PSA: F-14 Performance/FM Development Status + Guided Discussion

[Airhunter]

16 minutes ago, Hummingbird said:

First quick results after FM change, at SL & 400 KTAS:

 

DCS F-14B STR, 55,620 lbs, 4x AIM7 + 4x AIM9, SL, 15 deg C std. day:

400 KTAS (M 0.6) = 6.3 G 

Based on the performance charts, I calculated a 6.55-6.65 G's sustained turn rate here, a ~1 G improvement from 5 kft [5.6 G], which is a similar improvement seen  for example for the F-15 & F-16.

So the initial verdict is that at 400 KTAS (M 0.6) at SL the DCS F-14B appears a bit lacking, however at 5 kft I actually managed to sustain 5.6 G @ M 0.6 (389 KTAS), as on the charts, so here it appears spot on. So I'm not sure why it's not performing as expected at SL ?  

 

 

 

 

 

 

Are there even charts for SL?

[Victory205]

Nope. Should be obvious as to why not.

Extrapolations aren’t valid. Fly the profile level at the proper altitude for which performance data is available, at a demonstrated constant speed, and constant G. 

[Hummingbird]

3 hours ago, Airhunter said:

 

Are there even charts for SL?

No, but there are for 5 kft & 10 kft, thus its rather "easy" to calculate performance at SL.

 

I mean you wouldn't expect the F-14B to suddenly dump a 0.6G advantage in STR @ M 0.6 from 5 kft to SL, now would you?

Edited October 21, 2021 by Hummingbird

[Hummingbird]

To put the above graph into numbers:

F-14B/D vs F-15C sustainable load factor (G vs Mach), same load out (4x4 & ~55% fuel), ICAO Std. day.  
F-14 = 55,620 lbs
F-15 = 41,000 lbs

@ 5,000 ft
M 0.3 = 2.35 vs 2.15  (+0.20 G to F-14)
M 0.4 = 3.60 vs 3.05  (+0.55 G to F-14)
M 0.5 = 4.80 vs 4.05  (+0.75 G to F-14)
M 0.6 = 5.70 vs 5.10  (+0.60 G to F-14)
M 0.7 = 6.40 vs 6.30  (+0.10 G to F-14)
M 0.8 = 7.00 vs 7.50  (+0.50 G to F-15)

@ 10,000 ft
M 0.3 = 1.95 vs 1.80 (+0.15 G to F-14)
M 0.4 = 2.90 vs 2.60 (+0.30 G to F-14)
M 0.5 = 4.10 vs 3.40 (+0.60 G to F-14)
M 0.6 = 5.00 vs 4.30 (+0.70 G to F-14)
M 0.7 = 5.50 vs 5.25 (+0.25 G to F-14)
M 0.8 = 6.00 vs 6.40 (+0.40 G to F-15)

Sources:
The original F-14B & F-15C performance manuals.

 

Knowing the lift & drag equations and how they scale with altitude, it's pretty obvious that, unless the F-14 suddenly lost a lot of thrust, it should maintain roughly the same advantage in sustainable load factors vs the F-15C below M ~0.65 at SL as it does at 5 kft; Just as you see it do from 10 kft to 5 kft.  It makes no sense if all of a sudden the F-14 & F-15 are equal in STR at M 0.6 @ SL when the F-14 was dominating the F-15 with a 0.6 G advantage at the same MN at 5 kft. Hope that makes sense.
 

Edited October 21, 2021 by Hummingbird

[Hummingbird]

Credit where credit is due, at 5 kft they got it close:

5,000 ft ICAO std. day
M 0.4 (260 KTAS) = 3.50 G vs 3.50 G in manual (spot on)
M 0.5 (334 KTAS) = 4.65 G vs 4.75 G in manual (-0.1 G off)
M 0.6 (389 KTAS) = 5.60 G vs 5.60 G in manual (spot on)
M 0.7 (454 KTAS) =  6.30 G vs 6.40 G in manual ( -0.1 G off) 

So something is going wrong as altitude progressively decreases to sea level, as you don't suddenly lose a 0.6 G advantage in sustainable load factor going from 5 kft to sea level.

But as mentioned in the patch notes, it seems this tuning is a work in progress, and I wasn't expecting everything to be perfect right off the bat anyway.

@fat creasonI think you might wanna calculate the expected performance at sea level based on the available 5 kft & 10 kft performance graphs, plot it, and then tune the FM to precisely hit the new calculated plots. 

 

 

[Hummingbird]

Just to reinforce my point here, we can also compare the real life figures for the F-14B & F-16C at 10 kft and two speeds, and as they both use the GE engine we can rule out engine thrust loss vs alt as a factor:

 

F-16C, 26,000 lbs, 4xAIM120 + 2xAIM9 + centerline pylon (DI=50), 10 kft:

M 0.5 = 3.6 G

M 0.6 = 4.5 G

F-14B, 55,620 lbs, 4xAIM7 + 4xAIM9, 10 kft:

M 0.5 = 4.2 G

M 0.6 = 5.0 G

 

So a 0.5-0.6 G advantage for the F-14B at 10 kft and M 0.6 & 0.5 respectively.

Now here's what the same config F-16C as above gains in sustainable load factor going from 10kft to sea level:

M 0.5 = 5.0 G (+1.4 G vs 10 kft)

M 0.6 = 6.3 G (+1.8 G vs 10 kft)

 

In short we should expect a similar gain in sustainable load factor for the F-14 going from 10 kft to sea level, i.e. roughly +1.8 G @ M 0.6 and +1.4 G @ M 0.5.

In other words at sea level you'd expect the F-14B to be able to sustain about 6.8 G @ M 0.6 and 5.6 G @ M 0.5. (I calculated 6.6-6.7 and 5.6-5.7)

As mentioned earlier, it would not make any sense if at sea level the F-16C & F-14B all of a sudden became equal in STR at the mach numbers where the F-14B holds 0.5-0.6 G advantage  at 10 kft.

 

Finally the reason this is important is that often most guns only dogfights in DCS ends up near the floor, so you really feel any major discrepancies here.

Edited October 21, 2021 by Hummingbird

[Katj]

I have not done extensive testing but the F-14A seems to be able to punch through the sound barrier with a meaningful loadout now.

I just did one Rutkowski climb with the A and B and a 4 sparrows + 4 sidewinders loadout and there wasn't a huge difference between them. The A seemed faster at the top end.

I have to test more but it sure seemed promising.

[maxsin72]

4 hours ago, Hummingbird said:

Just to reinforce my point here, we can also compare the real life figures for the F-14B & F-16C at 10 kft and two speeds, and as they both use the GE engine we can rule out engine thrust loss vs alt as a factor:

 

F-16C, 26,000 lbs, 4xAIM120 + 2xAIM9 + centerline pylon (DI=50), 10 kft:

M 0.5 = 3.6 G

M 0.6 = 4.5 G

F-14B, 55,620 lbs, 4xAIM7 + 4xAIM9, 10 kft:

M 0.5 = 4.2 G

M 0.6 = 5.0 G

 

So a 0.5-0.6 G advantage for the F-14B at 10 kft and M 0.6 & 0.5 respectively.

Now here's what the same config F-16C as above gains in sustainable load factor going from 10kft to sea level:

M 0.5 = 5.0 G (+1.4 G vs 10 kft)

M 0.6 = 6.3 G (+1.8 G vs 10 kft)

 

In short we should expect a similar gain in sustainable load factor for the F-14 going from 10 kft to sea level, i.e. roughly +1.8 G @ M 0.6 and +1.4 G @ M 0.5.

In other words at sea level you'd expect the F-14B to be able to sustain about 6.8 G @ M 0.6 and 5.6 G @ M 0.5. (I calculated 6.6-6.7 and 5.6-5.7)

As mentioned earlier, it would not make any sense if at sea level the F-16C & F-14B all of a sudden became equal in STR at the mach numbers where the F-14B holds 0.5-0.6 G advantage  at 10 kft.

 

Finally the reason this is important is that often most guns only dogfights in DCS ends up near the floor, so you really feel any major discrepancies here.

 

I hope it would be possible to fix new FM as soon as possible, in any case not in almost one year as per the last update. I'm becoming old in the meantime

Edited October 21, 2021 by maxsin72

[Victory205]

10 hours ago, Airhunter said:

 

2 hours ago, Katj said:

…The A seemed faster at the top end.

The A is faster at the top end.

Edited October 21, 2021 by Victory205

[Hummingbird]

13 minutes ago, maxsin72 said:

I hope it would be possible to fix new FM as soon as possible, in any case not in almost one year as per the last update. I'm becoming old in the meantime

 

 

I think things are gonna go a little faster now (but I dont know ofcourse), also let's remember they did write it was work in progress. 

[maxsin72]

5 minutes ago, Hummingbird said:

 

I think things are gonna go a little faster now (but I dont know ofcourse), also let's remember they did write it was work in progress. 

Thx for the answer, a provisional fix perhaps could be to increase a bit F110/TF30 performance so the cat would be able to pull a little more.

Edited October 21, 2021 by maxsin72

[eatthis]

15 minutes ago, Victory205 said:

 

The A is faster at the top end.

 

why did the tf30 benefit more from ramair than the ge motors?

[lunaticfringe]

6 minutes ago, eatthis said:

why did the tf30 benefit more from ramair than the ge motors?

Primarily because the ramps weren't reprogrammed to match the flow properties of the F110.

[Kefa]

11 hours ago, Airhunter said:

 

Are there even charts for SL?

In the manual there are Specific Excess Power Diagrams for 1,3,5,6.5g.  I followed Ps=0 line down to sea level, looks like with 4x4,50%fuel, 55,620pounds F-14B tomcat sustains 6.5g at  around .62mach and then again at .95mach.  For 5G looks like it is at about .47mach and 1mach.  

[Hummingbird]

45 minutes ago, Kefa said:

In the manual there are Specific Excess Power Diagrams for 1,3,5,6.5g.  I followed Ps=0 line down to sea level, looks like with 4x4,50%fuel, 55,620pounds F-14B tomcat sustains 6.5g at  around .62mach and then again at .95mach.  For 5G looks like it is at about .47mach and 1mach.  

 

Ah yes, I completely forgot about those! That's excellent, then we have hard figures to go by:

At sea level we should get:

6.5 G @ M 0.62 / 410 KTAS (currently 6.35 G, so -0.15 G off)

5.0 G @ M 0.46 / 304 KTAS (currently 4.85 G, so -0.15 G off)

In short, it should be doable to fix for next patch.

 

 

Edited October 21, 2021 by Hummingbird
Typo

[Airhunter]

14 minutes ago, Kefa said:

In the manual there are Specific Excess Power Diagrams for 1,3,5,6.5g.  I followed Ps=0 line down to sea level, looks like with 4x4,50%fuel, 55,620pounds F-14B tomcat sustains 6.5g at  around .62mach and then again at .95mach.  For 5G looks like it is at about .47mach and 1mach.  

Yeah I don't care. I trust the SME more for it to "feel" right. 

[streakeagle]

SME is subjective.

The manual is hard engineering data.

When the two don't agree, I generally favor the hard engineering data unless there is a valid reason to dispute it.

[Hummingbird]

10 minutes ago, streakeagle said:

SME is subjective.

The manual is hard engineering data.

When the two don't agree, I generally favor the hard engineering data unless there is a valid reason to dispute it.

 

Correct, arguing against the flight test and engineering data is silly as you're not going to get anything else remotely as accurate.

[Victory205]

I didn’t do performance, however, the methodology used removes human error. 
 

Right now, we seem to have anecdotal claims without evidence. Same old story. The referenced DCS F16 was “perfect throughout the envelope”, yet it was recently changed by DCS because it wasn’t perfect. So is it perfect now but. It before, or was it perfect then and afu now?
 

Anyone purporting deficiencies in either direction needs show their work. Writing numbers on a forum doesn’t cut it, never has. Shouldn’t be difficult. 

[Hummingbird]

Well I can confirm that the FM has definitely improved, we're talking a bit of an inconsistency in performance only at sea level according to my testing. 

 

 

 

[SgtPappy]

47 minutes ago, Airhunter said:

Yeah I don't care. I trust the SME more for it to "feel" right. 

That's fine you don't have to care about hard data. Sometimes people prefer the flight model to "feel" right even if it's subjective.

Fortunately, people who do care about the data are also allowed to not care about solely if something "feels" right to an SME. And that has nothing to do with the quality of work that the SME's provide. 

I like blue and you like green - both are allowed and are valid so let's all stop the tribalism revolving around what the other party should care about more, yea?

Edited October 21, 2021 by SgtPappy

[Hummingbird]

Let me also just say to the HB devs & SME's, regardless of the slight discrepancy at SL & 5 kft, you did great work on the FM. It's close now, very close.

So please, don't look at my feedback as anything but constructive, and ofcourse ALWAYS remember to check yourselves to make sure I didn't make any mistakes in testing. It's a lot of numbers and stuff to keep track off, so there's always the possibility for mistakes.

Thank you for the hard work! 

 

Edited October 21, 2021 by Hummingbird

[Victory205]

There are objective data points from airshow benchmarks at SL, but they are generally not distilled down for temperature effects or even G meter resolution and location errors. There is a difference between cockpit G and test data derived from flight test sensors at or near the CG, or aero instruments vs flight test pitot static installations mounted on booms outside of the flow fields. 

[Katj]

The A is faster at the top end.

Yes, and the DCS and real A seem to be in agreement. Which is very good!

why did the tf30 benefit more from ramair than the ge motors?

I think one, albeit very oversimplified, explanation is that it has a higher bypass ratio which in turn will feed the afterburner with more oxygen (and mass).

[Spurts]

Oh?  I didn't realize they put in the TF30 specific tune already!  I thought that was going to have to wait.  As for the sustained G, I am not going to lose sleep over losing .15G at SL, a 3% or less error.  I am never doing a STR turn anyway.  I am always either climbing, diving, speeding up, or tightening down.