Heatblur: AJS-37 Viggen



I can’t see why not




Oi, you use the farps with the rest of your pull for power mates.


We are a special breed for sure. Probably suits us to have our own little area…


What would you say are the coordinates, elevation, and maximum bounds of this area. I need to know, for, uh, reasons?




Why not the whole ACE, while we’re at it! And the rest of the ARG/MEU. It would be cool to start a Combined Arms mission inside the well deck, ride an LCAC in to the beach, and commence destruction from the sand. Without getting sick inside your armor bathtub!


Road base? Did someone say road base?


Hmmm… F-18’s like road bases…

Actually I’m liking this idea more and more lol



Some of the strips near Lake of the Woods aren’t much better than that.


Just to dispel some nasty rumor that seems to keep floating back up regarding the Viggen navigator: While no, there is no lengthy navigation system alignment process during cold start, or IMU heaters to engage, there is, in fact, an inertial navigation system on the Viggen.

“But, but, but, but, but I heard it has a Doppler!”

Yes, the Viggen does have a Doppler velocimeter system that’s used to update the navigator’s velocity solution to correct for wind and for sloppy accelerometers, but Doppler alone does not make a complete navigator. While we all know how to use the Doppler navigation system in the Mi-8, velocity integration does not give attitude information, which the Viggen definitely has.

Rather than argue all engineer-y how there’s no way to make a navigation system like the Viggen’s work solely using Doppler measurements, I’ll let the AJS37 Manual speak for itself:

[quote=AJS37 Manual pg 129]
The AJS-37 Viggen is equipped with a rather advanced (for its time) navigation system. The
system is based on the principle of Automatic Dead Reckoning (ADR). By inputting the origin
point (the take-off position), course, airspeed and attitude, the current position can be established.

ADR principle
The initial position in entered into the system, and from this a three-dimensional vector is created
based on flight data from the Flight Data Unit (main pitot), attitude, course, and airspeed.
Inputs from the accelerometer unit small changes are taken into account in order to refine the
information from the flight data unit. The drift due to wind is compensated by either adding
pilot entered ( forecast) wind values or the movement detected from the Doppler unit.

Every 103 ms the calculated vector is used to calculate change in the ground-referenced
speed. This change in motion along the ground is added to the entered take-off coordinates
and will continually update this position during the flight. This is known as the
basic position, which is the basis of the navigation system.[/quote]

There are very likely gyros on the Viggen somewhere as well, to keep the artificial horizon on the HUD, but I haven’t been able to find any info on these.

So, while the navigator in the Viggen is most definitely not the inertial navigation system you’re familiar with, it is, in fact, using inertial measurement sensors (accelerometers) to create the navigation solution, aided by the Doppler velocimeter to correct for wind and to overcome noisy/biased sensors.


And, let me just add, the navigation system is updated by the pilot who can manually correct the waypoints, either visually or by ground map radar.


Counterpoint: ur a butt

On an actual note, I’ve noticed, for lack of a better word, significant lateral wobble intermittently in the aiming indicator for DYK precision mode. Ranging remains more or less correct, but it will sway across large swaths of the HUD. I’ve disabled target motion tracking (or whatever code 221 is in TAKT), I’m diving between 10 and 30 degrees, and my speed is ~Mach .85. Is there anything I could be doing that’s clearly wrong, or could this be a Viggen bug?


Yes indeed, if you want attitude information in a aircraft you usually have a gyro.

I wonder what’s hooked up to the secondary pitot system given that they speak of a mean one that goes to the FDU.


I’ve seen wobble in all the modes - sometimes the flight path marker just slowly oscillates side to side, about 1 second period or so. I wasn’t able to quickly find anything on the ED forums, but maybe @nicholas.dackard has a hint/suggestion for us?

If you’re able to capture a track or some video of it happening, we can post it to the ED forums, see if others are experiencing it or have an explanation/fix for it.


Stop trying to do everything in an inverted negative g manoeuver you tomcat lover.


NEVER! Check your non-inverted positive G privilege, grav-lord.


On my rocket run last night I experienced the aiming indicator “shaking” for lack of a better descriptor. I assumed it was due to poor skills but of all the things I expected to happen on the run, a single element of the HUD vibrating was not one of them.


My dive was a bit shallow, but this is what I’m talking about.

I suspect it has something to do with wind in the mission.