Is the F-18's FM finished yet?

[Maverick Su-35S]

Hi,

 

 

I'd just want to ask if this awesome bird's FM is finished? Nothing else!

 

 

Regards!

[Esac_mirmidon]

No.

[Raven68]

It will continue to be tweaked for some time.

[Pasquale1986]

Oh oh...The FM is WIP as Raven68 said. Even the internal build regarding a fix with the drag values with gear down isn't released yet iirc. So please, please not another FM-crusade at this point.

 

It's the early part of an Early Access release.

[Svend_Dellepude]

Maybe ED needs help..?

[Raven68]

Maybe ED needs help..?

I'm sure ED has it under control. They have good resources and SME's to take it on.

[Maverick Su-35S]

Copy! People don't get frustrated! I just asked and now I have my answer! If I was going to get something like: "yes, of course it's done, it's all good", then I would've started shooting, but as long as we're true with each other, there's no worry.

 

This is what I've found so far. The following might be helpful for the FM developers who are still working on it. No criticism yet, only spotted problems by some random guy for who the aerodynamics simulation is like a drug.

 

I've done 4 tracks, each one regarding a different subject. The difference is that the 4th track is a congratulations and not an issue.

 

1. Between some AoA and Beta (sideslip angle) ranges, the aerodynamic forces generated are a bit strange (at least that's how I find them) and also the expected rolling moments and rolling oscillations are non existent:

 

Between some AoA and Beta angles, the rolling moment becomes null.trk

 

2. When rapidly changing the AoA from a low to high value, the initial roll rates rapidly go to zero. Either the rolling inertia suddenly becomes as low as null as the AoA goes past some threshold or the lift differences due to the AoA difference between the wings become so predominant over the remnant roll rate that the roll rate becomes zero in no time. Don't want to make it sound strange but the way I feel it is like the FM is partially SFM, partially AFM. It's like no matter the speed or the weight (thus the moments of inertia) of the aircraft, the roll rates are "forced" to have X value at Y AoA and airspeed. Also from my opinion (hope this will be more appropriate when the FM is finished for the F-18 at least), the rolling moment coefficients are being simulated with the highest errors among all the aero coefficients that take place. I consider that the motions of the airplane should be more dynamic (forces and moments calculated on their own based only on accurate initial values) and not give the feeling that they are scripted or simulated only through big matrices of fixed values and tables. I don't know what the FM's core is based on in DCS but in other simulators there are data tables which contain only some necessary variables and from there on, the aerodynamics equations combined with the flight dynamic equations automatically calculate how should a force develop on a particular part of the aircraft and the resulting moment/moments. I'm not saying anything to criticize, but I'm partly sharing what I found and how the plane feels for me and it's not due to how the surfaces deflect due to flight controls logic, no..., it's about how the plane responds to each surface deflection and momentum (angular rates).

 

Roll rate becomes 0 rapidly with AoA onset. Feels like the rolling inertia becomes 0.trk

 

3. The flaps vary the pitching moment by a rather tremendous amount. Simply fly at maximum constant AoA, some 50 AoA and lower the flaps to full. Indeed the rudders will deflect towards generating a slight pitch down moment (maybe they are programmed so to act as airbrakes or to assist in pitching moments) and the elevators also initially deflect towards positive to reduce the AoA but after the AoA starts to drop, the elevators come back to full negative deflection. Somehow our plane now sits at around 15..16 AoA with full negative elevators and just some half rudder deflection towards pitching the nose down. I hope people won't consider the rudders deflection as the reason for the low AoA trim/settle, as their effect on pitching moment is far reduced from that of the elevators considering the fins dihedral from the vertical axis and low rudders surfaces and about half deflection.

 

The clue that the flaps increase the Cm towards negative (which is normal along with the droops as well) in a very exaggerated manner can be seen after pushing the stick full forward and watching how the AoA starts to accelerate violently towards higher negative values after passing through some -20..-25AoA. The plane will settle in a negative deep stall at around -50AoA and the AoA won't vary at all no matter how the controls are deflected:

 

Negative Cm vs flap is incredibly high.trk

 

4. The inertia coupling for which the F-18, especially the CF-18 (Canadian version) that develops within some circumstances of roll rates and alpha-beta combinations are on the other hand remarkably well simulated. This kind of eliminates (at least in this area) my above thought that the FM is scripted, yet anyway I believe it is partially in some places giving how the plane reacts sometimes.

 

Spot on inertia coupling + high AoA and beta through cross controls.trk

 

Congratulations on the inertial coupling phenomena which throws/departs the plane into a negative spin if the stick is pulled with cross controls (stick to one side, rudder in the other). Try not to affect this side of simulation which is otherwise authentic.

 

Here's a life test (I've provided it for different subjects before):

 

Anyway, in the first video the guy just held cross controls throughout both spin departs, yet in our sim the F-18 holds a rather constant rate negative spin. This might happen because probably the F-18 in the video had full authority over the rudders and ailerons deflections (no FBW filtering).

 

Those who deny videos as proof for one plane's behavior in the subject of comparing a simulation with it, when everything is plain sight clear, are just those who either don't understand or are blind (apparently) or don't want to recognize the true facts.

 

Regards & good day!

[Pasquale1986]

https://forums.eagle.ru/showpost.php?p=3579278&postcount=152

 

As stated in the above linked Newsletter

 

„Further tuning of flight model with touch and go performance, gear drag, half flaps drag, takeoff pitch characteristics, and extreme angle of attack performance.“

[wilbur81]

https://forums.eagle.ru/showpost.php?p=3579278&postcount=152

 

As stated in the above linked Newsletter

 

„Further tuning of flight model ... and extreme angle of attack performance.“

 

This is good news for sure.

 

I'm sure many here have seen this hornet display video....

 

 

but the high AOA, pirouette, etc. looks unreal! No offense at all to Wags demo video of the pirouette, but the Hornet stuff in this video is in another class altogether. It'd be awesome to get this kind of FM performance simulated. ED sets a high bar for us. :-)

[Eldur]

I just noticed one thing when trying (and failing) to set realistic temperatures for the Gulf. Max temp was 41.3°C on Jul 4th (which is a frozen joke for that area of the world, I was able to set up to 50°C in Caucasus instead). The engine performance felt like it was completely gone. Could hardly even pass M 1.5 at 37k ft. Wasn't there a rule of thumb that the temperature is 2°C less every 1k ft of alt? That'd be still -32.7°C up there, does that really lower the max speed by almost 0.3? I then tried the other extreme, well, almost; -7.5°C in Caucasus October - without any noticalbe gain over the "DCS standard day" at all.

 

Just wondering, don't have the hard data

[Ala12Rv-watermanpc]

I just noticed one thing when trying (and failing) to set realistic temperatures for the Gulf. Max temp was 41.3°C on Jul 4th (which is a frozen joke for that area of the world, I was able to set up to 50°C in Caucasus instead). The engine performance felt like it was completely gone. Could hardly even pass M 1.5 at 37k ft. Wasn't there a rule of thumb that the temperature is 2°C less every 1k ft of alt? That'd be still -32.7°C up there, does that really lower the max speed by almost 0.3? I then tried the other extreme, well, almost; -7.5°C in Caucasus October - without any noticalbe gain over the "DCS standard day" at all.

 

Just wondering, don't have the hard data

 

I were about to open a thread about this...simply put, is ambient temperature taking any effect in the actual FM?? (And not only for the hornet but for all the planes, especially the ones wih AFM)...according wih your test looks like yes but maybe as a constant after setting it in the ME??....

[wilbur81]

 

I referred to this video in my post above.... it is cool what the current DCS Hornet can do, but it is not nearly as impressive, rapid, or aggressive as what we see in the Swiss Hornet's demo that I posted a link to. Just watch Wags' video and then the one I've referenced and you'll see a significant difference. Not sure what to make of the 'software logic only available for demo hornets' comment above?

[IvanK]

"'software logic only available for demo hornets' comment above?"

 

Thats not what I said !

 

 

Early software loads in the FA18A/C didn't not incorporate pirouette logic. You could still perform a pirouetteish like maneuver but not as aggressively, repeatably and relatively care free as when pirouette logic was incorporated in later FCS software loads.

 

 

ALL FA18A/C's got pirouette logic in later FCS software loads .... The NATOPS that I provided a quote from discuss the incorporation of pirouette logic.. This incorporation came as a by product of FA18E/F FCS software development that was then inherited by the A and C.

 

 

Here is the section from the FA18C NATOPS:

 

 

Edited July 27, 2018 by IvanK

[wilbur81]

"'software logic only available for demo hornets' comment above?"

 

Thats not what I said !

 

 

Early software loads in the FA18A/C didn't not incorporate pirouette logic. You could still perform a pirouetteish like maneuver but not as aggressively, repeatably and relatively care free as when pirouette logic was incorporated in later FCS software loads.

 

 

ALL FA18A/C's got pirouette logic in later FCS software loads .... The NATOPS that I provided a quote from discuss the incorporation of pirouette logic.. This incorporation came as a by product of FA18E/F FCS software development that was then inherited by the A and C.

 

 

Here is the section from the FA18C NATOPS:

 

 

 

That makes a LOT more sense. Thanks for clarifying! :thumbup:

[Doum76]

Hi,

 

 

I'd just want to ask if this awesome bird's FM is finished? Nothing else!

 

 

Regards!

 

 

No offence man, but you<re an 2014 old user on the Forum, and you already seen a new module being finished after a month being out? :)

[IvanK]

=4c=Nikola err not sure what the issue is I haven't quoted you at all I was referring to was Wibur81'scomment not yours :)

[wilbur81]

I'm tired, gonna sleep. I apology.

 

Cheers

 

Sweet dreams. May you dream of real life and DCS Hornets pirouetting like crazy all over the skies. :-)

[Svend_Dellepude]

I'm sure ED has it under control. They have good resources and SME's to take it on.

 

Why? Are you volunteering? Let's see your Hornet 1,000 hour and Centurion patches, hoss.

 

The professionals are hard at work.

 

It was meant as a humorous remark to the OP, but I guess you guys haven't been in the FC3 area lately.

 

https://forums.eagle.ru/showthread.php?t=137234

[Raven68]

It was meant as a humorous remark to the OP, but I guess you guys haven't been in the FC3 area lately.

 

https://forums.eagle.ru/showthread.php?t=137234

 

Ok I see where you are going with that. Perhaps that link with a little verbiage would have helped frame what you meant. :)