reported F-16 Excessive AoA in level flight

[fapador]

13 hours ago, Exorcet said:

After reviewing it looks like the flight model is not as far off in cruise as I thought it might be, however it might still be slightly underperforming. I will continue to look into it to make sure I'm not making any mistakes. The F-16 being such a light fighter means it will struggle with heavy payloads and it seems like the wing tanks really produce a large amount of drag (speaking of which it would help if DCS listed drag indexes).

Some AOA  in slow speeds level flight is normal and expected.  At 300-330 kn CAS I see in track I would expect more of  a 3-4degree AOA max, with these loads. Also don't forget that at very high speeds >400 kn CAS  F-16 controls become very sensitive to the slightest stick deflection, something which is not very good depicted in this sim.

 

What ED should do, is have some staff have go at an expensive CAE simulator, record and extract data through various tests, then try to match their sim to that. Instead they are using diagrams  basing their models to that data and correct with CFD calculations. This however, will not  always lead to  normal correct responses. Also, interviewing real pilots can and will lead to different opinions about how the aircraft flies. A different approach is needed if they want to have a better derived flight model.

Edited March 25, 2022 by fapador

[fapador]

Hud tape Footage of Greek f16 block 52+ with CFT's fully loaded,  two external tanks LANTIRN pod . 4 degrees AOA in bank level flight showing it can achieve ~ speed 377 with rpm around 95% almost like your tape. Indeed DCS loads are too draggy IMO. There are other segments in the video to get a general response Idea.

 

 

Edited March 25, 2022 by fapador

[TobiasA]

But at which altitude? Is it mentioned somewhere? I could only see 5000ft at the end of the video. 

[Carbon715]

9 hours ago, TheBigTatanka said:

Right, we don't have drag indexes for ECM pod, litening pod, or HTS pod. We might be able to get that from the other sim, but who knows where they got it from.

Running the charts for optimum mach is the key, then figuring out where you want to cruise, and what kind of fuel flow you should expect at that altitude for that mach number. Can't wait to get home to test it.

Sent from my Pixel 3 XL using Tapatalk
 

So where are these magical "charts"

[TobiasA]

vor 2 Stunden schrieb Carbon715:

So where are these magical "charts"

Google HAF F-16 supplemental manual.
It is not allowed to be shared here, but unclassified afaik.

[Exorcet]

Current hypothesis the F-16 is fine, what is not fine are the wing tanks. They aren't modeled properly in the first place because the pylons are separate from the tanks. In reality they are one unit. I think this is leading to extra drag with any configuration with wing tanks as the pylons for them are counted when they shouldn't be. In addition the wing tanks drag increases with additional stores loading on the wing. I'm not sure how/if DCS models that but I wonder if the erroneous wing tank pylons are causing even more drag because of that.

This is based on testing maximum altitude for a given weight and DI against charts. When I don't have wing tanks things seem to match pretty well. With wing tanks, I either lose speed or have to descend. I'm still recording tracks and checking data, I plan to submit final findings to ED via PM (to avoid breaking the rule about posting real world data). However it might help if others do the same and compare center tank loadouts/DI to charts vs wing tank loadouts/DI to charts.

[TheBigTatanka]

Can do next week. I think that's a pretty good theory.

Sent from my Pixel 3 XL using Tapatalk

[SCPanda]

On 3/19/2022 at 3:07 AM, Exorcet said:

With the new flight model changes the F-16 seems to have become more responsive, but the AoA required for level flight has increased. It's especially obvious with two external tanks.

Pre patch single tank loadouts at altitude would sit around 3-4 degrees AoA, now even an AA loadout can exceed 5 degrees. Two tank loads can approach 7 and are far too draggy for the F-16 to maintain speed.

Is this expected behavior, or is the FM in need of more tuning?

F-162tank24k.trk 28.61 kB · 6 downloads

 

On 3/24/2022 at 11:40 PM, TheBigTatanka said:

Yeah, that's what I'm gathering too.   I'm away at ground school learning a new jet, but i ran some of the cruise charts yesterday for a few loadouts i commonly use, and the numbers matched what i remember from the new flight model.  I'll do some flight tests when I get home, but I'm excited about how it's looking. 

After the recent FM update (last patch), I feel like our F-16 has lost some thrust, both clean or loaded, burner or no burner. Like I was able to mantain certain speed at certain attitude or accelerate to certain speed before the patch, but after the patch I am no long able to. I fly this jet everyday so I am not making this up. Something is not right because there is no mention of thrust tweaking or drag tweaking in the last patch notes. 

[TobiasA]

vor 16 Stunden schrieb Exorcet:

Current hypothesis the F-16 is fine, what is not fine are the wing tanks. They aren't modeled properly in the first place because the pylons are separate from the tanks. In reality they are one unit. I think this is leading to extra drag with any configuration with wing tanks as the pylons for them are counted when they shouldn't be. In addition the wing tanks drag increases with additional stores loading on the wing. I'm not sure how/if DCS models that but I wonder if the erroneous wing tank pylons are causing even more drag because of that.

This is based on testing maximum altitude for a given weight and DI against charts. When I don't have wing tanks things seem to match pretty well. With wing tanks, I either lose speed or have to descend. I'm still recording tracks and checking data, I plan to submit final findings to ED via PM (to avoid breaking the rule about posting real world data). However it might help if others do the same and compare center tank loadouts/DI to charts vs wing tank loadouts/DI to charts.

I think that might be the case because wing tanks do have a large effect, probably larger than their DI would be.

Noticed that yesterday as well. 

Good catch, thanks!  

[Exorcet]

I've finished testing and I have two conclusions:

370 gallon tanks appear to be excessively draggy and prevent the F-16 from matching real world cruise performance.

TER racks are also excessively draggy

I also suspect that other AG racks like the BRU-57 might be overly draggy but I can't prove this.

Configurations I tested:

# AA/AG payload > weight - result

1 AA 4x120B,2x9M,300 gal > at 32124 - Pass

2 AA 4x120B,2x9M,2x370 gal > at 36050 - Fail

3 AG 2x120B,2x9M,2xMk84LDGP,300 gal > at 35728 - Pass

4 AG 2x120B,2x9M,2xMk84LDGP,2x370 gal > at 39657 - Fail

5 AG 2x120B,2x9M,2xAGM-88,300 gal > at 33579 - Pass

6 AG 2x120B,2x9M,2xAGM-88,2x370 gal > at 37505 - Fail

7 AG 2x120B,2x9M,4xAGM-65,300 gal > 34551 - Fail

8 AG 2x120B,2x9M,4xAGM-65,2x370 gal > 38479 - Fail

9 AG 2x120B,2x9M,4xAGM-65,2x370 gal,300 gal > at 41041 - Fail

The common trend is that centerline fuel tank payloads = pass, wing tank payloads = fail

I've sent this information with more detail to BIGNEWY.

[TheBigTatanka]

That's outstanding work. I've got a few more days of work, and then I'll be home to run the performance manual charts and test as well. Will add data. Great work man.

Sent from my Pixel 3 XL using Tapatalk

[Exorcet]

28 minutes ago, TheBigTatanka said:

That's outstanding work. I've got a few more days of work, and then I'll be home to run the performance manual charts and test as well. Will add data. Great work man.

Sent from my Pixel 3 XL using Tapatalk
 

Thanks, I'm looking forward to more data.

 

Also I need to make a small correction, I said TER racks but I meant LAU-88.

[TobiasA]

vor 6 Stunden schrieb Exorcet:

I've finished testing and I have two conclusions:

370 gallon tanks appear to be excessively draggy and prevent the F-16 from matching real world cruise performance.

TER racks are also excessively draggy

I also suspect that other AG racks like the BRU-57 might be overly draggy but I can't prove this.

Configurations I tested:

# AA/AG payload > weight - result

1 AA 4x120B,2x9M,300 gal > at 32124 - Pass

2 AA 4x120B,2x9M,2x370 gal > at 36050 - Fail

3 AG 2x120B,2x9M,2xMk84LDGP,300 gal > at 35728 - Pass

4 AG 2x120B,2x9M,2xMk84LDGP,2x370 gal > at 39657 - Fail

5 AG 2x120B,2x9M,2xAGM-88,300 gal > at 33579 - Pass

6 AG 2x120B,2x9M,2xAGM-88,2x370 gal > at 37505 - Fail

7 AG 2x120B,2x9M,4xAGM-65,300 gal > 34551 - Fail

8 AG 2x120B,2x9M,4xAGM-65,2x370 gal > 38479 - Fail

9 AG 2x120B,2x9M,4xAGM-65,2x370 gal,300 gal > at 41041 - Fail

The common trend is that centerline fuel tank payloads = pass, wing tank payloads = fail

I've sent this information with more detail to BIGNEWY.

Outstanding, thanks! 

The BRU-57 is so draggy that I never use it. It is like having your speedbrakes half opened. But sadly there is no public data about its drag index.

[BIGNEWY]

Hi all, 

the team have reviewed the data and have found exaggerated drag from stores in the transonic region, tests of AoA and speed will show incorrect results currently. 
It will be tweaked in a future patch.

Thank you to those who PM'd me about this.

thanks