DCS: AJS-37 Viggen Discussion

[renhanxue]

Soooo, who wants to revive that old split S debate again? Nobody? Well, too bad, because I'm doing it anyway, if only to lay down the facts! This is based on pages 50-52 in Fpl 37 aerodynamik III (pages 51-53 in the PDF since it counts the cover as page 1).

 

First, the scenario. The document states that ordinary split S technique is to start applying G load during the roll and reach max permitted load (8 G's) about at the same time as reaching a fully inverted state. If you disregard the time it takes to reach max G load, you arrive at the thick dashed line marked "Lägsta ing. höjd för halvroll" in this diagram:

 

 

On the Y axis, lowest possible entry altitude for a split S, with a clean AJ 37 at flight idle, and an exit altitude of 500 meters. The solid line is the same but for entry at the least optimal dive angle (steeper dive = split S exits at lower altitude, assuming the entry speed exceeds M 0.8 or so).

 

On the X axis, entry speed (Mach number).

 

The thin, numbered (barely legible) s-formed curves connect the entry point with the exit point and thus show the speed loss over altitude. All split S maneuvers exit subsonic regardless of the entry speed.

 

So, yeah, you'll need about a thousand meters of altitude (well, ish) to do a split S in an AJS 37. And that's that. The margins are really small, too and you risk superstall by exceeding max alpha, engine compressor stalls, flying into the ground because you didn't pull the stick hard enough, etc etc.

 

 

There's also this though, which shows the minimum altitude required to recover from a dive with 500 meters to spare, also at flight idle:

 

 

So you can recover from a vertical dive if you have about 500 meters. Maybe. The diagram hasn't been corrected for the time it takes to reach max permitted G loading.

Edited July 12, 2016 by renhanxue

[microvax]

Soooo, who wants to revive that old split S debate again? Nobody? Well, too bad, because I'm doing it anyway, if only to lay down the facts! This is based on pages 50-52 in Fpl 37 aerodynamik III (pages 51-53 in the PDF since it counts the cover as page 1).

 

First, the scenario. The document states that ordinary split S technique is to start applying G load during the roll and reach max permitted load (8 G's) about at the same time as reaching a fully inverted state. If you disregard the time it takes to reach max G load, you arrive at the thick dashed line marked "Lägsta ing. höjd för halvroll" in this diagram:

 

 

On the Y axis, lowest possible entry altitude for a split S, with a clean AJ 37 at flight idle, and an exit altitude of 500 meters. The solid line is the same but for entry at the least optimal dive angle (steeper dive = split S exits at lower altitude, assuming the entry speed exceeds M 0.8 or so).

 

On the X axis, entry speed (Mach number).

 

The thin, numbered (barely legible) s-formed curves connect the entry point with the exit point and thus show the speed loss over altitude. All split S maneuvers exit subsonic regardless of the entry speed.

 

So, yeah, you'll need about a thousand meters of altitude (well, ish) to do a split S in an AJS 37. And that's that. The margins are really small, too and you risk superstall by exceeding max alpha, engine compressor stalls, flying into the ground because you didn't pull the stick hard enough, etc etc.

 

 

There's also this though, which shows the minimum altitude required to recover from a dive with 500 meters to spare, also at flight idle:

 

 

So you can recover from a vertical dive if you have about 500 meters. Maybe. The diagram hasn't been corrected for the time it takes to reach max permitted G loading.

 

Cant give you rep again but great job there. Really good basis we can make assumptions on viggen behaviour with all the documentation you are digging up ! :)

 

probably one of the most well documented planes for a while we are going to get in DCS. :D

[Aginor]

Agree. Great job digging up that stuff! :)

[mattebubben]

Well i think part if the reason why there is so much info being dug up and posted on the forum is that pretty much any Swede that has an interest in aircraft

(and especially someone that grew up between the 70s and the 90s)

has a deep love for the Viggen.

 

And i think most feel like me in that they want to help spread that love and get others to love the Viggen as much as we do ^^.

 

So translating and getting information about it to you unfortunates that does not know the Glory of the Viggen is the least we can do if it result in just some of you getting it and reveling in the beauty and power of the Viggen.

[impeller]

Me and a friend visited Luleå F21 flight museum to see the viggen up close. We are so stoked now, pleas release it soon

Random pictures

It's truly a beautiful bird, can't wait.

 

 

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[Agremont]

Nice pictures!

[impeller]

Nice pictures!

 

 

 

Thanks

Finished of with the Draken

 

 

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[Darkbrotherhood7]

Damn, I really, really hate to see beautiful planes like the Viggen getting rust in the desert or museum etc.

 

But anyways, beautiful pics impeller.:thumbup: My hype is increasing!:D

[Agremont]

Those are some beefy landing gear!

[impeller]

Those are some beefy landing gear!

 

 

 

The engine bay (space) is massive. Hard to understand the power and heat going on at the end of the aircraft. Truly awesom

 

 

 

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[RaXha]

Those are some beefy landing gear!

 

 

 

They would have to be to withstand the force of carrier style landings in the forrests of lappland :D

[impeller]

They would have to be to withstand the force of carrier style landings in the forrests of lappland :D

 

 

 

Fallfors right? Idag åker man bara dit för att köra bil på bana

 

I wish fallfors still was an active field for training air forces.

 

 

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[Phantom453]

Those are some beefy landing gear!

 

Yeah, that caught my eye too. Unusual one single wheel behind another like that. You normally expect only two wheel to be side by side.

[Fri13]

Yes and no.

 

The Viggen isn't really multi-role in the full sense of the word. There are variants dedicated to different tasks, and LN is working on the attack variant. It lacks the advanced pulse doppler radar and radar guided missiles that the interceptor variant has. It's radar is made for air to ground operations. The only air to air weapons it carries are sidewinders.

 

The interceptor variant (JA) which we aren't getting had a pulse doppler radar capable of tracking several targets at the same time, with look down shoot down capability. It carried sidewinders and skyflash (similar to AIM-7) missiles, and late variants even carried the AIM-120 AMRAAM.

 

It is sad that we don't get the Interceptor variant (at launch, but maybe in future ;-).) as it has additional nice features:

 

The aircraft's principal sensor was an Ericsson PS 37 X-band monopulse radar, which used

a mechanically steered parabolic dish housed in a radome.[22] This radar performed several functions, including air-to-ground and air-to-air telemetry, search, track, terrain-avoidance and cartography.

[25] On the JA 37 fighter-interceptor model, the PS 37 radar was replaced by the more capable Ericsson PS 46 X-band pulse repetition frequency, which had an all-weather look-down/shoot-down capability reportedly in excess of 50 kilometers and continuous-wave illumination for the Skyflash missiles as well as the ability to track two targets while scanning.[23] According to Ericsson, it had a 50 per cent chance of spotting a low-flying McDonnell Douglas F-4 Phantom II within a single scan and possessed a high level of resistance to interference from ECM.[23]

 

The fighter-interceptor version of the Viggen, the JA 37, featured various avionics changes, including the extensive use of digital electronics alongside mechanical technology.[49] In 1985, the "fighter link" went into service,

permitting encrypted data communication between four fighters; this enabled one fighter to "paint" an airborne enemy with guidance radar for the Skyflash missiles of the three other fighters in a group while they had their search and guidance radar switched off.

This system was operational ten years before any other country's.[50] The autopilot was also slaved to the radar control to obtain better precision firing the cannon.[51] Once in service, the Viggen's software was regularly updated every 18 months.[52] In 1983, the mean time between failures (MTBF) was reported as 100 hours, a very high reliability level for the generation of avionics systems involved.[53]

https://en.wikipedia.org/wiki/Saab_37_Viggen#Avionics

 

But as we don't have that feature even for russian aircrafts, rendering their multiplayer combat performance far smaller than it would be otherwise, as Su-27S pilots could get huge range boost by letting rear pilot to guide missiles to target while closer range pilots just delivered missiles to optimum launch parameters and sucking incoming missiles while running away.

 

So if we get the interceptor anyday, it will get nice capabilities for squadron tactics too.

[Fri13]

They would have to be to withstand the force of carrier style landings in the forrests of lappland :D

 

[ame]

[/ame]

[Manuel_108]

 

Is that a Ram Air Turbine?

[microvax]

Is that a Ram Air Turbine?

 

No its main engine, thing in the middle is the ram air power generator. Often misunderstood viggen feature. )))

[RagnarDa]

DCS: AJS-37 Viggen Discussion

 

I am a little confused by the radar ranges reported.

 

 

 

In the AJ37 manual part2, the range setting can go as high as 120 Km.

 

In books, and on webpages they report the more powerful JA37 radar to have a scan-while-track range of only 48-50 Km.

 

 

 

I am no expert in radars, what does it all mean. Is range-while-search longer range than TWS, or why would the AJ radar be able to be set to 120 KM range?

 

 

 

Do you think the 48-50 Km range is meant as for fighter sized targets only? And that it would be able to see much further if it were a big bomber?

 

 

 

Could the long range setting in the AJ mean that a datalink could supply targets up to that range from other aircrafts? The jakt(hunter)-link was introduced in the mid 80'ties, but wasn't there a simpler link system in the AJ, or did it have no such system?

 

 

 

And if the AJ max setting was 120 Km, what do you reckon it would have been for the JA? Sadly we don't have the JA manual part2, so can't find that out, but a guesstimate could maybe be made.

 

 

 

Remember the AJ/S radar is somewhat low resolution. It has low PRF optimal for detecting high contrast objects in the sea or large terrain features (for navigation) at long ranges. I've calculated the resolution at max range (120km) to be in the ballpark of 500m. A pilot described it as you can possibly make out large buildings like the Globen-building (diameter 110m) but anything smaller is blurry. You won't normally detect a fighter-size target unless really close.

 

Edit: So lower PRF = longer range but lower resolution

 

Edit2: No link-system in the AJ or AJS.

Edited July 14, 2016 by RagnarDa

[QuiGon]

I am a little confused by the radar ranges reported.

 

In the AJ37 manual part2, the range setting can go as high as 120 Km.

In books, and on webpages they report the more powerful JA37 radar to have a scan-while-track range of only 48-50 Km.

 

I am no expert in radars, what does it all mean. Is range-while-search longer range than TWS, or why would the AJ radar be able to be set to 120 KM range?

 

Do you think the 48-50 Km range is meant as for fighter sized targets only? And that it would be able to see much further if it were a big bomber?

 

Could the long range setting in the AJ mean that a datalink could supply targets up to that range from other aircrafts? The jakt(hunter)-link was introduced in the mid 80'ties, but wasn't there a simpler link system in the AJ, or did it have no such system?

 

And if the AJ max setting was 120 Km, what do you reckon it would have been for the JA? Sadly we don't have the JA manual part2, so can't find that out, but a guesstimate could maybe be made.

 

Range setting? Maybe it's just the setting for the radar display. That doesn't say much about the actual radar range. The JA and AJ have different radars. The AJ radar is for A-G, while the JA radar is for A-A. There is also no datalink in the AJ.

 

But, I also would like to know how these two radars differ from each other. Does the AJ radar has an A-A mode? Vice versa?

 

Edit: sniped. Question above remains though

[RagnarDa]

The AJ and AJS radar has a air to air mode, just not like the ones you are used to ;) Not sure about A/G on the fighter-Viggen but I don't think so.

[QuiGon]

The AJ and AJS radar has a air to air mode, just not like the ones you are used to ;) Not sure about A/G on the fighter-Viggen but I don't think so.

 

Thanks, that sounds interesting. I guess you don't want to reveal already how it works exactly? :P

[microvax]

Who needs RADAR anyway. If you are flying at -5m RADAR altitude in submarine mode you cant see stuff anyway. ))

 

Same thing with KA50, you can fly so low that nothing apart from some robocop units detects you, problem is, you cant detect anything either. :D

 

Question is, would you [as a DEV] rate the Air to Air mode more or less usefull then the MIG21 Radar ? :D

 

Anyway, flew the Mirage in scramble from taxiway, no time for Radar warmup mode and it was loads of fun. So I guess you would keep the Radar off anyway as long as you arent using it for NAV fix or searching illegal fishing boats. ;) I think the Viggen will be quite good for heli hunting.

Good low speed charachteristics afaik, 2 AKAN pods and a mix of sidewinders RB05 or Mavs. What do you want more ? :D

[RaXha]

Question is, would you [as a DEV] rate the Air to Air mode more or less usefull then the MIG21 Radar ? :D

 

My guess would be less since it's not really an air to air radar at all. :) I'm no dev though. :P

[RagnarDa]

The radar in the attack-Viggens doesn't do any processing or interpretation of the radar-signal, it just shows you the raw input from the receiver (except for scaling of course and a anti-jamming filter). It is up to the pilot to figure out what everything is. Air-to-air mode is same as terrain-mapping mode except the antenna is pointed upward. Air contacts is shown as "blimps". Symbols on the radar-screen are fed from the navigation computer and shows where for example the current waypoint is believed to be. It might or it might not match with the real location as shown by the radar picture. As for comparison with the MiG-21 I unfortunately haven't had enough time to compare the two in-game but I wouldn't be surprised if the detection-ranges of air-targets is similar.

[Crowbar]

What kind of navigational aids can be used on a Viggen? I know it has the rudimentary INS but anything land-based?