Issues with the Jas39 gripen flight model

You aren’t genuinely curious.

You’ve already seen how I play Gripen against other Gripens. I played it against you and your wingman and both of you guys ended up going less than 1/1 in it. I basically used myself as bait for Bobslon to clean up in F-16.

Most of them were not.

I put challenge up for guys that claimed Gripen FM was balanced. A lot of guys just claimed it was a skill issue. I opened myself up to being proven wrong through gameplay because at the end of the day that is what really matters.

I put up data based on in-game testing. I put up data that is extrapolated through a calculation program.

You spent the thread attacking my integrity when I was completely transparent about the information I was presenting. You are actually doing it again in this thread…like the last time you claimed that you didn’t think the bleed rate of the Gripen was actually half that of any fighter…and once again I’ve shown that it is…not even compared to other game examples…but also to real life examples based on EM diagrams.

There was a point in the thread where I just decided I was done with it and thought I could bait a few 1v1s out of it. Ironically…the only guys that showed up were guys that I passionately dislike like MiG_23M (sorry brother but by principle I think you should be strapped to a rocket and fired into the sun. I’m sticking to my guns on that one), Ziggy, and like two other dudes…

Are you calling me a gripen main?

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It’s not on topic, what is … is the fact that Saab admitted their tailed control candidate had superior energy maneuverability than the canard delta type. We aren’t talking sustained turns, we are discussing the excess power currently.

On the topic of sustained turns, @Giovanex05 has shown that the turn rate currently overperforms according to the data points and previous fix.

Pretty much on the money here, why can’t we have productive discourse? Why can’t we report discrepancy / outliers without being told every single argument we make is wrong? Why aren’t you also asking the others to stop the toxic behavior? Why only Feet?

Your entire account is a troll account named after anothers’ prior name. Those who liked your comment are doing nothing to support the thread. These kinds of toxic and obtuse comments don’t occur on threads or reports that result in buffs to equipment. Please, stop the nonsense and if you’d like to participate at least do so while being productive towards the discussion.

That’s not what I said, no. Although you admitted to being Swedish if I recall correctly. It’s not a very good argument nor is it relevant and I shouldn’t have said what I said. You are, however, friends with a user who handed out death threats and was banned from the forum permanently. So, there is most certainly conflict of interest in regards to whether or not you (or your friends) would be keen on having the Gripen nerfed.

This discussion isn’t going to go anywhere, and the reports Gio is working on will still be passed. Should I choose to use @FeetPics data w/ assistance from Gio we could most certainly report the specific excess power as well. If I recall, Gio is tacking this into his overperforming turn rate report as well anyway. All this toxic discussion practice and undertone is just going to get people in trouble and threads closed. If y’all want my opinion, ask for it… otherwise I don’t feel like responding further is going to be heard in a meaningful way much less discussed.

edit. remove false flag attempt

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Gonna write this thing without tagging as too I would have to tag the whole thread lol.

First: the canard configuration being better or worse discussion leads mostly nowhere and that’s because it does not have an answer, as the question in practice is:
“is energyzing the flow on a larger wing worth but getting some negative lift by the canards worth it compared to getting positive lift from the elevator?”
And that question has a giant DEPENDS as an answer, as different wings and wing profiles can benefit from one or from the other solution.

Second: since the gripen is a more modern plane than the F-16, M2K, MiG-29 etc i do expect it to have a better polar curve than those planes. Can that polar curve offset the difference in thrust to weight? That remains to be seen, but I wouldn’t be surprised if it does.

Third: I think we can all agree that the gripen current performance is magnitudes of order too good at low speed, and in the topic i think I have proven that the current far too good polar curve of the gripen is the reason for that (and not engine/errors in simulation or other stuff).

Fourth: on the topic of bug reporting, I will soon do one for the 1.3 deg/sec over performance at 700kph, and after the FM is adjusted for that (if it will be but i see no reason for it to be not) we can look again at how good the thing will be at low speed and if it is following the same trend as current one (aka if it is losing fo few deg/s in STR when turning much slower than optimal speed) then we can look into that.

@Metrallaroja since you are a tech mod, as far as you know can math be used in bug reports?


I mean forgive me, I’m a complete nobody and relying entirely on everyone’s opinions thrown together into the melting pot…

Shouldn’t the answer be “It really depends on what Airframe you’ve slapped canards on”?

Gripen clearly makes very effective use of them, and I imagine being a FBW airframe probably makes it substantially easier to get the most effective use out of them?

I mean clearly they aren’t modelled right.

I’m not commenting on the Second point because again, that’s a “it depends” point as far as I know and I genuinely don’t think it worth me contributing.

MiG making the point that the SEP is bonkers is on the money. It feels quite frankly ridiculous to fly. I haven’t flown it in a while, but it does feel like it retains very well. Possibly too well? The conventional assertion with Deltas is the moment you put on any sort of Alpha, your wings become extremely draggy, in return for a lot of lift. In that sense I do think that there is definitely something not right with the model, in that it feels probably a little too capable at retaining.

Thanks for your efforts. I feel it’ll be nigh on impossible to get it perfect because muh sekrit documents at the minute.

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that is not what you previously stated though which is why i opposed you.

(your previous statement)

and this is where i think the main discussion is, and should be. i don’t think anyone opposes or questions that the 2x number is bonkers. the diskussion is mainly whether it should be at the same level or slightly above the other two or some tenths percent above.
The Lavi is a promising comparison indeed, the only thing i could think of that would matter is maturity as the Lavi didn’t make it that far into the test flight phase (what i can find on a quick glance on Wikipedia, not a great source i know, it flew only 82 sorties with 2 completed prototypes). there are also minor differences in design that would also cause differences both in the positive and the negative (as we don’t have the actual data for gripen we won’t know, although i would highly argue for the differences giving gripen the advantage because of the maturity).

main differences being the position of the canard being further back on the Lavi, lack of strake, the angle of the trailing edge of the main wing and the belly mounted air intake as opposed to the gripens side mounted air intakes. what those differences would result in i have not thought about yet but i think The Lavi is the closest we have at the moment. that combined with other research papers should get us closer to the actual performance compared to the current in game version.

which in of itself is wrong and i hope they very soon update the underlying code and general calculations of the flight models for all planes in game, its high time for an upgrade in that departement. all future additions of newer jets are going to have massive issues otherwise.

i think the issue we are seeing in game might be because of just that, Gaijin uses the additional lift created by the canards and just adds that to the main wing and treats them like one unit. this results in a lift/drag ratio that is wrong as the drag from the canards might not be calculated and only the lift is. (which would also explain the weird behaviour of the canards and the effect they have when landing, but i might be wrong here and might be misremembering).

I didn’t claim they did either, but at anytime the canards are pointed downwards (which is a majority of the time IRL, in game its modeled way wrong visually at least) or upwards enough the strake will still give the positive effect of vortex generation that the canards might not provide in those situations (until a point of course).

oh yeah, i’ve seen many miss that part, same with the F-16 LERX. i’ve seen people argue for that 2x number thinking it is correct because the M2K and F-16 doesn’t have anything that gives similar albeit lower effect as canards.

bringing it down to thrust to weight and wing loading is also a bit reductive but i see why we do it, its just perhaps a bit to reductive.

thrust to weight is good when combating drag, but there are other ways to combat drag that the gripen employ instead of adding more thrust (my previous statement on lower weight needed to be shifted and the lower AoA needed to generate the lift needed resulting in less drag still stands).

Wing loading i don’t understand why people bring up as its a measure of area to weight and isn’t really that important in a sustained turn or in any turn really. its mostly a measurement useful at level flight on commercial aircraft as far as i understand it. its not really useful in a discussion on the unconventional aircraft we are talking about.
the amount of lift per area is not taken into consideration. you can have two aircraft with the exact same wing loading but one has a WAY bigger lift per area than the other.
not only that but wing loading as a straight function of wing area to gross weight is disingenuous as all these aircraft also use the fuselage (among other things) to generate lift.

but if we want to compare straight numbers (which i don’t like. i have used wiki numbers so feel free to correct me if i used wrong numbers):

Wing loading

F-16: area of 28m^2 at empty weight of 8600kg gives 307kg/m^2
(gross weight 12.000kg gives 429kg/m^2)
(max 19.200kg gives 686)

M2K: area 41m^2 at empty weight 7500kg gives 190kg/m^2
(gross weight 13.800kg gives 337kg/m^2)
(max 17.000kg gives 415)

JAS39C: area of 30m^2 at empty weight 6800kg gives 227kg/m^2
(gross weight 8.700kg (??) gives 291kg/m^2)
(Max 14.000kg gives 467)

so its highly dependant on what numbers you use to calculate as well.



F-16C: full afterburner 131kN (13362kgf), Empty: 1.554 Gross: 1.112 Max: 0.696
M2K: full afterburner 95.1kN (9700kgf), Empty: 1.293 Gross: 0.703 Max: 0.571
JAS39C: full afterburner 80.5kN (8211kgf), Empty: 1.208 Gross 0.944 Max: 0.587

looks like gross weight are the numbers you see most places

so as far as i can find the Gripen is able to take of at much lower standard weights than the other two as they need to be loaded with more things (like fuel?) before takeoff?
i can see 3200kg internal fuel for F-16, 3100kg internal fuel for M2K and 2340kg internal fuel for JAS39C.
Something feels off, like i have found weird numbers somewhere. feel absolutely free to correct me.

i wanted to look at half fuel and two aim9/magic2 and compare wing loading to T/W and then do the same for Gross weight and combat weight(numbers from graphs).
M2K:Mirage 2000 Thread : Variants, performance, characteristics and sources - #1540 by DracoMindC lower graph in post used, combat load.
F-16: data from manual i can’t link. Gross weight: 10900kg
don’t want to spam more calculations so results:

(T/W)/Wing Load (Higher ratio = better)

Half fuel (weight of half internal max fuel) and 2 missiles (180kg):
F-16: T/W 1.287 Wing load: 371
Ratio: 0.35%
M2K: T/W 1.051 Wing load: 225
Ratio: 0.47%
JAS39c: T/W 1.007 Wing load: 272
Ratio: 0.37%

Gross (from above numbers):
F-16: T/W 1.112 Wing load:429
Ratio: 0.26%
M2K: T/W 0.703 Wing load: 337
Ratio: 0.21%
JAS39C: T/W 0.944 Wing load: 291
Ratio: 0.32%

Combat: (gripen unknown, i used F-16’s “sort of in the middle of gross and half fuel” number and estimated gripens middle. F-16 and M2K from graphs):
F-16: T/W 1.22 Wing load:389
Ratio: 0.31%
M2K: T/W 1.05 Wing load: 230
Ratio: 0.46%
JAS39C: T/W ? Wing load: ?
Ratio: 0.35% (estimated/guessed)

at gross weight Gripen has 23% better ratio between wing load and T/W than the F-16 (and 52% better than M2k) and at half fuel and two missiles (only) Gripen is 5% better than F-16 (M2K is an outlier here and can’t be correct, something is off) and combat load gripen is 13% better (which is interesting).

now the numbers for M2K seems way of here, i don’t know why the gross weight is so much higher compared to its empty/combat weight which makes the “half fuel, 2 missiles” calculations look really off. i wonder if they use a different method for empty/gross weight ?
Now this is ONLY Thrust to weight and wing loading.

even given T/W and wing loading which is brought up so often gripen is better ratioed in those two categories as well.
if you also take into account the L/D ratios of the planes Gripen should come out on top here as well given all of the previously talked about and linked papers on canards in general. by how much is a topic for debate. same goes for my calculations on circular motion.

now i will repeat that 2x SEP is bonkers. but i still believe that a number of 1.3x is within the realms of reason given my calculations so far (but i very much could be wrong and would love to be corrected if faults are found).

I’m going to refrain to answer the rest of your post as i don’t want to continue the off topic.


i haven’t claimed very much in relation to total performance and canards, just lift improvements.

Canards have been proven to be better than F-16 and M2K designs but not by much. its just an addition to several other things to be taken into consideration where gripen has the edge.
Now (again) 2x SEP is bonkers, but given what i have seen so far and calculations i have done, 1.3x isn’t really that crazy as many believe. its in the higher range yes, but not unbelievable.

i would love to hear your comment on my calculations on circular motions Issues with the Jas39 gripen flight model - #67 by Necronomica
and my calculations on T/W in relation to wing loading comparisons
Issues with the Jas39 gripen flight model - #167 by Necronomica

i think i know what you are trying to say here. but you are saying it wrong (or wrote wrong by mistake?)
a canard creates positive lift on unstable designs. it has to be countered by negative pitch resulting in negative lift. a canard doesn’t inherently produce negative lift.
and on gripen that is the case which is why the canard is pitched down in normal flight. but you can also have a down pitch on the trailing edge (to produce positive lift just like F-16) to counteract the unstable rotation. the F-16 only has the choice of lift from the aft (tail or trailing edge) whilst Gripen can do either canards, trailing edge or both depending on need for extra lift in different situations.

Gripen can do sort of the same though, having less negative lift/pitch on the canards and more positive lift on the elevons resulting in a higher total center lift.


i think in general there needs to be a big overhaul on the simulation code and flight model code. when even newer aircraft than this gets added they are going to be even more wrong than what we already have. especially since almost all newer jets are negatively stable and have FBW both of which the game currently does not have/cant simulate.

i think the main problem with gripen stems from what i guess is that they have just added the extra lift and wing area the canards generate to the main wing and then not calculated for the extra drag correctly. this might also be why the canards don’t really do anything (as far as i understand it) in game more than visually. especially during landing.


And I assume as a result, that that lift value is constant, dependent only on speed and AOA?

If so, that would explain a lot about the aircraft’s… behaviour.

It also doesn’t help that the Visual model just doesn’t have any bearing on what you’re trying to do with the aircraft.

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i hadn’t even thought about that, that would explain a lot yes.
we might ask @Gunjob for some insight here maybe?

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The Gripen will be getting some tuning in a future update. Sustained will be adjusted and reduced by ~0.5 to ~0.7.


Yes why not but wait a bit, the FM is going to get some fine tunning in sustained turn soontm


Ok, that’s good to hear, although 0.7 deg/sec is still to little if it needs to match the 21deg/sec at 700kph figure (let alone a realistic drag polar)
Still definitely better to wait until changes get carried out


I would assume by ‘fine tuning’ and the sustained being ‘adjusted’ they’ll be doing more than lower max sustained by a measly 0.7. Possibly keep the sustained somewhat high but reduce/adjust the curve so it’s not that high at the lower speeds

I assume this update from the devs are the result of them reading this thread. I’d be very surprised if a reduction of 0.5-0.7°/s sustained is all they gathered from it


That’s why I said it’s better to wait for those changes and then act accordingly:D


Thank you for answer! ^^
any sneak peaks into plans on ex: revising flight models in general, major code changes to accommodate inherently unstable aircraft, more accurately simulated canards/airflow? :)

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He isn’t a dev so i don’t think he would know

But he does great work

sometimes (like now) he has some insider info and communication with devs. sometimes he gives us looks into future plans and changes to make people stop freaking out over something already planned to be fixed :)


He does sometimes we will see

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i don’t need a reply but i do like the discussion and i am learning from it. so its up to you if you feel like you get something out of the discussion or not :)

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Well, it’s nice to somewhat have a conclusion to this. Let’s see what the devs make of it. Giovanex seem to be on the cusp of having a report ready if devs actually just lower sustained by 0.7