need evidence FCR TGT speed/closure bug or feature?

[Carbon715]

So I've noticed as I'm playing some paid viper campaigns, keeping speed or up with the AI is a PITA. So when I lock one up, I should get their speed/and closure, which I do. However it is off. Not by a ton but enough to where it's more trouble than it's worth using a lock method to reliably gauge speed and closure. Take for instance this image from BDs Gamblers Campaign mission 2 at the start. I lock this viper and get his speed as 274kts on the FCR. He is actually 271 when flying from. I am currently 303kts showing a closure of +40. That would indicate the target would be 263kts which the lock target still isn't. Is this an FCR issue or something else?

[itn]

IIRC FCR shows target speed in Ground Speed instead of CAS. I think it should show CAS and that this was reported long time ago with no results. 

[Lord Vader]

Hello @Carbon715

The Closure Rate of a tracked target in the FCR shows speed in TAS, while your HUD is displaying your own speed in CAS.

@itn Please link that report you mention and I must ask what are you basing your assumption the CR should be CAS and not TAS.

[Carbon715]

I'll report back when I can and try TAS on my HUD. I've heard from around that altimeter setting in the mission itself is screwing with the speed and closure the FCR displays though. Again I'll test when I can.

[itn]

19 hours ago, Lord Vader said:

@itn Please link that report you mention and I must ask what are you basing your assumption the CR should be CAS and not TAS.

I talked about target speed, not closure rate, being CAS. I believe CR as TAS is correct and make no claims about it.

For the target speed, I can only refer you to your own references and just ask you to re-check them. There are no documents that I know of that would satisfy your publicly stated requirements for evidence. However, I have been lead to believe the other well known and widely distributed F-16 manuals for other variants/nations all state the same thing: FCR in CRM(/SAM/RWS/TWS) shows target speed in calibrated airspeed. But again, those docs are not for 2007 USAF/ANG block 50 CM so I will just have to ask you to re-check your own references for the correct variant. Maybe it differs or maybe it doesn't.

Would have to re-test but IIRC last time I tested in DCS, it showed Ground Speed, not TAS nor CAS. Basically I chased a target in a heavy wind, and when closure was 0 per FCR, HUD and visually, the FCR target airspeed readout matched GS in my HUD perfectly. TAS not so much because of the wind, and CAS even less so because of altitude effects.

Best regards,
itn

 

 

 

[Lord Vader]

Thanks @itn, appreciate the link. 

[Carbon715]

18 hours ago, itn said:

I talked about target speed, not closure rate, being CAS. I believe CR as TAS is correct and make no claims about it.

For the target speed, I can only refer you to your own references and just ask you to re-check them. There are no documents that I know of that would satisfy your publicly stated requirements for evidence. However, I have been lead to believe the other well known and widely distributed F-16 manuals for other variants/nations all state the same thing: FCR in CRM(/SAM/RWS/TWS) shows target speed in calibrated airspeed. But again, those docs are not for 2007 USAF/ANG block 50 CM so I will just have to ask you to re-check your own references for the correct variant. Maybe it differs or maybe it doesn't.

Would have to re-test but IIRC last time I tested in DCS, it showed Ground Speed, not TAS nor CAS. Basically I chased a target in a heavy wind, and when closure was 0 per FCR, HUD and visually, the FCR target airspeed readout matched GS in my HUD perfectly. TAS not so much because of the wind, and CAS even less so because of altitude effects.

Best regards,
itn

 

 

 

The documents I have show CAS as well for tgt speed, explicitly saying "Calibrated Airspeed". As for closure I can't find anything denoting what kind of speed it's referenced off of.

Edit* I found in a CM-34-1-1 closure is kTAS

Edited September 4, 2024 by Carbon715