Difference in closure speeds between PID + PIC

[nomdeplume]

Noticed this for a while, but thought I'd finally ask about.

 

When tracking a target in PID/TWS mode, the closure rate is quite different (usually lower) than the rate when locked in PIC/STT, and also fluctuates a lot.

 

Maybe that is correct behaviour, but the icons on the VTB move smoothly as if they're being interpolated, and it seems like a highly undesirable thing for the system to do.

 

It seems reasonable that PIC would provide better information, but the way the closure rate in PID oscillates between values suggests it's calculating the rate based on a 'snapshot' of the target's position/velocity at the time it was last scanned, rather than an interpolation of its probable current position.

 

Attached is two screenshots taken a second or two apart, of the same non-manuevering, constant-speed aircraft. First picture is PIC, second is PID. You can see the big difference in closure rates presented, but it doesn't tell the whole story as in PID mode the closure would start at about +55 knots and decrease to -50 knots or so, then jump back to +55.

 

This behaviour seems to be consistent and easy to reproduce. It makes PID mode much less useful than it otherwise would be, both for engaging enemies and for using it to intercept friendlies (e.g. tankers) or just to stay 'tied' to your flight lead.

[Zeus67]

I will check, but you should have posted this in the bugs section.

I won't be ready for this Friday's release.

[nomdeplume]

Sorry, wasn't game to post it there in case it wasn't actually a bug. :)

 

Edit: as penance for not posting it in the right place, I've recorded a track and also uploaded a video. Might be helpful to be able to just see it.

 

Video is in the spoiler:

 

UBApeZayP1A

 

While I was editing the video, I noticed one of the times when I switched from PIC to PID, the distance went from 170 to 400 for one frame only, then back to 160. Don't know if this is a clue, or just an anomaly. Only happened once, but the recording was only at 30 FPS so it's possible it happens more often but just didn't get captured. But if it's occasionally getting incorrect values for the distance, it might explain the bizarre behaviour.

 

Sequence of stills of the distance anomally are attached. It's from just after 1m30s in the video.

M2000C Closure Rate.trk

Edited July 8, 2016 by nomdeplume

[Manuel_108]

Interesting. I just tried it and got the same results. I was closing in on an enemy Mig-23 and it showed -60.

[Rlaxoxo]

Noticed this a while ago I tought it was a feature since TWS isn't that accurate the clouse rate goes all over the place