[REPORTED] KEAS displayed on the HUD instead of KCAS

According to this post, the F-16s HUD in DCS is displaying KEAS rather than KCAS.

I've done a test myself and can confirm.

This obviously leads to pretty big discrepancies in speed readings, with all associated consequences.

IMPORTANT: KEAS instead of KCAS!

Ok, we might have stumbled on something big.

Kudos to the original poster on reddit

Summary:

It is very likely that ALL AIRCRAFT IN DCS DISPLAY KEAS INSTEAD OF KCAS on their digital insturments (i.e. HUD, MFDs etc)

This could lead to FM issues if devs used those numbers thinking it was KCAS.

Test:

I just tested F-18, F-15, F-16. Mirage-2000, Su-27.

Test parameters:

• Standard atmosphere
  
• No wind
  
• 35000ft
  
• Mach 0.9 or ~290 kts Equivalent Air Speed
  

Pay attention: it turns out the speed displayed as "IAS" in the F2 inforbar is the Equivalent Air Speed.

So, given 290kts EAS (from the infobar), we should have:

• KCAS: 310 kts
  
• KTAS: 518.5 kts
  
• GS: 518.5 kts (there's no wind)
  

All parameters match, except KCAS displayed on the HUD of the different airplanes is 291 kts instead of 310 kts.

That's 20kts difference, going to increase as speed and / or altitude increase.

All calculations are based on this page http://www.aerospaceweb.org/design/scripts/atmosphere/

The very worrying part:

Not sure if it's just a displayed speed issue, but if FMs are being made and tweaked based on what devs think is KCAS, but turns out it is actually KEAS, it could mean all FMs in the game are off.

Example: I have personally tested and reported that the F-16's level acceleration at 10k feet and above is severly slower than IRL. The reports have been acknowledged.

In some cases the timings were off by as much as 40%, so while there is still a high chance that the DCS F-16 is indeed undeperfroming, it might not be as bad as 40%, and if the speed displayed on the hud is taken as a measurment, the FM would result in a grossly over-powered F-16.

I hope you get what I mean.

@ED please check!

Found out this is a general DCS bug.

Posted here: https://forums.eagle.ru/showthread.php?t=276368

+1

That's one of the occasions where I would love to see ED's Yo-Yo chime in.

I personally PMd Yo-Yo, Kate and Wags about this. Yo-yo replied so I am sure they are aware.

Important to note that this is not just about one particular modules, but it's sim-wise.

Thinking about all the EM charts, analyses and comparisons the community has ran on these modules...jeez, those are all based on the wrong numbers!

Hopefully 3rd party devs didn't trust the in-game speed readings when testing their FMs :doh:

Thank you for checking on it.

@bkthunder Not sure how to go about proving this but, I was the original poster on Reddit (u/espressoandcream). Appreciate you taking the discussion over here for the ED folks (glad that they're aware and investigating). Now that my account is actually activated on the ED forums, I'd be happy to help with any future data gathering/investigating. What can I say, my IRL job is flight testing F-16's. Makes sense that I do it in my spare time too. :D

I'm pretty ignorant when it comes to flight models in DCS, but I can say from personal experience that something feels slightly "off" about the DCS F-16 when compared to real-world experience (hence why I was out doing the level accels that I mentioned on Reddit to gather data to compare to my own IRL experience). In addition to the obvious effects a bug like this would have on performance, I'm interested to see if there would be any trickle-down effects of using KEAS vs. KCAS, when it comes to stability & handling qualities. Probably not a whole lot at lower altitudes, but I can imagine there would be some noticeable difference up high.

Hopefully I didn't open too big of a "can of worms" with this one. Thanks!

@bkthunder Not sure how to go about proving this but, I was the original poster on Reddit (u/espressoandcream). Appreciate you taking the discussion over here for the ED folks (glad that they're aware and investigating). Now that my account is actually activated on the ED forums, I'd be happy to help with any future data gathering/investigating. What can I say, my IRL job is flight testing F-16's. Makes sense that I do it in my spare time too. :D

 

I'm pretty ignorant when it comes to flight models in DCS, but I can say from personal experience that something feels slightly "off" about the DCS F-16 when compared to real-world experience (hence why I was out doing the level accels that I mentioned on Reddit to gather data to compare to my own IRL experience). In addition to the obvious effects a bug like this would have on performance, I'm interested to see if there would be any trickle-down effects of using KEAS vs. KCAS, when it comes to stability & handling qualities. Probably not a whole lot at lower altitudes, but I can imagine there would be some noticeable difference up high.

 

Hopefully I didn't open too big of a "can of worms" with this one. Thanks!

Thank you.

@bkthunder Not sure how to go about proving this but, I was the original poster on Reddit (u/espressoandcream). Appreciate you taking the discussion over here for the ED folks (glad that they're aware and investigating). Now that my account is actually activated on the ED forums, I'd be happy to help with any future data gathering/investigating. What can I say, my IRL job is flight testing F-16's. Makes sense that I do it in my spare time too. :D

 

I'm pretty ignorant when it comes to flight models in DCS, but I can say from personal experience that something feels slightly "off" about the DCS F-16 when compared to real-world experience (hence why I was out doing the level accels that I mentioned on Reddit to gather data to compare to my own IRL experience). In addition to the obvious effects a bug like this would have on performance, I'm interested to see if there would be any trickle-down effects of using KEAS vs. KCAS, when it comes to stability & handling qualities. Probably not a whole lot at lower altitudes, but I can imagine there would be some noticeable difference up high.

 

Hopefully I didn't open too big of a "can of worms" with this one. Thanks!

Awesome, thanks for joining the discussion and, with your experience, hopefully ED will be listening. They sure have a history of being extremely reluctant to admit mistakes, maybe this time it'll be different. Personally I'm looking forward to your contributions here and a little envious of your awesome RL job :thumbup:

Any news on this?

Does this affect the mach indicator as well? I've been wondering why I get sonic booms when at M0.98.

Thanks for the update 9L...

Just a small update, the team is putting together a bit of a report on DCS FMs as part of this discussion, when that gets closer I hope we will have an answer to this and more. Thanks guys.

Thank you.

Any update on this?

Just a small update, the team is putting together a bit of a report on DCS FMs as part of this discussion, when that gets closer I hope we will have an answer to this and more. Thanks guys.

All HUD-airplanes are showing KEAS in the HUD. ED has to change that.

What speed is the DCS FMs based on?

Did quick tests & the nr's are correct as per TS linked redit tests. When is this going to be a confirmed as a MAJOR BUG?

Ok, we might have stumbled on something big.

Kudos to the original poster on reddit

Summary:

It is very likely that ALL AIRCRAFT IN DCS DISPLAY KEAS INSTEAD OF KCAS on their digital insturments (i.e. HUD, MFDs etc)

This could lead to FM issues if devs used those numbers thinking it was KCAS.

Test:

I just tested F-18, F-15, F-16. Mirage-2000, Su-27.

Test parameters:

• Standard atmosphere
  
• No wind
  
• 35000ft
  
• Mach 0.9 or ~290 kts Equivalent Air Speed
  
• Pay attention: it turns out the speed displayed as "IAS" in the F2 inforbar is the Equivalent Air Speed.
  

So, given 290kts EAS (from the infobar), we should have:

 

• KCAS: 310 kts
  
• KTAS: 518.5 kts
  
• GS: 518.5 kts (there's no wind)
  

All parameters match, except KCAS displayed on the HUD of the different airplanes is 291 kts instead of 310 kts.

 

That's 20kts difference, going to increase as speed and / or altitude increase.

 

All calculations are based on this page http://www.aerospaceweb.org/design/scripts/atmosphere/

 

The very worrying part:

 

Not sure if it's just a displayed speed issue, but if FMs are being made and tweaked based on what devs think is KCAS, but turns out it is actually KEAS, it could mean all FMs in the game are off.

 

Example: I have personally tested and reported that the F-16's level acceleration at 10k feet and above is severly slower than IRL. The reports have been acknowledged.

In some cases the timings were off by as much as 40%, so while there is still a high chance that the DCS F-16 is indeed undeperfroming, it might not be as bad as 40%, and if the speed displayed on the hud is taken as a measurment, the FM would result in a grossly over-powered F-16.

I hope you get what I mean.

@ED please check!

Jepp, they'll have to redo ALL FM's & God knows what else?

This has NOTHING to do with FMs, ED stated this clearly. It purely affects the numbers shown to us in the cockpit, nothing else

This has NOTHING to do with FMs, ED stated this clearly. It purely affects the numbers shown to us in the cockpit, nothing else

Link?

Hi!

Test parameters:

 

• Standard atmosphere
  
• No wind
  
• 35000ft
  
• Mach 0.9 or ~290 kts Equivalent Air Speed
  
• Pay attention: it turns out the speed displayed as "IAS" in the F2 inforbar is the Equivalent Air Speed.
  

So, given 290kts EAS (from the infobar), we should have:

 

• KCAS: 310 kts
  
• KTAS: 518.5 kts
  
• GS: 518.5 kts (there's no wind)
  

All parameters match, except KCAS displayed on the HUD of the different airplanes is 291 kts instead of 310 kts.

This has NOTHING to do with FMs, ED stated this clearly. It purely affects the numbers shown to us in the cockpit, nothing else

To know if the airspeed in HUD vs info bar is correct, ... etc ... it is easy to be checked with two points on the map (known distance), an air temperature (defined in weather page), and a watch.

Regards.

Link?

I see you didnt read the FM paper...

https://forums.eagle.ru/showthread.php?t=281651