DCS: AJS-37 Viggen Discussion

[Hummingbird]

According to several different sources this maneuver was practised a lot by Viggen pilots. The delta wing design is one reason why it is possible to achieve according to the same sources.

 

I would be very surprised if the Swedish pilot mentioned a lower altitude than what was the case. Chances are that he was even lower. You can say a lot about us Swedes, but bragging about achievements isn't something that is common practice. Unless your name is Zlatan Ibrahimovic of course.:D

 

Delta wing or not a 250 m turn radius sounds extremely implausible for a jet fighter, a successful split S at 500 m height even more so, esp. if he was supposed to have another 100 m to the deck after completion, which in effect would make it a 200 m turn radius. Not happening :)

 

As mentioned a clean F-16 can at best manage a 369 m turn radius at SL, do you honestly believe the Viggen is going to cut that almost in half?

 

In short either the pilot misremembered or the maneuver wasn't a perfect split S, i.e. it could've been done at a 120 deg roll angle instead of the 180 deg one of a perfect split S.

Edited June 26, 2016 by Hummingbird

[Andreas1811]

A Tip for Viggen-Lovers in September- Austria- Airpower 2016 in Zeltweg (Austria)

 

http://www.airpower.gv.at/fluggeraete/historische-flugzeuge/saab-37-viggen.html

[Skjold]

A Tip for Viggen-Lovers in September- Austria- Airpower 2016 in Zeltweg (Austria)

 

http://www.airpower.gv.at/fluggeraete/historische-flugzeuge/saab-37-viggen.html

 

Swedish Air Force Historic Flight (the guys that will be at that show in Austria) will be at many shows this summer. Their entire program is available here: http://swafhf.se/flygprogram.html

Edited June 26, 2016 by Skjold

[Hummingbird]

At first this story did sound quite optimistic to me but there are few unknown variables to consider.

 

The turning radius you are mentioning is measured at a constant speed and the Viggen looses a lot of energy in tight turns.

Using a standard turn calculation at 300kts, 82° AoB and 7.1G the turn diameter is 670m.

If the Viggen looses 100kts during this maneuver the turn diameter shrinks to 300m but you would still need to pull more than 7Gs to achieve that, which I doubt.

There must be something elso going on aerodynamics wise on the Viggen.

 

I used the max lift line on the F-16C's doghouse plot, so I am getting the absolute min turn radius :) I did make a tiny mistake though (not that it matters) in that I looked at the mil chart and not the max AB chart, so the actual min radius of the clean F-16 is infact 1080 ft and not 1211 ft. In other words the min turn diameter is 2160 ft or 658 m, not 738 m. 658 m is still a far cry from the 400 m the Viggen supposedly was able to pull off that maneuver within though, so this doesn't change anything.

 

Note that the Viggen isn't a simple delta and that the nose wing has been placed at this exact location because at high AoA the vortex from it joins the wing vortex.

They both stabilize each other and enable flight at even higher AoA than usual.

With an immense loss of speed and an extreme AoA this maneuver doesn't seem to be impossible.

 

The Viggen's canards act as vortex generators, that is true (there's even a doc on here explaining that in detail IIRC), but so does the F-16's LERX. Now the Viggen does also feature a lower wing loading than the F-16 but crucially it lacks high lift devices such as automatic LE & TE maneuver flaps, thus in the end I doubt there's much difference in the actual LW ratio and thus minimum turn radius of the two fighters - and certainly not a 50% difference :P

 

In short I honestly think the maneuver probably wasn't a perfect split S and instead done at a bit of an angle, otherwise it doesn't seem plausible, esp. since pull downs tend to increase the radius not reduce it.

Edited June 26, 2016 by Hummingbird

[Hummingbird]

Just for reference I fooled around a bit in the F-15C in DCS 2.0 today near the salt lake flats, and what I found is that I couldn't complete a perfect split S (i.e. 180 deg roll) with less than 975 m in height in a completely clean Eagle and 75% fuel.

[Dahlbeck]

Was that radar altitude? I.e. height over ground?

[Hummingbird]

Was that radar altitude? I.e. height over ground?

 

It was barometric (pressed ctrl Y twice), measured deck alt at 50-70 m barometic and then started testing.

[Hummingbird]

btw probably wasnt the salt lake flats (my NTTR geographics are none existant), as I can see that lies at an elevation of ~1,200 m, so must have been somewhere else. It was on the upper western edge of the NTTR map.

 

EDIT: Yeah lol most definitely aint there, completely different direction :D

Edited June 26, 2016 by Hummingbird

[Hummingbird]

Map starting point (where the A10 is):

[mattebubben]

Would be interesting if someone could try the maneuver in the Mirage 2000.

 

Since it having a very good instantaneous turn rate (being a delta and all)

It aught have a better chance then any other fighter in the game atm (atleast that would be my guess).

[Hummingbird]

Would be interesting if someone could try the maneuver in the Mirage 2000.

 

Since it having a very good instantaneous turn rate (being a delta and all)

It aught have a better chance then any other fighter in the game atm (atleast that would be my guess).

 

I tried it in 2.0 and there it can do it from about 750 m. But its STR is way below standard in 2.0 atm, so I wouldn't trust the result that much.

[JNelson]

I tried the su27 a couple times, got about 500m from 250kts in a split S, Mirage didn't fair too well, took like 800m doesn't have the rotation speeds at low speed I feel.

 

Edit: In 1.5.4

[Hummingbird]

Alright fixed the views in 1.5.4 and tested it at SL and the minimum height at which I can reliably finish a split S in the Mirage (clean) is 725 m. Entry speed was 600 km/h TAS full AB.

 

EDIT: Tried again and managed to cut it down to 680 m, but this was very tough to achieve (was litterally centimeters from the water)

Edited June 27, 2016 by Hummingbird

[J3ST3R]

Just out of curiosity, does anyone know where the Viggen is in terms of development or potential release times? I'm super excited for it.

[mattebubben]

Soon™

 

(This year and before the F-14 but no official date/Timeline has been announced)

[foxmaner]

Heard something about 2 weeks...

 

Skickat från min SM-A310F via Tapatalk

[Skjold]

Just out of curiosity, does anyone know where the Viggen is in terms of development or potential release times? I'm super excited for it.

 

Somewhere between now and the end of the universe.™

 

a DCS newsletter said first half* of this year, but since theres less then a week to go i highly doubt it. Later this year hopefully.

Edited June 27, 2016 by Skjold

[J3ST3R]

Touché gentlemen. Just wondered if there was a official statement I had missed as I've been away for a while.

[QuiGon]

Just out of curiosity, does anyone know where the Viggen is in terms of development or potential release times? I'm super excited for it.

 

For all we know it should be very close to release. If I would bet, i would put my money on August, but I would not also rule out a release in July.

[J3ST3R]

If it were July or August though, do you not think we would have heard something by now? The last thing is saw cobra write was they were aiming for early new year but then something like illness struck so it was delayed. As I say, I'm just curious.

[boopidoo]

For everyone discussing the split-S it is not necessary the case that the pilot in this case made a full split-S. What was described was a half-roll and hard pull towards the sea (not necessarily to vertical), when levelling out he more likely made another half-roll before levelling out (something I find more likely). In other words I do not think he did a complete split-S. Someone translated "halvroll" to split-S which is not 100% correct. "Halvroll" is only the first maneuver in a split-S, in this case rolling to inverted.

 

During my youth I heard of this incident from an airforce JA37 pilot (in around 1992-93). We also discussed how the Viggen fared in joint excersices against Norweigan F-16's, in short the Viggen pilots really didn't want to join in a dogfight but much rather took them out at a distance if possible. The relied heavily on their datalink which made it possible for pilots to engage targets more stealthily without using their radar. One group could locate and lock the targets while another group could flank and engage with sensors off. Often these tactics worked out quite well. If the F-16's managed to close in to a dogfight the Viggen pilots were at a clear disadvantage.

Edited June 27, 2016 by boopidoo

[renhanxue]

For everyone discussing the split-S it is not necessary the case that the pilot in this case made a full split-S. What was described was a half-roll and hard pull towards the sea (not necessarily to vertical), when levelling out he more likely made another half-roll before levelling out (something I find more likely). In other words I do not think he did a complete split-S. Someone translated "halvroll" to split-S which is not 100% correct. "Halvroll" is only the first maneuver in a split-S, in this case rolling to inverted.

 

 

That was me, and I'm pretty sure I'm right. "Halv roll" sounds like it would mean just a 180 degree roll, but that's not what it actually refers to in military Swedish (dunno about civilian acrobatic flying). It really does refer to a split S. See for example these two pages from the J 35F SFI, which show that the maneuver does involve rolling inverted and pulling down.

 

 

 

As you can see, in the Draken (which accelerated incredibly quickly in a dive and also had problems with generating enough force on the elevons at high loadings) entering a split S was normally (in peacetime) forbidden at any speed at altitudes below five kilometers. See also this diagram though, which shows a minimum required altitude of about 1500 meters if you're pulling 7 G through the entire maneuver:

 

Edited June 27, 2016 by renhanxue

[Cobra847]

Next to last research trip was conducted today, with the great JA-37Di at Graz-Thalerhof.

 

Unfortunately a bit different than our AJS-37; but still a great tool (amongst others) to ensure maximum graphical accuracy.

We were finally able to solve some cockpit accuracy issues due to lack of reference (on major cockpit parts, nonetheless!). Canopy elements can be a real PITA to get good reference for.

 

Progress is very strong, looking forward to being finally done!

Edited June 27, 2016 by Cobra847

[WARJUNIOR]

Next to last research trip was conducted today, with the great JA-37Di at Graz-Thalerhof.

 

Unfortunately a bit different than our AJS-37; but still a great tool (amongst others) to ensure maximum graphical accuracy.

Progress is very strong, looking forward to being finally done pretty soon!

 

Thanks for the update, Cobra. Looking forward to the viggen being done "pretty soon™".

[Cobra847]

Thanks for the update, Cobra. Looking forward to the viggen being done "pretty soon™".

 

I removed the trademarked quote; just in case anyone gets triggered. :D