DCS: AJS-37 Viggen Discussion

[El Hadji]

The problem is that he got filmed doing it...

 

This is a picture of two Drakens from F10 doing a low-pass over some friends in a canoe... (aparently the canoe flipped over when the planes passed)

 

Edited July 18, 2016 by El Hadji

[El Hadji]

Nice video of Saab A32 Lansen's from F6 during low-level flying over the Baltic sea in 1975:

 

Edited July 18, 2016 by El Hadji

[RaXha]

The problem is that he got filmed doing it...

 

This is a picture of two Drakens from F10 doing a low-pass over some friends in a canoe... (aparently the canoe flipped over when the planes passed)

 

 

Not really, the main problem was that his friends got serious burns on large parts of their bodies because he had the afterburner on full blow when he passed them...

 

This is a comment about the event from the trial:

Swedish:

Olyckan har orsakats av att föraren i samband med starten, med tänd efterbrännkammare, avvikit från startbanan och på låg höjd flugit över besökarna och därvid ansatt en upptagning varvid flygplanet erhållit en sådan attityd att besökarna skadats av flygplanets jetstråle och tryckvåg. Förarens beslut att göra en överflygning av besökarna kan ha påverkats av att han sett andra göra liknande manövrer utan att detta påtalats.

 

English:

The accident was caused by the driver who during takeoff, with lit afterburner, deviated from the runway making a low pass over the visitors and making a pull up in such a way that the aircraft ended up in an attitude that the visitors were injured by the aircrafts jet stream and shock wave. The drivers decision to do the overpass of the visitors may have been influenced by him seeing others doing the same without repercussions.

 

Source

 

 

Edit: I realized we might not be talking about the same incident?

Edited July 18, 2016 by RaXha

[El Hadji]

I was referring to the Tp84...

[RaXha]

I was referring to the Tp84...

 

As i said we might not be talking about the same incident, to many different low passes being discussed at once! :joystick:

[microvax]

BTW I just thought about the possible AOA issue with the engine.

 

Is there anything preventing you from pulling to much AOA, iirc the Viggen isnt FBW, but has some kind of system to give force feedback. So I guess it would give a lot of backpressure on the stick so you cant pull more AOA ?

[renhanxue]

BTW I just thought about the possible AOA issue with the engine.

 

Is there anything preventing you from pulling to much AOA, iirc the Viggen isnt FBW, but has some kind of system to give force feedback. So I guess it would give a lot of backpressure on the stick so you cant pull more AOA ?

 

There's a stick shaker, that's it. It has a few different modes of operation, so it can activate at different points - IIRC it activates earlier in more critical flight phases such as landing and low altitude flying etc.

[microvax]

There's a stick shaker, that's it. It has a few different modes of operation, so it can activate at different points - IIRC it activates earlier in more critical flight phases such as landing and low altitude flying etc.

 

Thx for le info. Sounds great to me. :)) Love having to judge the flight envelope myself. :D

[MA_Goblin]

Well I can vouch for low flight over sea any ways.

During my conscript time I served on the Robotbåt typ NKG and standing on the bridge during an exercise two AJ 37 passed beside us and that's about 10 m above sea level.

[renhanxue]

Thx for le info. Sounds great to me. :)) Love having to judge the flight envelope myself. :D

From around M 0.6 at sea level (increasing with altitude) and up there are also ample opportunities to exceed the load factor limit (8 G), and there is nothing to stop you from doing it :)

 

It is also very easily possible to overspeed a clean aircraft in level flight at low altitude. At low altitudes, the thrust-to-drag ratio at max AB reaches 1:1 well above Vmo (which is M 1.1 at sea level), and if you're lightly loaded it takes only 12 seconds from M 0.9 to M 1.1 at max AB.

[renhanxue]

I am interested in seeing the whole ATIS for fpl 37. :)

Anvisningar för typinflygning fpl 37, 1985 års utgåva

 

I haven't really proofed this PDF at all so yell if something's weird and I'll get you the original photos.

[Pocket Sized]

From around M 0.6 at sea level (increasing with altitude) and up there are also ample opportunities to exceed the load factor limit (8 G), and there is nothing to stop you from doing it :)

 

It is also very easily possible to overspeed a clean aircraft in level flight at low altitude. At low altitudes, the thrust-to-drag ratio at max AB reaches 1:1 well above Vmo (which is M 1.1 at sea level), and if you're lightly loaded it takes only 12 seconds from M 0.9 to M 1.1 at max AB.

 

Oh, that sounds wonderful! What are the consequences of over stressing/over speeding the Viggen?

[microvax]

Do we know for how long the AJS37 can fly inverted [until the engine starves] ?

[Agremont]

Just sat in an actual Viggen at the Aeroseum in Gothenburg. Really nice cockpit and quite roomy. At least in comparison to the Draken, which was almost claustrophobic.

 

I had great fun flipping switches! :D I didn't manage to find the gear lever though. I thought it was supposed to be somewhere to the left side of the pilot.

 

Anyway, I can recommend going there if you're ever in Gothenburg.

[microvax]

Just sat in an actual Viggen at the Aeroseum in Gothenburg. Really nice cockpit and quite roomy. At least in comparison to the Draken, which was almost claustrophobic.

 

I had great fun flipping switches! :D I didn't manage to find the gear lever though. I thought it was supposed to be somewhere to the left side of the pilot.

 

Anyway, I can recommend going there if you're ever in Gothenburg.

 

iirc its the handle to the left of the Radio. But not sure if that wasnt related to the thrust reverser.

[JanTelefon]

iirc its the handle to the left of the Radio. But not sure if that wasnt related to the thrust reverser.

 

The gear handle is left of the pilot seat. A large lever that reminds you a bit of a hand brake in a car. The reverser is activated by pulling a T-handle on the left side of the center panel. Roughly where the weapon selector rotary is in the Mig 21.

[renhanxue]

Do we know for how long the AJS37 can fly inverted [until the engine starves] ?

The SFI says you're allowed up to 10 seconds of flying with negative G load, but unless you're in full AB it's actually limited by the engine lubrication system, not by the fuel feed. The central feed tank has two compartments designed for keeping the fuel feed working while under negative load, with a total volume of about 2% of the internal fuel. This volume was deliberately chosen to provide sufficient fuel for those 10 seconds mentioned above assuming full AB at sea level. If you're using less thrust you're going to get the OLJETRYCK (oil pressure) warning way before the engine flames out from fuel starvation.

 

Just sat in an actual Viggen at the Aeroseum in Gothenburg. Really nice cockpit and quite roomy. At least in comparison to the Draken, which was almost claustrophobic.

 

I had great fun flipping switches! I didn't manage to find the gear lever though. I thought it was supposed to be somewhere to the left side of the pilot.

 

Anyway, I can recommend going there if you're ever in Gothenburg.

Very nice! I've been thinking I should go there since forever. I think it's time I get off my butt and call up my brother (who lives in Gothenburg) and ask him if I can come over and visit sometime.

 

Like JanTelefon says, the landing gear lever is to the left side of the pilot, it's just really far back and pretty low. I've marked it in red:

 

[Agremont]

The gear handle is left of the pilot seat. A large lever that reminds you a bit of a hand brake in a car. The reverser is activated by pulling a T-handle on the left side of the center panel. Roughly where the weapon selector rotary is in the Mig 21.

 

Hmm, I couldn't find it. maybe it was taken out.

 

Like JanTelefon says, the landing gear lever is to the left side of the pilot, it's just really far back and pretty low. I've marked it in red:

 

Maybe I wasn't looking far enough back actually. Oh well.

[El Hadji]

I heard another story about a J35 from F4 returning to base after having reported a bird strike. When the mechanics looked at the damages they found needles from a spruce tree so they confronted the pilot and questioned his bird strike report. He replied "So what? I can't help that the @$#o@#% bird was sitting in the top of a tree, can I?"

[RaXha]

I heard another story about a J35 from F4 returning to base after having reported a bird strike. When the mechanics looked at the damages they found needles from a spruce tree so they confronted the pilot and questioned his bird strike report. He replied "So what? I can't help that the @$#o@#% bird was sitting in the top of a tree, can I?"

 

Spoken like a true viking draken driver! :megalol:

[JanTelefon]

Hmm, I couldn't find it. maybe it was taken out.

 

I sat in that very cockpit earlier this spring, and I'm 99% sure it's still there.

 

Maybe I wasn't looking far enough back actually. Oh well.

 

It's really far back. Roughly by your butt cheek. :)

[renhanxue]

TIL that when they updated CK37 (the central computer aboard the AJS 37) from its original 60's incarnation to 80's technology, the CPU they chose was a 80286 together with the 80287 math coprocessor. If you had an IBM PC or PC clone in the mid-80's, you probably had a very similar CPU.

 

 

(I'm on vacation, that's why I'm posting so much)

[JaNk0]

Renhanxue, very informative information you're posting, greatly appreciated!

Do you know if the computer in early Gripen planes used the CK37 or perhaps an improved version?

[renhanxue]

Renhanxue, very informative information you're posting, greatly appreciated!

Do you know if the computer in early Gripen planes used the CK37 or perhaps an improved version?

Well, remember that the original CK37 was a dawn-of-the-digital-era design from the late 60's. The 80286 solution in the AJS 37 was kind of a kludge, really - they upgraded the core of the computer with 80's off-the-shelf components, new memory etc, but kept most of the old interfaces the same while adding a few new ones (such as the MIL-STD-1553B serial bus).

 

The Gripen A and B's computer was a completely new, modern (for the 90's) design and while I know very little about it I believe it was based on the PowerPC architecture (also popular in 90's Macintoshes), with CPU's made by Ericsson. There's a little information about it here: http://www.x-plane.org/home/urf/aviation/gripen/gripen-network.html

Edited July 19, 2016 by renhanxue

[Krieg]

Another fun anecdote regarding the avioics is that apparently when the inertial navigation system in the JA 37 was upgraded from the older "manual" system to a computerized system from the US, they found it troublesome with integration and simply let the computer simulate the old system and not really doing anything.

 

Sorry for link in swedish, but notes from a fairly interesting seminar on the man/machine interface on the (primaily fighter) viggen. [ame]http://www.aef.se/Kopierade_dokument/JA37_Pilot_och_system.pdf[/ame]