investigating STT shows wrong target speed on MFD

[Thunk]

Track files captured using DCS 2.5.6.60966; however, this has been present in all versions I have tried so far. The system is I7-6700, 32GB Ram, GTX1080 and Oculus Quest2. Captured flying the "Free Flight" instant action mission.

 

In the attached track file, the lead F-16 is shown as 440KCAS on the MFD when I'm in STT. Per the -34-1-1, figure 1-85, the target speed is displayed as KCAS on the MFD. I have the HUD velocity switch set to CAS (visible in the .trk).

 

As you can see in the track file, I hold distance at 390KCAS and the closure rate on the MFD / HUD is 0kts.  At 400KCAS, closure rate on the MFD / HUD is about +10kts and I'm clearly getting closer. Target speed 440KCAS, my speed 400KCAS with a closure rate of +10Kts and visibly getting closer doesn't add up.

 

Next, I lock up the high-altitude target. It's speed is shown on the MFD as 460KCAS. per the labels, I do seem to be closing on the target. With my speed at 305KCAS, closure rate is shown as more than +100kts, which again doesn't add up.

 

At the end of the second track file, I'm at 210KCAS and 0kts closure, holding position on the A-10, but the MFD shows its speed as 230KCAS. If that were true, closure should be -20kts, and I should be dropping back.

 

If I set the HUD to TAS, the numbers are still off, but closer. Therefore, it appears that the target speed shown on the MFD in STT is inaccurate.

 

https://1drv.ms/u/s!Au8NSvUcPq9khMsIukFPrIK2Wgf4Iw?e=bbWkgI

 

https://1drv.ms/u/s!Au8NSvUcPq9khMsJHMSNjnPQtdfqdQ?e=uFzaRL

 

Thanks,

 

Thunk

[Florence201]

I thought FCR speed was Ground Speed????

[MROK73]

39 minutes ago, Florence201 said:

I thought FCR speed was Ground Speed????

You get Target CAS and Closure rate as TAS. At least in real life...

[Florence201]

You are correct wrt real life, would be nice if ED could confirm their modelling of this

[MROK73]

2 hours ago, Florence201 said:

You are correct wrt real life, would be nice if ED could confirm their modelling of this

That's an issue! Not a bug... 

Edited February 5, 2021 by MROK73

[Frederf]

Closure is displayed as true radial velocity. If it says +500 then the closure is at a rate of 500 knots, i.e. every millisecond the F-16 and target are coming 10.1269 inches closer together.

 

Display of target KCAS on radar is an estimate of target's CAS based on his velocity, assumed winds at target location (to true velocity to TAS), and assumed air density (to convert TAS to CAS) at target location. The "at target location" is important since an F-16 at 30,000 locked onto a target at 5,000 should not assume the same wind or TAS/CAS relationship at target location as F-16 location. Because of the impect nature of these estimates it is not unreasonable for closure = 0 to not cause displayed CAS estimate to match displayed CAS exactly. It shouldn't be grossly off though. The display of pseudo-CAS on radar is to give the pilot an understanding of the target's maneuver potential which GS or TAS does not provide.

[itn]

This is still a thing. Seems to show GS instead of CAS in FCR.

FCR Ground Speed.trk