Viggen navigation goes crazy on red flag mission 3

Hi!

I have a problem with the Viggen's navigation system when I fly the third mission of the red flag campaign. I'll try to explain it the best that I can, although it plainly seems to go crazy at some random point.

So, I tried flying the mission twice. The first time everything was going OK until the time I was approaching WP2 (perhaps some 60km away from it). The waypoint seemed to move further and further in the same direction. By the time I reached the real waypoint location (as shown in the f10 map), the waypoint in the Viggen's navigation was still quite far away to the north. While holding over the real waypoint location, at some points the waypoint was also turning so as to stay at my 12 o' clock.

When I got the push order, I headed towards WP3 (Mount Irish) with the help of the f10 map, and got a visual fix of the waypoint. I supposed that this fixed whatever happened to the navigation system. However, while heading towards WP4, the system went crazy again with WP4 moving all over the place. The last two digits of the TERANAV (AKT POS) were stuck on 20 throughout this time.

The second time I tried to make sure that I did everything right:

REF LOLA - 9099 - LS

TAKT - 9 - B5

AKT POS - B5 - TID - 162700 - B5 (time on target 16:27)

AKT POS - B4 - TID - 086000 - B4 (Ingress speed 0.84)

AKT POS - B5 - TAKT - 000050 - B5 (pop-up point 000 degrees, 5km)

TAKT - 221 (motion measurement)

(A while ago I heard there was a bug when inserting time on target and ingress speed (I think that xxJohnxx mentions it in one of his tutorial on YouTube). The workaround was to select the related WP in AKT POS. I only tried this the second time I flew the mission, just in case...)

I turned the mode selector from BER to NAV once I entered the runway (I've heard that this is the right way to do it, but until now I was switching to NAV while still parked with no problems), I aligned as well as I could, and let the navigation system take its own reading between 100 and 200km/h during the take off run (in other words, I didn't press the reference button).

I slowly climbed to 15000 feet (approx. 4570 on my backup altimeter that I adjusted for the given QNH pressure--the main altimeter was tuned to the target's QFE) and at some point the teranav display's last two digits started showing 20, 21, 22, 23, and 24 as I was holding over WP2. Everything's normal so far.

When the push order was given, I headed towards WP3 and started descending. Flying over Mount Irish (WP3) fixed the deviation. The waypoint appeared to be in place (although the computer returned four or five km deviation by then) and as I passed over it the last two digits of the teranav display (AKT POS) showed 05 for the first time since I climbed to 15000 feet. Perfect!

I continued flying low towards WP4 and at some point in the middle of the way, the navigation started going crazy again. While still some 30km away (I think) from WP4, the navigation system was updated, WP4 switched to U5, but the bearing to U5 was the same as that I was following for WP4. I selected WP4 again and found out that it had moved somewhere to the south. I then selected WP5 (the target WP) but it was constantly updated to different positions. I consulted the f10 map and when I reached the real position of WP4, I turned north to head towards the target. As I did so (from approx 260 to 0 degrees) the target waypoint was continuously updated to stay at my 12 o' clock. So, all WP4, WP5 and U5 weren't just in wrong positions, but were also constantly updated in a crazy fashion.

The teranav second to last digit was on 2, sometimes on 5, and then it stayed on 1.

I never had any problems with the Viggen's navigation system until flying this mission. However, I can't see how the problem could be related to something in the design of this mission either. Regardless the differences, the navigation system went crazy in both attempts. I'll keep on testing, however am I missing something obvious?

By the way, I don't get any navigation system or other failure lights at any point during the mission.

...long text...

Hello John!

Just a quick guess:

Is there a doubled key-binding for T1 and TV which might have been activated unnoticed by you?

Not a radar fix, but a manual fix.

I can think of flying upon WP4, and when these happenings cut in, the position of the following waypoints would be shifted.

I would search in this field first, but to be honest, I don't give it too high chances ... :music_whistling:

Hello John!

 

Just a quick guess:

Is there a doubled key-binding for T1 and TV which might have been activated unnoticed by you?

Not a radar fix, but a manual fix.

I can think of flying upon WP4, and when these happenings cut in, the position of the following waypoints would be shifted.

 

I would search in this field first, but to be honest, I don't give it too high chances ... :music_whistling:

Thanks for getting into the trouble to read my long message TOViper :)

That's a great guess and indeed it would explain a lot! However, I have assigned T0, T1 & TV as a three position switch on an 'axis to button' axis on on my throttle and it's pretty difficult to accidentally hit TV with that. Furthermore, I do remember that I had my radar in A1 mode in both cases, so I couldn't have taken visual fix. Still, I will keep this in mind when I try flying the mission again.

Unless there's indeed some obvious mistake on my part, I suspect that there might be some bug triggered by the combination of the parameters I entered on the computer.

Thanks for getting into the trouble to read my long message TOViper :)

 

That's a great guess and indeed it would explain a lot! However, I have assigned T0, T1 & TV as a three position switch on an 'axis to button' axis on on my throttle and it's pretty difficult to accidentally hit TV with that. Furthermore, I do remember that I had my radar in A1 mode in both cases, so I couldn't have taken visual fix. Still, I will keep this in mind when I try flying the mission again.

 

Unless there's indeed some obvious mistake on my part, I suspect that there might be some bug triggered by the combination of the parameters I entered on the computer.

Can you create a video of the mission, starting from the beginning on where you enter the cockpit and lasting until you take-off, and another video when loitering at WP2 until approaching M5. Would be helpful to see.

Can you create a video of the mission, starting from the beginning on where you enter the cockpit and lasting until you take-off, and another video when loitering at WP2 until approaching M5. Would be helpful to see.

Yes, I'll try to do that. What software do you use for recording? I've never done that before.

Yes, I'll try to do that. What software do you use for recording? I've never done that before.

Since I have a NVIDIA Geforce card, I use the "internal" GeForce Experience recording software. It works absolutely fantastic. I never used other software, so I cannot give you any more advices, sorry.

Since I have a NVIDIA Geforce card, I use the "internal" GeForce Experience recording software. It works absolutely fantastic. I never used other software, so I cannot give you any more advices, sorry.

Sent from my SM-J510FN using Tapatalk

Hello John!

 

Just a quick guess:

Is there a doubled key-binding for T1 and TV which might have been activated unnoticed by you?

Not a radar fix, but a manual fix.

I can think of flying upon WP4, and when these happenings cut in, the position of the following waypoints would be shifted.

 

I would search in this field first, but to be honest, I don't give it too high chances ... :music_whistling:

I was trying to make that video today and spotted the problem. As you said, it was the T0-T1-TV switch being pressed at a very quick rate at spontaneous moments during the flight. It appears there's some kind of firmware/software problem with my throttle since these buttons are pressed without any user input. Many thanks TOViper!!!

I was trying to make that video today and spotted the problem. As you said, it was the T0-T1-TV switch being pressed at a very quick rate at spontaneous moments during the flight. It appears there's some kind of firmware/software problem with my throttle since these buttons are pressed without any user input. Many thanks TOViper!!!

De nada! :)