reported Caged FPM Behaves weird in crosswind.

[Deano87]

This particular bug is not FM related. It’s simply that the FPM is showing Incorrect information when drift corrected/caged. It’s exacerbated by banking the aircraft. Set up a mission with a strong high altitude crosswind (60knots for instance), spawn an F-16, put it into a 30 degree bank and set altitude hold. It will fly a perfectly level circle maintaining altitude pretty accurately. If you cage the FPM while you turn you will see it shows you descending on one side of the turn and climbing on the other. It’s all because when you bank the FPM’s rotation is based around the position of hidden uncaged FPM rather then itself. You can see the problem clearly while banking one way and the then other in crosswind. The FPM can move up and down 10 degrees while your actual vertical speed stays consistent. 
 

- Edit to include pic again from earlier in this thread -

 

Edited December 16, 2020 by Deano87

[Deano87]

Now that the F-16 is getting some love can we PLEASE get this sorted out.

This is still present in DCS Open Beta 2.7.6.12852. - Some 2 years after it was first reported.

This is one of the basic functions of one of the main instruments of the aircraft (HUD), This should be a HIGH priority imho.

Another issue that needs to be noted is that when the FPM is Drift corrected the pitch ladder should also continue to stay aligned with the FPM, currently what happens is the pitch ladder seems to rotate around the gun cross, this is incorrect. Do you want me to create a separate bug report for this?
 

Attached are a mission and two tracks showing this issue.
Mission is an F-16 in a 65kn crosswind at 35k ft, this is a perfectly normal wind speed for that altitude, Indeed I have personally seen over 150 knots at altitude IRL.

Test 1:

is simply me flying the aircraft directly cross wind and essentially just waggling the wings left and right and noting how the uncaged FPM stays roughly on the horizon while the caged one shoots up and down depending on the bank angle.
 

 

Test 2:

is me setting the aircraft into relatively steep bank and then setting the autopilot in ALT HOLD mode, As such the aircraft flies a perfectly flat 360, During that 360 I flick the FPM Drift Compensate switch on and off. Noting the position of the FPM in both cases.

 

 

 

Hope we can get some movement on this.
It would be nice to see the basics fixed before more new features get added imho.

Thanks
D

F-16 Hud Drift Crosswind.miz F-16 HUD Drift Prob1.trk F-16 HUD Drift Prob2 360.trk

[Deano87]

I was asked by @Wags in a YT comment to bump a previous bug report I made about the Drift C/O FPM being incorrectly modelled in crosswinds, However that post is locked so I cannot bump it. So I decided to make a new post and link to the old one.

Hope this helps Matt!

I've also checked and this is still an issue in the current Open Beta build.

 

Edited August 18, 2022 by Deano87

[Deano87]

Great to see this topic unlocked again. I hope this means it’s being looked at and on the radar for being fixed.  
 

If you need any more tracks to replicate the issue with the current beta build please let me know.

 

As I mentioned in a previous post in addition to the FPM not being in the correct place when drift compensated the pitch ladder should also be anchored around the FPM just like it is when not using Drift C/O. Currently when drift c/o is on the pitch ladder is anchored around the gun cross at the top of the HUD. This is incorrect.

[WHOGX5]

19 hours ago, Deano87 said:

Great to see this topic unlocked again. I hope this means it’s being looked at and on the radar for being fixed.  
 

If you need any more tracks to replicate the issue with the current beta build please let me know.

 

As I mentioned in a previous post in addition to the FPM not being in the correct place when drift compensated the pitch ladder should also be anchored around the FPM just like it is when not using Drift C/O. Currently when drift c/o is on the pitch ladder is anchored around the gun cross at the top of the HUD. This is incorrect.

I'd like to point out that the velocity vector not being in the correct place is not exclusive to Drift C/O. If the velocity vector for whatever reason goes outside of the HUD and gets crossed out, it will display the same incorrect pitch movements as it does in Drift C/O. You'll also see similar behaviour with the target locator line. If you hook a LINK 16 track on the HSD with PDLT that is a decent angle off of your nose, if you bank the aircraft the TLL will point in an incorrect direction. Depending on which direction you roll it might point up into the sky or down towards the ground even though you're flying in a straight line. As you turn directly into the direction that is indicated by the TLL it will start rotating and changing angle as the angle from your nose to the target decreases. So instead of guiding you straight towards the target via a simple planar turn it will make you perform some weird, squiggly, three dimensional turn instead. Also, if you turn off HUD blanking, take your crosshair in the JHMCS and overlay it directly on top of the gun cross in the HUD, you'll see that there is a difference in angle between the TLL in the HUD and the JHMCS and as you turn towards the target and/or bank the aircraft you'll see the angular difference between these two TLL's change. So there's defintitely some incorrect mathematical equations in the core HUD integration.

Now, I haven't made a bug report on any of this because I simply can't be bothered to spend hours recording a bunch of tracks and scouring through manuals for references, but I'd bet you a hundred buckaroos that all of these issues I've mentioned stem from the exact same faulty calculations that cause the Drift C/O FPM issues.

Edited August 20, 2022 by WHOGX5

[Mikaa]

On 8/20/2022 at 6:47 AM, WHOGX5 said:

I'd like to point out that the velocity vector not being in the correct place is not exclusive to Drift C/O. If the velocity vector for whatever reason goes outside of the HUD and gets crossed out, it will display the same incorrect pitch movements as it does in Drift C/O. You'll also see similar behaviour with the target locator line. If you hook a LINK 16 track on the HSD with PDLT that is a decent angle off of your nose, if you bank the aircraft the TLL will point in an incorrect direction. Depending on which direction you roll it might point up into the sky or down towards the ground even though you're flying in a straight line. As you turn directly into the direction that is indicated by the TLL it will start rotating and changing angle as the angle from your nose to the target decreases. So instead of guiding you straight towards the target via a simple planar turn it will make you perform some weird, squiggly, three dimensional turn instead. Also, if you turn off HUD blanking, take your crosshair in the JHMCS and overlay it directly on top of the gun cross in the HUD, you'll see that there is a difference in angle between the TLL in the HUD and the JHMCS and as you turn towards the target and/or bank the aircraft you'll see the angular difference between these two TLL's change. So there's defintitely some incorrect mathematical equations in the core HUD integration.

Now, I haven't made a bug report on any of this because I simply can't be bothered to spend hours recording a bunch of tracks and scouring through manuals for references, but I'd bet you a hundred buckaroos that all of these issues I've mentioned stem from the exact same faulty calculations that cause the Drift C/O FPM issues.

 

I noticed something similar in the Hornet HUD as well, as the vv exceeded view limits, however I haven't tested it again recently. You're most likely right that there's a miscalculation in the core HUD code.