Issues with the JAS 39 Gripen flight model

well their are some things that don’t work harrier is a good example it low speed thrust is higher then it should as it it was correct it would not work

That’s one of the very rare examples of were war thunder simulation right now is not good enough. Another is the fact that most in game unstable aircraft are modelled as stable (this is not a pure simulation problem but rather a problem on how the part that calculates how to damper/magnify mouse aim inputs would react). But in general the problem is not the simulator, and it is not in the case of the gripen induced drag

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ah ok

you are right it has better energy retention than the F16A, but based on my experience that won’t make a difference in game unless you were doing a 1v1. which rarely happens in 12.0-12.7 and with the addition of amraams even close engagments with missiles are gonna start to become less, so i don’t think the gripen being like 3-4% better then it should would make a difference…

Lift coefficient doesn’t reach 0, the aircraft overall still has quite a lot of lift caused from pressure on the body that is maintained as long as the line of travel is still forward when the nose is pointed up. This is why the Cobra works, but requires rapid attainment of AoA… and stability is not ideal without this rapid attainment. Angle of attack onset must be sufficiently rapid to overcome these instabilities and go beyond the point of flow separation. If this doesn’t occur, yaw and roll instabilities follow.

That’s all fine and dandy, but another issue entirely with most of these newer Western aircraft such as F-16 and Gripen is that they exhibit practically no instability at near-stall conditions or at high AoA… You just get less effective control over your current situation. Other aircraft like the MiG-29 have wing rock or oscillations modeled and are actually likely to enter spin conditions… And for some reason less recoverable than the F-16s or Gripen.

In fact, in full real you can deflect maximum stick on the Gripen and it will simply start accelerating and hold a steady turn at a low airspeed rather than stall.

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It’s the difference between being able casually ignore any enemy you face and having to think about how you approach a situation. The Gripen is dominating top tier due to the excessive countermeasures, energy retention, overperforming ordnance.

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The Lift coefficient does reach 0 at an high enough drag, when the aircraft AoA is over 90 degrees it is actually negative, the reason it doesn’t fall is because, as you said, the whole thing happens quickly.
If you were able to hold over 90 degrees AoA at some point the aircraft would start significantly falling down (unless thrust/weight above 1 obviously)

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what i said in the topic is why a cobra makes you lose a ton of energy, drag massively increases while lift decreases

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don’t know about the ordnance thingy mate russian ones are way better, and 16v16 is too messy to determine that you can casually ignore any enemy you face or having to think about how you approach a situation, i’ve played it and there’s no time to think just empty your misslies and return to base or die, this thing got nerfed heavily from the moment it was dropped and it does not need another nerf.

The airflow from the canards actually has positive interactions with the main wing. The result is more lift than the sum of them individually.


Which ordnance is overperforming?


Yes, I was just being specific. Lift does not reach zero during the Cobra maneuver, while it is very low it is not 0. Drag of course is very high and is the focus of the maneuver - to rapidly slow. Its’ primary use (quite useful for this) is to prevent overshoots and to win tight one circle engagements.

High AoA aerodynamics isn’t really relevant to the discussion though, I’ll drop it for now. The JAS-39 can’t do anything high AoA period.


Probably 9m, which tbf its very strong, r73 requires me to wait until i see their engines so they cant dodge it or to catch my opponent off guard not to mention much less range, but ill take that trade as i have r27et for range.

F-16As doing turns at 40 degrees AoA is bs and it is certainly an issue, but that’s for the F-16 topic.

The gripen is actually quite limited in the AoA it can reach in game, it wont pull beyond 24.5 degrees without doing wonky maneuvers and instead just stays “on rails” at 23.8 degrees if you set 100% trim and do a steady turn at full afterburner.
The reason why they limited the pull is probably because the plane is already overperforming in slow speed drag, if they would let it pull more that overperformance would be absolutely massive (while aircraft such as the Mig-29 basically can’t sustain a turn at 28 degree AoA, you would probably see the gripen happily rotating at well over that value with current drag curve lol)


Well, certainly the Gripen flight model could see several revisions. The issues span to the underperformance of the MiG-29 and Su-27 as well. Annoying they can’t pick one method of solving the issue and stick to it when modeling all FMs. Instead we have MiG-29s and Su-27s dumping all airspeed in one turn and F-16s / Gripen’s heavily overperforming in AoA or excess power.

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i guess the 9M which is underperforming in lock range

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Idk about the Su-27, but the MiG-29 is very accurate and I don’t feel like it is dumping that much speed to be honest. The F-16s dumb about the same amount of speed until below 500kph (and at that point one circle performance matters far more and without 40degree AoA the F-16s would lose).
The Gripen instead preservers energy far too well now.

Still let’s keep the focus on the gripen for this thread, I will look for that extended polar approximation with Cl^4 and try to get where it comes from. If it’s not some empirical thing for some ideal type of wing we could get a still overperforming but more believable drag curve.
Also I think the extra 1.3 deg/sec baseline it has at 700kph can be already reported

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Just link this thread and explain the specific excess power being a massive statistical outlier doesn’t appear to be accurate or historical as well when you do the report where it’s 1.3° / s higher than expected.

They’ll tack it on and rework it. At least, they said it would be fixed if someone reported it. No one reported it.

Funny that, the people saying I’m biased didn’t or couldn’t report the issue. Glad you’re working on it… let us know if there are any death threats or associated things like I got.

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I’ll just add my post to this one since this seems to be the thread that people want to comment on

Why Compare F-16A to Mirage 2000 to Gripen?

All 3 of these planes are fully fledged 4th Generation single seat fighters of similar size with fly by wire systems. I say fully fledged because planes like the F-14 and MiG-29 are also 4th Gen but do not use fly by wire systems. The fly by wire system enables two things; it allows the pilot to very confidently push up against the limits of what the airframe is capable of, and it also allows aircraft designers to make an airplane with marginal or negative stability.

With a conventional aircraft with normal controls the center of gravity has to be forward of the center of lift; this is so that the natural tendency of the aircraft is to want to point the nose down. This is smart because it means that a plane will naturally want to pitch down and maintain an attitude that keeps the airplane in a state where it stalls…it will point nose down and you will be able to recover.

The downside to this is that trim is needed in order to counteract the stability of the plane. It means that a certain portion of control pressure is needed to keep the plane flying. This also makes the plane easy to fly and is necessary in conventionally stable aircraft. What a fly-by-wire system does is use a computer to calculate and micromanage how to fly the airplane at a rate that a human would never keep up with. It also means that designers can move the CG closer to the center of lift or even behind it; and that means that it takes less control input to maintain the same flight profile.

This is cringe nerd crap. Okay but why compare all 3 of these planes? Well it is because they are similar; they all take advantage of the relaxed stability that FBW is able to offer. The other reason to compare them is because they are all some variation of a triangular wing with roughly similar wing loading etc. If the F-18 was in-game we would also be comparing it to that.

The other reason to compare them is because they have been flown against each other in training and the Gripen flight model is not really based on any real hard evidence like an EM diagram. But there is enough anecdotal evidence that all of these planes have roughly similar capabilities in a dogfight; it is close enough in real life that the main factor in who wins comes down to the scenario and pilot skill.

There are a couple of interviews with pilots online and piecing together how accurate they are takes some consideration. And then we have to reconcile those anecdotes with how the game chooses to model things itself; for instance nobody in real life is casually ripping a 14G turn at Mach 1. And also winning a dogfight IRL might just come down to pull really hard for initial turn and then throwing HMD missile across the circle in a way that isn’t present in-game.

Muh Anecdotes

Let’s get to some anecdotes.

The first one is from an interview with an F-16 pilot

The second one is from a Saab representative iirc.

And this is from an interview with a Gripen pilot

So which one of these anecdotes is true? Are they all true? How true are they? And if they are true are they accurately represented in the game?

My personal opinion is that all of these things are true to an extent; the Gripen in real life is not some undefeatable monster in BFM. It has some stuff it can do against F-16 like win the initial turn due to higher initial turn rate and then patiently sit behind it while the F-16 runs itself out of energy. The fact that the F-16 is limited to 24 degrees AoA in real life means that it has some limitations in a dogfight and has a cap on how well it can convert excess speed into angle/position.

At the same time the F-16A has a good chance of winning a dogfight depending on the circumstances. His best option IRL is probably to merge against the Gripen and fly a trajectory that helps avoid the initial turn rate advantage and then use marginally better sustained turn rate and better power to weight ratio to regain all of the lost position/keep Gripen in-check. It is also likely that if the F-16A doesn’t play to his thrust to weight advantage or if he allows the Gripen to develop an energy advantage early on that he loses the fight because of the Gripen having a little lower wing loading.

Keep in mind in this scenario all of these anecdotes are true. The Gripen can have a higher initial turn rate than the Mirage 2000 (but its close), a worse sustained turn rate than the F-16 and F-18, and still “carve through the air better” and lose less speed in similar performance turns.

When you take all of the anecdotes across the internet and various aviation magazines, interviews, etc it should seem pretty obvious that all 3 of these airplanes are awfully close in dogfighting capability. In reality the strength that the Gripen has over the F-16 is probably the same strength that the F-18 has over the F-16…but just a bit better at it.

How Is It Modeled In-Game?

War-Thunder unfortunately does exist in its own cinematic universe. The flight models that we have in-game will by and large match the EM diagrams that are available for the most part. However a key area where War Thunder deviates from reality is that it doesn’t accurately model the IRL flight control systems or G-limitations of some planes. This has especially important implications for planes like the F-16A that due to game design decisions are able to exceed their flight computer imposed G limitations as well as their own AoA limitations.

This actually isn’t as big of a deal as it sounds like on the surface because basically every flight model exceeds their G limitations by a significant margin; this is why every plane is easily aimable while flying in mouse aim at Mach 1. This is why the 18G F-104 Pencil is a thing. This modeling decision was more or less fine up until the F-16A and MiG-29 were added because the energy retention and thrust of previous fighters just wasn’t nearly as high; the F4 Phantom exceeding it’s real life g limit wasn’t nearly as noticeable because it wouldn’t maintain it. This is also why flying a lot earlier supersonic jet fighters feel like drifting a bathtub while playing in mouse aim.

How this increased G limit effects the accuracy of the flight models in the game; especially 4th Gen fighters is that they pretty much are all able to generate higher initial turn rates than they otherwise would IRL. Remember that the F-16A has two types of limitations; a G-limiter and an AoA limiter IRL. Because of the fact that neither of those things are represented in the game…it means that as a flight model set the F-16A that we have in-game has access to a flight envelope that it would never come close to in real life.

The main difference that the F-16 in-game has is in its ability to convert excess speed into initial turn and the ability to perform maneuvers at basically double the AoA limit of its real life counterpart. The second part really isn’t a factor that effects RB players but if you play the F-16A with SAS set to Manual in SB you can pull up to 40-45 AoA which means that in very slow speed fights the F-16 has an advantage that would cause it to fall out of the sky in real life.

Of any of the flight models that we have had in-game…the F-16A is probably one of the most inaccurate and overperforms its real life counterpart by a wide margin. This is especially true for the Blk 10 variant which is the best maneuvering of all the F-16s .

Let’s also keep in mind that the F-16A and MiG-29 have already been nerfed since release. One of the ways that Gaijin has kind-of-sort-of countered the usefulness of exceeding operational G-limits is by increasing the amount of drag that occurs while pulling very hard at high speeds. These are the flight model changes that hit the MiG-29 especially hard and also hit the F-16 to a lesser extent when they also removed the pseudo-G limiter that it used to have.

I lay all of this out so that people understand that when I compare the Gripen to the F-16A…it isn’t because I think they need to be equalized…but rather as a datapoint for something that we know is over-performing and over-performs in an extremely egregious way.

Muh Specific Excess Power

SEP is basically a measure of how much energy a plane is generating or losing in its current flight configuration. If you enter your plane into a max performance turn it is going to lose speed or altitude until it stabilizes at a corner speed. SEP is a good measure of how well a plane utilizes the energy that it has and how it recovers it.

Muh Graphs
This is a graph of SEP measured on WTRTI from 600kph down to 400kph for the F-15A, F-16A, Mirage 2000, and the Gripen.

The only thing that this graph tells us is that the F-15A has the worst energy retention of the bunch and that the Gripen has the best…and it is by a wide margin.

This doesn’t necessarily tell the whole story because all of these planes will have different angles of attack in order to max perform their turns. For all of these planes their AoA ranges from 22 degrees to 24.5 degrees.

In fact one of the reasons that the M2K looks very appealing in the SEP graph is because it is pulling a noticeably lower AoA then anything else.

The Full Picture
These two graphs aren’t really enough to draw any conclusions from because they don’t clearly showcase how different all of these planes end up performing. In order to do that we need another graph; and it’s basically the same one I posted before.

This is initial turn of all of these planes measured over 8 seconds. The reason that it is only 8 seconds is because as SEP gets closer to 0 the readings that WTRTI gives tend to bounce around and I don’t feel like doing math. The speed range is also dictated by being below a threshold that reasonably avoids pilot black out. In pretty much all of these planes if you try to max performance turn while above 700kph your pilot will black out and then you will accelerate past 700kph again.

So what does this graph do for us? It helps us reconcile the efficiency of the different air frames with the way they are modeled in the game. Our dashed lines are the turn rates after a certain period of time.

There are a couple of conclusions that we can draw from this chart about initial turn rates.

First off the Gripen absolutely blows everything else out of the water. It has the highest initial turn rate and maintains it longer than anything else. The margins that the Gripen beats everything else by is extremely wide.

Second we can see that the F-16A beats everything else on the chart for its initial turn rate…but it comes at a cost too. It pays for that initial turn rate with energy loss.

The Mirage 2000 represents an interesting case because mouse aim limits the amount oof AoA that it produces which is why its SEP number looked so good in the previous chart. It’s initial turn matches the F-15 but maintains it for longer. Even with reduced AoA though it still bleeds speed faster than the Gripen.

Let me put this in laymans terms; by the time that the F-16A and Mirage 2000 reach 24 degrees per second…the Gripen is still pulling at 29.1 degrees per second. And by the time both of those planes reach the lower end of the turn speed…the Gripen is still chugging along at a comfortable 25.7 degrees.

What It Means?

In-game the F-16A enjoys an initial turn rate advantage over its real life counterpart by wide margins; so much so that it ends up being higher than the Mirage 2000.

In reality the Mirage 2000 should enjoy an initial turn rate advantage over the F-16A. It should also enjoy better low speed performance…which it actually does as long as SAS Manual is not engaged.

The Gripen on the other hand takes the over-performing F–16A…and separates itself by an even wider margin. This SEPeration is actually even more obvious in the SEP graph where at high speeds the Gripen is losing energy at what averages out to half the rate of the F-16A.

As far as gameplay is concerned that means that whenever the Gripen goes up against any fighter it is likely to find itself at a higher turn rate than whatever it faces, while also having similar or smaller radius and at a higher energy state. It means that what by all means looks like a close fight in real life is decisively one-sided in favor of the Gripen.

Is This Realistic?

No. It is not realistic at all. It’s not realistic by any reasonable standard. Yes…all of these flight models will hit some datapoints on the turning graphs that are available. There are no graphs available for the Gripen; at least none that go into any sort of detail.

What we do know about the Gripen is basically that it is a close fight with other 4th Gen planes, that it is probably capable of around 20 degrees per second for sustained rate, and that its low power to weight ratio is offset by lower wing loading.

We also know that the plane is unstable and has a canard. There is nothing in my research that suggest that the canard is inherently more efficient than the conventional layout of the F-16; in both planes they basically function as additional wing area to an extent. In fact I think the strength of the canard layout is that unstable designs are able to fly at higher AoA limitations without risking deep stalls…i.e falling out of the sky.

With that being said I also don’t see a reason why a full delta-wing on an unstable platform would not be equally capable if given the same total wing loading. At the end of the day all 3 of these planes are poorly balanced pizza slices that are being flung through the air at high speeds. I just have not seen any evidence that putting canards up front should translate in the efficiency increase that we see in-game.

I am not saying that the Gripen shouldn’t be more efficient than the Mirage 2000 or the F-16A…but the benchmark we are using is one of the most over-performing and unrealistic planes in the game…and it completely blows it out of the water.

Additional Information

Here are new charts for F-16C, Gripen, M2K, and Su-27 based on minimum fuel value instead of 20 minute value from previous chart. Gaijin min fuel value is 30% of total so might be a little more fair as opposed to 20 minute value that gives 2/3rds tank for Gripen and 1/3 tank for Su-27.

These are rough max performance turn rates of Gripen, Su-27, F-16C, and Mirage 2000.

These are the SEP values for the Gripen vs Su-27, F-16C, and Mirage 2000.

Basically, the Gripen will blindly destroy any other plane in the game because of extremely generous specific excess power values. Not only does the plane have a better initial turn than everything else…but it will maintain that turn for significantly longer than anything else.

In effect what this means is that the only thing a Gripen player needs to do to win a dogfight is to just hold the S key and hold lag pursuit against any comparable opponent.

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Was fun while it lasted…