DCS: AJS-37 Viggen Discussion

you all have corrupted me after nearly 300 pages of low flying Viggens, the first thing that came to mind watching the demo flight was, man that thing is flying kinda high...

you all have corrupted me after nearly 300 pages of low flying Viggens, the first thing that came to mind watching the demo flight was, man that thing is flying kinda high...

Airshow regulations. :P Also they probably dont want to risk loosing the only flying airframe left in the world. ;-)

Although a mach 0.9 pass at 50m

(since supersonic would probably not be allowed)

would have been amazing.

http://moments.redbull.tv/events/meta/102?cttp=heat:2401&burl=http%3A%2F%2Fwww.redbull.tv%2Flive%2FAP-1P2RMZN451W11%2Fairpower

;)

(since supersonic would probably not be allowed)

...and here's why:

...and here's why:

I do not see the problem :lol:

Neither do i.

As long as they dont do it over my house and my car is not nearby then i dont see any problem with that.

And actually on the Topic of the Viggen and Super Sonic passes.

Many years ago (think it was early 90s or very late 80s) a Viggen Pilot (who was a childhood friend of my father)

did a super sonic pass at about 150-200m above a town in "Northern" Sweden Called Härnösand.

The other pilots in the flight said he would not dare to do it so ofc he did xD (it was his home town).

Not surprisingly there were a "Few" windows broken and a deal of outrage from the city officials etc and he got a warning from the airforce but that was that.

What a horrible and boring job being a Fighter Pilot in peace time must be ^^.

...and here's why:

Those M2000 pilots got arrested because of this..lol

But I don't see any problem, they actually made a favor I think.:music_whistling::lol:

Any people close to Kleine Brogel, Belgium next weekend?

The Viggen is gonna be there!!! (+ Draken and Tunnan) :D

http://www.sanicole.com/index.php/en/

Leatherneck why you do dis.

Studies start soon, no Viggen in sight. There will be terrible cases of "Two souls alas! are dwelling in my breast." x) :P

But honestly better that then planes falling out of the sky. :D

For you chart-nerds out there I generated this little thing from the FM:

Please note that errors in the chart doesn't necessarily mean errors in the FM but more likely in how I calculated the numbers.

For you chart-nerds out there I generated this little thing from the FM:

[ATTACH]147965[/ATTACH]

Please note that errors in the chart doesn't necessarily mean errors in the FM but more likely in how I calculated the numbers.

ouhh noice, thx for the sneak peek. :D

Could we also have an instant turn diagram ?

And engine fuel consumption at 100% RPM and AB stages 1-3 ?

#diagramlove

That is a very nice diagram, RagnarDa! Especially since I haven't seen one like it in the SFI.

I can provide one for fuel consumption, though, if you promise not to fall off your chair when you see it, because it ain't pretty:

Yes, max zone 3 drinks 15% fuel per minute around M 0.7 and even more than that at higher speeds.

At 8 km altitude it's slightly less bonkers, but still.

That is a very nice diagram, RagnarDa! Especially since I haven't seen one like it in the SFI.

 

I can provide one for fuel consumption, though, if you promise not to fall off your chair when you see it, because it ain't pretty:

 

 

 

 

Yes, max zone 3 drinks 15% fuel per minute around M 0.7 and even more than that at higher speeds.

 

Holy shit, that's around 7 minutes of total fuel time. I can easily see myself running out of fuel a bit too many times...

Holy shit, that's around 7 minutes of total fuel time. I can easily see myself running out of fuel a bit too many times...

It's no different from the Mig-21 really. You just need to be frugal with the AB...and throttle.

Yeah I mean the f15 also runs just about 7.5 minutes of full burner on internals.

su27 runs 9,3.

Mirage is the exception with 11,5 minutes.

Interesting is what the engine consumes at 100%RPM at tree top level and how fast you can get with that and 4 mavs/2 aim9s. :)

When doing ground attack in the mirage I do stick to the tree tops at 100%rpm, head in, accel to attack speed in AB and just safe the excess fuel for egress at Warpspeed.

100% dry thrust takes you to around M 0.85 at sea level with 2x rb 75, both ECM pods, an empty drop tank and 100% internal fuel. Probably similar for 4x rb 75. Adding two AIM-9's doesn't add a whole lot of drag either.

For you chart-nerds out there I generated this little thing from the FM:

[ATTACH]147965[/ATTACH]

Please note that errors in the chart doesn't necessarily mean errors in the FM but more likely in how I calculated the numbers.

Sustained G increasing linearly from M0.9 to M1.1 ... This is probably a world first.

Look at what happens with the sustained G between M0.9 and M1.1 at 5Km altitude for MiG-21bis and MiG-29 and 20kft for F-15C.

So the Viggen can sustain 6.5G at M1.1 at 5Km altitude... That is pretty damn impressive. Look at the poor MiG-29, without any stores it can sustain only 5.2

100% dry thrust takes you to around M 0.85 at sea level with 2x rb 75, both ECM pods, an empty drop tank and 100% internal fuel. Probably similar for 4x rb 75. Adding two AIM-9's doesn't add a whole lot of drag either.

Sounds cool, now we would need to know how much fuel that consumes. :D

but thx for le info !

Sustained G increasing linearly from M0.9 to M1.1 ... This is probably a world first.

 

Look at what happens with the sustained G between M0.9 and M1.1 at 5Km altitude for MiG-21bis and MiG-29 and 20kft for F-15C.

 

So the Viggen can sustain 6.5G at M1.1 at 5Km altitude... That is pretty damn impressive. Look at the poor MiG-29, without any stores it can sustain only 5.2

Yeaah the linearity confused me a bit as well, dunno if that is simply thanks to the canards and the fact that the faster you go the less AOA you have and the less induced drag which is huge with the Viggen to my understanding. That could be an explanation.

Dunno though. Maybee I should really read the NASA paper on the viggen aerodynamics. :D

Sounds cool, now we would need to know how much fuel that consumes. :D

 

but thx for le info !

It's the line marked "max släckt" in the fuel diagram I posted above, so a bit over 2% internal fuel per minute.

Sustained G increasing linearly from M0.9 to M1.1 ... This is probably a world first.

 

Look at what happens with the sustained G between M0.9 and M1.1 at 5Km altitude for MiG-21bis and MiG-29 and 20kft for F-15C.

 

So the Viggen can sustain 6.5G at M1.1 at 5Km altitude... That is pretty damn impressive. Look at the poor MiG-29, without any stores it can sustain only 5.2

Well, it can reach that load factor but the question is if there's enough thrust to sustain it. Here's a a graph of the max attainable load factor for a clean AJ 37:

The load factor limitations are the solid lines with numbers on them - read them like height curves on a map. "Higher up" = higher load factor. The colored zones show what the reason for the load factor limit is at that particular altitude and speed. The key on the right should be mostly understandable but to be clear, from top to bottom the reasons are:

- 18° alpha

- -22° elevon deflection (they won't go further)*

- the "pitch gearing", the gearbox that attempts to maintain a constant (well, ish) relationship between stick force and load factor regardless of speed and altitude

- limitations on the elevon hydraulic forces (there's not enough force in the system to push the elevons as hard as necessary)

For Mach 1.1 in particular or altitude 6km in particular these two graphs may be easier to read:

SPAK = the autopilot's artificial stick forces etc active, GSA = no such conveniences.

* The elevon situation is actually more complex than this. The elevons can be deflected 27° upwards and 21° downwards, but not all of this is available to respond to pitch inputs. On the AJ 37, 22° up and 16° down is available for pitch input, the rest is reserved for roll inputs.

The JA 37 has it considerably better by the way, they redid most of the control surface systems and the same max attainable load factor graph just looks like this:

Max permitted load factor (8 G) is easily attainable throughout most of the normal flight regime and even all the way up to 7 km and M 1.8.

Well, it can reach that load factor but the question is if there's enough thrust to sustain it.

To answer my own question: no, seems unlikely. Can't find figures for 5km, but at 1 km you can only sustain just under 5 G at M 1.1.

Graphs for M 0.9 and M 1.1 respectively at 1 km:

On the Y axis, thrust (kN), on the X axis load factor. Solid line is total drag, the horizontal lines are available thrust at full military ("MS") and max AB zone 1, 2 and 3 respectively.

Sorry if this has already been answered:

How do you engage the different AB zones? Is it just by moving the throttle (are there bumps for every zone?)?

the gearbox that attempts to maintain a constant (well, ish) relationship between stick force and load factor regardless of speed and altitude

The Viggen has such a feature? That's pretty neat!

To answer my own question: no, seems unlikely. Can't find figures for 5km, but at 1 km you can only sustain just under 5 G at M 1.1.

:thumbup:

I see in the diagram that at 1Km altitude and M1.1 the Viggen will sustain about 4.6G. In similar conditions a MiG-29 will sustain 6.1G (see attached diagram).

Here is a little calculation, yeah it's really rocket science :D

4.6/6.1=0.75

At 5000m and M1.1 the MiG-29 will sustain 5.2, see diagram in my previous post.

5.2*0.75=3.92

Here you go, a Viggen at 5000m and M1.1 will sustain about 4G

Thanks for your posts, good stuff!

I see in the diagram renhanxue posted that Viggen can sustain 7.5G at 1Km altitude and M0.9. That's not bad at all! Actually, this is pretty awesome IMO. This aircraft will easily sustain 8G at sea level.

I put the Viggen data for M0.9 and 1.1 at 1Km altitude in a diagram to compare it with MiG-21bis performance using the most powerful ЧР engine mode. See below how it looks like.

At M0.5 the MiG-29 can sustain about 5.1G. So for M0.5 I decided to put the Viggen somewhere in the middle between MiG-21 and MiG-29.