F-35A versus Saab Grippen NG

The F-35 compared with other modern jets.
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hornetfinn

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Unread post15 May 2019, 10:23

magitsu wrote:Is it guaranteed that non-fixed radar produces less frontal RCS? I remember reading something that suggested such a mechanism it requires would produce higher RCS (apart from having an extra mechanism in the plane that can fail).


No it's not guaranteed but definitely very possible. I could see tilting the radar antenna back and keeping it still normally, just like the fixed and tilted-back antenna in Super Hornet. This would lower the RCS significantly if the tilt angle is more than 10 degrees (15 degrees or more preferable) from vertical. Even if it's turned in azimuth the RCS will not increase that much if the tilt angle is kept all the time. This is why I think RBE2 AESA is pretty bad for Rafale RCS as it's totally vertical without any tilting. They obviously went for maximum radar antenna size and thus performance. Moving antenna needs to be slightly smaller than what's possible with fixed antenna and needs quite a bit more space due to turning mechanism. Such vertical antenna can have RCS somewhere in the region of 0.1 to 1 square meter alone. Tilted back antenna will have at least an order of magnitude lower RCS, possibly a lot lower (2-3 orders of magnitude possible). Of course that is only part of the overall RCS of the aircraft.

The turning mechanism will likely have some detrimental effect on RCS, but I'd say the orientation of the antenna has much bigger effect. I'm sure there are ways to mitigate the effect with some shielding, but it's still likely easier to design fixed antenna for low RCS. I don't think that this matters much with 4th gen fighters. It's likely that VLO aircraft like F-35 and F-22 would see comparatively fairly large increase in RCS as they have so small RCS otherwise.
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Unread post15 May 2019, 11:13

XanderCrews wrote:No it doesn't. The engine face has always been hidden on Gripen (kudos) but the Canards are the dogs bullocks sticking out. And there is no lipstick one can put on them. Even if they are planformed to the delta wing, its been explained in here several times that theres no fixing them.


How do the Chinese manage to fix theirs on the J-20 and claim an RCS of 0.05 sq m which optics calculations, e.g APA, have confirmed is a LO if not VLO airframe ?
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Unread post15 May 2019, 11:34

XanderCrews wrote:
As you know Gripen did one competition in Switzerland -- we do have some info about that one because of the leaks, and because of official documents. As linked to in a previous page, RCS reduction was actually one of the technical requirements.


"Reduced" from what? and in the end it was picked based on cost. MOREOVER, and just to beat this dead horse one more time-- The Swiss Bought off on a Gripen CONCEPT. an ESTIMATE.

I'm not trying to beat a dead horse here, and I'm not trying to be difficult, but the bottom line is the Gripen E in the swiss competition was a PAPER PLANE. When Saab was shopping around the Gripen NG concept, it was (rationally so) catering the concept to whatever the customer wanted to emphasize. If the Swiss wanted that, they were going to present a Gripen NG concept that fit that.

I don't think the Swiss completely bought off the concept -- one of the reasons why Gripen scored so poorly in the Swiss eval, was that in the first (2008) eval they basically used the Gripen C, not the Gripen NG (which did not exist at the time). They did do a "paper eval" of the future version of all 3 fighter jets, however the Swiss did of course realize that Gripen E was far away from production and therefore introduced an "uncertainty factor" when assessing the improvements. I am not entirely sure how it worked, but the way it was explained to me was that each score would be multiplied by the "uncertainty factor", which for Gripen NG was much higher than for Rafale and Typhoon, one source claimed it was 0.72 for Gripen, perhaps Swiss can confirm? So for instance, if the score for one parameter increased from 4 to 6.5 (according to Saabs specifications of the future Gripen E), then in the eval they would calculate the new Gripen score to be 6.5*0.72 = 4.68. So in this example the Gripen score would increase from 4 (Gripen C) to 4.68 (Gripen E). Rafale, due to the maturity of the system would have a much larger "uncertainty factor" (i.e. closer to 1), and Typhoon would be somewhere between Gripen and Rafale.
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XanderCrews

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Unread post15 May 2019, 20:03

marsavian wrote:
XanderCrews wrote:No it doesn't. The engine face has always been hidden on Gripen (kudos) but the Canards are the dogs bullocks sticking out. And there is no lipstick one can put on them. Even if they are planformed to the delta wing, its been explained in here several times that theres no fixing them.


How do the Chinese manage to fix theirs on the J-20 and claim an RCS of 0.05 sq m which optics calculations, e.g APA, have confirmed is a LO if not VLO airframe ?


How do the chinese claim something? Is that a serious question?


Do you really need to compare the shapes of the J-20 with the Gripen E?


Geewhiz mars, one of them looks like an F-22/F-35 with the wings on backwards, and the other looks like an F-20 with the wings on backwards. Which do you think is considered VLO? F-22 or F-20?
Last edited by XanderCrews on 15 May 2019, 22:13, edited 1 time in total.
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Unread post15 May 2019, 22:01

Source for J-20 0.05 sq m RCS, chief designer interview ..

viewtopic.php?p=403134#p403134

Regardless of what its actual stealth is it is being advertised as a stealth fighter by the Chinese. The proposed naval YF-23, NATF had canards too.
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Unread post15 May 2019, 22:24

marsavian wrote:Source for J-20 0.05 sq m RCS, chief designer interview ..

viewtopic.php?p=403134#p403134

Regardless of what its actual stealth is it is being advertised as a stealth fighter by the Chinese.



Image


The Chinese made a decision and thats going to balance across all their requirements. why is it Mars, that we look at a Super Hornet and say "Radar blocker? thats not ideal." but we can't look at Canards and say the same thing?

Will gladly argue until the cows come home about how the F-22/35 looking J-20 with the wings on backwards is still stealtheir than the F-20 looking Gripen with the wings on backward.


I will concede that Canards aren't a deal breaker, if you'll concede there are "slight" differences between J-20 and Gripen in the shaping department?

The proposed naval YF-23, NATF had canards too.


and?


this entire subject has turned into a comedy. :doh:
Last edited by XanderCrews on 15 May 2019, 22:39, edited 1 time in total.
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Unread post15 May 2019, 22:38

loke wrote:
XanderCrews wrote:
As you know Gripen did one competition in Switzerland -- we do have some info about that one because of the leaks, and because of official documents. As linked to in a previous page, RCS reduction was actually one of the technical requirements.


"Reduced" from what? and in the end it was picked based on cost. MOREOVER, and just to beat this dead horse one more time-- The Swiss Bought off on a Gripen CONCEPT. an ESTIMATE.

I'm not trying to beat a dead horse here, and I'm not trying to be difficult, but the bottom line is the Gripen E in the swiss competition was a PAPER PLANE. When Saab was shopping around the Gripen NG concept, it was (rationally so) catering the concept to whatever the customer wanted to emphasize. If the Swiss wanted that, they were going to present a Gripen NG concept that fit that.

I don't think the Swiss completely bought off the concept -- one of the reasons why Gripen scored so poorly in the Swiss eval, was that in the first (2008) eval they basically used the Gripen C, not the Gripen NG (which did not exist at the time). They did do a "paper eval" of the future version of all 3 fighter jets, however the Swiss did of course realize that Gripen E was far away from production and therefore introduced an "uncertainty factor" when assessing the improvements. I am not entirely sure how it worked, but the way it was explained to me was that each score would be multiplied by the "uncertainty factor", which for Gripen NG was much higher than for Rafale and Typhoon, one source claimed it was 0.72 for Gripen, perhaps Swiss can confirm? So for instance, if the score for one parameter increased from 4 to 6.5 (according to Saabs specifications of the future Gripen E), then in the eval they would calculate the new Gripen score to be 6.5*0.72 = 4.68. So in this example the Gripen score would increase from 4 (Gripen C) to 4.68 (Gripen E). Rafale, due to the maturity of the system would have a much larger "uncertainty factor" (i.e. closer to 1), and Typhoon would be somewhere between Gripen and Rafale.



They ended up purchasing it based on cost anyway. For as much as people think the Gripen NG/E was a simple follow on, (except when its not of course, when it goes full 6th gen) there is indeed risk. The Norwegians for all the complaints about wikileaks were seriously concerned about the Gripen NGs ability to deliver, and its future especially upgrades and spares. It was surrounded by uncertainty and risk more than people realize, and not all of that has gone away. Even the Super Hornet ran into some big issues. S-92 which is basically a super sized blackhawk was hot on the heels of the USMC's V-22 program. Especially given the V-22s crashes. The Marines dug in on V-22, but the pressure was there. And eventually one day an S-92 crashed and killed a bunch of people revealing serious transmission issues. Things are not always as straight forward as they seem.
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Unread post15 May 2019, 23:38

marsavian wrote:
XanderCrews wrote:No it doesn't. The engine face has always been hidden on Gripen (kudos) but the Canards are the dogs bullocks sticking out. And there is no lipstick one can put on them. Even if they are planformed to the delta wing, its been explained in here several times that theres no fixing them.


How do the Chinese manage to fix theirs on the J-20 and claim an RCS of 0.05 sq m which optics calculations, e.g APA, have confirmed is a LO if not VLO airframe ?


You're not really using APA, (Koop, Goon and co clown club) as a source, are you? You've just lost the argument before you started.
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Unread post16 May 2019, 07:48

XanderCrews wrote:They ended up purchasing it based on cost anyway.


Cost and technical requirements... They made clear 2 things: 1. Gripen was not the most capable of the three (actually it was the least capable) and 2. in the end it was deemed to meet minimal requirements. Also strange that it was invited to this second round, especially since SH and F-35 are also in the race this time around. If for some (political) reason F-35 is not chosen then the SH seems the obvious choice, right? Highly capable and much cheaper than Rafale/Typhoon. Thus that leaves no room for a fighter that does not meet requirements -- unless of course it does...
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Unread post16 May 2019, 12:49

loke wrote:
XanderCrews wrote:They ended up purchasing it based on cost anyway.


Cost and technical requirements... They made clear 2 things: 1. Gripen was not the most capable of the three (actually it was the least capable) and 2. in the end it was deemed to meet minimal requirements. Also strange that it was invited to this second round, especially since SH and F-35 are also in the race this time around. If for some (political) reason F-35 is not chosen then the SH seems the obvious choice, right? Highly capable and much cheaper than Rafale/Typhoon. Thus that leaves no room for a fighter that does not meet requirements -- unless of course it does...


That is incorrect. In the Swiss competition, the Gripen didn't even meet the basic requirements and it was specifically noted that the Gripen was behind in multiple scenarios to the F-18 that it was slated to replace.
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Unread post16 May 2019, 13:50

loke wrote:Where did Saab claim an RCS value of 0.1 square meters? I have seen that some people on the internet make such claims, but I cannot recall having seen Saab make such a claim. Can you please provide the link to this claim from Saab.


As you're probably aware (but I'll indulge you nevertheless) that 0.1 square meter claim comes from an official Swedish government document which stated that the RCS goal for the Gripen E was to be those 0.1 square meters.
Unfortunately the site/page where I saw that documents hosted (keypublishing.com forum) is apparently down for maintenance but here's the full link nonetheless:
https://forum.keypublishing.com/forum/m ... 5-03/page2


marsavian wrote:Ricnunes, I think the SH's all round RCS reductions are better than you think seeing all the work done around the body and don't forget the slanted tails already being an advantage there.


I'm not saying that there couldn't be some RCS improvements on other aspects such as sideways for example.
However one must understand that none of the 4.5th fighter aircraft (including the SH) are true stealth or VLO aircraft and they can never be, so any company developing these aircraft can and will center on the aspect where a considerable diference in terms of lowering the RCS can or could be made which is frontal which is also the same aspect which is expected to be facing the enemy most of the times (if things go well, that is).
As opposed true stealth or VLO aircraft like the B-2, F-22 or F-35 are built to have very low RCS values on all around aspects (but of course the frontal aspect will always be the lowest value).

As such, I'm pretty sure that the RCS improvement designs on the SH are centered on the frontal aspect, this even if there's a chance of having some (marginal, I would say) improvements on other aspects.
A 4th/4.5th gen fighter aircraft stands about as much chance against a F-35 as a guns-only Sabre has against a Viper.
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Unread post16 May 2019, 14:00

As you're probably aware (but I'll indulge you nevertheless) that 0.1 square meter claim comes from an official Swedish government document which stated that the RCS goal for the Gripen E was to be those 0.1 square meters.


Which is still downloadable on a moved link from the dead original link.

https://www.foi.se/rest-api/report/FOI-R--0338--SE
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Unread post16 May 2019, 14:03

playloud wrote:IIRC, the claim was 0.1 m2 for the Gripen A, with improvements in both the C and E.

LOL, that's for laughs! :mrgreen: :doh:



swiss wrote:The YF-16 has an RCS of 1.2m2 with MSA Radar. So i would guess 1m2 or even a bit lower cold be possible for the Gripen-E thanks to the AESA and RAM.

But as Hornetfinn pointed out. We talk about small differences here. :wink:


I didn't know that the YF-16 (the F-16 prototype) had a lower RCS than the production F-16A. Are you sure?
It would be interesting to know what made the RCS go up from the YF-16 (1.2m2) to the F-16A (3m2 to 5m2, depending on the source).

Yes, I agree that the Gripen E could have a RCS of 1 square meter. That value I would "buy it". Lower than that, I strongly doubt it (for all the reasons previously mentioned).
Actually I believe that I mentioned on one of my posts here regarding the 0.1 square meter claim for the Gripen RCS that by moving the decimal point one place to the right that we'll get a RCS value much closer to the truth or actual value.
A 4th/4.5th gen fighter aircraft stands about as much chance against a F-35 as a guns-only Sabre has against a Viper.
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Unread post16 May 2019, 15:13

marsavian wrote:
As you're probably aware (but I'll indulge you nevertheless) that 0.1 square meter claim comes from an official Swedish government document which stated that the RCS goal for the Gripen E was to be those 0.1 square meters.
ier than you with 0.1

Which is still downloadable on a moved link from the dead original link.

https://www.foi.se/rest-api/report/FOI-R--0338--SE

I've seen heroin addicts kick it easier, than you with the 0.1
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Unread post16 May 2019, 16:13

ricnunes wrote:
swiss wrote:The YF-16 has an RCS of 1.2m2 with MSA Radar. So i would guess 1m2 or even a bit lower cold be possible for the Gripen-E thanks to the AESA and RAM.

But as Hornetfinn pointed out. We talk about small differences here. :wink:


I didn't know that the YF-16 (the F-16 prototype) had a lower RCS than the production F-16A. Are you sure?
It would be interesting to know what made the RCS go up from the YF-16 (1.2m2) to the F-16A (3m2 to 5m2, depending on the source).



Dare I ask why the YF-16 is in this thread - they were a bit smaller with a smaller / different nose as well and never had an FCR - only a ranging radar for testing the gun and were never representative of anything operational.

I don't know where these figures are coming from however the production F-16A had Have Glass from the early 80s to reduce its RCS.
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