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After 2.7 patch the lift curve problem gets even worse


oldtimesake

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vor 5 Stunden schrieb Frederf:

Tacview only knows object attitude and motion vector. "AOA" is just difference between two. Tacview has no idea of winds.

I believe that TacView knows two points in a track and then constructs the flight path from it. 

There is no other way to do it without constructing files of several Mb per each object. 

If we would have a higher AOA due to a bad lift coefficient, then we would see a higher drag and higher energy loss, thus having a worse sustained turn rate especially on altitude. 

Which we do see in certain areas below Mach 0.5 and is known and waiting for a fix. Pretty sure the AOA readout is off. 


Edited by TobiasA
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29 minutes ago, TobiasA said:

 

 

I find it hard to believe the thrust is off, because I have similar end speeds in BMS if you want to compare this.

 

However, I think I get your point. I fly with tanks most of the time in both sims, and the noticable difference is a way lower drag when you fly without a jammer that does not exist in DCS. I do understand that the sustained turn rate matches if you increase power (which add to the lift by the angle of the AOA, actually) so it might be a factor of two things. That would mean the the thrust curve would be off too, probably also parasite drag being too low and induced drag too high. Drag figures are declassified (there are some NASA numbers somewhere), as well as the lift coefficients (BMS relies on those) so I do not think those are far off. The actual thrust curve of the -129 engine might be a different story, getting accurate numbers on those might be an issue. It could as well be a bug in the way the FLCS handles TEF/ LEFs.

We all can agree it is not on-point yet.
I am also not that happy with it, I thought after two years it would be somewhat comparable to "other sims" and since the viper is my first module and my start in DCS, it's not a good start. But- we don't have many flight simulators anymore. It's basically a hardcore mod from a sim dating back to the 90's, some WWII stuff, a civilian simulator, another civilian simulator, some smaller projects and that's it. After a first shock, I decided to buy some maps and otherwise take a rest from buying another EA module from ED, went on to fly helicopters and the viggen to enjoy finished modules and otherwise enjoy it. The viper will get better one day after that hornet is finally done. I had probably bought the hornet and SC if the viper would have been in a better state, but I lost interest in it after seeing it is EA and... I went another road. Will probably never own it, more likely to get the Tomcat (plus SC). I'm here for the viper, and I came to stay.
It is actually cool to fly helos and jets in the same simulator. And I want to take my focus out of stuff that bothers me (like what really drives me nuts is that radar cursor bullseye info) and focus on things I love, like cruising through the virtual skies in that bubble canopy or trying to not die in the Huey. I will spend more money here, but what and how fast depends on the vipers progress tbh.

There is nothing that we can do other than pointing out what is wrong, since we EA buyers are in fact testers and as such, we cannot expect that everything that it implemented is correct. As such we should strive to give positive and constructive feedback, we might be pissed sometimes but we should see the greater good for the flightsim community.

Hardcore sims make it hard for beginners to start, DCS provides an easy entry with the Su-25T as a free module, FC3 as an easy start and this gets people hooked to flightsims. While I enjoy hardcore sims, there aren't many new people over there. DCS is a different thing in that aspect. You can fly FC3 modules without a HOTAS for hundreds of dollars and even enjoy them without head tracking. That's a very low entry for some people. Still, you have the A-10, F-18, F-16, Viggen, AV-8B  and numerous others as "hardcore modules", high fidelity or a lot of prop planes and helicopters.
Let's see the greater good instead of the viper desaster. Pretty sure it won't happen again, but the Hind and Apache will tell the story.

 

I'm glad that you get my point to some extent. The drag curve above Mach 0.9 is not classified (published in AGARD-242 test report). The drag at Mach 0.8 can be found in a text book, but below Mach 0.8 we can not find a reliable drag polar. I think the dev is trying some curve fitting which poses big challenge.

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vor 2 Stunden schrieb oldtimesake:

 

I'm glad that you get my point to some extent. The drag curve above Mach 0.9 is not classified (published in AGARD-242 test report). The drag at Mach 0.8 can be found in a text book, but below Mach 0.8 we can not find a reliable drag polar. I think the dev is trying some curve fitting which poses big challenge.

There was some NASA data wind channel test going on... I believe there are sources. Not publically available, but also not classified afaik.

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15 hours ago, oldtimesake said:

 

I'm glad that you get my point to some extent. The drag curve above Mach 0.9 is not classified (published in AGARD-242 test report). The drag at Mach 0.8 can be found in a text book, but below Mach 0.8 we can not find a reliable drag polar. I think the dev is trying some curve fitting which poses big challenge.

 

NASA TP1538 has steady flow Cx and Cz tables for Mach 0.6, 30,000ft. But it also uses pitch rate derivatives Cx-q and Cz-q to calculate total Cx and Cz, and also delta LEF tables. So you would also need to account for LEF and pitch rate in such cases, and then transform them back to CL, CD. (From body-axis to wind-axis.)

 

1.jpg

 

Elevator position would be close to zero in a lower mach steady turn due to relaxed static stability so I think one can just use 𝛿h=0 in those tables. We also need to find out pitch rate and that one could be tricky, rendering the result not so reliable I guess.

 

Just pointing out a direction.


Edited by LJQCN101

EFM / FCS developer, Deka Ironwork Simulations.

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50 minutes ago, LJQCN101 said:

 

NASA TP1538 has steady flow Cx and Cz tables for Mach 0.6, 30,000ft. But it also uses pitch rate derivatives Cx-q and Cz-q to calculate total Cx and Cz, and also delta LEF tables. So you would also need to account for LEF and pitch rate in such cases, and then transform them back to CL, CD.

 

1.jpg

 

 

Looks like this also includes the effects of the leading edge flap deflection, I assume, which is subscripted as lef.  What is subscript sb, speed brake?

"Subsonic is below Mach 1, supersonic is up to Mach 5. Above Mach 5 is hypersonic. And reentry from space, well, that's like Mach a lot."

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39 minutes ago, Machalot said:

Looks like this also includes the effects of the leading edge flap deflection, I assume, which is subscripted as lef.  What is subscript sb, speed brake?

Yes, lef as I mentioned, and sb is speed brake.

 

One could just use the control law to calculate how much deflection the LEF would be, but note that DFLCS uses a different schema than the one in TP1538.

 

2.jpg

EFM / FCS developer, Deka Ironwork Simulations.

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8 hours ago, LJQCN101 said:

 

NASA TP1538 has steady flow Cx and Cz tables for Mach 0.6, 30,000ft. But it also uses pitch rate derivatives Cx-q and Cz-q to calculate total Cx and Cz, and also delta LEF tables. So you would also need to account for LEF and pitch rate in such cases, and then transform them back to CL, CD. (From body-axis to wind-axis.)

 

1.jpg

 

Elevator position would be close to zero in a lower mach steady turn due to relaxed static stability so I think one can just use 𝛿h=0 in those tables. We also need to find out pitch rate and that one could be tricky, rendering the result not so reliable I guess.

 

Just pointing out a direction.

 

There is no proof this paper is about the production F-16 model (or maybe a prototype), especially given the low lift curve slope.

At 10deg AOA the untrimmed CL is less then 0.7 while the flight test value is 0.85.

 

 


Edited by oldtimesake
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On 4/18/2021 at 3:50 AM, TobiasA said:

I believe that TacView knows two points in a track and then constructs the flight path from it. 

There is no other way to do it without constructing files of several Mb per each object. 

If we would have a higher AOA due to a bad lift coefficient, then we would see a higher drag and higher energy loss, thus having a worse sustained turn rate especially on altitude. 

Which we do see in certain areas below Mach 0.5 and is known and waiting for a fix. Pretty sure the AOA readout is off. 

 

This is my understanding as well, its hard to really say for sure something is off and especially by how much without being able to look at and test the actual EFM.

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On 4/18/2021 at 1:50 AM, TobiasA said:

I believe that TacView knows two points in a track and then constructs the flight path from it. 

There is no other way to do it without constructing files of several Mb per each object. 

Would be a nice feature to be able to tag objects in the mission for a high fidelity track file.

"Subsonic is below Mach 1, supersonic is up to Mach 5. Above Mach 5 is hypersonic. And reentry from space, well, that's like Mach a lot."

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