DCS: AJS-37 Viggen Discussion

[Nerd1000]

I don’t want to rain on the parade but if Leatherneck are going to deliver a true rendition of the AJS Viggen then those who intend to use that chart for planning how to deal with the other aircraft in the table are most likely going to be very disappointed:

 

 

The Viggen is NOT a good sustained turning fighter (Instantaneous yes, sustained no) and that it should have as good a sustained turning capability as the M-2000 defies logic:

 

 

1) Both planes have about the same span loading, i.e. wingspan/weight

 

2) The M-2000 has a somewhat lower wing loading

 

3) The M-2000 has a much higher thrust to weight ratio

 

4) The Viggen is a very, very stable aircraft and a lot of the weight is carried by the carnard. The M-2000 OTOH has fly by wire relaxed stability which significantly reduces trim drag in turns.

 

 

Now all these things taken together with the laws of aerodynamics and flight mechanics suggest that the M-2000 should make very short work of the Viggen in a sustained turn fight and makes me very suspicious as to the veracity of the table…….

Note the altitude and mach number. 0.9M is rather fast for a turning fight, don't you think? Makes me wonder whether it is relevant in the slightest.

[IASGATG]

Note the altitude and mach number. 0.9M is rather fast for a turning fight, don't you think? Makes me wonder whether it is relevant in the slightest.

 

Well the diagram says 14°/s for the F-15A. The actual F-15C rates in at around 13°/s sustained. The A and the C are different jets though, so the A might be able to sustain it better with the lower weight. That being said a completely clean and bingo Eagle only hits about 13.5°/s.

 

This is all for that speed/altitude.

 

As for your concerns about 0.9M, it's actually a pretty good benchmark number for that altitude engagement. It's only like 460kts CAS up at that alt.

 

I'd be curious to see what numbers people have for the other jets to weigh the validity of the picture.

[Dahlbeck]

Isn't the corner speed for at least the F-16 usually more around 350-400 KIAS at "normal fighting altitudes"?

[SkateZilla]

it's not classified as STOL or Anything with the Words Short Take Off or Landing.

 

it simply has a Thrust Reverser to use instead of a Brake Chute, which allows it to slow down, as well as taxi backwards.

[Pilum]

I just reported it as i saw it i cant say either way how accurate the chart is.

 

And im also not sure if its correct that The AJ 37 is that close to the M-2000 in terms of Substained turn.

 

But also to take into account is even if the Viggen would have a Comparable Substained Turn rate (if the chart is anywhere accurate) then the viggen most certainly bleed speed at a much higher rate then the mirage 2000 while doing those maneuvers.

 

 

But as already stated i simply saw the chart thought it was interesting and posted it here i cant confirm or deny if its accurate.

 

And until someone posts more charts of the Viggens flight / Turning performance it would be hard to say either way (Until the module comes out atleast)

 

But the Viggen does have a better Substained Turn rate then you might think.

 

Yes its not in the league of the F-15/F-16 or Su-27 / Mig-29

 

But its most certainly not a slouch when it comes to maneuvering.

Especially when compared to older aircraft.

 

Mattebubben: I know you only posted the chart and did not defend or vouch for it so no worries there. :)

 

I just think there is something strange with it. Maybe someone mixed up instantaneous with sustained numbers I don't know but at least the M-2000/Viggen comparison does not make sense IMHO. I don't think Tharos who AFAIK first posted the chart ever replied to the question where it came from and it would be interesting to learn the history behind it.

 

However, noticed you say the Viggen has a better sustained turn rate than I think so I would appreciate to know what that means? So what does the Viggen do? I have not done any calculations myself or seen any charts so I would be interested to hear how you came to that conclusion. Maybe we are using different terminology here because you say bleeding energy while doing those manouvers which I don't associate with sustained performance. However, if you are talking about instantaneous turn rate the I agree that the Viggen is no slouch as you put it.

 

Finally, charts of both would be nice but based on the four points I made previously I think anyone who thinks they will show similar sustained turn performance will most likely be sorely disappointed.

 

Note the altitude and mach number. 0.9M is rather fast for a turning fight, don't you think? Makes me wonder whether it is relevant in the slightest.

 

Actually, I think if you look a doghouse turn charts for jet fighters you will see that M=0.9 is a pretty good speed for sustained manouvering. IIRC then there is a nice M-2000 doghouse chart somewhere in the RAZBAM part of the forum.

[Vladinsky]

it's not classified as STOL or Anything with the Words Short Take Off or Landing.

 

it simply has a Thrust Reverser to use instead of a Brake Chute, which allows it to slow down, as well as taxi backwards.

 

Except in the manual. (page 3)

 

[mattebubben]

However, noticed you say the Viggen has a better sustained turn rate than I think so I would appreciate to know what that means?

 

Sorry might have been bad formulating on my part.

 

What i ment with that is It has a better Sustained turn then one might think.

 

And not you in particular.

 

Im trying to find a good chart etc right now.

 

But most pilot info (Both from swedish viggen pilots international pilots having tested the viggen aswell as pilots that have done practice dogfights against viggens)

 

indicate that it has a decent sustained turn rate and bleeds speed at a slower rate then one might expect (from just looking at Thrust/Weight / looking at the aircraft etc)

 

But unless someone happens to come across a chart/Paper on the matter we might have to wait until its released.

 

And while i would be surprised if its this comparable to the Mirage 2000 it should be pretty good for an attack aircraft.

 

But it would be interesting to find a source about that chart or atleast more info about it (like who made it and when).

Edited May 6, 2016 by mattebubben

[Angelthunder]

Can anyone guess which AJ 37 Viggen bases will be chosen for it's own map from Leatherneck.Will it be Angelholm AB or will we get several Swedish Air Force bases or civilian airports to take-off and land around Sweden.And will it eventually be a seperate map release like NTTR.

[MA_Goblin]

Cleaning the runway :thumbup:

 

[YOUTUBE]www.youtube.com/watch?v=mJo7aqOfRww[/YOUTUBE]

 

Edited May 8, 2016 by hakjar

[mattebubben]

Can anyone guess which AJ 37 Viggen bases will be chosen for it's own map from Leatherneck.Will it be Angelholm AB or will we get several Swedish Air Force bases or civilian airports to take-off and land around Sweden.And will it eventually be a seperate map release like NTTR.

 

Will very much depend on the map size etc.

 

To start with the Map will need to have a swaith of ocean.

 

And probably cover Gotland.

 

With maby a Strip of the European mainland (Kaliningrad/Lithuania or any of the soviet territories in the area)

 

So it very much depends and we will have to wait and see.

 

Its even possible that they dont pick any main bases of the units that operated the AJS 37 but instead pick forward operating bases etc.

 

We will have to wait and see.

[Skjold]

Can anyone guess which AJ 37 Viggen bases will be chosen for it's own map from Leatherneck.Will it be Angelholm AB or will we get several Swedish Air Force bases or civilian airports to take-off and land around Sweden.And will it eventually be a seperate map release like NTTR.

 

I would expect it to be small, gotland perhaps?

[Pilum]

I did a quick calculation of the relative performance between the Mirage 2000 and Viggen based on this document that I got from my teacher in ”Flygsystemlära” at KTH in the early 80’s. At the time he was working in the military conceptual design department at SAAB but also lectured at KTH. Me and my fellow students used it as a basis for a group assignment for the performance estimate of a conceptual fighter plane that was part of the course curriculum. The document itself was used internally at SAAB for concept study work to compare different configurations such as deltas, swept wing and canards.

 

Disclaimer: The estimate below is in no way accurate in absolute numbers but should give a decent relative rating between the different configurations. The difficult part here is estimating the induced drag but the doc has some rule of thumb estimates and there is one for an unstable delta and a stable canard that I have used:

 

So a rough esitimate of turn performance at Sea level M=0.8:

 

Viggen assuming T/W=0.8 : 12.3 deg/s

 

Mirage 2000 assuming T/W=1.02 : 15.9 deg/s

 

I did the comparison at sea level since I did not have any data for 15,000 ft. In addition, I did not have any Cdo data and used the same for Viggen and M-2000 which should definitely not be to the Mirage’s advantage since the Cdo for Viggen is most likely quite a bit higher.

 

Anyway, I think the numbers illustrate the point I was trying to make: The Viggen may have a good instantaneous turn rate but is not so good when it comes to the sustained turn rate. In fact the Viggen should be very good at instantaneous turns since a canard usually has a higher trimmed Clmax than a delta so it should beat the M-2000 here anyway.

 

Ref doc used for estimate: SAAB document TP27R ”Metodik och formler för överslagsmässiga beräkningar av aerodynamiskt prestandaunderlag för militära FPL-projekt” by B. Andersson. (Rough translation of title: Methodology and formulas for rough aerodynamic performance estimates).

 

Since this was just a relative ballpark estimate it would be nice with some charts on the Viggen though: I have turn data for the Danish Draken from the Danish flight manual but not anything on the Viggen. Maybe this can be found in the AJS 37 SFI? Would be great if someone with access could check….:)

[MYSE1234]

Both part 2 and part 3 of the AJ37 SFI previously posted, have chapters dedicated to manoeuvre performance listed in the index. Sadly none of those pages are in the actual documents we have access to (the links in the beginning of this post).

[Pilum]

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:

[mattebubben]

I did a quick calculation of the relative performance between the Mirage 2000 and Viggen based on this document that I got from my teacher in ”Flygsystemlära” at KTH in the early 80’s. At the time he was working in the military conceptual design department at SAAB but also lectured at KTH. Me and my fellow students used it as a basis for a group assignment for the performance estimate of a conceptual fighter plane that was part of the course curriculum. The document itself was used internally at SAAB for concept study work to compare different configurations such as deltas, swept wing and canards.

 

Disclaimer: The estimate below is in no way accurate in absolute numbers but should give a decent relative rating between the different configurations. The difficult part here is estimating the induced drag but the doc has some rule of thumb estimates and there is one for an unstable delta and a stable canard that I have used:

 

So a rough esitimate of turn performance at Sea level M=0.8:

 

Viggen assuming T/W=0.8 : 12.3 deg/s

 

Mirage 2000 assuming T/W=1.02 : 15.9 deg/s

 

I did the comparison at sea level since I did not have any data for 15,000 ft. In addition, I did not have any Cdo data and used the same for Viggen and M-2000 which should definitely not be to the Mirage’s advantage since the Cdo for Viggen is most likely quite a bit higher.

 

Anyway, I think the numbers illustrate the point I was trying to make: The Viggen may have a good instantaneous turn rate but is not so good when it comes to the sustained turn rate. In fact the Viggen should be very good at instantaneous turns since a canard usually has a higher trimmed Clmax than a delta so it should beat the M-2000 here anyway.

 

Ref doc used for estimate: SAAB document TP27R ”Metodik och formler för överslagsmässiga beräkningar av aerodynamiskt prestandaunderlag för militära FPL-projekt” by B. Andersson. (Rough translation of title: Methodology and formulas for rough aerodynamic performance estimates).

 

Since this was just a relative ballpark estimate it would be nice with some charts on the Viggen though: I have turn data for the Danish Draken from the Danish flight manual but not anything on the Viggen. Maybe this can be found in the AJS 37 SFI? Would be great if someone with access could check….:)

 

Well going by those numbers and comparing to the chart.

 

The Viggen is not really over performing its more of the Mirage 2000 under performing on the chart (dont know how much impact the added Altitude would have on the Turn rate)

 

So the chart data might very well be accurate for the AJ 37 its just that Some of the other aircraft (Especially the Mirage 2000) have stats that are lower then they should be.

[Pilum]

Well going by those numbers and comparing to the chart.

 

The Viggen is not really over performing its more of the Mirage 2000 under performing on the chart (dont know how much impact the added Altitude would have on the Turn rate)

 

So the chart data might very well be accurate for the AJ 37 its just that Some of the other aircraft (Especially the Mirage 2000) have stats that are lower then they should be.

 

Yes, I think you may be right about the Mirage 2000 being higher IRL because it does have an impressive suite of leading edge slats and I don't think the SAAB doc had those in mind. It actually only mentions LE devices in conjunction with the swept wing estimates IIRC.

 

And as to altitude influence: there is no problem when it comes to the aerodynamics but the problem is what kind of thrust do the engines give at M=0.8 at 15000ft? Anyone have links to that kind of data?

[MYSE1234]

Yes, I think you may be right about the Mirage 2000 being higher IRL because it does have an impressive suite of leading edge slats and I don't think the SAAB doc had those in mind. It actually only mentions LE devices in conjunction with the swept wing estimates IIRC.

 

And as to altitude influence: there is no problem when it comes to the aerodynamics but the problem is what kind of thrust do the engines give at M=0.8 at 15000ft? Anyone have links to that kind of data?

 

I did find a performance document for JA37, so it's a bit different, but it might shed light on things, not sure.

[ame]http://www.temporal.com.au/viggen_final.pdf[/ame]

Edited May 8, 2016 by MYSE1234

[Pilum]

Thanks MYSE. I actually had that and it's an interesting analysis but I'm not sure to what extent the data there for RM8B can be used for RM8A though. In addition, we need data for the Mirage 2000 engine at 15000ft as well to do a comparison.

[robban75]

On the topic of Viggen weights. In the book "System 37 Viggen" the empty weights given for the AJ 37 is 10570/10630kg, and JA 37 11790kg. Take off weight for JA 37 is 16200kg.

 

In the book there are several comparisons made against the MiG-23 and Mirage F1.

 

Time from take off to Mach 1.6 @ 11000 meters, armed with 4x AAM.

 

JA 37 5,5 min

MiG-23 8,5 min

Mirage F1 18 min

 

Turn rate @ Mach 0,8 at SL, armed with 4x AAM.

 

JA 37 12,7 deg/sec

MiG-23 17,5 deg/sec

Mirage F1 13,0 deg/sec

 

It is difficult to turn an attack aircraft into a fighter. The Viggen can deliver on most points, such as acceleration and climb performance. But it does fall short when it comes to turn performance. Pilots says so themselves. Although, this is in comparison to more modern fighters, such as the F-15, F-16, MiG-29 and Su-27.

[WinterH]

Doesn't that figure of 17.5 deg/sec look strange for MiG-23 though ? May be it is instantanous turn rate for MiG, vs sustained for Viggen and Mirage F1 in that list?

 

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.

Edited May 8, 2016 by WinterH

[BlackLion213]

Time from take off to Mach 1.6 @ 11000 meters, armed with 4x AAM.

 

JA 37 5,5 min

MiG-23 8,5 min

Mirage F1 18 min

 

Turn rate @ Mach 0,8 at SL, armed with 4x AAM.

 

JA 37 12,7 deg/sec

MiG-23 17,5 deg/sec

Mirage F1 13,0 deg/sec

 

Interesting stuff, climb and acceleration seem quite impressive. Especially since acceleration is regarded as the MiG-23's greatest strength.

 

Do you know if the listed turn rates are ITR or STR?

 

I wouldn't be surprised if the Viggen was a mid-pack STR, but it's delta/canard design leaves me wondering if it might have an impressive ITR. The control-ability at low airspeeds and high lift that allow for it's STOL capability seem like potential assets when it comes to rapid pitch rates.

 

The Mirage 2000C has a really impressive ITR that serves it quite well in WVR, though it's STR is similar to the F-15C. It feels much more agile than the F-15C to me, largely because of that ITR. It bleeds a lot of airspeed, but the nose remains point-able even after it has bleed a lot of energy. That rapid loss of airspeed precludes an amazing STR.

 

Might the Viggen do the same? Does anyone have good ITR vs STR data for the Viggen?

 

-Nick

[mattebubben]

Well one thing that very much helps the Mirage in its Pointability (at high alpha / low speed) Is the FBW.

 

And the AJS 37 is very much lacking when it comes to FBW so its more hands on and

should be a bit harder to control/master even if it should be very controllable at lower speeds.

Edited May 8, 2016 by mattebubben

[Pilum]

 

Turn rate @ Mach 0,8 at SL, armed with 4x AAM.

 

JA 37 12,7 deg/sec

MiG-23 17,5 deg/sec

Mirage F1 13,0 deg/sec

 

It is difficult to turn an attack aircraft into a fighter. The Viggen can deliver on most points, such as acceleration and climb performance. But it does fall short when it comes to turn performance. Pilots says so themselves. Although, this is in comparison to more modern fighters, such as the F-15, F-16, MiG-29 and Su-27.

 

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.....:smilewink:

 

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......:music_whistling:

 

Doesn't that figure of 17.5 deg/sec look strange for MiG-23 though ?

 

In a sense yes but sustained turn rate is very much dependent on span loading and aspect ratio and if a Mig-23 spreads its wings......

 

Assuming the T/W ratio is in the same ballpark as the Viggen then it may be reasonable.

 

 

Do you know if the listed turn rates are ITR or STR?

 

Might the Viggen do the same? Does anyone have good ITR vs STR data for the Viggen?

 

-Nick

 

It's STR for the Viggen anyway: In my calculation the return value on Cl is around 0.45 for STR. A canard like the Viggen should have a trimmed Clmax of more than 1.1 at 18 deg alfa and a good pilot should be able to go a bit higher than that. :)

 

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!"

Edited May 8, 2016 by Pilum

[Fri13]

Interesting stuff, climb and acceleration seem quite impressive. Especially since acceleration is regarded as the MiG-23's greatest strength.

 

Do you know if the listed turn rates are ITR or STR?

 

 

http://www.fighter-planes.com/info/mig23_flogger.htm

Note : According to the MiG-23ML manual, the MiG-23ML has sustained turn rate of 14.1 deg/sec and a maximum instantaneous turn rate of 16.7 deg/sec. The MiG-23ML accelerates from 600 km/h to 900 km/h in 12 seconds at the altitude of 1000 meters. The MiG-23 accelerates at the altitude of 1 km from the speed of 630 km to 1300 km in just 30 seconds and at the altitude of 10-12 km will accelerate from Mach 1 to Mach 2 in just 160 seconds.

[mattebubben]

On the topic of Viggen weights. In the book "System 37 Viggen" the empty weights given for the AJ 37 is 10570/10630kg, and JA 37 11790kg. Take off weight for JA 37 is 16200kg.

 

In the book there are several comparisons made against the MiG-23 and Mirage F1.

 

Time from take off to Mach 1.6 @ 11000 meters, armed with 4x AAM.

 

JA 37 5,5 min

MiG-23 8,5 min

Mirage F1 18 min

 

Turn rate @ Mach 0,8 at SL, armed with 4x AAM.

 

JA 37 12,7 deg/sec

MiG-23 17,5 deg/sec

Mirage F1 13,0 deg/sec

 

It is difficult to turn an attack aircraft into a fighter. The Viggen can deliver on most points, such as acceleration and climb performance. But it does fall short when it comes to turn performance. Pilots says so themselves. Although, this is in comparison to more modern fighters, such as the F-15, F-16, MiG-29 and Su-27.

 

 

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.