F-14B acceleration correct?

[sLYFa]

1 hour ago, Victory205 said:

CG

That is the missing variable. I have yet to find a source for even empty weight CG. The AAA-1 refers to a separate document that is nowhere to find... 

Since the FM does consider CG, maybe HB can give some data on this? 

[Victory205]

Don’t forget runway slope. 

 

What are your acceptable distance parameters? Ten, fifteen feet or so?

[captain_dalan]

On 5/20/2021 at 6:15 PM, Victory205 said:

Do you have anything more than a “hunch”? Is there a way, especially for those with a keen focus on performance, to ascertain the accuracy of the various available indications of velocity in the sim?

 

Your testing and subsequent decrees were all based on a hunch?

 

Growing up in a digital world creates biases and complacency. Think.

I grew up in the 80's and the 90's mate.....
As for the hunch, it's based on my programmer experience and it seems to me like the info bar represents the data as perceived by the sim, that is the "server side" logic or how the "world" in which you fly sees you. In the end, it's this that matters when the sim decides if you gonna collide with something or something collides with you.  Again, it will take an ED representative to either confirm or deny this.

[Katj]

I grew up in the 80's and the 90's mate.....
As for the hunch, it's based on my programmer experience and it seems to me like the info bar represents the data as perceived by the sim, that is the "server side" logic or how the "world" in which you fly sees you. In the end, it's this that matters when the sim decides if you gonna collide with something or something collides with you.  Again, it will take an ED representative to either confirm or deny this.

I think this is appropriate to share here:


TL;Dr The infobar does, in stark contrast to reason, NOT show IAS or even CAS, but EAS (equivalent airspeed i.e. CAS corrected for compressibility).

Edit: And F10 map doesn't show TAS like it says but ground speed. Which would be fine if it were labeled correctly.

[Victory205]

52 minutes ago, Katj said:

I think this is appropriate to share here:


TL;Dr The infobar does, in stark contrast to reason, NOT show IAS or even CAS, but EAS (equivalent airspeed i.e. CAS corrected for compressibility).

Edit: And F10 map doesn't show TAS like it says but ground speed. Which would be fine if it were labeled correctly.

 

It is amazing to see the difference in mindset. There is a reason I say that “ego is the enemy”. The goal is not to be right, it’s to find the accurate answer. Pretty easy to see the effects of “you don’t know what you don’t know”, and how people who presuppose outcomes are a waste of time. 

 

When flight testing, every instrument is calibrated before being used for data acquisition. Does anyone here know the basic means of verifying something as simple as airspeed? Hint, it doesn’t involve asking a vendor if an instrument is “accurate”.

[Lurker]

It shouldn't really matter. For example, if you are testing "weights" it doesn't matter if you use stone-age scales, or high tech, high precision digital scales. As long as everyone who does the tests agrees on the SINGLE AGREED METHOD of testing. In my really ridiculous example, as long as everyone agrees to use the same types of scales then this is what matters. From my (limited) physics background this is the basics of any testing methodology. 

Edited May 26, 2021 by Lurker

[Wolfman289]

I could be completely off with this, but I wonder if one of the issues is that the info bar may be accurate to the sim, but is it accurate to real life as well? We are trying to compare a real life chart of the F14's performance to its performance in a sim. It would be extremely difficult(more like impossible) for the sim to be dialed in so that dimensions and other measurements are completely exact like in real life. HB could tune the F14 to match every real world chart that they can find, but if the sim is not perfect in it's measurements when compared to real life then the performance would still be inaccurate if that makes sense?

 

Pretty tricky thing to do. Thank you to HB and Victory and the other SME's that are helping sort through it all.

[TLTeo]

1 hour ago, Lurker said:

It shouldn't really matter. For example, if you are testing "weights" it doesn't matter if you use stone-age scales, or high tech, high precision digital scales. As long as everyone who does the tests agrees on the SINGLE AGREED METHOD of testing. In my really ridiculous example, as long as everyone agrees to use the same types of scales then this is what matters. From my (limited) physics background this is the basics of any testing methodology.

To some extent yes, but if your method of testing either a) has large systematic errors built in (say, because it turns out the most accurate way to get flight parameters is the infobar, and we think it displays TAS rather than ground speed or something) or b) has large statistical errors built in (let's say we are flying the turns ourselves, and we're not maintaining airspeed or altitude constant very well), then the resulting error bars from our chosen agreed method will be so large that we can't actually draw any useful conclusion. Acceleration is a derived quantity, so it's more complicated than just measuring something directly.

 

Mitigating issue a) is why IRL flight instruments are calibrated. Factoring in issue b) is why (among other things) performance charts should be interpreted with caution.

Edited May 26, 2021 by TLTeo

[draconus]

2 hours ago, Wolfman289 said:

It would be extremely difficult(more like impossible) for the sim to be dialed in so that dimensions and other measurements are completely exact like in real life.

It's not that hard and it's correct (beside Stennis). That's really important thing in a sim. Who would model millions of polygons just to end up with wrong size aircraft? You can also test it in multitude ways like overflying or taxing constant speed over known distances like runway or from place A to B.

[Hummingbird]

9 hours ago, Katj said:

I think this is appropriate to share here:


TL;Dr The infobar does, in stark contrast to reason, NOT show IAS or even CAS, but EAS (equivalent airspeed i.e. CAS corrected for compressibility).

Edit: And F10 map doesn't show TAS like it says but ground speed. Which would be fine if it were labeled correctly.

 

You know you can press it twice to get TAS & TMN, right?

 

F-15 as tested in DCS (TAS & TMN for checks) vs the real life performance chart:

 

 

In short, ED's F-15C is litterally spot on when it comes to Ps=0, and such a perfect match with the performance charts makes it's clear ED calibrated their FM performance using the infobar. Hence the infobar is ofcourse the standard measuring device we need to use when testing, as the devs themselves have also requested in the past when we were submitting test results for other aircraft in the sim.

 

The above also shows getting a perfect or near perfect match is very doable, it just takes time, and I have faith Heatblur will get the F-14 there. We, as customers, just need to be understanding of the scale of the undertaking and be patient. Quality takes time.

Edited May 26, 2021 by Hummingbird

[Katj]

 
You know you can press it twice to get TAS & TMN, right?
 
F-15 as tested in DCS (TAS & TMN for checks) vs the real life performance chart:
 

 
In short, ED's F-15C is litterally spot on when it comes to Ps=0, and such a perfect match with the performance charts makes it's clear ED calibrated their FM performance using the infobar. Hence the infobar is ofcourse the standard measuring device we need to use when testing, as the devs themselves have also requested in the past when we were submitting test results for other aircraft in the sim.
 
The above also shows getting a perfect or near perfect match is very doable, it just takes time, and I have faith Heatblur will get the F-14 there. We, as customers, just need to be understanding of the scale of the undertaking and be patient. Quality takes time.

Yes, I'm aware that you can toggle it. I don't know if it really shows TAS, though, it could be ground speed for all I know. I haven't investigated that, and I don't intend to.

The F-15 matching whatever is shown in the infobar could be a coincidence, it's not proof that whatevers in the infobar is correct. Also, ED probably have access to debug tools from which they can get all kinds of data, I very much doubt they use the infobar.

I don't care so much about all that, though. I just want the Tomcat to cut through the sound barrier like a 68° wedge.

[Donut]

Wow, what a fascinating and...spirited conversation this has become!

 

In regards to my OP, from what I can gather from this discussion, it seems that the FM changes should result in a less draggy and faster accelerating F-14B.  

[Hummingbird]

4 hours ago, Katj said:

The F-15 matching whatever is shown in the infobar could be a coincidence, it's not proof that whatevers in the infobar is correct. Also, ED probably have access to debug tools from which they can get all kinds of data, I very much doubt they use the infobar

 

When it matches in Ps=0 through the entire speed range, then coincidence is pretty much ruled out. Besides like I said, the devs themselves have said to use the infobar for testing.

[captain_dalan]

8 hours ago, Katj said:

Yes, I'm aware that you can toggle it. I don't know if it really shows TAS, though, it could be ground speed for all I know. I haven't investigated that, and I don't intend to.
 

Fairly easy to check really, once you have the mach numbers and a good conversion chart or calculator. The only reason why i haven't done it is because my tests were sub 500ft ASL (i use those Ps charts) and when that low, there is hardly a difference in the numbers.

Still i would like for an official developer to chime in, or at the very least someone post an official quote, so the matter could be laid to rest.

[fat creason]

4 hours ago, Hummingbird said:

Besides like I said, the devs themselves have said to use the infobar for testing.

 

No one at HB uses the infobar as far as I know. I wouldn't trust the infobar much at all, read this if you haven't seen it. Most of the FM tables in the F-14 use CAS and Mach number because CAS is an analog to dynamic pressure. The infobar shows EAS or TAS (or maybe even groundspeed, who knows), neither of which are very useful for FM work. There are several "truth data" sources available to developers via the API. I can compare multiple values for IAS and Mach number, none of them agree completely. I'm currently doing some digging to figure out which is the most correct.

Edited May 27, 2021 by fat creason

[Hummingbird]

31 minutes ago, fat creason said:

No one at HB uses the infobar as far as I know. I wouldn't trust the infobar much at all, read this if you haven't seen it. Most of the FM tables in the F-14 use CAS and Mach number because CAS is an analog to dynamic pressure. The infobar shows EAS or TAS (or maybe even groundspeed, who knows), neither of which are very useful for FM work. There are several "truth data" sources available to developers via the API. I can compare multiple values for IAS and Mach number, none of them agree completely. I'm currently doing some digging to figure out which is the most correct.

 

I was asked to use it by the ED devs a while back for any tests I did, making sure to toggle for TAS & TMN, as it is supposed to accurately record the actual motion of the aircraft within the simulation. 

 

If it wasn't accurate, then how are the various devs ever supposed to make their aircraft perform realistically relative each other?

 

Note: When the infobar isn't set to TAS, but IAS, it shows what'ever figure is shown on the HUD of the aircraft.

Edited May 27, 2021 by Hummingbird

[Hummingbird]

35 minutes ago, captain_dalan said:

Fairly easy to check really, once you have the mach numbers and a good conversion chart or calculator. The only reason why i haven't done it is because my tests were sub 500ft ASL (i use those Ps charts) and when that low, there is hardly a difference in the numbers.

Still i would like for an official developer to chime in, or at the very least someone post an official quote, so the matter could be laid to rest.

 

Yes, that would be nice. Although I kind of already got the answer back when I was litterally asked to use it for testing.

[fat creason]

26 minutes ago, Hummingbird said:

If it wasn't accurate, then how are the various devs ever supposed to make their aircraft perform realistically relative each other?

 

Note: When the infobar isn't set to TAS, but IAS, it shows what'ever figure is shown on the HUD of the aircraft.

 

 

 

This is a good question that I have no answer to, other than to take the infobar with a big pinch of salt. At the very least, it's not displaying IAS. That reddit post lays out the evidence that many of the HUDs and the infobar are all showing EAS which is mislabeled as IAS and F10 shows ground speed, not TAS. Most FM charts are going to use IAS, CAS, or Mach number. The infobar true Mach number is probably accurate since that's super easy to compute: TAS/SpeedOfSound. TAS is going to be the easiest of all parameters to measure since it's the inertial/physical speed at which an aircraft is traveling + wind. As you go to EAS > CAS > IAS, the "accuracy" of those numbers comes down to the "correctness" of the modeled errors being added. Things also get more complex at supersonic speeds since the equation to compute CAS from dynamic pressure breaks down.

Edited May 27, 2021 by fat creason

[Hummingbird]

As I've observed it when flying all the different type aircraft ingame the IAS on the infobar merely mirrors what the HUD or instrument gages in the simulated aircraft show. But the TAS & TMN figures on the infobar show the actual/true movement of the aircraft within the sim, and hence the performance of atleast ED's aircraft are calibrated according to the figures displayed here. That's all I know, or think I know, we'll see if the devs suddenly say different, because like I said I was specifically asked to use the infobar for testing.

 

tbh I was convinced that TAS & TMN as recorded by the infobar was what all the various devs were using to measure & calibrate performance, so I'm kind of mindblown atm.

Edited May 27, 2021 by Hummingbird

[fat creason]

The number you're seeing labeled as IAS in the infobar and various HUDs/gauges isn't IAS though, it's EAS or something else that's definitely not IAS. TAS and TMN are the only numbers I'd borderline trust there. I didn't work on the CADC in the F-14 but I'll be checking to make sure we don't have the same problems as the modules in the post above. Pretty sure we don't but will verify to be certain. You definitely don't want to be using infobar airspeed when testing F-14 performance, go with Mach number or the airspeed in the cockpit itself. Infobar may as well not exist when I'm doing work on the FM.

Edited May 27, 2021 by fat creason

[Hummingbird]

15 minutes ago, fat creason said:

The number you're seeing labeled as IAS in the infobar and various HUDs/gauges isn't IAS though, it's EAS or something else that's definitely not IAS. TAS and TMN are the only numbers I'd borderline trust there. I didn't work on the CADC in the F-14 but I'll be checking to make sure we don't have the same problems as the modules in the post above. Pretty sure we don't but will verify to be certain. You definitely don't want to be using infobar airspeed when testing F-14 performance, go with Mach number or the airspeed in the cockpit itself. 

 

 

But if the infobar, when set to TAS & TMN, merely shows the actual/true movement of the aircraft within the simulation (i.e. it's just a recorder), then how can it be wrong?  I'm struggling to understand how it could be off.

 

As for when testing the F-14, I was always using TAS & TMN as shown on the infobar, as I do it for all aircraft. As noted ED's F-15 matches the performance charts perfectly when doing this, i.e. its performance as recorded using the TAS & TMN (& G) readings shown on DCS's infobar perfectly matches the performance as shown on the F-15C's performance graph illustrated as G vs TMN. 

 

 

Edited May 27, 2021 by Hummingbird

[Donut]

So HB is saying don't trust the info bar...and they don't use it for testing; but, ED uses it and apparently it matches up to real life performance charts.

 

Maybe this explains why the Tomcat's performance is off...?

[Victory205]

Nope.

[jcdata]

Funny but disconcerting thread...

Sent from my SM-G998U using Tapatalk

[draconus]

11 hours ago, captain_dalan said:

Still i would like for an official developer to chime in, or at the very least someone post an official quote, so the matter could be laid to rest.

Here:

 

10 hours ago, Hummingbird said:

But if the infobar, when set to TAS & TMN, merely shows the actual/true movement of the aircraft within the simulation (i.e. it's just a recorder), then how can it be wrong?

Well, the report is about the incorrect IAS, not TAS/TMN.