FBW issue with wing tanks

Hello,

I just done a little flight with a buddy using the new stable release [1.5.3.51218.38], payload Matra Magic II + wing tanks, max fuel.

After a while my aircraft started to shake, very slowly increasing shaking (I could see the flight controls moving like crazy).

I think it started as soon as the tanks went empty.

This happened to my buddy too, shortly after.

The only thing that worked to stop the shaking was to switch to VRILLE, this removed the shaking completely.

As soon as I flipped the switched back to NORM, shaking resumed, without any reduction in shaking strength.

Then we had two different things happening, my buddy tried to switch back to NORM, then hit the jettison button for the tanks, this resulted in an instant blackout and spin, followed by a crash.

On my side, I kept my tanks and attempted landing. As I touched ground my aircraft instantly turned into a fireball...

I'll try to make a track that reproduces the problem (but not today), did anyone observed anything similar?

Is it anything like this?

 

 

I've tried and tried to recreate to no avail.

 

The other person reported some steps and had a good video but even doing it just like that I couldn't recreate, until I recreate I'm not sure there is much I can do so any details you can provide will be helpful, thanks!

Same kind of buffeting, except I was at moderate speed (around 350) and not maneuvering at all, it just started out of nowhere. The effect was still there even at low speeds.

I'll PM you tonight's track, if you're lucky (and survive the boredom) you'll be able to get to the point it starts (it happened when wing tanks emptied), I didn't have time to replay it so I don't know if that will work for you, I was planning to do a shorter flight with less fuel in an attempt to recreate this, later this week.

Edit: the track is 40.30mb big, I'll post it to a file sharing hosting site tomorrow.

Check at 1:25, thank you :)

Tacview-20160314-201652-DCS.txt.rar

Hi,

Good luck to CptSmiley with this one.

I had it once, the past week; was testing something else and was "far" into the mission (in time) so didn't back up the track. I certainly will next time if it's helpful.

I think I had the big tanks.

I didn't try the NORM/VRILLE switch though. Instead, I switched to GAINS secours. That made the trick... for a while. About 5-10 minutes later, the shaking began in emergency gain too.

I had a re-spawned aircraft too, wondered if that might be a cause (aka wrong variable initialization?); and IIRC I was playing with the vide-vite (fuel jett.) to check for bug fixing in that area.

Hope this helps, even if it's thin...

buffeting ver 1.5.3.51218

I tried to get a short track but was unable. I could not start with external tanks empty.

here is the mission I used. I set the fuel in the mission editor to 44% and 24% but in the cockpit it would not go below 5028k.

Aircraft configuration;

- external tanks times 3

- magic on station 9

To duplicate;

Once externals tanks empty, enter buffeting at around mach .94 while turning to the left. Once buffeting is enter it will not stop. It will diminish below 200 knots. If magic is fired above 200 knots, uncontrollable roll happens. Below 200 knots, severe buffeting. I will try to get a track, might be long.

720.525 second track. Problems start at around 689 to 693. fuel was at or below 2000k

Awesome, thanks guys, will try to recreate with this newer information.

Hello, I sent you my track from yesterday's flight (PM).

The flight is one hour long until the issue but I replayed it three times at speed x15, and everytime the issue would appear at 11:09:40 from the in-game clock (around 3250 fuel remaining, it was just before emptying the drop tanks).

The speed never exceeded mach 0.8 during that flight.

P.S.: My Wingman experienced the same issue at 11:23:30, he dropped the tanks and did a high rate roll that blacked him out (not spin actually) at 11:26:40.

My landing attemp occurs at 11:36:50 (it looked like the aircraft flipped to the left with high rate as soon as wheels touched ground), I had switched to VRILLE and wasn't experiencing the crazy flight controls at that moment.

Hi,

I just reproduced the subject bugs. Airplane started shaking in level flight as soon as the external fuel tanks were emptied. I also experienced the rapid roll after firing a magic.

All fixed in development! Turns out with wing tanks on I was reducing mass at twice the rate for each tank per amount of fuel loss. Which also means it was losing inertia at twice the rate. By the time you had nearly empty wing tanks you had nearly 0 inertia, and if you flew much longer your inertia would actually go impossibly negative causing the outrageous roll.

 

Jettisoning the tanks accelerates the sequence after you've lost a decent amount of fuel...

 

Fix will be in the next update for you guys.

:thumbup:

That was quick! CptSmiley, you seem to be a very talented programmer! I sure hope you keep working with Razbam on next modules :)

Would it be possible to get a fix now ? like a file to download or something ? I know with Leatherneck, whenever their MiG-21 was ''broken'' by an update (which I understand can happen from time to time during a beta), they would usually publish their own temporary fix so that people could at least keep flying until the next official update by ED.

I do have to say this was one of the trickier ones to solve and track down.

Those are the most rewarding ones! :)

Would it be possible to get a fix now ? like a file to download or something ?

I would advise not to. Sure, I would like to get a fix ASAP, too, but not that hard.

Iwouldn't want if if it creates more problems (e.g. many people not so computer-oriented trying to tweak their DCS installation and failing to do so properly ; yes, even a file to copy/paste can be though!!).

Plus it would be a workaround of the quite efficient auto-updater system (not a wishable thing), plus given how often Razbam puts out updates (every one or two weeks), it's not worth it; especially as it doesn't prevent flying "at all", it just prevent using the big tanks.

Sorry if it doesn't suit you. Just a personal opinion.

Those are the most rewarding ones! :)

 

 

I would advise not to. Sure, I would like to get a fix ASAP, too, but not that hard.

 

Iwouldn't want if if it creates more problems (e.g. many people not so computer-oriented trying to tweak their DCS installation and failing to do so properly ; yes, even a file to copy/paste can be though!!).

Plus it would be a workaround of the quite efficient auto-updater system (not a wishable thing), plus given how often Razbam puts out updates (every one or two weeks), it's not worth it; especially as it doesn't prevent flying "at all", it just prevent using the big tanks.

Sorry if it doesn't suit you. Just a personal opinion.

The big tanks are kinda essential with some of the missions my squadron does and the bug also prevents from firing MAGICs, which is kindda of a big deal. Leatherneck always promptly provided their customers with the OPTION to fix their module between official updates and it never hurt anyone that I know of. Worst case scenario you delete everything, do a repair and you are golden. If you don't feel comfortable doing it, you also have the option to wait.

The big tanks are kinda essential with some of the missions my squadron does

Yeah, I guess. But we're talking one or two weeks tops. Is it that hard? I mean, it's a beta and we all know it; let's take the time to enjoy the new 530Ds and radar for the time being (that's what the aircraft was meant to do anyway).

and the bug also prevents from firing MAGICs, which is kindda of a big deal.

Does it? Didn't know that...:huh:

If you don't feel comfortable doing it, you also have the option to wait.

Personaly I would feel confortable, not a problem. :)

But I've seen too many people coming back to the developper(s) (not only in DCS) because they tried to apply a fix (or a mod) and broke their install doing so. I noticed that most people will prefer to get an answer like "the problem will be automatically correct next week" rather than a "download this, put it there, don't forget to unzip, don't forget to make a back-up..." one.

Your point about choice is fair, but then I'll also say that given the choice, most people just "can't wait" and try to apply the fix, even if they're at risk of not doing it OK because they don't really understand the whole file/folder/update process (but won't admit it, because in these days & age...)

And all the time the developpers spent to get a specific fix out, plus explaining/rescuing lost users, is time they can't spend on more bug fixing or feature coding. IMO it's kind of a waste, to gain just a week or two.

Anyway, it's not my decision; I voiced an opinion & concerns, 'nough said about it :)

Yea whenever a magic is launched, it makes the aircraft roll uncontrollably (never seen a roll rate like that in DCS lol, almost got dizzy).

Well I just tried it on 1.5.3 update 1, no roll issue (I had the big tanks on).

Another possible temporary "fix" would be to roll back to the last version until then - of course this means letting go of the other changes

We had this bug with the latest patch (open beta today) twice in our training. One pilot had this in normal flight with the large wing tanks, the other direct after dropping his tanks.

Well I just tried it on 1.5.3 update 1, no roll issue (I had the big tanks on).

I had the roll issue after the shaking. Maybe the 2 bugs are linked ?

I had the roll issue after the shaking. Maybe the 2 bugs are linked ?

You need to empty the tanks before getting the issue (as there is a negative inertia build-up as fuel is consumed).

Once you have this impossible inertia, the aircraft will be extremely touchy and will react to the slightest perturbation (fire a missile, drop a tank, touch down).

I think the shaking is only a side effect from the FBW laws.

WHen I had the issue, switching to VRILLE removed the shaking but I still did a super-bouncy landing that flipped me instantly.

My encounter with this bug had a bit of an uncommon ending which might indicate another bug; after running the tanks dry I got the vibration which I also discovered could be 'fixed' by switching to VRILLE. After refuelling, I switched it back to normal and the vibration was gone.

Also after refuelling, I pulled back and to the right as hard as I could (okay, I wasn't completely full and a little bit frustrated), and my aircraft acquired a modest but annoying roll to the right. Checking the external view, I discovered my left wing tank had disappeared. Not sure if I'd managed to pull excessive G's or if perhaps I'd collided with the tanker.

So, I decided to jettison the right wing tank to rebalance the aircraft, and that's when the aircraft went into a rapid and uncontrollable spin.

Shouldn't the FBW bug have been triggered by the (uncommanded) loss of the left tank? Is it adjusting only based on expected aerodynamic changes or to actual changes?

As soon as the shaking starts, and you switch to VRILLE to make it home. But, you cant land the plane, as soon as the plane touch down it crashes, either you jump up and start to spin or explodes.

I have tried to switch to NORM just before landing, it dosent prevent you from crashing..

So keep the two wing tanks at home..... :(

Guys, why do you put more effort into this?

CptSmiley said he found the problem, and was fixing (or has fixed) it in his dev version. It's sensible to expect this will be part of the next update.

In the mean time, why not simply not use wing tanks, and concentrate on other areas of the aircraft? I will do that.

It's a beta, we found something broken, now let's wait to get the needed fix about it ;)

Guys, why do you put more effort into this?

 

CptSmiley said he found the problem, and was fixing (or has fixed) it in his dev version. It's sensible to expect this will be part of the next update.

 

In the mean time, why not simply not use wing tanks, and concentrate on other areas of the aircraft? I will do that.

It's a beta, we found something broken, now let's wait to get the needed fix about it ;)

Dude the next update will be in like 2 weeks!, and VEAO is planning on update its HAWK at the same time so they will probably break the entire game doing so. I'm a big baby and I want my toy to be fixed asap!