Major Flight stability bug

[Shinbet]

My F15E is very unstable in the air, any small stick Input and the jet goes nuts, elevator ossolating, yawing, very easy to wing bend and over G, the stability with wing bend is worse than normal, my CAS is obviously on, my stick is properly tuned, cannot fly straight whatsoever, pretty bad flight model bug

 

anyone else have this problem because some people in the server I play on are also complaining of the same issue 

 

 

4YA_Aerobatics_Online_Caucasus_Beta_V2.40_[01_SUNRISE]-20230724-143239.trk

Edited July 25, 2023 by Shinbet

[razo+r]

I feel like it's a bit less stable but far from unflyable.

[caponi]

i had to increase my pitch curve from 8 to 20 ... with a 20cm stick extension
But it is flyable ...

 

[afnav130]

The FM is getting better but it still "wanders" too much for an F15. 

[Bosun]

Did you all have your CAS on?  Because auto start doesn't turn that on automatically.

 

[Holbeach]

19 hours ago, Shinbet said:

My F15E is completely unstable in the air, any small stick Input and the jet goes nuts, elevator ossolating, yawing, very easy to wing bend and over G, the stability with wing bend is worse than normal, my CAS is obviously on, my stick is properly tuned, cannot fly straight whatsoever, pretty much an  unflyable flight model bug

 

anyone else have this problem because some people in the server I play on are also complaining of the same issue 

Check for double bindings, because mine is rock solid and very precise in all axes.

..

[FusRoPotato]

Can confirm. Something is still wrong with weight, inertias, or base FM logic. At some point in flight, the aircraft becomes super twitchy and unstable, usually at Winchester. It's as if extra weight is being removed from some component and creating negative mass.

Edited July 26, 2023 by FusRoPotato

[afnav130]

I still think, based on feel, that after takeoff turning OFF the CAS switches then turning them back on evens the jet out. 

[Yeti_JTF111]

Can confirm as well and interesting point about the Winchester. It recently happened to me after cleaning the jet off of munitions and being around 5000 pounds during air to air refueling. Any pitch input would send the aircraft oscillating like crazy. I then reloaded a scenario I made to practice AAR with 10,000 pounds or so and the aircraft was fine.

[Raven (Elysian Angel)]

47 minutes ago, Yeti_JTF111 said:

I then reloaded a scenario I made to practice AAR

At what speed was the tanker set in both scenarios? I did notice that the (lack of) stability varies wildly based on which speed you're refuelling at: even small changes on the pitch ratio indicator have seriously noticeable impacts on flight stability. There's quite the difference between tanking at 280KIAS and 320KIAS.
That being said, I also have a 20cm extension and I don't use any curves. 

[Rainmaker]

According to your track....it appears you took off without ever aligning INS?  Is this truly the case?

[tae.]

Something is definitely causing more weight to be shaved off from the aircraft after weapons drops or something similar.

Me and WSO did 3-4 sorties dropping GBU-24s, each one increased the airframe performance gradually and substantially.

By the 5th takeoff, we could go 90 degrees nose up with 24,000 lbs of fuel and 3 GBU-24s onboard, and easily accelerate to Mach 1.

In level flight we could get from 300 knots to 600 in just 2-3 seconds. Felt like we were in Ace Combat.

We didn't last much longer because the flight model goes out the window, so we got into an uncontrollable pitch oscillation and I blacked out permanently, forcing the WSO to eject us.

 

tl;dr, yes there is definitely something VERY messed up with the flight model right now. My initial thoughts are that dropping weapons is subtracting more weight than it should, but it needs more testing.

Edited July 30, 2023 by tae.

[PLUTON]

I don't have to test all these flight differences
but just noticed that i come out 10 times in flight
and that the 10 flights are all different and that my F15 behaves differently each time.

[RaisedByWolves]

You sure you do not have other things mapped to your flight controls? Happens a lot with updates. I dunno.

[Akrescue130]

6 hours ago, CptSmiley said:

Thanks guys please provide tracks of these observations.  Otherwise it will be hard to investigate.  

Here's some logs of me attempting to do what tae was talking about, but found a different bug with jettisoning fuel tanks a few times

dcs.log.old Drop tank bug f15.trk dcs.log Drop tank bug f15 2nd time.trk

[Akrescue130]

6 hours ago, CptSmiley said:

Thanks guys please provide tracks of these observations.  Otherwise it will be hard to investigate.  

Here is another one just from jettisoning bombs. 

Jettison bug f15.trk

[tae.]

I was just able to reproduce this PURELY on the ground by doing the following:

1. Rearm with just three fuel tanks (wings+centerline)
2. Emergency Jettison
3. Repeat 4-5 times

If you do it more than 5 times the flight model will break so badly that you will black out on the ground and the jet will explode and be catapulted many miles away.

Will post track shortly.

Edited August 1, 2023 by tae.

[tae.]

Here is a track where the final jettison sent me forward at Mach 66.47, sending the jet approximately 27 nautical miles away. Note that the jettison prior tips the jet back onto the rear gear noticeably. 11:10am onwards in the log is where that flight began.

dcs.log F15E_FM_weight_bug.trk

[McCloud]

I'm still getting the wibbly wobbly in the air. Full AA setup with three bags.

The problem persists even when ii reset the CAS. Trying to land is iffy at best.

[tae.]

1 hour ago, McCloud said:

I'm still getting the wibbly wobbly in the air. Full AA setup with three bags.

The problem persists even when ii reset the CAS. Trying to land is iffy at best.

If you added the external fuel tanks with a re-arm, their weight is not being calculated at all. This bug is not fixed yet and should be fixed in the next patch as Smiley mentions above.

The current workaround is to have the external fuel tanks on the jet at the start of the mission. If that's not a possibility, then recommend to not use them at all.

A fun little side note, is that after flying the jet for almost two weeks with this workaround now, I can pretty confidently say it has been a bug since release. The jet handles WAY differently with the workaround. A lot less "crazy" performance, and much more in line with the other aircraft in DCS.