correct as is Current F-15 Speed

[trenchfeet]

Should the F15 be performing at M2.3 at 30k currently under load? is this normal? 

[draconus]

More info needed. What load/setup? You mean level flight?

[trenchfeet]

Full 120 load/ half load and no load, level flight between 30k and 60k. With out tanks.

[Breakshot]

15 hours ago, trenchfeet said:

Should the F15 be performing at M2.3 at 30k currently under load? is this normal? 

I think something is going on with drag with stores, also F15 is barely affected by difference in ambient temperatures like all the other jets (especially REDfor jets). So yes, with bags doing M2.3 seems unreasonably fast.

[FoxAlfa]

Can you give exact stats and load so I can cross check? Thank you!

Edited February 8, 2022 by FoxAlfa

[trenchfeet]

Just simply jump in the f15 load up with 120’s apply full burner and point to the moon. I found it will keep climbing and speed keeps increasing. You can do this on the growling sidewinder and lob 120’s from further the aim54 can reach, crank or notch and nothing will hit because you are out running and turning anything, it’s not sr71 like the bug last time but I just don’t see how this is possible. Just would like a second opinion if the performance is accurate for a f15.

[dundun92]

5 hours ago, trenchfeet said:

Just simply jump in the f15 load up with 120’s apply full burner and point to the moon. I found it will keep climbing and speed keeps increasing. You can do this on the growling sidewinder and lob 120’s from further the aim54 can reach, crank or notch and nothing will hit because you are out running and turning anything, it’s not sr71 like the bug last time but I just don’t see how this is possible. Just would like a second opinion if the performance is accurate for a f15.

what is the exact loadout though (6 AMRAAM? 8 AMRAAM? 1,2 or 3 bags)? We need to know so we (and ED) can cross check with the RL manual

 

EDIT: OK you said above no bags, im gonna assume 8 AMRAAMs for worst case, and check

Edited February 9, 2022 by dundun92

[nighthawk2174]

Isn't stores drag still broken for the F15?

Edited February 9, 2022 by nighthawk2174

[dundun92]

Just now, nighthawk2174 said:

Isn't stores drag still broken for the F15?

 

No, that got fixed. Whether its "fully" or realistically fixed, IDK, I havent tested personally, but there definitely is stores drag, has been for a few months now

Edited February 9, 2022 by dundun92

[stefasaki]

It’s most likely at ISA +5 which is the standard dcs day. However temperature does not have an effect on the eagle in the game and its performance is mostly consistent with a -10 day on the charts. This also explains the mach 2.606 max speed that we have on a clean eagle in the game. The eagle’s flight envelope is accurate enough I think, there are much bigger differences for other airframes. It would just need a dependency on temperature (which has a huge influence)

[Cmptohocah]

On 2/9/2022 at 6:28 PM, dundun92 said:

what is the exact loadout though (6 AMRAAM? 8 AMRAAM? 1,2 or 3 bags)? We need to know so we (and ED) can cross check with the RL manual

Your mention of the drop-tanks got me thinking: in the manual max Mach number for jettisoning them M1.5 - I wonder if that's modeled in DCS or not?

[BIGNEWY]

Please remember our 1.16 rule here when posting. 

thanks

[BlackPixxel]

I have made a comparison of the acceleration at 8.4 °C vs 40 °c in a level flight at 12 km altitude some days ago.

 

8.4 °C:

40 °C:

As you can see, the acceleration is just stretched a bit in time as it gets warmer. But the top speed stays the same.

 

Meanwhile the Su-27 shows massive differences:

8.4 °C:

40 °C:

Su-27 at warm temperatures accelerates alot slower and reaches a much slower top speed (look how the warm curve begins to show the approach of a max value with a bend, while the cold curve is growing linear at the same time.)

 

One of them is wrong (or both are wrong). ED needs to take a look at those FM's again.

[BIGNEWY]

please include your track replays from the tests. 

thanks

[BlackPixxel]

45 minutes ago, BIGNEWY said:

please include your track replays from the tests.

Here are the tracks for F-15C and SU-27

 

f15_high.trk f15_low.trk high_temp.trk low_temp.trk

[GGTharos]

2 hours ago, Cmptohocah said:

Your mention of the drop-tanks got me thinking: in the manual max Mach number for jettisoning them M1.5 - I wonder if that's modeled in DCS or not?

And what do you think should happen if you dump it at M1.6?

[okopanja]

39 minutes ago, GGTharos said:

And what do you think should happen if you dump it at M1.6?

No clue on this, but your question made me wonder.

What happens in general with aircraft stability when the large draggy object is jettisoned at high mach speed?

Does the aircraft pitch up/down? If I remember correctly, with both F-15 and F-16 there is no effect at all,  but is this true in reality?

Edited February 11, 2022 by okopanja
typos

[draconus]

27 minutes ago, GGTharos said:

And what do you think should happen if you dump it at M1.6?

Unforseen consequences

Possible collision and some damage.

[Cmptohocah]

15 minutes ago, draconus said:

Unforseen consequences

Possible collision and some damage.

Or they fail to detach.

 

45 minutes ago, GGTharos said:

And what do you think should happen if you dump it at M1.6?

Not what's happening now , which is I presume nothing.

Edited February 11, 2022 by Cmptohocah

[Exorcet]

Mach 2+ sounds reasonable without tanks. The F-15 stores drag was excessive before (not counting the 0 drag bug). Remember 4 of the missiles should be very low drag.

[Breakshot]

So basically F15 isn't affected by air temperature changes like other planes - GG FM is OP

Why is flanker so handicapped by ambient temperature!? Surely same laws of physics must apply for all AC....

Edited February 11, 2022 by Breakshot

[dundun92]

7 hours ago, BIGNEWY said:

Please remember our 1.16 rule here when posting. 

thanks

I was under the impression that this doc was OK as this was uploaded by Chizh himself on the DCS userfiles?

https://www.digitalcombatsimulator.com/en/files/645686/

[Breakshot]

20 minutes ago, Gypsy 1-1 said:

How exactly is the F15 not affected by ambient temperature currently? 

Someone could probably test the thrust and top speed curves and compare with the public manuals. Last time I checked (more than a year ago) you couldnt really perform a Rutowski profile climb and hit the charted speeds at high alt. I guess this may have been fixed hence why people think it's overperforming?

Look at the clear charts posted by BlackPixxel above. The numbers dont lie. Something is going on, unless of course F15 is immune to temperatures compared to all other jets?

[okopanja]

1 hour ago, Gypsy 1-1 said:

But they are meaningless without any real world reference? You can't compare a Su-27 with an F-15 like that.

There is at least document for F-15C (and I assume they have it for flanker), and clearly you can see the differences in graphs for different temperatures.

If he is right, for flanker there is no such difference, but this difference has to be there. Same physics laws apply to both, although their profiles may differ.

I do not know how comprehensive are EDs unit tests are and if they keep the full suite of automated tests for each aircraft. Perhaps others should be checked as well?

I do no think they do the true simulation of the aerodynamics (I gather this would be computationally very expensive), but rather create parametrized flight model based on analyzes they make. Modeling these things is not easy, lots of parameters is involved, and when you modify one, the other one goes totally wrong (look at the AIM-54 for instance). I am pretty sure they are having hard time modifying and testing it every time they have to correct a bug.

 

[draconus]

2 hours ago, okopanja said:

I do no think they do the true simulation of the aerodynamics (I gather this would be computationally very expensive), but rather create parametrized flight model based on analyzes they make.

https://www.digitalcombatsimulator.com/en/support/faq/general/

You can read on what is PFM. Does it sound like your "true simulation of aerodynamics" I can't say.