Jump to content

So about the M2000 FM and current state...


falcon_120

Recommended Posts

Even if I don't the only thing your test shows is that mirage generates more drag at low speed which is already known

 

 

It doesn't generates more drag at "low speeds". It generates much much more drag at an AOA of 10 to 12 deg.

 

 

 

Another possible explanation is that engines have different idle thrust, might not make a big difference but has to be taken into account

 

 

I don't know what the idle thrust of Mirage 2000 engine is and I bet you also don't know.

Two examples. MiG-29 engine RD-33 has an static idle thrust of 180Kgf (source, flight manual). Su-27 engine AL-31F has an static idle thrust of 250Kgf (source, technical description manual). Let's put Mirage's engine idle thrust somewhere in between, let's say 200Kgf.

 

At 300kts and 10deg AOA, Mirage 2000's total drag is of SEVERAL TONS. 200Kgf of idle thrust is not gonna make much of a difference.

 

Besides, you don't know (and I don't know) how Mirage's engine idle thrust changes with flight conditions. For example, in MiG-29's case the static idle thrust value quickly decreases with speed and at a low M number of about 0.16-0.17 it is zero, then increasing the speed further it gets a negative value of about -270Kgf at an M number of about 0.57 (source, MiG-29 practical aerodynamics manual). So in the test I made here, in the 300-150kts speed range, Mirage's engine idle thrust might be small positive, might be small negative. But anyway it is negligibly small compared with the drag.

 

So please keep the idle thrust out of this discussion as this doesn't have a considerable effect.

Link to comment
Share on other sites

All the aerodynamic improvements of the Mirage 2000 are there to make it better than Mirage III so it remains competitive Vs other 4th Gen fighters.

Add full thrust and wonder what would your STR become if you lower the drag ?

AFAIK the STR is where it needs to be compared to other fighters.

 

I even had to remind those refinements to remind people that it isn't a "blue Mirage III".

 

When the Hornet came out, people believed that Mirage 2000 STR was higher.

After proper testing it has been reported to be slightly lower, which is ok

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

picture.php?albumid=1787&pictureid=11403

picture.php?albumid=1787&pictureid=11404

 

Considering the poor drag performance of the Mirage 2000: maybe we should try this standard Mirage III procedure to see if it can be done or if the drag is so bad that we crash the plane in the mud?


Edited by arnokm
Link to comment
Share on other sites

  • 2 weeks later...

 

 

At the end of the video the pilot lands and performs aerobraking. As can be seen, the speed is decreasing very very slowly. Deceleration from 140 to 110 kts takes about 12.5 seconds. During this time the longitudinal G is between -0.15 and -0.13.

 

Let's see how the simulator compares to that.

 

In the attached tracks I deliberately land at high speed, so that when the speed drops to 140 kts I am already stabilized with the inverted T on the horizon line (or close to) and the engine is already in idle.

 

In track 1a I land with 100% fuel and deceleration from 140 to 110 kts takes 5.3 seconds. That is 2.35 times less than it takes for the real aircraft in the video. Longitudinal G is, as expected, more than double the value from the real aircraft.

 

In track 2a I land with 30% fuel and deceleration from 140 to 110 kts takes 4.6 seconds. That is 2.71 times less than it takes for the real aircraft in the video. Longitudinal G is, as expected, more than double the value from the real aircraft.

 

The aircraft in simulator decelerates so fast not because the wheel drag is too high or the engine idle thrust is too low (although the wheel drag might be slightly too high). These are relatively minor forces compared to airframe drag. It decelerates so fast because of aerodynamic drag that is way waaaaay too high. This is obvious when the nose wheel is lowered to the runway - the longitudinal G decreases proportionally with lowering of the AOA.

 

When aerobraking at 13 deg AOA and there is still enough speed, if you increase the AOA by as little as 1-1.5deg (not demonstrated in the video, but anyone can try) the longitudinal G raises to the amusing value of about -0.5 (for comparison, during takeoff with 100% fuel and no stores, the longitudinal G is about 0.68 ).

 

This test for deceleration during aerobraking is not revealing some minor unimportant inaccuracy that manifests itself only on aerobraking and everything else is fine. Is the same very high drag at an AOA of 13 deg also acting during flight? You bet it is!!! Now if you go back to post #34 and read about the turning test described there, you will understand perfectly why the DCS M2000C results are in a completely different league from the other planes tested F-18 and F-16 (result for F-15 test too, in post #38 ).

 

I performed a perfectly horizontal slow speed flight test with the M2000C (no track attached). For an AOA of 29 deg the speed was 92 kts and the required engine rpm was 88%. IMO the numbers are not bad. I also think the drag at a low AOA of 2-3 deg is generally adequate.

 

In conclusion. The drag at low AOA is OK. Then increasing the AOA the drag gets too high and at some mid-range AOA, drag is way too high. You don't have to be a mathematician to see from the aerobraking test that at 13 deg AOA the drag is not off by some 10%. It is much much more. Increasing further the AOA from this mid-range AOA, the difference in drag between simulator and real aircraft definitely gets smaller and at max AOA of 29 deg drag is, let's say credible.

Add full thrust and wonder what would your STR become if you lower the drag ?

AFAIK the STR is where it needs to be compared to other fighters.

 

When the Hornet came out, people believed that Mirage 2000 STR was higher.

After proper testing it has been reported to be slightly lower, which is ok

 

 

I don't care how the M2000C simulator compares with a turn performance diagram that you know very well it is an estimation. All I care about are demonstrable facts. The drag being much too high at an AOA of 13 deg is a demonstrable fact.

 

Even if that well known turn performance diagram was from the real Mirage 2000C flight manual, and the simulator aircraft would perform exactly like that, that still wouldn't change the fact that at an AOA of 13 deg the drag in simulator is much too high. If the real aircraft in a sustained turn where the AOA is 13 deg (at whatever speed that might be) performes similarly with DCS M2000C simulator, this means in simulator besides the drag at 13 deg AOA being too high, the thrust is also too high.

test1a.trk

test2a.trk


Edited by Fox One
Link to comment
Share on other sites

The landing deceleration isn't a good way to test aerodynamics.

Aerodynamics isn't the only force, there is also ground friction.

 

So find a way to compare at 13° in flight and then it will be interesting...

 

And I wasn't talking about any chart.


Edited by jojo

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

My two cents on the current FM subject:

 

I find hard to land with the Mirage 2000 comparing to other tested aircraft... And, I admit the main problem is AOA vs Thrust balancing, which is very hard to obtain, need a constant adjustment. Anyway I don't know, but my personnal intuition is that real pilots never have the hard time we have in DCS for landing with M2k...

Link to comment
Share on other sites

DCS has a problem with sticky gears. It's been well documented by the fact that most aircraft that should taxi at idle power, require much more than idle power to start rolling. I think it's the tire/ground friction dynamics that are at fault here.

Link to comment
Share on other sites

My two cents on the current FM subject:

 

I find hard to land with the Mirage 2000 comparing to other tested aircraft... And, I admit the main problem is AOA vs Thrust balancing, which is very hard to obtain, need a constant adjustment. Anyway I don't know, but my personnal intuition is that real pilots never have the hard time we have in DCS for landing with M2k...

 

Then you aren't using the proper technique.

It very easy using the HUD. Just align the symbols on runway threshold around -3° glide path at 14° AoA.

 

>] -O- [<

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

The landing deceleration isn't a good way to test aerodynamics.

Aerodynamics isn't the only force, there is also ground friction.

 

 

Thank you for giving exactly the answer I was expecting :D

 

 

In my second track (test2a) where I land with 30% fuel when the speed is 135kts and the inverted T is perfectly on the horizon line, the longitudinal G is -0.45. In the real aircraft in the video it is -0.15

 

In simulator, if you lower the nose gear to the runway, at 135kts the longitudinal G is -0.1

This deceleration is of course caused by aerodynamic drag and wheels drag. But I am generous and let's pretend the aerodynamic drag is zero and this -0.1 is entirely wheel drag.

If you remove this -0.1 from the deceleration of -0.45 that is recorded at 135kts, you still have a deceleration of -0.35 that is more than double the value from the real aircraft.

 

And all of this is ignoring the fact that when the real aircraft is aerobraking at 135kts at 13 deg AOA most of the aircraft weight is still supported by wing lift. Therefore, the load on the main wheels is fairly low and so the wheel drag is quite low. But I was being generous again...

 

I am sorry to say, but it looks like I am wasting my time trying to tell you anything. You have decided in your mind that the simulator is accurate and you will fight to death anyone who sais otherwise.

Link to comment
Share on other sites

Those 2 documents related to M2000 accidents shows interesting Jx records during landing (google & record the .pdf):

BEAD-air-A-2011-004-I

BEAD-air-A-2013-006-I

 

 

What I understand (M2000C with 800kg of fuel landing):

During aerobraking: Jx = -0.19 (146kts to 117kts in 8s) but we don't know the AoA so it's not a max value

 

3 wheels on the ground without gear braking: Jx = -0.05 above 100kts

With chute: Jx = -0.15 below 100kts

During gear breaking, Jx should be between -0.2 & -0.3.

 

If 0 > Jx > -0.2 there is a break problem

Link to comment
Share on other sites

Thank you for giving exactly the answer I was expecting :D

 

 

In my second track (test2a) where I land with 30% fuel when the speed is 135kts and the inverted T is perfectly on the horizon line, the longitudinal G is -0.45. In the real aircraft in the video it is -0.15

 

In simulator, if you lower the nose gear to the runway, at 135kts the longitudinal G is -0.1

This deceleration is of course caused by aerodynamic drag and wheels drag. But I am generous and let's pretend the aerodynamic drag is zero and this -0.1 is entirely wheel drag.

If you remove this -0.1 from the deceleration of -0.45 that is recorded at 135kts, you still have a deceleration of -0.35 that is more than double the value from the real aircraft.

 

And all of this is ignoring the fact that when the real aircraft is aerobraking at 135kts at 13 deg AOA most of the aircraft weight is still supported by wing lift. Therefore, the load on the main wheels is fairly low and so the wheel drag is quite low. But I was being generous again...

 

I am sorry to say, but it looks like I am wasting my time trying to tell you anything. You have decided in your mind that the simulator is accurate and you will fight to death anyone who sais otherwise.

 

You had all this info since post 34, why do you need to mix it up with toxic bs and unnecessary walls of text?

 

Video evidence showing horizontal g at a given AoA ---->>> in DCS it is very different---->>> drag vs AoA might be off --->>> please investigate

 

starting off a discussion with something like "wow this whole thing is amusingly bad" might trigger some negative responses, believe it or not.

Link to comment
Share on other sites

Hey Fox One. Bear in mind that French Air Force gave extensive feedback on the module and was happy with the flight model... for me that is a good indication that it is quite true to the omreal aircraft...

 

Good feedback means the current FM is surely quite good enough, but it does not mean it cannot be improved or don't need adjustment... I guess that comparing real in-flight aircraft behavior to a simulation is not so easy for a pilot. Simply imagine you have to compare the simulation of the car you actually drive every day... Except if the simulation make very notable mistakes within your usage/test spectrum, you will probably say "yes, this is good enough".


Edited by sedenion
Link to comment
Share on other sites

From what I read on Checksix (the main portal for french simmers), several people including the head of the project for the Armée de l'Air said that the main goal for them was to train actual pilots to procedures and not learning how to use the aircraft itself. While they agreed that the flight model is good they didn't said it was accurate, that's a big difference to be noted.

 

But hey ! If it's good enough for real pilots, it's good enough for me. Razbam is doing a great job with the Mirage ; after a short hiatus they resumed their work and made the Mirage one of the most interesting plane to fly on DCS World. I don't think we should expect any change for the flight model, it would surely lead to disappointment.

3rd Wing | 55th Black Alligators * BA-33

Εις ανηρ ουδεις ανηρ

Link to comment
Share on other sites

A flight model is complex to develop.

Ground behavior is also another subject by itself.

When you change one parameter, you can impact a lot of different areas. So there is a point of diminishing return.

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

I am not a subject matter expert but I think the current FM definitely looks right in terms of performance numbers. The only complaint I have is that it feels "on rails", kinda like sfm flight models from the lomac days. Now, having an FM feel natural is a really difficult thing to get and maybe ED could help in that regard.

[sIGPIC][/sIGPIC]

Link to comment
Share on other sites

I am not a subject matter expert but I think the current FM definitely looks right in terms of performance numbers. The only complaint I have is that it feels "on rails", kinda like sfm flight models from the lomac days. Now, having an FM feel natural is a really difficult thing to get and maybe ED could help in that regard.

 

What is natural with fly by wire on all 3 axis.

This is a different general of flight control compared to F-15C, MiG-29 and Su-27 from FC3.

 

Add turbulence and wind in ME and it will be less on rails. :smilewink:

Mirage fanatic !

I7-7700K/ MSI RTX3080/ RAM 64 Go/ SSD / TM Hornet stick-Virpil WarBRD + Virpil CM3 Throttle + MFG Crosswind + Reverb G2.

Flickr gallery: https://www.flickr.com/gp/71068385@N02/728Hbi

Link to comment
Share on other sites

"This is a French Air Force-approved simulator" is a nice trick that probably works on naive and uninformed people. Then convince a French Air Force pilot to register on the forum and say the real aircraft behaves just like the simulator in the tests described above and he really sees no problem at all. Go ahead. I'm serious. Get a real pilot here to tell everybody how the real aircraft would behave in the tests described here.

 

I don't want to get involved in the arguments and pedantics that go on here, but I would say that the last time we got a career pilot of one of the aircraft modelled in DCS telling us his opinion of a flight model he got dissed, insulted and basically made out to be lying by those who just wouldn't accept that something wasn't as they thought it should be, because the real aircraft wasn't as they thought it would be (from their armchair).

 

I know RL pilots (ex-RAF) that have refused to even register here due to the attitude of many members and another one who was a commercial dev for FSX, made a wonderful fighter for DCS World and kept it entirely to himself for the same reason. He showed me a number of screenshots of his plane and I would have paid a lot to have it!

 

So bringing real military pilots here does not, by any stretch, mean that their word will be accepted. Sad as that is.

Kneeboard Guides

Rig: Asus B650-GAMING PLUS; Ryzen 7800X3D ; 64GB DDR5 5600; RTX 4080; VPC T50 CM2 HOTAS; SN-1 Pedals; VR = Pico 4 over VD Wireless + Index; Point Control v2

Link to comment
Share on other sites

I don't want to get involved in the arguments and pedantics that go on here, but I would say that the last time we got a career pilot of one of the aircraft modelled in DCS telling us his opinion of a flight model he got dissed, insulted and basically made out to be lying by those who just wouldn't accept that something wasn't as they thought it should be, because the real aircraft wasn't as they thought it would be (from their armchair).

 

I know RL pilots (ex-RAF) that have refused to even register here due to the attitude of many members and another one who was a commercial dev for FSX, made a wonderful fighter for DCS World and kept it entirely to himself for the same reason. He showed me a number of screenshots of his plane and I would have paid a lot to have it!

 

So bringing real military pilots here does not, by any stretch, mean that their word will be accepted. Sad as that is.

 

And NO ONE's word should be accepted as a gospel, even if they have logged thousands of hours. Why? because without a sound argument backed by evidence, sound reasoning, and or math all you have left is a subjective informed opinion; which is not objective. Regardless of however pedantic you feel others discourse is. Waving your proverbial jedi hand around, and in general being demeaning to others in the very same forum of discussion does not speak very highly of you, or your claims.

 

I have over 10k hours in real aircraft, and i would never pretend to give my word and have it accepted on my word only, nor would i be able to prove such credentials in a place like this. SO jumping in to a forum and claiming you are something is easy, demonstrating you are knowledgeable and able to have discourse is preferable.

 

So, if your ret. buddies raise their noses at this aviation-sim discourse and shop-talk arguments that are usually superficial anyways, i am not impressed. least of all by someone raising their nose at this discourse in a second hand fashion. Wiser aviation veterans already know this, don't look down upon it, but rather see it for what it is, there is no need, and no desire to look down upon an aviation enthusiasts forum - if you do you need that chip knocked off your shoulder before nature or physics does it for you.

 

In sum, if you have a point to make, remember that everyone is anonymous and you have to go through the effort of proving whatever point you have to make, mixed in with people in a forum that includes very ignorant but enthusiastic persons to very knowledgeable persons.

Link to comment
Share on other sites

And NO ONE's word should be accepted as a gospel, even if they have logged thousands of hours. Why? because without a sound argument backed by evidence, sound reasoning, and or math all you have left is a subjective informed opinion; which is not objective. Regardless of however pedantic you feel others discourse is. Waving your proverbial jedi hand around, and in general being demeaning to others in the very same forum of discussion does not speak very highly of you, or your claims.

 

I have over 10k hours in real aircraft, and i would never pretend to give my word and have it accepted on my word only, nor would i be able to prove such credentials in a place like this. SO jumping in to a forum and claiming you are something is easy, demonstrating you are knowledgeable and able to have discourse is preferable.

 

So, if your ret. buddies raise their noses at this aviation-sim discourse and shop-talk arguments that are usually superficial anyways, i am not impressed. least of all by someone raising their nose at this discourse in a second hand fashion. Wiser aviation veterans already know this, don't look down upon it, but rather see it for what it is, there is no need, and no desire to look down upon an aviation enthusiasts forum - if you do you need that chip knocked off your shoulder before nature or physics does it for you.

 

In sum, if you have a point to make, remember that everyone is anonymous and you have to go through the effort of proving whatever point you have to make, mixed in with people in a forum that includes very ignorant but enthusiastic persons to very knowledgeable persons.

 

This is often a difficult thing for people to understand. Kind of ties in with a sarcastic comment I made recently about 'professionals'. Just because you have experience with something doesn't actually mean all that much, when getting into really technical nitty gritty details. You can't just say ''Oh I'm a pilot'' and hand wave away arguments, because, contrary to their often inflated opinions of themselves, pilots are fallible beings, too (thus the occasional crash in the news when a ''pilot'' does something utterly retarded that gets himself and others killed). You have to be able to back up what you're saying with credible, hard evidence, not just your experience/memories. Those are a viable starting point to begin investigating, but they are not the final destination.

Де вороги, знайдуться козаки їх перемогти.

5800x3d * 3090 * 64gb * Reverb G2

Link to comment
Share on other sites

And here I have to say that I don´t agree with you. All humans are fallible, but when a person have spent 15 years flying a certain type of aircraft you better believe what he/she has to say. It´s true that one place for accurate information is performance manuals, but over time many new possibilities are found in aircraft by pilots that are not reflected back on the documents.

 

I have no idea how the Mirage FM is as I´m using my time to work on the MiGs, so I can´t say how accurate is the FM, just wanted to point about the pilots experience.

 

This is often a difficult thing for people to understand. Kind of ties in with a sarcastic comment I made recently about 'professionals'. Just because you have experience with something doesn't actually mean all that much, when getting into really technical nitty gritty details. You can't just say ''Oh I'm a pilot'' and hand wave away arguments, because, contrary to their often inflated opinions of themselves, pilots are fallible beings, too (thus the occasional crash in the news when a ''pilot'' does something utterly retarded that gets himself and others killed). You have to be able to back up what you're saying with credible, hard evidence, not just your experience/memories. Those are a viable starting point to begin investigating, but they are not the final destination.
Link to comment
Share on other sites

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...