DCS: AJS-37 Viggen Discussion

[BlackLion213]

Great info guys, thanks. :)

 

-Nick

[Pilum]

Are you sure that 17.5 for the Mig-23 is Substained turn Rate and not instantaneous turn rate?

 

And does it Specify what Mig-23 variant it is?

 

Since there is a huge difference in Maneuverability performance between the different mig-23 variants.

 

The Manual numbers for the mig-23ML/MLA is a Max sustained turn rate of 14.1 deg/sec and a maximum instantaneous turn rate of 16.7 deg/sec.

 

With the earlier Mig-23s being alot less maneuverable.

 

And while the last Mig-23MLD variant had some modifications i find it hard to think the Sustained turn went from 14.1 to 17.5 =P.

 

(Especially as most MLDs were upgraded From ML/MLAs and as such there were no Huge changes to account for that change in performance)

 

So is it possible they confused Instant turn rate with Sustained turn rate for the Mig-23.

 

Since that takes it alot closer to the manual specs and also more inline with the other 2 (if still slightly ahead)

 

Ahh dang xD Fri Beat me to it.

 

Yes, and I calculated that while it is theoretically possible for the Mig-23 to do 17.5 deg/s sustained at M=0.8 from an aerodynamic standpoint since it would require a T/W ratio of 0.83 which is reasonable BUT the g-load would be 8.7 g with fully forward wings which would most likely snap them right off....

[mattebubben]

Yes, and I calculated that while it is theoretically possible for the Mig-23 to do 17.5 deg/s sustained at M=0.8 from an aerodynamic standpoint since it would require a T/W ratio of 0.83 which is reasonable BUT the g-load would be 8.7 g with fully forward wings which would most likely snap them right off....

 

The Mig-23s G-Limit is stated as 8.5 and im pretty sure that is not with the wings fully forward so a 8.7G Turn would most likely snap the wings like twigs.

 

But we are getting off topic with the Mig-23 talk ^^.

Edited May 8, 2016 by mattebubben

[Hummingbird]

A little note: The comparison chart showed earlier is part of an early edition of the Fighter Weapons Symposium series by Dick Pawlovski & Glenn Hall.

 

 

 

 

Here's a Mirage 2000 chart from a later edition, also for 15,000 ft (been posted quite a few times by now):

 

 

 

STR at 15 kft = 12.5 deg/sec

 

The charts in this series are however calculated and thus should never take precedence over the EM charts in the official performance manuals which by comparison are based on real flight testing. The charts in the FWS series gives you a rough idea of how some aircraft compare and are generally more accurate the newer the edition.

 

Just a heads up before anyone starts drawing any conclusions based on that earlier chart.

Edited May 8, 2016 by Hummingbird

[robban75]

Thanks for posting those figures Robban. Have to confess I'm pretty pleased with my ballpark estimate for the AJ at 12.3 deg/s.....

 

No problem! If you read swedish I can highly recommend the book, System 37 Viggen, Flyghistorisk Revy by Ulf Edlund and Hans Kampf. :)

 

You can actually get decent turn performance in an attack aircraft as well if you choose the right configuration. It's history now but there were many proponents of a more conventional Gripen swept wing design both internally at SAAB and at KTH, FMV and FFA but the canard faction won out in the end. I happen to side with the former but then I'm a big fan of professor Sven-Olof Ridder......

 

I really liked the 2107 design. See link below. :)

 

http://img.photobucket.com/albums/v486/robban75/URGripen1-1.jpg

 

The unstable delta/canard config was in the end chosen mostly due to superior transonic and supersonic maneuverabilty.

 

But I digress. :music_whistling:

[robban75]

Also surprised at Viggen, according to list, is quicker to reach M 1.6 @ 11K figure than MiG.

 

I am not claiming being an aerodynamicist by any stretch, don't get me wrong. But MiG-23 is known for it's speed and acceleration, that is apparently even better than some of 4th gen fighters, yet it is also known for being pretty horrible as a dogfighter, even less of a close-up fighter than it's predecessor MiG-21.

 

I have found those figures very surprising.

 

Something that comes up several times in the book "System 37 Viggen" is the brute force of the engine and the acceleration it provided at zone 3 afterburner. :)

 

One pilot describes the performance on dry thrust as being not too impressive. Zone 1 was used to maintain combat speed when heavily loaded with bombs and missiles. Zone 2 was used for acceleration, and on take off. Zone 3 on the other hand, is were stuff really started happening. The word accelerate doesn't quite describe it. The Viggen bolts(correct word?) away!

 

Using zone 3 on take off you rotate after 400m, and the end of the runway is passed at 800km/h. A km later you have Mach 0,8. You pull up at 4-5 G while the speed continue to increase to Mach 0,9. The climb angle is now close to 80 degrees, at 6,000m it starts to ease out so that at 10,000m it is a mere 30 degrees. On a cold winters day the time from take off to 10,000m took less than 90 seconds!

 

With 50% fuel and zone 3 the acceleration is so strong that keeping your head from touching the head rest was quite difficult. After pull-up the climb angle had to be no less than 85 degrees. Even the slightest lowering of the nose and a transonic warning would go off(yellow light) following supersonic speed.

[renhanxue]

Yep, I did see some parts of the SFI were posted earlier but sadly I have not found any turn data either but since these parts of the SFI are AFAIK now no longer secret then maybe some kind soul could scan them? :music_whistling:

I would have done so if those chapters had been in the binders I got to see at Krigsarkivet. They were not, though, and as far as I understand it it's because they haven't been sent to the archives (or they could just be misplaced, the collection of secret publications seems to be in a bit of a mess with regards to sorting - in one of the AJ 37 SFI binders I found a 30-page document detailing basic fighter training procedures for fighter squadrons equipped with J 35D and J 35F, and I have been unable to get a satisfactory answer as to why it was there).

 

I've requested to have the AJS 37 SFI declassified too though and the missing chapters might turn up there. No answer yet, however, and it could take months before I hear anything.

 

Footnote: As I heard it, Chuck Yeager tried out the Viggen and his comment was something like this goes the legend: "Well, it's a nice plane but I have never flown one that slows down so fast when you try to turn it!"

Yeager hated the Viggen and spent a whole interview (in Flygvapennytt or possibly in Flygrevyn, IIRC? - I think it's reproduced in one of the Viggen books too) being salty about it, probably because he was exiled to the back seat in the SK 37 despite being Chuck f'in Yeager. I'll try to find it, it's hilarious, he just goes on and on and on about how awful it is.

Edited May 9, 2016 by renhanxue

[robban75]

Yeager hated the Viggen and spent a whole interview (in Flygvapennytt or possibly in Flygrevyn, IIRC? - I think it's reproduced in one of the Viggen books too) being salty about it, probably because he was exiled to the back seat in the SK 37 despite being Chuck f'in Yeager. I'll try to find it, it's hilarious, he just goes on and on and on about how awful it is.

 

Yeah, the entire interview is published in the book I quoted above. :) And yes, he really was noticably offended by having to fly from the rear seat. :D I can understand him though. He was mostly negative in the interview but there were some positives. He liked the power to weight ratio, how stable it was in flight and that it was very easy to fly. :thumbup:

 

Another interesting story is about the "wacka" maneuver. It's basically a cobra as far as I understand it. The pilot explains that he first encountered it when dogfighting a J 35 Draken. He was almost ready to take make a kill when the Draken in front of him swiftly raised its nose and with the sudden speed loss swooshed by him.

He later asked the Draken pilot about it and decided to try it himself. The Draken pilots never had to worry about over stressing the airframe, the Draken could withstand anything. With the Viggen I had to be more carfeul. I entered the maneuver when the speed was around 350km/h. Stick full back, rapid nose up. Barely 4G, angle of attack probably around 45-50 degrees. The maneuver was easy to perform.

Max allowable AoA for the AJ 37 was 18 degrees. However it was quite easy to make a half roll with AoA of 27 degrees. It was important to be in full zone 3 burner during the maneuver.

Edited May 9, 2016 by robban75

[renhanxue]

Also surprised at Viggen, according to list, is quicker to reach M 1.6 @ 11K figure than MiG.

 

I am not claiming being an aerodynamicist by any stretch, don't get me wrong. But MiG-23 is known for it's speed and acceleration, that is apparently even better than some of 4th gen fighters, yet it is also known for being pretty horrible as a dogfighter, even less of a close-up fighter than it's predecessor MiG-21.

 

I have found those figures very surprising.

I have no idea if the numbers for the MiG-23 are accurate, but I translated a few climb and acceleration graphs from the AJ 37 flight manual (SFI) for those who do not speak ärans och hjältarnas språk. Since the graph labels are the same for all the graphs, if you want to go look up more numbers for other situations you can use these as a key.

 

First, the aircraft loadouts are divided into five groups: clean aircraft with no external load (rent fpl), and four groups numbered 1 through 4. Loadouts that are representative for each group can be found in this table, which lists both aircraft weights and drag indexes:

 

 

Note that 100% fuel means 100% internal fuel. If the drop tank is fitted, max fuel is 124%. To understand the leftmost column, use this key of abbreviations:

 

 

 

Now, takeoff and acceleration to M 0.55 (distance-economical airspeed at sea level):

 

 

 

Climb with clean aircraft:

 

 

 

Climb with the heaviest and draggiest loadouts possible:

 

 

 

If you want more graphs, see part 3 of the SFI.

Edited May 9, 2016 by renhanxue

[Pilum]

@Robban and renhanxue: Thanks for the info posted and the elaborations on what Mr Yeager had to say on the Viggen. If he was relegated to backseat driver I can see that coloring his assessment ;). Also, a special thanks renhanxue for the SFI parts and translation posted: Great info and hope your request for the complete AJS 37 SFI gets processed and “avhemligad” so we can see the turn rate and other performance goodies for ourselves.

 

About the Gripen: OT for sure, but since the subject came up: Those of you who can, either read the whole story in “Ridders reservation” published by Mach magazine May 1989, or the Royal Institute of Technology report “Flygtekniska problem med canardkonfigurationer”, KTH AERO MEMO FI 192, by Sven-Olof Ridder more prosaically known as “Ankdödaren” (The canard killer) in the Swedish aeronautical community (in some parts anyway :)). There is a 13 point “canard killing” summary listed in this report which has never been successfully refuted by the acolytes of the canard and which is worded so it's accessible both to laymen and professionals alike. Highly recommended reading.

 

All this may come across as too negative but make no mistake I’m not dissing the Viggen’s combat effectiveness: It’s just when it comes to the merits of a canard I side with professor Ridder that’s all. As my avatar and sig implies I have worked with EW systems, including the Viggen’s, and when it comes to the combat effectiveness it rates high IMHO opinion but that is more due to the system capabilities in terms of datalink, radar and EW systems etc. all working in synergy rather than the aerodynamics.: I mean the other guy can have a tremendous turn rate capability but how will it help him if he can’t find or lock up his enemy due to a confusing radar display or if his first warning of a Viggen in the vicinity is a RB 74 up his tailpipe? :music_whistling:

[robban75]

If my memory serves me correctly, there should be a switch in the cockpit labeled war/peace. The Gripen has one also and it is located on the right side panel slightly behind the pilot. It is tied with a very thin copper wire which locks it in peace mode.

 

Forcing the switch to war mode boosts(at least) engine and radar performance. I don't remember by how many percent though.

 

Anyone here to shine a light on this? :)

[Jediteo]

Nothing like that in the AJS. There used to be a small metal plate in the JA37 to limit the top end of the afterburner in order to lessen the wear on the engine, but no avionics changes beyond operating procedures in peacetime / wartime.

[Pilum]

If my memory serves me correctly, there should be a switch in the cockpit labeled war/peace. The Gripen has one also and it is located on the right side panel slightly behind the pilot. It is tied with a very thin copper wire which locks it in peace mode.

 

Forcing the switch to war mode boosts(at least) engine and radar performance. I don't remember by how many percent though.

 

Anyone here to shine a light on this? :)

 

I guess many of us who have worked with the systems can but the problem is that even after so many years and the Viggen decommissioned and all it's still difficult to know what is open info now days and what is still classified which is why I tend to stay away from discussions involving these systems. All I can say is that I almost choked on my coffee when I first read to what level of detail the Viggen and Gripen EW systems were described here:

 

[ame=http://www.vikingroost.org/pdf/MMrapport__utg_2.pdf]Svensk Motmedelshistoria[/ame] .

 

I think it's a very good read. :smilewink:

 

EDIT: I know it's in Swedish but for those of you who, as renhanuxe so eloquently put it, do not speak "ärans och hjältarnas språk" there is always google translate to lean on!

Edited May 11, 2016 by Pilum

[Mjau]

I guess many of us who have worked with the systems can but the problem is that even after so many years and the Viggen decommissioned and all it's still difficult to know what is open info now days and what is still classified which is why I tend to stay away from discussions involving these systems. All I can say is that I almost choked on my coffee when I first read to what level of detail the Viggen and Gripen EW systems were described here:

 

Svensk Motmedelshistoria .

 

I think it's a very good read. :smilewink:

 

EDIT: I know it's in Swedish but for those of you who, as renhanuxe so eloquently put it, do not speak "ärans och hjältarnas språk" there is always google translate to lean on!

 

This is not my area of expertise so I might misunderstand, but this sounds amazing:

 

"Även prov med långa remsor, remsband, som var hoprullade kring en tyngd, provades mot danska radarstationer med låg bärfrekvens. Verkan var helt bedövande och delar av Danmark mörklades av de långa ledande remsorna, som kortslöt kraftledningar."

 

So, just chaff deployed from a dispenser mounted on one Draken had the effect of basically blinding parts of Denmark and even shortcutting powerlines? :huh:

 

I suppose low freQ radar sacrifices "signal strength" for longer range but still... Will the viggen have these amazing pods? :D

[renhanxue]

I interpret that as the lines falling over power lines by accident, short circuiting them.

[renhanxue]

I think it's a very good read.

It definitely is. I noticed one sentence when talking about Lansen countermeasures, namely:

Störgrupp A avsåg utrustning för att störa fiendens navigering. Sådan togs fram och gjordes operativ, men är nu skrotad.

I'm pretty sure that refers to RT-02, a network of fixed jamming stations that was supposed to interfere with the Soviet equivalent of LORAN radio navigation - in the ideal case imitating the signals and faking them so well that the Soviet aircraft wouldn't notice that it was leading them wrong. Read that article, it's very interesting.

 

 

Speaking of radar and ECM, if you're interested in the subject as a layman and want an accessible and reliable source to learn from, I highly recommend Lärobok i telekrigföring för luftvärnet: radar och radarteknik, which goes over all the elementary radar knowledge first (it's a very nice and pedagogical explanation and it's very nice to have it in Swedish) and then covers a lot of countermeasure methods in general terms. It is available for free online:

 

[ame]http://www.luftvarn.se/hot/tklv.pdf[/ame]

Edited May 11, 2016 by renhanxue

[Mjau]

I interpret that as the lines falling over power lines by accident, short circuiting them.

 

Oh yeah, that does make more sense! :D

 

I imagine EW systems must be the most difficult to simulate in DCS? Probably a lot of guesswork as most of it is classified.

 

I've heard a lot of times the Gripen is supposed to have a really good EW suite. Maybe the Viggen had to. Wonder if that in anyway would be possible to represent in the sim

[Pilum]

Well the Viggen EW suite, everything from RWR, jammers and chaff dispensers are covered in the link I provided. If you read about KA, KB, U22 and U22A you will see that that the focus is on deception jamming, not noise jamming.

 

In fact the jamming model in DCS is very crude: It is basically WW2 level technology barrage noise jamming which means that the radar burns through at long distances. This is very different from more advanced modern techniques where the victim does not even realize he has been deceived, such as the RT-02 navigation jamming renhanxe linked to.

 

I agree it would be nice with a more sophisticated jammer model but I don't think that is going to happen since even if the U22 etc are modeled with the deception modes detailed in the doc I linked the crux is that that needs to be translated to how the radar model in the target aircraft would be affected and how this would look on the display. There are clues to how this could be rendered in the doc renhanuxe linked, showing how deception jamming could be presented in the affected aircraft but since this would involve updating how this is rendered in ALL aircraft in DCS I seriously doubt it's gonna happen...:smilewink:

 

The doc renhanuxe posted is IMHO a gem if you are interested in EW and the first time I saw it I was surprised to see active illumination of chaff for deception, towed decoys and advanced deception jamming techniques so well described. All this is a bit different from the current wait until burnthrough then turn and notch and dump chaff modus operandi DCS fosters......

 

How good the Viggens EW suite actually was is to some extent covered in the doc i linked. However, when it comes to the effectiveness of the Gripen EW suite, I think I will pass on that one.....:smilewink:

[dartuil]

Hello can someone from LN tell me :

When AJS-37 be out in june (lol let me dream) will it be out for 2.0 or 1.5 first? :)

[Agremont]

Hello can someone from LN tell me :

When AJS-37 be out in june (lol let me dream) will it be out for 2.0 or 1.5 first? :)

 

Good question. That never even crossed my mind.

 

I hope 1.5 as I don't have Nevada.

[Vitormouraa]

Hello can someone from LN tell me :

When AJS-37 be out in june (lol let me dream) will it be out for 2.0 or 1.5 first? :)

 

I think nobody knows at this time. They didn't say anything about releasing the Viggen in 2.0 first or vise versa. We need to keep the eyes open and see what they say.

[hughlb]

Aren't Leatherneck developing terrain to go with the Viggen? If they were planning to release the terrain and aircraft together, they'd have to wait for the 2.5 merge. But I'm speculating.

[Skjold]

Aren't Leatherneck developing terrain to go with the Viggen? If they were planning to release the terrain and aircraft together, they'd have to wait for the 2.5 merge. But I'm speculating.

 

They are, but that doesn't mean that it has to come along with the Viggen itself it could be added later.

[Valinor]

I was out from the loop a little bit, was the Viggen supposed to come at the end of May? Or June? Or later?

[Sim Flyer]

The latest news from ED says first half of 2016 so i am guessing before end of June but as always everything is subject to change :)