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Is the FM right? This thing is like acrobatic supermaneuverable wonder.


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On 1/15/2021 at 3:16 PM, Skysurfer said:

The fact you can go M1.45 at sea level until your fuel runs out should raise somequestions. Despite what some people say the thing can turn and outclimb anything in the game.

 

You realise low and fast was the main design goal right? The operational limit was probably for maintenance above all else, we don't really have the maintenance aspect in DCS, though it would be better if we had improved engine damage modelling, kinda like HB's F-14A. 

 

But as for operational limits the Tomcat can go to +9G but operationally, late in its life time, was operationally limited to something like +6.5 or something.

 

I watched your 3 videos which were fairly impressive.

 

Though I noticed a pattern, in 2 of your kills, you got them against aircraft that weren't reacting due to a lack of SA and nothing on their RWR; you could do a similar thing in basically every aircraft so long as you can catch up. You also had a pretty good tactic against Hornets getting too greedy - outrunning them at low altitude, something the Viggen was designed to do, and the Hornet isn't exactly the fastest thing around either.

 

The first one seemed to forget about you when you turned hot, and then put his tail on you as you got close; even though your first missile missed, the Hornet didn't deploy countermeasures, which was also common to all of your engagements.

 

The second Hornet was firing AIM-120s at 15+nmi against a tail-aspect target going supersonic, near and through a mountain range, while the Hornet was subsonic - I'm not sure what that Hornet was hoping to achieve.

 

Then the Hornet got greedy, probably thinking you were just running away, the Hornet looks to have lost sight of you as you turned and was slow to react (and went for a 1 circle when it was probably the wrong thing to do, if the Hornet went 2-circle, it might have worked better), you were in a high energy state, and so you were able to get a very good instantaneous turn (like you should be able to), that the Hornet was slow to react to (it looks like he only saw you just before you looped around) and you downed him with a missile. 

 

On 1/15/2021 at 10:48 PM, Skysurfer said:

You don't use it as a dogfighter. The AJS37 with 4x AIM-9L's is an excellent interceptor and boom and zoom aicraft. Does it better than anything in the game since the operational limit of 1350kph doesn't seem to apply in DCS.

 

It's about as good as a MiG-21bis, only with an even less useful RADAR in A/A, but compensated by superior AAMs, and an ever so slightly better RWR and that's it.

 

 

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12 hours ago, Northstar98 said:

 

You realise low and fast was the main design goal right? The operational limit was probably for maintenance above all else, we don't really have the maintenance aspect in DCS, though it would be better if we had improved engine damage modelling, kinda like HB's F-14A. 

 

But as for operational limits the Tomcat can go to +9G but operationally, late in its life time, was operationally limited to something like +6.5 or something.

 

I watched your 3 videos which were fairly impressive.

 

Though I noticed a pattern, in 2 of your kills, you got them against aircraft that weren't reacting due to a lack of SA and nothing on their RWR; you could do a similar thing in basically every aircraft so long as you can catch up. You also had a pretty good tactic against Hornets getting too greedy - outrunning them at low altitude, something the Viggen was designed to do, and the Hornet isn't exactly the fastest thing around either.

 

The first one seemed to forget about you when you turned hot, and then put his tail on you as you got close; even though your first missile missed, the Hornet didn't deploy countermeasures, which was also common to all of your engagements.

 

The second Hornet was firing AIM-120s at 15+nmi against a tail-aspect target going supersonic, near and through a mountain range, while the Hornet was subsonic - I'm not sure what that Hornet was hoping to achieve.

 

Then the Hornet got greedy, probably thinking you were just running away, the Hornet looks to have lost sight of you as you turned and was slow to react (and went for a 1 circle when it was probably the wrong thing to do, if the Hornet went 2-circle, it might have worked better), you were in a high energy state, and so you were able to get a very good instantaneous turn (like you should be able to), that the Hornet was slow to react to (it looks like he only saw you just before you looped around) and you downed him with a missile. 

 

 

It's about as good as a MiG-21bis, only with an even less useful RADAR in A/A, but compensated by superior AAMs, and an ever so slightly better RWR and that's it.

 

 

 

Yes, someone with less or no SA will always lose, regardless of airframe. I don't know the specifics of whether the AJS actually could go that fast as all the published perf. charts end at the stated limit speeds but I do know for a fact that it is 1) way better than the Mig-21 both in top speed and climb performance (worse in turning obviously) and 2) working in the industry and having studied aircraft design and performance I know for a fact that thermal heating and designing a non-variable intake would be an issue and/or next to impossible to sustain. Especially in the 70's. I guess this isn't so much of an issue of Heatblur simulating the thing compeltely wrong or being off on thrust and drag values but either a bug or the simple fact that most of these modules don't have an extensive damage model. These limits are there for a reason and ignoring them should have at least very simple consequences. They have gone to great lenghts with this in the Tomcat (comp. stalls, G limits and aiframe + component fatigue) but even on the Tomcat after almost 2 years the flight model is still being tuned and new bugs get introcudes every now and then (as of the current OB build). In my opinion, after the Tomcat is done or out of EA they really need to revisit the Viggen, address the main issues, take a new look at the FM and perf. figures and polish it up. It was supposed to be out of EA last year but that didn't happen either.


Edited by Skysurfer
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On 1/16/2021 at 5:30 AM, Freefall57 said:

Dmitri and Skysurfer should go online and use this new found super maneuverability of the Viggen to dominate. Out turn and out climb them all!

 

Speedwise, this has been common practice on cold war servers for some time. Turning, not so much - it turns well but only does so once or twice before it falls down and can't get up. I haven't really looked into climb performance, but the thing has a delta wing and a boatload of thrust, I wouldn't be real surprised if it was in the realm of the MiG-19 or so.

 

The big questions I have regarding its FM are speed related, but its turn performance is about what I'd expect. The only caveat is that it seems to gain early-release F-14 levels of "free lift" if you force the flaps down by lowering the gear, but it's very rarely done and it usually isn't enough to make a difference anyway. It tightens its turn circle with no real penalty to rate or airspeed but that's about it.

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Excuse the double post...

 

On 1/21/2021 at 4:40 AM, Dragon1-1 said:

It's not unrealistic, there's a reason it's called "AJS-37". Remember, it's a supersonic aircraft with a very powerful engine and canards, meaning it's actually a surprisingly competent fighter. Yes, M1.45 at sea level is realistic performance for an engine this powerful. It can turn and it can climb, and it can carry four Sidewinders. This would put it in league with the MiG-23, sans the radar. However, if you're launching heaters under GCI guidance, the Viggen's radar works just fine... which is also how you would use a MiG-23 with GCI.

 

Viggen isn't very competent in guns combat, but that's because its gunpods are inaccurate and way too spread out to be really good at air to air, not to mention it has to sacrifice a pair of Sidewinders to carry them, which are its real teeth. As a fighter, the AJS-37 works exactly like it does in ground attack role. One pass, haul ass. It's not the greatest interceptor in the world, but it's not the A-10, either.

 

Case in a point, it's the only aircraft that is acknowledged to have locked the SR-71 up on FCR. I don't think it was the AJS-37 specifically, but the Viggen seems to have changed relatively little between versions.

 

As already pointed out, no, it can't do 1.45 on the deck. Even if you ignore the aircraft's stated limitations (which the community seems to think are "suggestions" - there are no "recommended" maximums in aviation, unless you don't fancy living until retirement), SAAB's planned record attempt aircraft was to be stripped of weapons systems and radar, polished metal, and with all external antennas stripped away. Yes, it's a ridiculously powerful engine, but that isn't the only factor here. The MiG-25 has two ridiculously powerful engines and can barely clear the sound barrier on the deck. The Viggen is a cleaner airframe maybe, but you're still fighting drag in the thick air as well as running into operational limits of both airframe and engine, to say nothing of how profoundly uncomfortable high speed, low level flight is (both for you and the airframe).

 

MiG-23's Vne is 1450km/h, 100km/h above the AJS-37 but exactly on par with the JA-37. The 29's is... somewhere in the same vicinity. 1450 I think, I very much doubt it'd be higher than 1500 at best.

 

The Viggen locking up an SR-71 story is bandied about a lot but is neither impressive nor the full story. Warsaw Pact nations practiced intercepts against them regularly and at least one account exists of a MiG-23 achieving lock and asking for permission to fire (no doubt just to say he was in position to do it, it was still over NATO territory at the time). There is no special magic attribute about the SR-71 that makes it hard to lock, it's a large, tremendously fast moving object and its low frontal RCS isn't going to help as much against look-up, nor do much to offset the fact there's nothing else up there and its closure rate is massive. The main difficulty is in getting your timings right, as you only have a few seconds from it entering your lock range to passing inside your minimum launch range. If you're trying to intercept one in pursuit, you've already screwed up. Now getting an effective shot away, that would be something to brag about - but thankfully nobody has the rights to that one.


Edited by rossmum
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The fundamental issue (which is not just the Viggen's) is that in DCS top speed is set exclusively by thrust and drag, while in practice Vne is just a safety limit due to various effect like excessive heating. That's not really something that can be solved by HB, until it gets implemented by ED. The Viper has the same issue (and I wouldn't be surprised if in fact most modules did).


Edited by TLTeo
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1 hour ago, TLTeo said:

The fundamental issue (which is not just the Viggen's) is that in DCS top speed is set exclusively by thrust and drag, while in practice Vne is just a safety limit due to various effect like excessive heating. That's not really something that can be solved by HB, until it gets implemented by ED. The Viper has the same issue (and I wouldn't be surprised if in fact most modules did).

 

 

You can stall the MiG-21bis' engine by exceeding whatever stated maximum speed, but given that we don't have persistent airframes and always start with a brand new engine (effectively) is probably why its been omitted.

 

Though on the other hand, you can break the engine in the Huey if you overtemp it for too long, I imagine you could do the same thing for other aircraft and tie it into the damage model for the engine, as with what @Skysurfer said above.

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Sure, but neither are quite comparable because neither of those has anything to do with the whole aircraft heating up excessively. As far as I understand, that's the main thing setting vne on the Viper and Viggen.

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9 hours ago, rossmum said:

The MiG-25 has two ridiculously powerful engines and can barely clear the sound barrier on the deck. The Viggen is a cleaner airframe maybe, but you're still fighting drag in the thick air as well as running into operational limits of both airframe and engine, to say nothing of how profoundly uncomfortable high speed, low level flight is (both for you and the airframe).

 

It's not really a fair comparison since MiG-25 engines are turbojets and it was most certainly not designed for high performance at low altitudes, unlike Viggen. 

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8 hours ago, TLTeo said:

Sure, but neither are quite comparable because neither of those has anything to do with the whole aircraft heating up excessively. As far as I understand, that's the main thing setting vne on the Viper and Viggen.

Yeah, you would have to model structural deformation and damage due to aero heating. 

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20 hours ago, Dudikoff said:

It's not really a fair comparison since MiG-25 engines are turbojets and it was most certainly not designed for high performance at low altitudes, unlike Viggen. 

 

True, but the point is that people really overestimate the performance of a lot of aircraft, and reputations for being "fast" rarely include qualifiers. For a fairer comparison, the F-111 - which could go fast down low, but even that could only push about 1.2 at sea level. If there's a manned aircraft that's ever been able to maintain 1.45 at sea level, without being a stripped-out, mirror-polished record attempt modification, I'm not aware of it. Honestly (and not just from this module) it seems that when it comes to DCS, people only ever seem interested in capabilities, and would rather pretend limitations aren't a thing.

 

As for the consequences: this is exactly why some are needed, or none. Having some modules suffer consequences for exceeding limitations while others don't is not good in a sim with multiplayer functionality, because there will always be minmaxing and most of us probably have done it at some point, possibly even without realising it. "Just don't play multiplayer" isn't a solution, especially not with DCS' notoriously horrible AI. Either everything should exhibit limitations, or nothing should. I personally prefer the former as it makes things more interesting and requires people to actually use their brains rather than just send it and know the lack of out-of-envelope modelling will keep them safe. The 21's engine flaming out when oversped is a best case scenario, with fairly minor consequences (at least, as long as you know how to relight the engine) - which would work well enough for any module, I think. I'd love to see cumulative stress with each flight but realistically speaking, it isn't going to ever happen, and if it did most servers would go out of their way to disable it.

 

As for any other attribute, I can't really see where OP is coming from. The climb rate with drop tank and only two AAMs is pretty excellent, but seems (at a glance) to hit the numbers it's meant to.


Edited by rossmum
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46 minutes ago, rossmum said:

As for the consequences: this is exactly why some are needed, or none. Having some modules suffer consequences for exceeding limitations while others don't is not good in a sim with multiplayer functionality.

 

It's not good for a sim at all - it's inconsistent.

 

I wish DCS could pick xxxx and then stick with it consistently, instead of having this mix-up, and its the same in many other areas too; from how things are named, to tutorial missions and manuals, to what switches do when you left-click or right-click (and whether or not you can click the ejection handle to eject and/or click the throttles to idle), to limitation modelling, to 3D asset quality (while I'm grateful for new stuff, I'd rather concentrate on updating the old, then adding new stuff) and one of my main gripes; eras (which is literally a mile wide and an inch deep, spanning 70 years, but pick any one decade and there's basically nothing anything like comprehensive, with only WWII being the exception).

 

Quote

"Just don't play multiplayer" isn't a solution, especially not with DCS' notoriously horrible AI. Either everything should exhibit limitations, or nothing should. I personally prefer the former as it makes things more interesting and requires people to actually use their brains rather than just send it and know the lack of out-of-envelope modelling will keep them safe. The 21's engine flaming out when oversped is a best case scenario, with fairly minor consequences (at least, as long as you know how to relight the engine) - which would work well enough for any module, I think. I'd love to see cumulative stress with each flight but realistically speaking, it isn't going to ever happen, and if it did most servers would go out of their way to disable it.

 

Absolutely agreed.

 


Edited by Northstar98
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Modules I own: F-14A/B, F/A-18C, Supercarrier, F-16CM, AJS-37, F-5E-3, MiG-21bis, Ka-50, A-10C (+ A-10C II), UH-1H, Mi-8MTV2, P-47D, P-51D, FC3, MiG-15bis, Yak-52, CA, C-101, Hawk

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The flight model is, of course, not perfect.

It feels pretty decent in large portions of the envelope, but some things I'm not so sure about.

E.g. takeoff with dry thrust is very precarious, but from what I've been told is how they usually took off from a decent runway.

Also stall behaviour seems way too nice. The Viggen was susceptible to a (recoverable) superstall at AOA around 30 deg or so, but in DCS this is not the case.

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To be fair, most DCS players are going to be concious of the risk of losing the engine past 20-25 degrees and thus are unlikely to pull that hard. I don't even think I've done it, and my favourite party trick is parading the 21 about with the AoA pegged and the nose pointed to the moon.

 

Might be time to do some more destructive testing later...

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22 hours ago, Northstar98 said:

It's not good for a sim at all - it's inconsistent.

Well, in Viggen's case, overheating the airframe (as opposed to the engine) wouldn't do much to kill it. Prolonged, it might jam the landing gear, speedbrakes and RAT doors, but that's about it. IRL, the airplane would be as good as totaled, but in DCS, we don't have a system that would account for that.

 

I hope they fix it in the dynamic campaign. Flying the plane that far outside its limits should, realistically, cost you the aircraft, even if you get away with your life. The gap between "only good for spare parts" and "instant fireball" is actually considerable, and there's also a fair number of situations which leave aircraft serviceable, but dramatically shorten its operational life. The Tomcat had its limits reduced multiple times, when fresh from the assembly line, it could go over Mach 2 and 9G. Later on, it was more like Mach 1.6 and 6.5G at most. 

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On 1/21/2021 at 2:37 PM, Rudel_chw said:

+1 ... Wish Heatblur reads this topic ... I'd love to fly the JA  ... maybe they could sell is as an expansion Module with a price lower than the one of a full Module 

 

IIRC, but maybe i mixed something, HB wanted to make JA-37 but they refused to give them some data to model crucial systems like datalink etc. And HB didn't want to make some made up unrealistic guestimated bogus, what is very right choice.

 

But even 1980s Cold War JA-37 would be great, with AA radar, Sparrow-like missiles, more powerfull engine. All depends on data available i guess.


Edited by bies
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Came here for a read if the viggen is worth buying, I don't own it, but here are some things to consider:
Exceeding the Vne can be modelled quite easy. It can break your engine blades by exceeding the speed of sound inside the engine, ripping apart the whole engine. If the air inside your engine goes supersonic, your engine goes down the drain. At best it has a flameout, at worst parts of it rip everything apart.
https://www.airspacemag.com/military-aviation/how-things-work-supersonic-inlets-35428453/#:~:text=When a jet airplane is flying faster than,with fuel—is capable of handling supersonic air flow.
Flutter can occur (and will, on the F-16, with certain A/G stores above ~550kts sea level) which can result in hung stores or damage the airframe if you ignore it. The reason why you often see AIM-120's on the outer stores is that they stabilize the wing more than a sidewinder does. Another limit in the F-16 is the bubble canopy which might even break because it will heat up and get weak.
You simply do not exceed Vne because there is a specific reason for it and it will fubar important parts of the plane you are sitting in.
A Vne of 800kts (1480 km/h) at sea level seems to be a "magic border" which no one has not exceeded yet... The tornado rides that line, and it is said that it can exceed it. But then, you probably shouldn't.

Viggen sounds fun tho.

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