DCS: AJS-37 Viggen Discussion

[Vectury]

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/

Edited September 6, 2016 by Vectury

[microvax]

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

[RagnarDa]

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.

[microvax]

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

[renhanxue]

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.

 

Edited September 10, 2016 by renhanxue

[Marsvinet]

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...

[Buzzles]

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.

[microvax]

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.

[renhanxue]

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.

Edited September 11, 2016 by renhanxue

[Fox One]

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

[microvax]

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 !

[microvax]

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

[renhanxue]

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.

Edited September 11, 2016 by renhanxue

[renhanxue]

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.

Edited September 12, 2016 by renhanxue

[QuiGon]

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?)?

[Fox One]

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!

[Fox One]

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.

[MYSE1234]

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?)?

 

At max mil. you have to push the throttle sideways, toward the side of the aircraft, and then forward slightly to engage the first AB stage. There is a detent for every stage, but you only have to move the throttle sideways for the first stage. After that it's only force.

 

EDIT: Found this video showing the whole thing.

At the 2m 45s mark.

Edited September 12, 2016 by MYSE1234

[QuiGon]

Yes, you only have to move the throttle.

At max mil. you have to push the throttle sideways, toward the side of the aircraft, and then forward slightly to engage the first AB stage. There is a detent for every stage, but you only have to move the throttle sideways for the first stage. After that it's only force.

 

EDIT: Found this video showing the whole thing.

At the 2m 45s mark.

*video*

 

Thanks, great answer! :thumbup:

[mattebubben]

And also related to that Video.

 

Extra Points for anybody able to id the Viggen variant by looking at the cockpit.

 

Its not super difficult to guess right but you need some basic Viggen Knowledge.

 

Would be especially impressed if a non swede gets it right.

Edited September 12, 2016 by mattebubben

[microvax]

And also related to that Video.

 

Extra Points for anybody able to id the Viggen variant by looking at the cockpit.

 

Its not super difficult to guess right but you need some basic Viggen Knowledge.

 

Would be especially impressed if a non swede gets it right.

 

Its not an JA [has the wrong radar screen], it is not an AJ [projector for maverick image], its not an SF [missing the downward periscope in place of the radar screen.] so I would guess its an SH37 ?

[QuiGon]

And also related to that Video.

 

Extra Points for anybody able to id the Viggen variant by looking at the cockpit.

 

Its not super difficult to guess right but you need some basic Viggen Knowledge.

 

Would be especially impressed if a non swede gets it right.

 

It's not the JA-37 :D

 

Edit: Damn, too slow...

[mattebubben]

The point Goes to Microvax.

 

Its a SH 37 (or a AJSH 37) the Ocean Recce variant.

 

Just as you did The easiest ways to narrow it down is to look at the Radar Screen as only the AJ and SH (The SK had a dummy screen but its easy to tell apart for other reasons) has that old round type of radar Screen.

 

The Second way and that lets you tell apart the AJ and SH is looking to the right of the hud again like you did is by looking for the VID.

 

If there is no VID (Maverick sight there) then its a SH 37 unless the picture is mid-early 1970s as the AJ 37 did not get the VID untill mid-late 70s when it got the AGM-65 capability.

 

And if that case you can ID the SH by the fact that in the area where the VID should be you instead have a Row of buttons.

 

This is an example of a SH 37 picture with the buttons very visible.

 

But yea we have taught you guys well in the ways of the viggen ^^.

 

And soon my friends we will hopefully be able to put all that training into action.

Edited September 12, 2016 by mattebubben

[Sim Flyer]

This is indeed a very nice cockpit, cannot wait to start interacting with it and learning how to use this plane :)

[Pocket Sized]

Is that the thrust reverse lever just under the airspeed/mach indicator?