 m^2 (same as Su-35) to 1100 m^2 radar aperture. Considering similar levels of radar stealth, as well as reported Chinese radar detection ranges vs 0 dBsm, the J-20 can radar-detect the F-35 between 42-75 km, allowing it to cue its EODAS.

Likewise, the networking advantage of the F-35 is overstated, considering the Chicoms managed to get their hands on the F-35's subsystems data, and have a notable IT industry themselves, see Huawei / Baidu / DJI. There's nothing stopping the Chinese from replicating the F-35's networking advantages into the J-20.


You're not a serious person.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:07
by gta4
We should definitely remind Mr. inst about the turning capability of F-35 which helps it to dominate a neutral turning fight:

Image

Image

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:10
by wrightwing
The J-20 will NEVER have a lower RCS than either the F-22 or F-35. It will NEVER have superior avionics, sensor fusion, networking. It will NEVER enjoy T/W advantages. Stop posting youtube and APA nonsense.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:12
by citanon
inst wrote:@citanon: first, long time no see! Second, the main problem with the J-20 is that its capabilities are seen as static, when, like the F-35 and Su-27, it has high development potential. Second-generation datalinks and avionics on the J-20 can end up being replaced by more modern types during its lifetime, and if we estimate the J-20's combat weight at 31000-32000 kg, it gets a .9-1.1 TWR at different fuel weights, which is comparable to that of the F-35, which we don't call an interceptor. More importantly, with later engine upgrades, it can begin to sport F-22-like 1.1 to 1.4 TWRs, and if TVC is added to later airframes, the tailfins and strakes could be potentially ditched, creating an aircraft that is stealthier than the F-35 at the least, and potentially stealthier than the F-22.


I think at this point in the version 1.0 the J20 still looks like a learning as you go platform, which dictates small production numbers, which in turn dictates the most efficient strategies for leveraging its available capabilities, which in turn influences the requirements, etc. It's a big feedback cycle that drives the development in a certain direction.

The Chinese may choose to make iterative changes, but they may also decide to do a clean sheet design once component capabilities are mature. They do have a lot of money and are starting from zero for the 5th gen. At this point I don't think they've committed either way.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:36
by inst
Depends on how you define turn performance. The F-35 is extremely strong in ITR; this was a design choice, since ITR lets you scoot out of the way of missiles near the end of NEZ. STR, on the other hand, is not emphasized, because when you're fighting HOBS maneuverability is obsolete, as Lockmart stated.

4.2G Sustained Turn, likewise, is not a good sustained turn capability; compared to Eurofighters, F-22, and the Su-35, it's outclassed. The F-35 is supposed to more more agile than a loaded F-16, and I definitely see that to be the case, but the F-35

For maneuverability videos, here's roughly 180 degrees in 5-6 seconds, or 30-36 degree ITR.

https://www.youtube.com/watch?v=3kKFEraGVzI

There's another video where the J-20 does a long turn of about 270 degrees in about 14 seconds, but I can't find that.

Here's this video, check the footage leading to 3:08, https://www.youtube.com/watch?v=ZLLg77TK3pE&t=151s

About 270 degrees in 12 seconds, implying 22.5 degree / sec.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:47
by inst
wrightwing wrote:The J-20 will NEVER have a lower RCS than either the F-22 or F-35. It will NEVER have superior avionics, sensor fusion, networking. It will NEVER enjoy T/W advantages. Stop posting youtube and APA nonsense.


The modernized Type-59s are probably better than the M60s, if there are still any left in service. It has nothing to do with whether China has better R&D and design capability than the US, but rather that the M60 is obsolete as is the Type-59, but the Type-59 is still being developed. Likewise, the J-10C is superior to the F-16, not because the Chinese are better than the Americans, but because the J-10C is still being developed, while the F-16 got APG-80 is EOL, and for that matter, the J-10C is a 1990s design while the F-16 is a 1970s design.

The question is essentially research tempo; will the Chinese be able to get WS-15 into service, as well as TVC-ed J-20s into service, before the F-35 and F-22 are replaced by the F-X and F-XX? Before, we could be reasonably confident that they would not, but with the ramping up of Chinese R&D rate this is now an open question.

As to EODAS, check this out: https://tiananmenstremendousachievement ... s-nose.jpg We don't know if the J-20 has 360 degree EODAS coverage, but it looks as though it'll have at least 270 degree EODAS coverage.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:49
by gta4
inst wrote:4.2G Sustained Turn, likewise, is not a good sustained turn capability;


Your figure is terribly wrong.

First, It is >4.6g instead of 4.2g. Secondly, it is a threashold value instead of the true value (the former is always inferior than the latter). The most important thing is that, it is at 5000 kg fuel, 15000 ft (instead of at sea level)!

If you need the same A/B duration, a Su-27 must carry 6200kg fuel, resulting in even worth sustained G than F-35 at the same hight.

Anyway, since you are either blind or ignorant, it would be normal if you refuse to post any reliable rebuttal

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:53
by gta4
inst wrote:For maneuverability videos, here's roughly 180 degrees in 5-6 seconds, or 30-36 degree ITR.

https://www.youtube.com/watch?v=3kKFEraGVzI



Sorry to slam your face one more time:

https://www.youtube.com/watch?v=RfQZs5ERqP4

check 00:39. J-20 is significantly outcalssed by a fighter-bomber

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 01:56
by inst
gta4 wrote:We should definitely remind Mr. inst about the turning capability of F-35 which helps it to dominate a neutral turning fight:

Image

Image



Via Key Aviation:

"While the pilots have made it clear that the F-35 is very capable and has impressive performance. Hyperbole isn't needed. The pilot referring to 28 degree pedal turn isn't talking about a banking, sustained turn. A pedal turn is nose pointing-yaw rate at slow speeds.
The F-35 control laws limit roll and yaw to 25 degrees/second aproaching +/- g limits."

http://forum.keypublishing.com/showthre ... sion-(2016)-take-III/page145

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:05
by inst
Actually, since we've all gotten emotional, it's probably wise not to play.

About the F-18: I see a 90 degree turn in 3 seconds, a nice 30 degree ITR for a fighter noted for its ITR.

@ Citanon: We can probably compromise here; if you go with the more Russian designation versions and see different versions of the J-20 as fundamentally different aircraft, not unlike how later versions of the F-16 are more equipped for strike / BVR, increasing weight without wing area, resulting in higher wing loading.

From this angle, though, if you assume Chinese sources are talking about J-20 developments, instead of simply the LRIP J-20, we're looking at something around 100 or so initial J-20A variants with the current 142kn engines, then future developments will fill out the 500-700 number.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:06
by gta4
inst wrote:For maneuverability videos, here's roughly 180 degrees in 5-6 seconds, or 30-36 degree ITR.

https://www.youtube.com/watch?v=3kKFEraGVzI



Sorry man, according to this video, J-20 turned only 90 degrees instead of 180 degrees. The camera is also rotating which caused some illusion:
roof edge.jpg

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:08
by eloise
inst wrote:

As to turning capabilities, we've seen videos of the J-20 with 20 deg / sustained turn rate, which puts it higher than the F-35, which has around 10-15 degree STR
4.2G Sustained Turn, likewise, is not a good sustained turn capability; compared to Eurofighters, F-22, and the Su-35, it's outclassed. The F-35 is supposed to more more agile than a loaded F-16, and I definitely see that to be the case, but the F-35

Firstly, you are mistaken between sustained G value in 15k feet, Mach 0.8 condition with maximum sustained G values. As you go higher, air density is lower so sustained G capability reduced. So your comparison is horrible. It is like saying top speed of car 1 is 50 km/h on flooded road while top speed of car 2 is 100 km/h on dry road so car 2 is faster than car 1


Secondly, the threshold of sustained G value for F-35 at 15K feet, Mach 0.8 is 4.6G for F-35A and 5G for F-35C not 4.2G. The demonstrated sustained G at that condition is 4.95G for F-35A 240-1 configuration

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:09
by inst
@gta4: check out 0:09 on that video, then, it's roughly 90 degrees in 3 seconds.

In either case, let me leave on something we can all agree on. Raytheon's MSDM and SACM systems are radical gamechangers, and relatively mature; if the J-20 is intended as an interceptor, it will be extremely difficult for it to successfully intercept once Raytheon's systems come online due to their ability to intercept enemy missiles.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:13
by gta4
inst wrote:The pilot referring to 28 degree pedal turn isn't talking about a banking, sustained turn. A pedal turn is nose pointing-yaw rate at slow speeds.
The F-35 control laws limit roll and yaw to 25 degrees/second aproaching +/- g limits."


First, your link shows no proof that 25deg/sec is the upper limit.

Secondly, even though the 28deg/sec is not a conventional banked turn, when F-35 excecutes this turn, how could a fighter counter this maneuver if it is not capable of the "pedal turn"? The only way it could counter this maneuver is to perform a 28deg/sec sustained banked turn, which is not likely to happen.

So the question is, could J-20 perform pedal turn? Unlikely. The PLA fanbase would have boasted it if otherwise.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:17
by eloise
inst wrote:About combat ranges, the J-20 is reported to have 1500-2000 km internal fuel range. The F-35 is reported to have around 1250 km internal fuel range. That's a substantial range advantage.

F-35 in air to air configuration is credited to have 760 nm combat radius, which translate to at least 2815 km in range.
Image

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:37
by garrya
inst wrote:On the other hand, you ask me to specify radar aperture advantage. That's to say, since the J-20 is larger than the F-35, and you can measure it, it has a larger space for its radar antenna. From observations and measurements, the J-20 has a 1000 m^2 (same as Su-35) to 1100 m^2 radar aperture. Considering similar levels of radar stealth, as well as reported Chinese radar detection ranges vs 0 dBsm, the J-20 can radar-detect the F-35 between 42-75 km, allowing it to cue its EODAS.

I don't know where you get your figure but I am sure it is utter nonsense.
Current F-35 is even stealthier than F-22 and it is so stealthy that it actually caused trouble for Red/Green flag exercise since PAC-2/3 and S-300 radar ( yes US do own a S-300 battery, look it up ) can't even detect it
During a recent exercise at Mountain Home Air Force Base, Idaho, F-35 squadrons wanted to practice evading surface-to-air threats. There was just one problem: No one on the ground could track the plane.

“If they never saw us, they couldn’t target us,” said Lt. Col. George Watkins, the commander of the 34th Fighter Squadron at Hill Air Force Base, Utah.

The F-35s resorted to flipping on their transponders, used for FAA identification, so that simulated anti-air weapons could track the planes, Watkins said.

“We basically told them where we were at and said, ‘Hey, try to shoot at us,’ ” he said, adding that without the transponders on, “most likely we would not have suffered a single loss from any SAM threats while we were training at Mountain Home

https://www.airforcetimes.com/story/mil ... /87760454/

Even Eurofighter head of future requirement admitted that AWACs need to be stationed at specific direction to negate F-35 VLO advantage
According to Laurie Hilditch, Eurofighter's head of the future requirements capture, the F-35's frontal-aspect stealth can be defeated by stationing interceptors and AWACS at a 25º to 30º angle to the F-35's most likely approach path to a target.

https://www.flightglobal.com/news/artic ... 35-345265/

and you are telling me the tiny fighter radar (even Mig-31 radar is tiny in comparison to AWACS or S-300, PAC-2 radar) can somehow detect F-35 from 42-75 km ? Nope. Not gonna happen.
I also would like to see the " measurement" that you used to come to your conclusion

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:49
by gta4
To inst:

You are using a speed-up version of the J-20 video. Check the original one:

https://www.youtube.com/watch?v=6bzCob_7oJw

Why are you cheating? You sped it up by almost 200%!

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:54
by gta4
eloise wrote:
inst wrote:About combat ranges, the J-20 is reported to have 1500-2000 km internal fuel range. The F-35 is reported to have around 1250 km internal fuel range. That's a substantial range advantage.

F-35 in air to air configuration is credited to have 760 nm combat radius, which translate to at least 2815 km in range.
Image


Please note: range > radius*2 (not equal!) Normally, range is atleast 3 times as big as radius, because you need to remain on station and perform some maneuvers at A/B.

F-35 used to cover 1400km and consumed only 5000lbs of fuel.
https://www.aopa.org/news-and-media/all ... ight-stuff

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 02:59
by eloise
gta4 wrote:
Please note: range > radius*2 (not equal!)

I know, that why i used at least

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:01
by gta4
eloise wrote:
gta4 wrote:
Please note: range > radius*2 (not equal!)

I know, that why i used at least


True, but I am sure someone as ignorant as inst will forget this detail :mrgreen:

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:10
by inst
gta4 wrote:To inst:

You are using a speed-up version of the J-20 video. Check the original one:

https://www.youtube.com/watch?v=6bzCob_7oJw

Why are you cheating? You sped it up by almost 200%!



Your video is dated October 1st, my video is dated September 30th, and I'm not aware that the former video was sped up.

===

@garrya: Both PAC-3 and S-300 are on PESA. They're also ground-based radars, which seem to have an intrinsic disadvantage over air-based radars; see, for instance, the E-2D's PESA APY-9 can detect targets at over 550 km. PAC-3 is getting a GaN AESA upgrade this year, by the way.

Another factor is scaling; it takes about a 4x increase in radar power to create a 2x increase in range. AESA has less of a scaling issue compared to PESA; AESA increases in both transmit power and receive power with size.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:11
by gta4
inst wrote:@gta4: check out 0:09 on that video, then, it's roughly 90 degrees in 3 seconds.


since your video is sped up, all your claims about the turn rate of J-20 backfired.

In the non-sped up video, the J-20 spent 7 sec to turn a little more than 90 deg.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:15
by inst
gta4 wrote:
eloise wrote:
gta4 wrote:
Please note: range > radius*2 (not equal!)

I know, that why i used at least


True, but I am sure someone as ignorant as inst will forget this detail :mrgreen:


Actually, the figure I gave you was combat radius, not range. I guess the overall impression you're giving me is not that the F-35 is qualitatively superior (even though it's stealthy, has good avionics, and good subsystems), but that the F-35 community is somewhat insecure; the F-35 project has gotten a terrible rap in the media, and from objective results it's one of those Churchill things; you know, "The Americans always make the right choice, but not before exhausting all other alternatives". The F-22 community, on the other hand, was more given to take this in stride, given its comprehensive superiority in everything but IR sensors. Anyways, I'm out for tonight.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:26
by gta4
Another reason why we need to double check the source before citing it:

inst claims that F-35's yaw rate is limited to 25deg/sec, but in fact it is way beyoud 90deg/sec and it is still under control:

https://www.youtube.com/watch?v=5hERYdmjZWA

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:27
by garrya
inst wrote:@garrya: Both PAC-3 and S-300 are on PESA. They're also ground-based radars, which seem to have an intrinsic disadvantage over air-based radars; see

The only different between ground radar and airborne radar is radar horrizon, which is irrelevance here since F-35 didn't use nap of the earth tactic. Other than that they have the same limitation. Even though ground radar in question are PESA , their aperture and transmitting power is so big that they can easily get bigger detection range than fighter radar.

inst wrote:for instance, the E-2D's PESA APY-9 can detect targets at over 550 km

What is the RCS of target though?
inst wrote:Another factor is scaling; it takes about a 4x increase in radar power to create a 2x increase in range.

No, with others factors remain the same, to get 2 times the range, you need at minimum 16 times transmitting power ( not take into account loss )
Image

inst wrote:AESA has less of a scaling issue compared to PESA; AESA increases in both transmit power and receive power with size.

No, AESA radars often have better range than PESA radars because on an AESA design, the low noise amplifier is put near the receiver , before the lossy components, thus AESA radar can achieve better signal to noise ratio compared to PESA
Image

P/s: please read more about basics of radar before you writing those claims, it is rather laughable
https://basicsaboutaerodynamicsandavion ... ermeasure/
https://basicsaboutaerodynamicsandavion ... s-part-ii/

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:33
by inst
gta4 wrote:
inst wrote:@gta4: check out 0:09 on that video, then, it's roughly 90 degrees in 3 seconds.


since your video is sped up, all your claims about the turn rate of J-20 backfired.

In the non-sped up video, the J-20 spent 7 sec to turn a little more than 90 deg.


Actually, the first video cut together two videos.

Likewise, even the F-22 can turn 90 degrees in 7 seconds, absence of evidence is not evidence of absence.

For more objective sourcing, i.e, no one's sped it up or slowed it down, check out the Zhuhai video:

http://www.cnn.com/2016/10/31/asia/chin ... show-j-20/

Roughly 4 seconds to do 90 degrees, 6-8 seconds to do 180 degrees.

But it's all up to you.

Also, 5 G at Mach 0.9 for the F-35 is roughly a 11 deg/sec turn rate. If you extrapolate to Mach .7, you get 14deg/sec, which is not good either. Check out the F-16A chart for comparison, the F-16C/D is 18 deg/sec peak turn rate, while the Eurocanards are around 22 deg-sec STR.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:39
by garrya
inst wrote:
Also, 5 G at Mach 0.9 for the F-35 is roughly a 11 deg/sec turn rate. If you extrapolate to Mach .7, you get 14deg/sec, which is not good either. Check out the F-16A chart for comparison, the F-16C/D is 18 deg/sec peak turn rate, while the Eurocanards are around 22 deg-sec STR.

Inst, the value for F-35 is at 15000 feet, not at sea level.The different due to altitude is massive.
For example:
Image
For sea level performer look at this

Between 2:44-2:52 ( or 8 seconds ) , f-35 finished a 180 degrees turn, that equal to average turn rate of 22.5 degrees/second

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:45
by gta4
inst wrote:
gta4 wrote:
inst wrote:@gta4: check out 0:09 on that video, then, it's roughly 90 degrees in 3 seconds.


Also, 5 G at Mach 0.9 for the F-35 is roughly a 11 deg/sec turn rate. If you extrapolate to Mach .7, you get 14deg/sec, which is not good either. Check out the F-16A chart for comparison, the F-16C/D is 18 deg/sec peak turn rate, while the Eurocanards are around 22 deg-sec STR.


You are terriblly wrong
14deg/sec is extremely high at 15000ft.
Sustained G and T to W.jpg

YOU ARE COMPARING TURN RATE AT 15000 FT to THAT AT SEA LEVEL AGAIN, POOR PETHETIC CHEATER!

Thank you for proving my opinion :mrgreen:

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 03:58
by inst
@garry: you're right about requiring a fourth-power increase in transmission energies to get 2x increase in range, it's been a while and I've forgotten. About AESA vs PESA, scaling the diameter of the radar aperture by 2 gives you a 4x increase in total transmit power as well as a 4x increase in total signal received. PESA, since it's based off a magnetron, gives you only a 4x increase in total signal received, and the magnetron has to be independently scaled in power to match AESA scaling.

About E-2D, APS-138 on E-2C had about 224 km vs 0 dBsm. The APS-145 is claimed to have been a 40% improvement on the APS-138, giving you about 314 km vs 0 dBsm, which already outperforms the stated ranges of PESA PAC-3 and S-300. The APY-9 is supposed to be a two-generation jump from APS-145, using the APG-68 on the F-16 to the APG-80 as a baseline, you'd get a rough doubling of range, implying detection of 0 dBsm at over 628, and implying over 353 km detection vs -10 dBsm (the typical RCS of stealth aircraft vs anti-stealth radars).

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 04:17
by gta4
Another reason why we need to double check the source before citing it:

inst claims that F-35's yaw rate is limited to 25deg/sec, but in fact it is way beyoud 90deg/sec and it is still under control:

https://www.youtube.com/watch?v=5hERYdmjZWA

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 04:30
by garrya
inst wrote:@garry: you're right about requiring a fourth-power increase in transmission energies to get 2x increase in range, it's been a while and I've forgotten. About AESA vs PESA, scaling the diameter of the radar aperture by 2 gives you a 4x increase in total transmit power as well as a 4x increase in total signal received. PESA, since it's based off a magnetron, gives you only a 4x increase in total signal received, and the magnetron has to be independently scaled in power to match AESA scaling.

It doesn't work like that !!!
A bigger aperture result in higher gain, which mean more power concentration.But the relationship is not linear.

Detection range also depending on radiation factor whether it is Taylor , Blackmann ,Hamming or Cosine

inst wrote:About E-2D, APS-138 on E-2C had about 224 km vs 0 dBsm. The APS-145 is claimed to have been a 40% improvement on the APS-138, giving you about 314 km vs 0 dBsm, which already outperforms the stated ranges of PESA PAC-3 and S-300. The APY-9 is supposed to be a two-generation jump from APS-145, using the APG-68 on the F-16 to the APG-80 as a baseline, you'd get a rough doubling of range, implying detection of 0 dBsm at over 628, and implying over 353 km detection vs -10 dBsm (the typical RCS of stealth aircraft vs anti-stealth radars).

a) you should provide some source or photos for your claims

b) For those figures you provided, what was the radar mode ? ( look up or look down?, Cued search or volume search ?) what were the probability of detection (Pd) and probably of false alarm (Pfa) ? (since they can mean very different SNR)
Image

c) using generation jump to estimate radar range is ........, i can't even ........ :doh:
Image

TBH, before trying to estimate radar range, you should learn the basics first
https://basicsaboutaerodynamicsandavion ... ermeasure/
https://basicsaboutaerodynamicsandavion ... s-part-ii/

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 04:32
by inst
@garrya: in the CNN (actually CCTV) video, the J-20 makes a 90 degree turn in about 3 seconds between 0:20 to 0:30. That's about 30 degree STR. There's also the initial 6.5 second 180, so if we assume 180 degrees implies STR, it would come out to about 28 degree STR.

But notice how the F-35, at sea level, produces vortices, and classically speaking, 180 degrees is not considered STR. So we either accept that the J-20 has 28 degree ST and the F-35 has 22.5 degree STR, or neither figure is STR and both are about 28-30 degree ITR craft.

There's one other interesting calculation I've located. The 5G requirement for the F-35 is at 15000 ft, at Mach 0.8. That implies a turn rate of only 7.57 degrees / second under that regime. This is about half of the F-16 running at the same conditions.

@gta4: First, what people think of me on the internet isn't such a big deal, it's not like you're going to dox me and harass me with e-mails from the F-35 fanclub; I assume the NSA knows who I am but the NSA isn't going to run these kinds of ops. Second, I don't care about Yaw rate, and if you'd check the extrapolation of figures, it seems reasonable that STR on the F-35 isn't that hot.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 04:33
by inst
@ GarryA: I'm measuring by diameter, so scaling by 2x gives you 4x the aperture area. Using diameter, range increases are roughly linear, using area, they're square root. Do you get my point?

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 04:48
by garrya
inst wrote:@garrya: in the CNN (actually CCTV) video, the J-20 makes a 90 degree turn in about 3 seconds between 0:20 to 0:30. That's about 30 degree STR. There's also the initial 6.5 second 180, so if we assume 180 degrees implies STR, it would come out to about 28 degree STR.

Iam pretty sure , just last page gta4 proved that your video was sped up.Moreover, assuming both turn was ITR that would mean aircraft lose energy over time so the first few second always result in faster turn rate than the total time

inst wrote:There's one other interesting calculation I've located. The 5G requirement for the F-35 is at 15000 ft, at Mach 0.8. That implies a turn rate of only 7.57 degrees / second under that regime. This is about half of the F-16 running at the same conditions.

How do you come up with 7.57 degrees /second ????
Moreover, the chart gta4 put up is for Mach 0.9 not Mach 0.8. Look at the F-15 chart i put up and you will see the different in sustained G between the 2 speed
Image
inst wrote:@ GarryA: I'm measuring by diameter, so scaling by 2x gives you 4x the aperture area. Using diameter, range increases are roughly linear, using area, they're square root. Do you get my point?

Radar do not work like that. I already explained why.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:04
by eloise
inst wrote:@garrya: in the CNN (actually CCTV) video, the J-20 makes a 90 degree turn in about 3 seconds between 0:20 to 0:30. That's about 30 degree STR. There's also the initial 6.5 second 180, so if we assume 180 degrees implies STR, it would come out to about 28 degree STR.

http://edition.cnn.com/2016/10/31/asia/ ... show-j-20/
J-20 made a 90 degrees turn in the time from 0:10 to 0:15 or total of 4 seconds => 22.5 degrees/seconds turn rate
J-20 made a 70 degrees turn then roll to other direction in the time from 0:20 to 0:24 or total of 3 seconds=> 23 degrees/seconds turn rate
Both are not full 360 degrees turn so it is questionable whether they are STR or not

Want to play the numbers game?
In video below F-35 made a 70 degrees turn and climb in the time from 1:29 to 1:31 or total of 2 seconds => 35 degrees/second turn rate LOL

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:23
by inst
@garrya: Alternately, you could claim the second video was slowed down. In either case, I'm pointing you to a CNN source with the aircraft doing 30deg/sec turns both to the 90 degree and 180 degree point. The CNN source does show that the video was taken by CCTV, but CCTV is less likely to speed up the video compared to hobbyists taking videos with DSLR.


About F-35's turn rate, we have Mach 0.8 = 1160*.8 km/h at 15000 ft. Convert to m/s, and we get 2320/9 m/s

Using standard acceleration formula, with 5g inputted, we get r * 49 m/s^2 = (2320/9)^2, giving us a turn radius of 1356.1098.

The circle's circumference is ~8520 m, the airspeed in a sustained turn is 2320/9 m/s, meaning that the F-35 travels about 3% of the total circle per second. Multiplied by 360, we get about 11 deg / second, when the F-16, by comparison, is doing 14 deg / second in this regime.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:25
by inst
@Eloise: Actually, it's not a 70 degree turn, I was originally going to argue it was 2 seconds, but if you go up to a full 3 seconds, you get a 90 degree turn. For the F-35, likewise, if you apply the 3 second trick, you see 90 degrees worth of turn, so it's roughly a 30degree/sec turn.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:30
by eloise
inst wrote: Alternately, you could claim the second video was slowed down. In either case, I'm pointing you to a CNN source with the aircraft doing 30deg/sec turns both to the 90 degree and 180 degree point. The CNN source does show that the video was taken by CCTV, but CCTV is less likely to speed up the video compared to hobbyists taking videos with DSLR.

CCTV has many reasons to speed up the video such as for propaganda purpose. It still measure to only 22.-23 degrees/seconds according to my MK1 eyeball estimation
Btw, what do you say about the video where F-35 done 35 degrees/second while climbing at the same time? :wink:

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:31
by eloise
inst wrote:@Eloise: Actually, it's not a 70 degree turn, I was originally going to argue it was 2 seconds, but if you go up to a full 3 seconds, you get a 90 degree turn

Pilot of the J-20 turned 70 degrees then he stopped, same for F-35 as it was climbing

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:35
by inst
At :20, you see the bottom of the aircraft. At :23, you see the engines of the aircraft, which is a 90 degree turn.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:42
by eloise
inst wrote:At :20, you see the bottom of the aircraft. At :23, you see the engines of the aircraft, which is a 90 degree turn.

I don't think so If it was a 90 degrees turn you will not see the engine of the aircraft, because the viewer do not move with the aircraft and only stay in one point, so if it was a 90 degrees turn his view will be nearly perpendicular to the top of the aircraft

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:45
by inst
Actually, I'm going to ignore eloise, you're free to ignore me as well; I find he's particularly mendacious. Perpendicular to the top of the aircraft is parallel to the edges of the XY-plane of the aircraft, or you're seeing the aircraft by its edges. You're seeing the engines, so it's 90 degrees.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 05:58
by eloise
inst wrote:Actually, I'm going to ignore eloise, I find he's particularly mendacious.You're seeing the engines, so it's 90 degrees.

Ignore me because i make too much sense?
Image

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 06:22
by inst
Your diagram works great for model airplanes at short-distances, but if the aircraft is over 1-2 km off engines are sufficient. Mendacious as always.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 06:46
by eloise
inst wrote:Your diagram works great for model airplanes at short-distances, but if the aircraft is over 1-2 km off engines are sufficient. Mendacious as always.

Think before you type next time.
Image

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 07:43
by inst
It's easy to win an argument if you misinterpret a point. You arranged your image horizontally, instead of vertically. If you had the aircraft at C, it would actually be facing down, because the belly was shown at C.

In either case, my point IS invalid, simply because reviewing the video, it takes place at relatively close distances to the viewer. Doing a 1km-based calc would give you 70 degrees based off a 300 m/s airspeed,

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 13:47
by ricnunes
@inst,

The "misconceptions" here are all on your part!

Anyway, that's look at your "misconceptions":

- First and like citanon said, the Canards serve primarily the purpose to help to improve takeoff or resuming taking off on shorter runways - Something important for an Interceptor by the way. Or are you going to say that the Saab Viggen (one of the first fighter aircraft that I remember that uses Canards) is more agile than the F-16 because it uses canards?? :roll:
Also about canards, the use of them on aircraft like the Rafale or Typhoon or even the J-20 is there for a reason:
Canards also serve to overcome the limitations of Delta Wing design in terms of agility/maneuverability (they bleed energy fast and thus looses lift fast during tight maneuvers).
So and since the Canards objective is also to reduce the Delta Wing's limitations is also the reason why you basically only see them on Delta Winged aircraft like the Viggen, Gripen, Rafale, Typhoon and your "beloved" J-20!
Then you claim that Canards won't or wouldn't affect RCS or "stealth aircraft" much because there are "concepts" of proposed 6th gen fighter aircraft that have Canards.
Let me tell you "a secret": There were also some the concepts for some programs that originated on the JSF program (you know the program that originated the F-35) which "used Canards", so do does this means that the final aircraft of those programs in this case the F-35 also uses Canards?? Or course not!
Besides there's no Stealth aircraft in service (or entered on service in the past) - F-117, B-2, F-22 and F-35 that uses Canards and that's for a reason! Heck even "your" Chinese "Stealth" J-31 also in development doesn't use Canards as well as the Russian T-50.

- Secondly, you say "the J-20 is said to...", "the J-20 is reported to..." but where are your sources?? A speeded up Youtube video?? :roll:
At the same time you ignore every source that have been kindly provided to you!

-Third, you said that the F-35 range is 1250 km internal fuel range. But first that value is wrong! The F-35A combat radius in an air-to-air configuration is 760 nautical miles (nm) which is more than 1407km and again this range is combat radius or taking of from an airbase, reaching a point and returning to the same airbase of origin. You can check an actual diagram of the F-35's 760nm combat radius here:
viewtopic.php?f=22&t=49956
Next you say that the J-20 has 1500-2000 km with internal fuel range and again where and what are your sources??
And what range is that?? Combat Radius?? Ferry Range?? These details makes all the difference or else you're just comparing apples with oranges!

- Fourth, then you ramble about T/W ratio when it is well known that the Chinese industry lags behind in terms of effective performing engines and continue your ramble about the J-20 using 3D titanium and yet you ignore that the F-35 is made with extensive use of advanced composite materials which are even more lightweight than titanium! Resuming you came up with magical values with absolutely NO valid source and compare them to well known and official data/values from the F-35! Nice way to make comparisons :roll:

- Fifth and in line with fourth, perhaps the most comical of your "J-20 magical values" is RCS. You say that the J-20 RCS is -30 to -40 dBsm on some angles (You're really trying to convince us that the J-20's RCS is similar to the F-35?? Really?? :roll: ) and then you proceed to say that in FRONTAL ANGLES the J-20 RCS is -10 or -5 dBsm, really???
Let me tell you "another secret": Aircraft have LOWER RCS in their FRONTAL ANGLES. What does this mean?? It means that in all and every other angle the RCS is HIGHER (compared to the frontal angle). So there's a snowball chance in hell for the J-20 to have an RCS as low as -30 to -40 dBsm in any possible angle!!
With luck you may be right with your J-20 -10 or -5 dBsm (around 0.3 or 0.1 square meters) values for its frontal angle which would be the lowest RCS value possible for the J-20 which is still very, very far from the lower than 0.001 square meter RCS value of the F-35 which is an average angle RCS which means that the frontal angle of the F-35 is quite lower than 0.001 square meter.
So please do us all a favour: Spare us from lies and/or propaganda!

- Sixth, your radar aperture explanation (that the bigger the nose, bigger the radar aperture) is as in line with the J-20 RCS, simply hilarious!
So in your opinion the Mig-25 and/or the Mig-31 are the fighter aircraft with the biggest radar aperture?? Right... :roll:
Besides it's also hilarious that you say that the J-20 radar will be able to detect a F-35 at 75km when nobody knows for sure that will be the J-20 radar's performance which according to some experts it will be a radar called KLJ-5.
Also curious is that last year the Chinese unveiled an AESA radar, called the KLJ-7A which has a reported detection range of 170Km for a 5 square meter RCS target. Using an RCS for the F-35 of 0.001 square meters (and the real F-35 RCS is reportedly lower than this) means that the Chinese AESA KLJ-7A radar can at best detect a F-35 at a maximum range of 22Km (only Twenty Two Kilometers - this is almost nothing nowadays). OH, and let's not forget that detecting is one thing but TRACKING is another different thing! What does this mean? It means that the tracking range for that AESA KLJ-7A radar against a F-35 is quite lower than 22Km - And basically you can only shoot what you can TRACK!
And you're saying that the KLJ-5 will be able to detect the F-35 more than three (3) times further (than the KLJ-7A)?? LOL, keep dreaming :doh:
Source on the AESA KLJ-7A radar - it's in French but the paragraph "A noter que le chiffre de 170 kilomètres en portée de KLJ-7A devrait être obtenu en mode Air-Air, sur une cible standard d’une SER de 5 m²." should be clear:
http://www.eastpendulum.com/airshow-chi ... esa-klj-7a

- Seventh, the following comment from you:
the main problem with the J-20 is that its capabilities are seen as static

It's really funny because I have the idea that it's you that thinks that the F-35 capabilities are static when even it's software was designed as an Open Architecture in mind which grants it upgrade/improvement capabilities never seen in any other fighter aircraft. So, let me ask you one thing? Is the J-20 software designed to have an Open Architecture in mind?? And please don't reply me with:
"It's is reported that the J-20 <insert your wildest dreams here>"

- Finally regarding to J-20 vs F-35 agility and TWR. You only came up with nothing but your "wildest dreams" and speculations without ever posting sources - For example I did post an account from a Norwegian pilot (which flew both F-16 and F-35) and clearly states that the F-35 is superior in terms of agility. Yet, your "wildest dreams" seem to contradict this real pilot.
So if you can post speculations so can I and as such I will post now what I believe is my only speculation of this long post:
- The J-20 won't even beat a F-16 in terms of agility/maneuverability and TWR and much less it will ever beat a F-35 (namely the -A variant)!

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 14:02
by zwz
inst wrote:
In either case, my point IS invalid, simply because reviewing the video, it takes place at relatively close distances to the viewer. Doing a 1km-based calc would give you 70 degrees based off a 300 m/s airspeed,


To inst:

I have to inform you that, changing 70 deg heading does not mean turning 70 deg. It could be only 40 deg if you turn at 30 deg AOA.

Watch the video below: F-16 and F-18 are turning at 60-80deg/sec by your standard:

http://v.youku.com/v_show/id_XMzAyMjE0MjY0.html

http://www.bilibili.com/video/av3518523/

Do you think J-20 is outclassed by 4th gen?

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 17:20
by sferrin
inst wrote:@garrya: Both PAC-3 and S-300 are on PESA. They're also ground-based radars, which seem to have an intrinsic disadvantage over air-based radars; see, for instance, the E-2D's PESA APY-9 can detect targets at over 550 km. PAC-3 is getting a GaN AESA upgrade this year, by the way.

Another factor is scaling; it takes about a 4x increase in radar power to create a 2x increase in range. AESA has less of a scaling issue compared to PESA; AESA increases in both transmit power and receive power with size.


And yet Patriot was recently able to shoot down a tiny toy drone with a miniscule RCS.

Re: F-35 vs J-20

Unread postPosted: 23 Mar 2017, 20:54
by garrya
inst wrote:@garrya: Alternately, you could claim the second video was slowed down. In either case, I'm pointing you to a CNN source with the aircraft doing 30deg/sec turns both to the 90 degree and 180 degree point. The CNN source does show that the video was taken by CCTV, but CCTV is less likely to speed up the video compared to hobbyists taking videos with DSLR.

Others have addressed this point so it is unnecessary for me to comment more

inst wrote:About F-35's turn rate, we have Mach 0.8 = 1160*.8 km/h at 15000 ft. Convert to m/s, and we get 2320/9 m/s

Using standard acceleration formula, with 5g inputted, we get r * 49 m/s^2 = (2320/9)^2, giving us a turn radius of 1356.1098.

The circle's circumference is ~8520 m, the airspeed in a sustained turn is 2320/9 m/s, meaning that the F-35 travels about 3% of the total circle per second. Multiplied by 360, we get about 11 deg / second, when the F-16, by comparison, is doing 14 deg / second in this regime.

I haven't double check your calculations yet, but
a) the speed for F-35 KPP is Mach 0.8, speed in gta4 chart is Mach 0.9, from the manual page i posted there more than 1 G different between 2 speed.

b) F-16 configuration in the chart is 50% fuel and 2 wing tip AAM. F-35 in similar configuration can fly almost twice as long because it carry significantly more fuel

c) Your own calculations doesn't support your claims. You said earlier that F-35 can only sustain 7.5 degrees/second at 15000 feet, Mach 0.8. Your calculation shows that it can sustain 11 degrees/second. That is around 46% bigger than in your previous claim

Re: F-35 vs J-20

Unread postPosted: 24 Mar 2017, 04:57
by gta4
garrya wrote:
b) F-16 configuration in the chart is 50% fuel and 2 wing tip AAM. F-35 in similar configuration can fly almost twice as long because it carry significantly more fuel

c) Your own calculations doesn't support your claims. You said earlier that F-35 can only sustain 7.5 degrees/second at 15000 feet, Mach 0.8. Your calculation shows that it can sustain 11 degrees/second. That is around 46% bigger than in your previous claim


Under the "same A/B duration" condition, F-35 out-turns Su-27 in a sustained turn fight
viewtopic.php?f=55&t=52918

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 01:08
by arian
This thread is going places, drawing conclusions on an obviously and poorly done fake video, and an endless discussion about things that no one knows anything about based purely on internet rumors and make-belief.

As for the F-35 vs. J-20, or any other aircraft, the real issues that matter aren't turn rate and speed and physical characteristics of the plane etc. If maneuverability is what you're pinning you hopes in in 2017, you're going to die a fiery death just like every MiG-29 has met a fiery death anytime it has come up against woefully inadequate fighters in terms of maneuverability. Meaning, it doesn't matter all that much.

What matters is how these planes fit into the overall system of each country. They face a different set of circumstances than we face, and hence they will design and optimize on something different than we will. This set of circumstances is a lot wider than simply the opposing side's main fighter.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 10:02
by inst
About the canards, note that the Viggen's canards are non-moving, but with tail-flaps. For the J-20, similar lift advantages could have been obtained through the Viggen's configuration, improving RCS at the same time, since the moving surface is now on the rear. There's also the issue of the ventral strakes on the J-20, commonly used to improve high AOA performance; previously, I had thought that the J-20 had an easy transition to a X-36 layout, like Boeing's proposed F-X fighter (which uses canards, but has no rudders: the point is that the absence of rudders cancels out the presence of canards), but I've been watching videos arguing that with TVC, the J-20's aerodynamic layout provides for superior high alpha control (see US RCPowers playing with RC models).

@GarryA: I miscalculated the 8.6 turn rate, I had used 45 m/s^2 instead of 49 m/s^2, which ironically almost matches the difference between the 5G I used and the 4.6G that is the cited sustained turning rate for the F-35.

On a more interesting note, let's talk radars again, check this out:

viewtopic.php?p=267142#p267142

Here, hornetfinn gives us scaling of APG-81 from 700 to 800 (my measurements suggest it's 750), and it follows the linear diameter rule. Converting it down to 0 dBsm, we get ~275 km detection on 17 kw with a 700 mm diameter.

It's hard to get wattage numbers for AEW&C, so let's look up the S-band AN/SPY-1 first. Ignoring the AN/SPY-1's different reception aperture, we get a detection range of roughly 1185 km vs 0 dBsm, since it has roughly 352 times the power output of the APG-81. Since it's S-band, we see reduced RCS to ~.01, or detection ranges of approximately 375 km vs a -20 dBsm target.

Here, I just found a document with claims of the APS-138's wattage. It's not fully credible, since it's the US DoD republishing a translated Chinese paper, but we'd assume the Chinese, operating AEW&C, would know the rough ballpark powers:

http://oai.dtic.mil/oai/oai?verb=getRec ... =ADA302748

The APS-138 is cited as having 1 MW peak power, with a 370 km detection range vs an A-6 Intruder. Now, assume the F-35's AESA is scaled from 17 kw to 1000 kw. We'd get roughly a 2.77 scale of detection range, ignoring the change in aperture size, so we'd go up to 760 km vs 0 dBsm or 428 km detection range vs -10 dBsm. But the APY-9 is a PESA radar (probably because phase modulators handle higher energies better), so some loss of performance must occur compared to an AESA implementation. At the same time, though, the increased aperture size must compensate to some extent.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 10:22
by inst
@arian: I'm having fun here. This is the first time I've heard of pedal turns, and while I'd insist it's just an instantaneous turn, even possibly just a yawing action, it's interesting to note this about the capabilities of the F-35. Also, please note that I've talked repeatedly about the uselessness of maneuverability in dogfighting against HOBS missiles. But maneuverability still matters as a show of intent; I would actually have seen the YF-23 as superior to the F-22, since the YF-23 is better suited to attack roles and would have better BVR capabilities (larger radar, better stealth, better supersonic kinematics), but the F-22 had TVC and the YF-23 didn't. If the J-20 can't maneuver, it's unsuited for non-interception missions (but we've seen it maneuver to 20 deg/sec at least instantaneously, when the MiG-31 is known to have an instantaneous turn rate of 2.16 degrees at speed).

As to what makes sense for the Chinese, the thing is, the J-20 is actually going to end up facing the F-35 very soon. The Chinese are violating what we consider Japanese airspace, and the JASDF is regularly dispatching aircraft to escort them out. In fact, recently a J-11 and F-15J got into a pseudo-dogfight; the reason you don't hear about it is because the F-15J ended up shooting flares and leaving (this is not dissimilar to the Hellenic Air Force and the Turkish Air Force doing weaponless dogfights on their border). In the next few years, we may end up hearing of F-35s barking out the GPS coordinates of intruding J-20s and vice versa (although you'd contest that the J-20 would be able to IR-detect the F-35).

In fact, if we're talking about the needs of the Chinese, this is one of the reasons they rushed the aircraft into service; the F-35 was entering service soon, and the Chinese had no stealth fighters to contest it. They'd be at a strong disadvantage with their "bullying" actions if they didn't have aircraft capable of contesting incoming F-35s; the J-11s are kinematically equal or superior to older F-15Js. That's to say, if you're considering what role the Chinese need the J-20 to fulfil, they need it to counter the F-35.

Against the United States, they're at least 10 years away from military parity just in their own region; the PLAAF is advancing relatively quickly in capabilities, but stuff like the DF-21D and DF-26 get countered almost as soon as they come up, Raytheon's SM-6 system seems relatively capable of stopping everything but a multi-thousand missile barrage, while the E-2D is effective anti-stealth counter to the J-20. But against the JASDF, until recently they had a numerical superiority and material parity; the Japanese have roughly 300 4th generation aircraft, often including antiquated versions of the F-15, while the Chinese have roughly 400 fourth generation Flankers and Flanker-derivatives, and then 250+ J-10s.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 11:48
by inst
Also, @GarryA: Two other things about radar ranges:

http://webcitation.org/6Qpsm5PUo?url=ht ... 010807.pdf

http://69.73.131.148/6Qpsm5PUo?url=http ... 010807.pdf
if the former doesn't work
Check this out, it states (back in 2007) that the F-22's radar is expected to increase in range from over 100 mi to over 250 mi, on a 925mm radar. This puts Chinese radar claims into perspective; on a 1000mm radar you get a claimed range of 450 km, whereas the F-22 claims a range of more than 400 km. If the technology wasn't mature then, it must have been mature for the APG-81, which was reported to have jammed the APG-77.

=====

One other thing; if you're looking at PAC-3 and S-300s failing to track F-35, there's an extremely simple explanation for this. They're both X-band radars, not UHF-band radars. Using a base 300 km range, (if we assume it's against 0 dBsm), tracking ranges drop to 30 km with -40 dBsm, and with other information on stealth technology on this website, it suffices to guess that the F-35 and F-22 could be -50 dBsm craft, using -25 dBsm shaping and -25 dBsm RAM. That drops their detection ranges down to 17 km. Using the same figures, the J-20 should be able to detect the F-35 at about 25 km with radar, meaning it's still going to be an AEW&C + IR detection fight.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 12:19
by inst
I'm procrastinating on other things, but here's a source that states that the obsolete Lockheed E-121 had a radar with 450 km range and 3 MW peak power output. It's crazy.

http://www.dean-boys.com/ec-121.htm

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 16:12
by gta4
inst wrote:I'm procrastinating on other things, but here's a source that states that the obsolete Lockheed E-121 had a radar with 450 km range and 3 MW peak power output. It's crazy.

http://www.dean-boys.com/ec-121.htm


Take your time. Learn something. Next time when you try to fool us, do not compare turn rate at 3000 m with that at 4527 m. Do not cite a sped-up video.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 18:43
by ricnunes
inst wrote:One other thing; if you're looking at PAC-3 and S-300s failing to track F-35, there's an extremely simple explanation for this. They're both X-band radars, not UHF-band radars.


Really I've been wondering how long would it take in order for you to come up with the UHF/VHF radars...

First of all there's the fact that VHF radar have low targeting precision hence why they aren't used to guide missiles (for this task it's used more precise radars such as X-band). Resuming UHF and VHF radars are only good for detection or if you prefer Early Warning. What does this means? It means that even if you detect lets say a F-35 with a UHF/VHF radar you wouldn't or couldn't engage or guide a missile against the F-35 (or any other fighter aircraft for that matter).

Secondly, UHF/VHF are NOT a magical solution against "Stealth" or more precisely against the F-35.
The "best" and most powerful of such radars in existence today and likely for quite some time into the future is the Nebo-M AESA VHF radar which is usually used in conjunction with the S-400 (NATO name: SA-21 Growler) air defence system.
According to the manufacturer (I'll post the Nebo-M brochure below) the Nebo-M is able to detect a 1 square meter RCS target at a distance of 480Km in a circular (360º) scan or alternatively it's able to detect the same 1 square meter RCS target at a distance of 510Km in a sector (90º) scan.
If we assume the F-35 RCS to be 0.001 square meter (which is reportedly lower) it means that the "greatest" and "best" VHF radar in existence today, the Nebo-M is able to detect the F-35 at best at a maximum range 85Km in a circular scan or at a maximum range 90Km in a sector scan and all of this without any EW/ECM/Jamming present.
Considering the F-35 can pinpoint any radar with its ESM equipment and for example a Small Diameter Bomb (SDB) has a range above 110Km (and the F-35 can carry 8 of them internally) then there isn't much that such radars can do against the F-35 or at least they are very, very far from being a "magical solution against stealth".

Image

Image

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 20:06
by wrightwing
The materials used on the F-35 are effective against all radar frequencies, not just X band. Every frequency has greatly reduced (and tactically significant) detection/tracking ranges.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 22:24
by garrya
inst wrote:@GarryA: I miscalculated the 8.6 turn rate, I had used 45 m/s^2 instead of 49 m/s^2, which ironically almost matches the difference between the 5G I used and the 4.6G that is the cited sustained turning rate for the F-35.

No ,it doesn't
4.6G is the threshold for A version but the demonstrated value is already 4.95G for F-35 240-3

inst wrote:On a more interesting note, let's talk radars again, check this out:

viewtopic.php?p=267142#p267142
Here, hornetfinn gives us scaling of APG-81 from 700 to 800 (my measurements suggest it's 750), and it follows the linear diameter rule. Converting it down to 0 dBsm, we get ~275 km detection on 17 kw with a 700 mm diameter.

It's hard to get wattage numbers for AEW&C, so let's look up the S-band AN/SPY-1 first. Ignoring the AN/SPY-1's different reception aperture, we get a detection range of roughly 1185 km vs 0 dBsm, since it has roughly 352 times the power output of the APG-81. Since it's S-band, we see reduced RCS to ~.01, or detection ranges of approximately 375 km vs a -20 dBsm target.

Here, I just found a document with claims of the APS-138's wattage. It's not fully credible, since it's the US DoD republishing a translated Chinese paper, but we'd assume the Chinese, operating AEW&C, would know the rough ballpark powers:

http://oai.dtic.mil/oai/oai?verb=getRec ... =ADA302748

The APS-138 is cited as having 1 MW peak power, with a 370 km detection range vs an A-6 Intruder. Now, assume the F-35's AESA is scaled from 17 kw to 1000 kw. We'd get roughly a 2.77 scale of detection range, ignoring the change in aperture size, so we'd go up to 760 km vs 0 dBsm or 428 km detection range vs -10 dBsm. But the APY-9 is a PESA radar (probably because phase modulators handle higher energies better), so some loss of performance must occur compared to an AESA implementation. At the same time, though, the increased aperture size must compensate to some extent.

1) You can't compare different radar like that (estimate range from peak power) because their duty cycle and beamwidth aren't the same, the cited figure isn't necessary for the same radar mode either (even for the same radar different mode can mean different beamwidth and also different PRF) .
2) You estimation calculation doesn't take into account loss ( reflection doesn't travel a direct path )
3) Those radar you taken as example working at massively different frequency. APS-138 at UHF , SPY-1 at S band , APG-81 at X band. Different frequency mean very different RCS and very different gain value even if radar aperture are of similar size.
4) You can't ignore something as important as aperture size.

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 22:57
by garrya
inst wrote:if the former doesn't work
Check this out, it states (back in 2007) that the F-22's radar is expected to increase in range from over 100 mi to over 250 mi, on a 925mm radar. This puts Chinese radar claims into perspective; on a 1000mm radar you get a claimed range of 450 km, whereas the F-22 claims a range of more than 400 km

450 km detection range against target with RCS around 10 dBsm will be reduced down do around 44km against targets with RCS around -30 dBsm even without others background interference

inst wrote: If the technology wasn't mature then, it must have been mature for the APG-81, which was reported to have jammed the APG-77.

You don't need a more powerful radar/jammer to jam a certain radar. You only need to achieve a certain noise-signal ratio , which is actually quite easy for stealth fighter thanks to their low radar cross section
Image
Image
http://bit.ly/2nir279
inst wrote:
One other thing; if you're looking at PAC-3 and S-300s failing to track F-35, there's an extremely simple explanation for this. They're both X-band radars, not UHF-band radars.

an/mpq-53 is actually G/H band
US also purchased S-300P from Belarus in 1994 and S300V from Russia in the 90th anniversary
AFAIK ,original S-300P used 5N66 Clam shell and 30N6 FLAP LID radar which work at S band and I/J band respectively
S-300V used 9S15MV or 9S15MT BILL BOARD surveillance radar and 9S19 High Screen radar both are centimetric radar but not sure their exact frequency
Regardless, CNT RAM have very wide bandwidth
inst wrote:
Using the same figures, the J-20 should be able to detect the F-35 at about 25 km with radar, meaning it's still going to be an AEW&C + IR detection fight.

I will for a moment, ignore the fact that you think J-20 radar can have longer detection range than ground SAM radar. 25 km is much smaller than your original figure of over 75 km

Re: F-35 vs J-20

Unread postPosted: 25 Mar 2017, 23:43
by botsing
ricnunes wrote:
inst wrote:Considering the F-35 can pinpoint any radar with its ESM equipment and for example a Small Diameter Bomb (SDB) has a range above 110Km (and the F-35 can carry 8 of them internally) then there isn't much that such radars can do against the F-35 or at least they are very, very far from being a "magical solution against stealth".

Image

Image

Just for your info, that is where Pantsir-S1 is meant for: to protect bigger asset anti-air systems versus Tomahawk and SDB like systems.

(not to argue but simply as a system within system information part)

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 01:39
by inst
@garry: It's 450km claimed vs 0 dBsm and 250 vs -10 dBsm. Going by claims about the F-35's radar, as well as claims about the F-22's radar, it's believable; the Chinese currently claim they're #2 after the US in radar technology, and given their military R&D spending, exhaustive espionage program (while the base design of the J-20 was probably the J-10, it's obvious that they made a lot of what they hacked out of Lockmart's subcontractors), as well as considerable consumer electronics industry, this claim is also plausible, although I suspect the Israelis might have something to say about that. Using hornetfinn's estimates about the APG-81, we'd extrapolate a Su-35-scaled F-35 radar with 0 dBsm detection at 500-562 km, so putting the Chinese knockoff at 80-90% is believable.

Against a -50 dBsm F-35, you'd get 25 km detection, which isn't that good, though.

===

About whether the J-20 can outrange ground radar, there's a rather simple explanation. For instance, we can look at the Smerch-A Pulse Doppler, which had a claimed range of 100 km against some sort of airborne target, but used a 400 kw peak power. The Zaslon PESA on the MiG-31, by comparison, had a claimed range of 200 km and a peak power of only around 10 kw. The point is that significant improvements in radar technology mean that new radar can outperform antiquated radar of much smaller size, and even with spans of only a decade, we see significant improvements in radar technology; for instance, APG-77 is claimed to have about 160 km worth of detection / tracking range, but APG-77v1 is supposed to have 400 km of detection range, a 1.5 fold improvement, simply using newer technology.

As to whether the J-20 can outrange, say, the SPY-6 radar systems on newer Arleigh Burkes, or upgraded PAC-3s (GaN radar is coming to PAC-3 this year), I'd say no; the aperture difference is simply too great. But whether it can outrange a more antiquated legacy system, I'd say yes simply because of how rapidly radar technology has improved.

====

About misusing the APS-138, I've just stated the comparison between the Zaslon and Smerch system, and you're correct. I've tried assiduously to dig out figures on AEW&C performance but I've been completely unable to find figures for modern AESA and PESA AEW&C, instead of obsolete systems like the EC-121, which uses 3 MW of peak power. Likewise, aperture matters, as does band. But I do think I've made my point in other ways; it is plausible that the reported 450 km vs 0 dBsm / 1 m^2 RCS is true, if you go by figures suggesting that comparable US airborne technology can achieve greater ranges. If I've misstated my figures, this is in response to newer information, such as the likely -50 dBsm on the F-35 and F-22.

====

@wrightwing:

The F-35 suffers from resonance effects at low-frequency, however, and for that matter, the JY-26 was reported to have detected F-22s flying in Korean exercises. Likewise, IIRC, RAM varies in type and works best against specific frequencies, covering all frequencies requires multiple layers, increasing operating costs and aircraft weight.

@ricnunes:

Increases in computing power promise to make UHF/VHF more viable as a tracking system, and likewise, any use of counter-stealth radar cannot be solitary, we aren't arming E-2D with AIM-120s, for instance. In the E-2D's case, what's more likely to happen is that once a target is detected, it datalinks the region information off to the F-35s, which can then use their EODAS to search the region for the target, then transfer tracking information off. Then the forward picketing F-35s will knock down the foe, while all the opponent sees is the AEW&C craft in the back. If we look at a Chinese clone of this tactic; they have a Divine Eagle high-altitude drone of appreciable size using bistatic radar, the J-20 has been demonstrated to have the apertures for EODAS, if not necessarily the software, and the J-20 is relatively stealthy. In either case, my guess is that UHF does not wholly defeat stealth, it only reduces detection degradation to roughly 40-60%.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 02:21
by arian
Inst, you're taking things too much as binary. "If J-20 can't maneuver..." No one is saying J-20 can't maneuver. I'm sure it can turn right if it wants to turn right.

If we look at a Chinese clone of this tactic; they have a Divine Eagle high-altitude drone of appreciable size using bistatic radar


Where are you getting all this stuff from? Pop-science articles and youtube videos? Bistatic radar? That's not a bistatic radar, if carrying a radar is its intended purpose. And a prototype of "something" is now "the Chinese have it". Have what? Perhaps it is intended for ground surveillance with a SAR radar like Global Hawk.

A LOT of made-up info on the internet, and often poorly made up.

Try taking the BS you read on Wikipedia with a mine-full of salt.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 02:43
by garrya
inst wrote:@garry: It's 450km claimed vs 0 dBsm and 250 vs -10 dBsm. Going by claims about the F-35's radar, as well as claims about the F-22's radar

I never heard such official claim about F-22 and F-35 radar.
As far as i know 450 km is against target with RCS around 10 m2
inst wrote:About whether the J-20 can outrange ground radar, there's a rather simple explanation. For instance, we can look at the Smerch-A Pulse Doppler, which had a claimed range of 100 km against some sort of airborne target, but used a 400 kw peak power. The Zaslon PESA on the MiG-31, by comparison, had a claimed range of 200 km and a peak power of only around 10 kw.

AFAIK, Peak power of Smerch-a RP-25 is 600 watt , not kw
Image
https://books.google.co.uk/books?id=BNl ... &q&f=false
Anyway, citing peak power without knowing duty cycle is very misleading. 2 radar, one with peak power of 10 kW and 1 % duty cycle the other with peak power of 1 kW and 10% duty cycle will have similar detection range ( assuming range ambiguity isn't an issue)

inst wrote:for instance, APG-77 is claimed to have about 160 km worth of detection / tracking range, but APG-77v1 is supposed to have 400 km of detection range, a 1.5 fold improvement, simply using newer technology.

Can you tell me where you get that information from?

inst wrote:The F-35 suffers from resonance effects at low-frequency

The smooth curve on F-35 actually reduce surface scattering significantly compared to full facet design such as one of F-117 ( i gave links in previous post already )
inst wrote:the JY-26 was reported to have detected F-22s flying in Korean exercises.

The question is at what aspect ? and did F-22 carry Lundberg lens? such as those in photo below
F-22:
Image
F-35 :
Image

inst wrote:Likewise, IIRC, RAM varies in type and works best against specific frequencies, covering all frequencies requires multiple layers, increasing operating costs and aircraft weight

It depend on the kind of RAM and LM patent suggest that their RAM has very wide bandwidth between 0.1 Mhz up to 60 Ghz while still thin and light enough to be put on fighter aircraft
https://www.scribd.com/document/3420932 ... l-material

P/s: bravo for remain calm, that a good trail

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 02:47
by arian
botsing wrote:Just for your info, that is where Pantsir-S1 is meant for: to protect bigger asset anti-air systems versus Tomahawk and SDB systems.


Yes and no. Systems like Pantsir and Tor and Tunguska etc were designed for a 1980s-1990s war to protect high value targets against things like cruise missiles and LGBs. A time when such attacks would have been carried out by a limited number of munitions because it was not possible to have massed simultaneous attacks. And being less numerous, the number of high-value targets needing protection was also limited.

Ie in a world like Desert Storm where 10-20% of the minitions would be guided weapons. Not for a world where 90-100% of munitions would be so, and where a single plane can launch a dozen or more SDBs against a target. In such a world, the defender would need masses of Pantsirs to defend a single target, because the systems are limited both in sector coverage and the number of simultaneously engaged targets, which means individual units can be easily overwhelmed. But then it becomes cost prohibitive to have so many defensive systems defending high-value targets, when the other side can produce tens of thousands of JDAMs per year as if they were potatoes.

So in a sense SDBs, and other systems which rely on stealth rather than numbers, were the response to defensive systems like Pantsir or Tor, rather than the other way around. To defend against SDBs etc., one would need 360 deg coverage with fire and forget missiles, and dozens if not hundreds of them ready to fire.

That's how we get Syria where even though the Syrians now have modern AD systems like Buk and Pantrsir protecting high value targets around Damascus, the Israelis can attack with impunity.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 02:52
by botsing
Totally agree arian, I just wanted to point out that layer of defense and where it was meant for.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 03:05
by inst
arian wrote:Inst, you're taking things too much as binary. "If J-20 can't maneuver..." No one is saying J-20 can't maneuver. I'm sure it can turn right if it wants to turn right.

If we look at a Chinese clone of this tactic; they have a Divine Eagle high-altitude drone of appreciable size using bistatic radar


Where are you getting all this stuff from? Pop-science articles and youtube videos? Bistatic radar? That's not a bistatic radar, if carrying a radar is its intended purpose. And a prototype of "something" is now "the Chinese have it". Have what? Perhaps it is intended for ground surveillance with a SAR radar like Global Hawk.

A LOT of made-up info on the internet, and often poorly made up.

Try taking the BS you read on Wikipedia with a mine-full of salt.


arian: There's also the KJ-2000, KJ-500, and KJ-3000. The KJ-2000 and KJ-500 are L-band, while the band of the KJ-3000 is unknown. There was a recent export of ZDK-03 AEW&C to Pakistan, although I'm doubtful of its capability.

You are also right that I'm mischaracterizing the argument as one of the J-20's maneuverability, when it's actually about whether the F-35 is more maneuverable than the J-20. On this subject, the evidence we've been shown suggests that the J-20 has demonstrated ITR of at least 22.5 degrees, and that the F-35 has ITR of at least 30 degrees under certain regimes and that the F-35 has STR of roughly 10.8 degrees at 15,000 feet and at Mach 0.8 with 60% fuel loading.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 03:35
by gta4
inst, do not try to confuse indicated air speed with true air speed. If you cannot out-smart us, do not try to fool us:
viewtopic.php?f=55&t=52918&start=15

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 05:17
by arian
inst wrote:arian: There's also the KJ-2000, KJ-500, and KJ-3000. The KJ-2000 and KJ-500 are L-band, while the band of the KJ-3000 is unknown. There was a recent export of ZDK-03 AEW&C to Pakistan, although I'm doubtful of its capability.


Yes China is developing AWACS planes. No surprise there. And it doesn't mean anything inherently about "anti-stealth" capabilities or much at all in fact. The US and its allies in Asia also have about 130 AWACS planes combined in operation.

China still faces about a 10:1 numerical inferiority towards its adversaries in Asia, whether it be in terms of aircraft, or ships or other assets. And enemies which currently have a large technological and capability gap with China.

But lets not get carried away with imaginary "bystatic radar UAVs" that don't actually exist, or other such internet rumors.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 15:26
by gta4
Anyway, J-20 has no DAS that covers the rear hemisphere. That is a decisive disanvantage

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 15:45
by ricnunes
inst wrote:@garry: It's 450km claimed vs 0 dBsm and 250 vs -10 dBsm. Going by claims about the F-35's radar, as well as claims about the F-22's radar, it's believable; the Chinese currently claim they're #2 after the US in radar technology,


I could also claim that I'm Santa Claus or Donald Duck or even Donald Trump :roll:
That's does mean this is true. Actually such claim would only mean that I'm a liar!

China still lags behind in terms of avionics and engines (two of the most important components for fighter aircraft) not only to the USA but also it lags behind Western Europe countries (such as UK and France) and it even lags behind Russia and then there's also Israel. So no, China is not #2 and it's not even #3 or #4. Perhaps a #5 and this if we consider "Western Europe" as a whole.

And just because China build the vast majority of the world's electronics doesn't mean that they can assembly these components and make systems like we have in the F-35.
First, many of those electronics "blueprints" come from western countries and/or western companies. They are mainly built in China because of one sole reason: They are cheaper to manufacture in China, period!
Secondly it order to build effective and integrated systems like you have in the F-35 you need to develop an effective but overly complex SOFTWARE. Speaking of which of many world renown software do we have which is developed in China??
You simply can't ignore software - For example it's the software which allows F-35's DAS to be used in several and simultaneous different tasks such as Pilot's 360º vision, Missile Warning System, IRST, etc...
And if you think that developing Software is "easier" than Hardware than you don't have a clue!
And the reason for this is that in order to develop a combo of advanced Software coupled with advanced hardware you need a vast "KNOW HOW" which is still lacking in China. Countries like China which trends to supress "free thinking" tends to lack in terms of "Know how".
Note that I'm not saying that there isn't any "Know how" in China, of course there is. However the "Know how" to create completely new stuff in China is at best "limited".
And just because you can build some parts of the F-35 (due to espionage or any other means) doesn't mean you can build the other parts "missing" and much less how to "glue them" together as an single effective system.


inst wrote:@ricnunes:

Increases in computing power promise to make UHF/VHF more viable as a tracking system, and likewise, any use of counter-stealth radar cannot be solitary, we aren't arming E-2D with AIM-120s, for instance. In the E-2D's case, what's more likely to happen is that once a target is detected, it datalinks the region information off to the F-35s, which can then use their EODAS to search the region for the target, then transfer tracking information off. Then the forward picketing F-35s will knock down the foe, while all the opponent sees is the AEW&C craft in the back. If we look at a Chinese clone of this tactic; they have a Divine Eagle high-altitude drone of appreciable size using bistatic radar, the J-20 has been demonstrated to have the apertures for EODAS, if not necessarily the software, and the J-20 is relatively stealthy. In either case, my guess is that UHF does not wholly defeat stealth, it only reduces detection degradation to roughly 40-60%.


The world's most advanced "Increases in computing power promise to make UHF/VHF more viable as a tracking system" culminated in the Nebo-M AESA VHF system which as you can see from my last post it's far from being an effective counter-F-35 system. Note again, that this is an AESA (VHF) radar and it's likely the best we have around the world in terms of ground based detection against the F-35.
Moreover, for you as well as for many other "F-35 critics" which I've been having discussion with over the web it seems that radar (and other) technologies which promise to be good "anti-Stealth" measures will evolve (to the point of rendering stealth "useless") but at the same time people like yourself trend to think that for some odd reason that "Stealth technology" will stay "static" forever and thus that it won't ever evolve/improve.

Besides you can only reach to a certain point with UHF/VHF radar or with any other radar technology - Remember that you cannot break the "laws of physics"!

I also find somehow amusing your following comment:
" any use of counter-stealth radar cannot be solitary"

Guess what?? Neither is the use of the F-35 (or any other Western Stealth combat aircraft)!

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 15:53
by ricnunes
arian wrote:
botsing wrote:Just for your info, that is where Pantsir-S1 is meant for: to protect bigger asset anti-air systems versus Tomahawk and SDB systems.


Yes and no. Systems like Pantsir and Tor and Tunguska etc were designed for a 1980s-1990s war to protect high value targets against things like cruise missiles and LGBs. A time when such attacks would have been carried out by a limited number of munitions because it was not possible to have massed simultaneous attacks. And being less numerous, the number of high-value targets needing protection was also limited.

Ie in a world like Desert Storm where 10-20% of the minitions would be guided weapons. Not for a world where 90-100% of munitions would be so, and where a single plane can launch a dozen or more SDBs against a target. In such a world, the defender would need masses of Pantsirs to defend a single target, because the systems are limited both in sector coverage and the number of simultaneously engaged targets, which means individual units can be easily overwhelmed. But then it becomes cost prohibitive to have so many defensive systems defending high-value targets, when the other side can produce tens of thousands of JDAMs per year as if they were potatoes.

So in a sense SDBs, and other systems which rely on stealth rather than numbers, were the response to defensive systems like Pantsir or Tor, rather than the other way around. To defend against SDBs etc., one would need 360 deg coverage with fire and forget missiles, and dozens if not hundreds of them ready to fire.

That's how we get Syria where even though the Syrians now have modern AD systems like Buk and Pantrsir protecting high value targets around Damascus, the Israelis can attack with impunity.


Exactly Arian!

Actually with my example I took into consideration that the SDB is actually a stealth bomb which makes it much, much harder to be intercepted any Air Defence Systems such as the mentioned Pantsir or Tor.

Moreover, remember that each F-35 (namely the F-35A and F-35C) can carry eight (8) of them internally so you would not only have the stealth advantage but with this same weapon (SDB) you have the numbers - Even if systems like the Pantsir or Tor protecting a target like the Nebo-M could effectively intercept a SDB (which I have my doubts due to the SDB's Stealth) you could "saturate" the target with lots of SDBs.

Re: F-35 vs J-20

Unread postPosted: 26 Mar 2017, 22:51
by wrightwing
Don't forget that any SEAD/DEAD mission would also include MALD/MALD-J, as well as deception jamming/electronic attack of the Tor/Pantsyr systems, that are trying to intercept SDB/JDAM/JSOW/JASSM/etc....

Re: F-35 vs J-20

Unread postPosted: 27 Mar 2017, 10:56
by weasel1962
One area of R&D to look at countering massed PGM attacks are lasers. USN already deployed Kratos to counter swarming drones. If it can counter swarms, then massed PGMs as a target set won't be too far off. China’s Poly Tech was seen deploying a 50-70W laser “silent hunter” recently at IDEX 2017 which is significantly higher powered than Kratos.

Also adding an Arian disclaimer that these are manufacturer claims, read at your risk etc etc etc…..

Re: F-35 vs J-20

Unread postPosted: 27 Mar 2017, 11:07
by ricnunes
weasel1962 wrote:One area of R&D to look at countering massed PGM attacks are lasers. USN already deployed Kratos to counter swarming drones. If it can counter swarms, then massed PGMs as a target set won't be too far off. China’s Poly Tech was seen deploying a 50-70W laser “silent hunter” recently at IDEX 2017 which is significantly higher powered than Kratos.

Also adding an Arian disclaimer that these are manufacturer claims, read at your risk etc etc etc…..


Yes, I also believe that at some point into the future that "Lasers" or other types of "energy directed weapons" will be the way to go.
But independently of the evolution of such weapons into reliable and powerful weapons one thing still remains the same - You have to be able to detect and track the target(s) in order to shoot it(them) down and it doesn't matter with what you're shooting at it, doesn't matter if you're shooting with a gun, a missile or a laser.

Resuming if those PGM's are stealth and thus hard to detect it will be hard to shoot them down even with advanced weapons such as laser or any other kind of "energy directed weapon". Basically you can only shoot what you can "see".

Re: F-35 vs J-20

Unread postPosted: 27 Mar 2017, 11:23
by weasel1962
Agreed. At the same time, we all know stealth does not mean invisibility. It just means having to be a lot nearer to detect. Ground based radars have an advantage cos these can be much higher powered. Then, bigger radar target for ARMs which goes back to lasers/CIWs defending these and so on.

Faster PGMs also mean shorter time to target. That's why Boeing did a lot of work even for unpowered SDB-1s to reduce flight path decreasing flight time. So is Raytheon. Also, could mean powered versions like spear CAP 3 may be more effective than unguided ones if the time to target is a critical factor. Maybe increased munition weight, trading off range, to add armor to munitions increasing laser resistance may be something we'd see beyond just stealth. Just need more defense $$$. Any wonder why defense contractor shares tend to go up?

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 01:15
by jessmo111
Back to topic. This fat sow of a fighter will never be able to turn and burn with an F-35! Its seriously underpowered for its massive size. The Chinese have been running a disinformation campaign for years trying to get you to believe this. They want you to believe that the plane is in the 30k weight class (ie the weight of an F-35). This plane is closer to the F-111s weight class, with an F-15 level engine. If the J-20 can keep up with the F-35 in a turn, then I have land to sell you, and this woman can beat me in a foot race.

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 04:09
by neurotech
jessmo111 wrote:Back to topic. This fat sow of a fighter will never be able to turn and burn with an F-35! Its seriously underpowered for its massive size. The Chinese have been running a disinformation campaign for years trying to get you to believe this. They want you to believe that the plane is in the 30k weight class (ie the weight of an F-35). This plane is closer to the F-111s weight class, with an F-15 level engine. If the J-20 can keep up with the F-35 in a turn, then I have land to sell you, and this woman can beat me in a foot race.

The F-111 is a lot heavier than a F-15, and had TF30 engines that are significantly less powerful than the F100 engines in the F-15.

VADM. Tom Connelly famously quoted the problem with the F-111B is "There isn't enough thrust in Christendom to fix this plane." meaning to make the jet work as a fleet defense fighter. Does anyone think the J20 will be any different?

Remember that thrust vectoring doesn't make a jet magically agile, if it don't have the thrust/weight ratio. The F-22 will loose airspeed/energy pretty quick in high alpha maneuvers, just like any other jet. At the airshows, the F-22 does those tight maneuvers at low speed, and able to use the high thrust/weight ratio for staying in the air in the high-alpha state.

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 07:17
by Corsair1963
neurotech wrote:
jessmo111 wrote:Back to topic. This fat sow of a fighter will never be able to turn and burn with an F-35! Its seriously underpowered for its massive size. The Chinese have been running a disinformation campaign for years trying to get you to believe this. They want you to believe that the plane is in the 30k weight class (ie the weight of an F-35). This plane is closer to the F-111s weight class, with an F-15 level engine. If the J-20 can keep up with the F-35 in a turn, then I have land to sell you, and this woman can beat me in a foot race.

The F-111 is a lot heavier than a F-15, and had TF30 engines that are significantly less powerful than the F100 engines in the F-15.

VADM. Tom Connelly famously quoted the problem with the F-111B is "There isn't enough thrust in Christendom to fix this plane." meaning to make the jet work as a fleet defense fighter. Does anyone think the J20 will be any different?

Remember that thrust vectoring doesn't make a jet magically agile, if it don't have the thrust/weight ratio. The F-22 will loose airspeed/energy pretty quick in high alpha maneuvers, just like any other jet. At the airshows, the F-22 does those tight maneuvers at low speed, and able to use the high thrust/weight ratio for staying in the air in the high-alpha state.


Super Agility is hardly a critical factor in a 5th Generation Fighter. Honestly, I hear supporters of the PAK-FA always boasting that it's far more agile than the J-20. Yet, I would be far more concern with the Stealth (RCS) and Sensors of the two. Then low speed agility....

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 13:56
by gta4
One must know that carnard is less effective than tail plane under high alpha, because the local alpha of canard is higher than the wing, causing the carnard to stall early. In this case, the carnard generates only drag and no lift or other useful control force. So far, no carnard fighter could handle high alpha (including EF2K, rafale, JAS39). Even the mighty X-31 loses to a hornet in a knife fight when thrust vector is disengaged.

The F-35 is an intersting case. The ability to performe X-31's J-turn (or pedal turn) at a constant 28deg/sec without thrust vectoring is a serious advantage in a conventional one-circle or two-circle fight. The adversary must sustain the same rate of turn, otherwise it will lose. So far, no adversary (including Su-27, Mig-29, J-31, J-20) has demonstrated anything close.

A common criticisms for F-35's high rate maneuver (e.g. pedal turn) is that this maneuver is conducted at high alpha and thus low energy. However, this is not a problem, because F-35's energy recovery is so good that it out-accelerates Su-27 by 20% at subsonic:
viewtopic.php?f=55&t=52510

Even J-20 may be equipped with thrust vectoring and handle some high alpha, will it be able to acheive the same energy recovery? Thrust vectoring does no help to acceleration, IMHO

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 21:45
by citanon
This is off topic but as long as we are talking about aerodynamics I've got a question:

Why does the f35 often seems to be at positive AoA during level flight?

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 22:43
by kimjongnumbaun
citanon wrote:This is off topic but as long as we are talking about aerodynamics I've got a question:

Why does the f35 often seems to be at positive AoA during level flight?


This is difficult to answer without knowing the flight envelope of the plane. It could just be that its cruising speed is higher than the aircraft it's taking photos with.

http://snagfilms-a.akamaihd.net/49/1c/2 ... d-kc767jpg

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 23:43
by count_to_10
citanon wrote:This is off topic but as long as we are talking about aerodynamics I've got a question:

Why does the f35 often seems to be at positive AoA during level flight?

All aircraft fly at a positive AoA in level flight -- though there is probably a certain amount of arbitrariness about how zero AoA is defined for a given aircraft.

Re: F-35 vs J-20

Unread postPosted: 28 Mar 2017, 23:55
by count_to_10
gta4 wrote:One must know that carnard is less effective than tail plane under high alpha, because the local alpha of canard is higher than the wing, causing the carnard to stall early. In this case, the carnard generates only drag and no lift or other useful control force.

That would be true for stable canard aircraft, but unstable canard aircraft actually keep their canards at a lower angle of attack than their main wing. Additionally, the control surfaces on the trailing edge of the main wing can also contribute to pitch moment.

That said, this is all treating the wing and canard/tail in isolation from the shape of the whole aircraft. Things like the angle of the chines on the nose of an aircraft can greatly affect stability. I'm pretty sure that you could design an aircraft that is stable in level flight with a tail at the same AoA as the main wing.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 01:56
by gta4
count_to_10 wrote:but unstable canard aircraft actually keep their canards at a lower angle of attack than their main wing.


But for unstable canard, since the plane always tends to pitch up, the carnard need to provide a nose down moment to maintain balance, resulting in negative carnard lift. This has a negative impact on total lift.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 02:19
by gta4
Additionally, the control surfaces on the trailing edge of the main wing can also contribute to pitch moment.


IMHO, I have only seen this during take-off and landing, but I have never seen any canard aircraft use the trailing edge of the main wing to trim in a high-G maneuver. Is it due to the fact that the trailing edge of the main wing are designed for take-off and landing only (about 1G), thus the structure strenth is insufficient for high-G maneuver?

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 02:45
by count_to_10
gta4 wrote:
But for unstable canard, since the plane always tends to pitch up, the carnard need to provide a nose down moment to maintain balance, resulting in negative carnard lift. This has a negative impact on total lift.

They don't need to provide negative lift, just be at a lower angle of attack than the main wing (when in level flight). In a hard pitch up, they are definitely providing lift. Some of the Eurocanards are actually stable aircraft when their canards are allowed to free-stream.
gta4 wrote:
IMHO, I have only seen this during take-off and landing, but I have never seen any canard aircraft use the trailing edge of the main wing to trim in a high-G maneuver. Is it due to the fact that the trailing edge of the main wing are designed for take-off and landing only (about 1G), thus the structure strenth is insufficient for high-G maneuver?

On take-off and landing, they presumably deploy flaps, which means the canards also go to a high angle of attack. I'm not sure how hard a turn would cause the flight control laws to deflect the rear control surfaces as well as the canards.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 03:24
by steve2267
citanon wrote:This is off topic but as long as we are talking about aerodynamics I've got a question:

Why does the f35 often seems to be at positive AoA during level flight?


I'll take a stab at this question.

I presume citanon is inquiring about the seemingly high angle-of-attack of F-35s flying at relatively low airspeeds in level flight. This youtube video seems to do a decent job at illustrating what I am trying to say:



Somewhere here on the F-35 Lightning II forum on F-16.net, someone mentioned that the F-35's horizontal tail flies at a positive angle of attack, that is, the horizontal tail is generating positive lift. Conventional aircraft (tube / wing / horizontal tail / vertical tail) horizontal tails typically generate negative lift (i.e. push the tail down) to counteract the nose down pitching moment created by the wing's generation of lift (since all conventional aircraft airfoils - at least with which I am familiar - have a negative pitching moment (i.e. nose down) when positive lift is created). However, the F-35 has significant fuselage and forebody shaping:
  1. nose chine
  2. air intake chine
  3. small leading edge root extension (LERX)
I believe the fuselage/forebody shaping permits the F-35 to generate significant lift, enough to overcome the nose down pitching moment created by the wing's lift generation, if the angle of attack is high enough. Note the nose chine slopes slightly down when the aircraft is sitting level on the ground:

Image

In this next photo, the aircraft is at a significant angle of attack, and it should be obvious that the angle of the nose/forebody chine is now at a positive angle (presumably) to the flight path vector, enabling the nose chine, air intake chine, and LERX to all generate positive lift, overcoming the wing's nose down pitching moment.

If true, then the horizontal tail can either be flown at a nominally zero lift (trimmed) state, or possibly at a positive lift state if the forebody lift is greater than that necessary to overcome the wing's nose down pitching moment.

That's my take on it, anyway. Any confirmation (or correction) is welcome.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 05:24
by citanon
Don't know whether your explanation is true or not but it's a fascinating thesis.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 05:32
by vanshilar
citanon wrote:This is off topic but as long as we are talking about aerodynamics I've got a question:

Why does the f35 often seems to be at positive AoA during level flight?


This comes up, most often with the infamous F-35 vs F-16 Thunderbirds publicity photos.

It's been mentioned elsewhere by somebody else that those photos tend to be taken at low speed, i.e. for example where a helicopter is the camera platform. Thus the reason why the F-35 often seems to be at positive AOA is simply because the flight computers are scheduled that way for low speeds -- to have the plane rely more on body lift (via positive AOA with the body) as opposed to with the wings and the tails.

For example, though it's hard to tell in many of the shots, it seems like the F-35 only has the leading slats down, whereas the F-16 has both leading slats and trailing flaps down for additional wing camber. Thus if you're looking at the AOA in terms of the wing's leading edge to the wing's trailing edge, the AOA of both are actually fairly similar. See for example this image:

http://static4.businessinsider.com/imag ... hunda2.jpg

So if both planes had to go even slower, then the F-16 would have to start relying on more body lift (pointing the nose upward), whereas the F-35 can then choose to use the flaps -- the wing has additional available camber, so to speak.

As mentioned above, the F-35 (like the F-22) have chines that are actually slanted downward (they don't actually generate vortices when the plane is flying level though, because the nose is still expanding outward there). This means that the body needs to be at a higher AOA compared to the F-16 in order for them to generate vortices (and I'm guessing also means that they stay effective at higher AOA than for the F-16).

As for why they chose to schedule the flight computers this way, perhaps it's for stability reasons, or for fatigue reasons (if the body generates some lift then less forces have to be transferred from the wings to the body to keep the body up), or for better maneuverability, or maybe it has a better L/D this way, or whatever. Who knows. But it's how they chose to schedule the plane's aerodynamic surfaces for when the plane is flying at low speeds.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 10:20
by citanon
Thanks for that explanation. Makes sense.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 22:53
by count_to_10
Interesting point on body lift and the possible effect on structural lifetime.

Re: F-35 vs J-20

Unread postPosted: 29 Mar 2017, 23:42
by sprstdlyscottsmn
Look at the difference in the H-Stab position in that photo too.

Re: F-35 vs J-20

Unread postPosted: 30 Mar 2017, 00:27
by nutshell
In just 2 posts in this page there are enough reasons why this board is an amazing source of infos; vastly superior to pretty much every dedicated military "enthusiast" websites

Re: F-35 vs J-20

Unread postPosted: 02 Apr 2017, 22:52
by gta4
inst wrote:@arian: I'm having fun here. This is the first time I've heard of pedal turns, and while I'd insist it's just an instantaneous turn, even possibly just a yawing action, it's interesting to note this about the capabilities of the F-35.


You are having a mental health condition and I'm not joking. How on earth could it be instantaneous turn while its angular velocity is constant? The turn rate of instantaneous turn drops over time!

viewtopic.php?f=55&t=52965

"Pedal turn" is neither sustained turn, nor instantaneous turn. However, its effect is equivalent to a sustained turn of 28 deg/sec, because it changes its heading at a steady 28deg/sec, and an enemy fighter could not counter it unless it performs a sustained 28deg/sec turn (conventionally or yawing).

Re: F-35 vs J-20

Unread postPosted: 03 Apr 2017, 16:56
by steve2267
sprstdlyscottsmn wrote:Look at the difference in the H-Stab position in that photo too.


Yes, but...

A photograph is a snapshot at a point in time. I went back and re-watched the youtube video to which I linked above, and I can see the F-16 stabilitor varying angle a lot. So I cannot say with any degree of certainty that the Viper's tail is generating negative or positive lift in this flight regime (i.e. slow, level flight). I recall JohnWill mentioning that the Viper's tail generates positive lift (at times -- supersonic?). Dunno if it also generates positive lift slow and level. I am going to "guess" not, as it would only begin generating appreciable lift where the LERX/strakes begin, whereas the F-35 nose chines, at a visibly larger angle of attack, would seem to be generating more lift closer to the nose, which will generate more of a nose-up pitching moment since it will have a longer moment arm back to the CG compared to to the F-16 strake-CG moment arm. I'd file this comment in the FWIW section...

Re: F-35 vs J-20

Unread postPosted: 03 Apr 2017, 19:44
by sprstdlyscottsmn
steve2267 wrote:
sprstdlyscottsmn wrote:Look at the difference in the H-Stab position in that photo too.


Yes, but...

A photograph is a snapshot at a point in time. I went back and re-watched the youtube video to which I linked above, and I can see the F-16 stabilitor varying angle a lot. So I cannot say with any degree of certainty that the Viper's tail is generating negative or positive lift in this flight regime (i.e. slow, level flight). I recall JohnWill mentioning that the Viper's tail generates positive lift (at times -- supersonic?). Dunno if it also generates positive lift slow and level. I am going to "guess" not, as it would only begin generating appreciable lift where the LERX/strakes begin, whereas the F-35 nose chines, at a visibly larger angle of attack, would seem to be generating more lift closer to the nose, which will generate more of a nose-up pitching moment since it will have a longer moment arm back to the CG compared to to the F-16 strake-CG moment arm. I'd file this comment in the FWIW section...

Of course it's a FWIW comment. The fact that nothing is ever truly static on these planes caught my mind before I even posted. And you bring up many good reasons why it is hard to eyeball. All the reasons you bring up however further point to the plausibility that the F-35 in that still is using more tail lift than the F-16 in that still. Also good to think about is that when TEFs are deployed there is more downwash off the back of the wing further reducing the AoA of the H Stab (increasing potential for downforce). It really looks like, in that still, the F-16 is using primarily wing lift while the F-35 is using a more distributed lift.

Again, FWIW.

Re: F-35 vs J-20

Unread postPosted: 04 Apr 2017, 15:52
by steve2267
sprstdlyscottsmn wrote:Of course it's a FWIW comment. The fact that nothing is ever truly static on these planes caught my mind before I even posted. And you bring up many good reasons why it is hard to eyeball. All the reasons you bring up however further point to the plausibility that the F-35 in that still is using more tail lift than the F-16 in that still. Also good to think about is that when TEFs are deployed there is more downwash off the back of the wing further reducing the AoA of the H Stab (increasing potential for downforce). It really looks like, in that still, the F-16 is using primarily wing lift while the F-35 is using a more distributed lift.

Again, FWIW.


My "FWIW" comment was a self-deprecating comment intended to caution the reader to take what I was writing with a grain of salt. It was not intended to deprecate or to take a swipe at what you had written. :D

I had thought to write something very similar to what you had written, but then I thought about the "point in time" characteristic of a photo, and re-viewed the video. When I saw the F-16 stab moving up and down, it gave me pause as to whether or not I could say for sure if the F-16 tail is generating positive lift. I think you have a better handle on that than I.

But I agree for all reasons stated -- forebody shaping, (generally visible) higher angle-of-attack that the F-35 is probably either neutral or positive lift on its stabilators. IMO, a pretty nifty design feat accomplished without canards. That is, the F-35 designers appear to have achieved all positive aspects of a canard, while retaining all the positive aspects of a horizontal tail.