Issues with the JAS 39 Gripen flight model

Yep, But ill also add to my previous statement that i have done no meassuring and i’m going solely on the “turn time” numbers on the stat cards.

Edit:
Mig_23 even did research on this and made a report on it when gripens turn rate at release was 25deg/s
https://community.gaijin.net/issues/p/warthunder/i/YKhI5oNKuwKG

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They did it too much.

Previous report clearly states that Gripen should have 20 degree per second but right now it doesnt even come close to what it should be.

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@MiG_23M Hey, do you have the possibility to test this new turn rate?

i don’t know how to do stuff like that (but if you have the time i would love to learn).

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I agree with you, wholeheartedly.

FM should be as close to their irl counterparts, it favors better balancing, if it has a realistic FM it’s easier to balance than changing it every 2 month.

Gripen still feels weird because canards behave unlike they should, at least it’s no longer broken and may lose to the other UFO that is the F16A and I’m quite happy with it.

We’ll have to wait and see.

Thanks for the answer peeps !

New data suggests it is still overperforming slightly in rate and heavily in SEP. I’ll be able to write more details in a few days. 20 deg/s sustained turn is likely possible, but not on full fuel load. Likely not even on half.

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I don’t think they ever tuned the flight model like they said in changelog

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Still the 15 deg/s seems pretty unrealistic, it seems more like gaijin placing a bandaid on a problem they either don’t care to fix or dont know how to fix. Ive been dogfighting against the gripens recently in some customs and in actual matches with my f16 and im winning nost of my fights cause im able to outturn them. I think if they fix SEP they should change back the their turning cause right now they dint seem like a 4th gen fighter to fight against.

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I mean the F-16 is overperforming heavily as well right ?

I don’t think the F-16 is the best point of comparison.
But yes it does seem to lose to the F-16 which is a great start from how BS the FM was previously

Who said it’s 15 deg/s? It’s certainly not worse than the phantoms right now.

Not in sustained turn rate necessarily. Only in stability and AoA beyond 25°, which it never exceeds in normal air RB outside of stalls.

The Gripen exceeded the specific excess power of superior energy maneuverability fighters like the F-16 by 2x before these changes. I’ll test it again soon… But it was quite absurd and the overperformance translated to air RB as well.

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Necronomica mentioned it. Also it definitely isnt accurate rn that a min fuel gripen cant turn with an f16.

That’s not surprising. No way the US was left unable to be the meta nation. Just wait until we get the Typhoon that cant out-turn a mig-23 or F-4

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I dont expect this from A and C model, maybe JAS39E can do that tho.

Gripen squadrons have made the claim of 20 deg/s without context. The truth depends highly on payload, but that isn’t modeled in-game.

For example, with two AIM-120’s and two AIM-9’s & a drop tank… the top speed is reduced to mach 1.4 at altitude from 1.8-2… this makes it inferior even to the F-18 in BVR considerations irl whereas it can get to mach 2 fairly quickly in-game before the thrust was fixed… even with max payload.

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That goes in both ways, other planes also have reduced top speed when equipped with ordinance.

Yes, I compared it to the other slowest BVR contender the F-18, and the Gripen is abysmal in this regard. Well below peers.

There is things to consider though:

First don’t know if the limit comes from the drop tank, maybe the drop tanks are limited to 1.4M, we would need to check if they have a safety limit for those. No idea honestly.

Secondly: This kind of confirms that the Gripen is an exceptionally low drag design, if it’s top speed is impacted by that much just by carrying ordnance.

Although I again, don’t know how fast other planes are with similar loadouts, maybe they have roughly the same speed loss, but you make it sound like they don’t so I figured the statement about the drag is justified.

The Gripen has a number of devices used to increase lift when angle of attack is involved. The delta canards design is better suited to high speed but the engine is not. Optimizing drag for supersonic speed was necessary. Turning at subsonic speeds should result in worse performance because of the high lift devices and relatively low T/W in comparison to other fighters. Stability is high, stall speed is low, but the basic design is not suited for high turn rates.

A couple of issues, the thrust overperforms slightly (but matches the correct curves now)… and the aircraft FM was adjusted to match sustained turn charts while remaining wholly statically stable. This means that the canards produce positive instead of negative lift and aid the aircraft in ways they shouldn’t.

Yes, the canards aid them because they contribute to lift right now.

But that also means that the FM underperforms in agility because of it.
If they were to fix the stability then the Gripen should have snappier control but less sustained performance, right?

No

Also no

The canards contribute to lift, so the entire FM is erroneously modeled to match the turn rates with the aid of the canard. Change this to unstable and the negative lift from the canard would be detrimental to the performance but obviously that would need to be amended when they fix the FM.

Because the FM is accounting for the positive stability already, it doesn’t “underperform” in sustained turn. It is modeled to match the few known parameters while being statically stable. These are turn rate, top speed (clean) and acceleration. For the instant turn rate and sustained turn rate to match real world data while also being statically stable, the resultant specific excess power was far too high. The energy loss rate at higher angles of attack was too low.

To amend the issue would require a ground-up fix with essentially a new FM and they can’t do unstable designs until they rework instructor. They won’t be able to fix the Gripen until the entire FM portion of the engine is overhauled.

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