Flight Model artefact ? -

This discussion has gone quite off-topic (although I do appreciate any effort to test and improve the FM). I doubt that the weird peak that I highlighted in the OP is related to other problems (real or supposed) in the FM. I think this spin-off discussion would be better suited in a separate thread, so as to keep from muddling the issues.

We'll do!

Regards!

 

I do happen to disagree, with solid grounds, on that particular point. I'm sorrry I can't elaborate why; and I certainly can't enter an aerodynamicists debate (I'm simply not qualified for this).

You can't elaborate why but you do happen to disagree..., ok! Sooner or later the truth about those apparently "magical" stakes will come out. If they were for lift enhancement they have been place in the wrong spot at the wrong size.

I've done a short calculation based on theory and some real data on a wing similar to that of the Mirage which clarifies that the simulated lift on the DCS Mirage's wings is beyond normal (much higher).

It will be discussed on the following thread:

https://forums.eagle.ru/showthread.php?t=197059&page=7

Regards!

- The filed you opened is for AI planes. Player's FM is different and located in mod folder and you probably can't open it.

- Mirage has strakes on air intake sides generating vortexes over the wing roots, and the sealed SLATs are generating vortexes for the rest of the wing.

OK. Thank you! So that .lua file is for the AI and not for a player flown aircraft. Then if that lift coefficient of 1.28 (which seems to be maximum in the tables) is for AI, I wonder what's the value simulated for the player's aircraft and why would it differ?

Meanwhile I've moved to the thread you suggested me for more elaborate discussions about the Mirage's flight model.

Regards!

Perhaps this picture can provide some clue about the thrust / lift performance.

It's a -5 but performance should be similar

Perhaps this picture can provide some clue about the thrust / lift performance.

It's a -5 but performance should be similar

Very cool, may I ask you where did you found this one ? are there others pictures like this one ?

Very cool, may I ask you where did you found this one ? are there others pictures like this one ?

Also the plane at that moment was in a clean configuration with 50% fuel.

Perhaps this picture can provide some clue about the thrust / lift performance.

It's a -5 but performance should be similar

Hello man,

It is a useful picture from which someone can rapidly determine the lift slope by having the actual alpha, knowing the zero AoA lift coefficient (using 0 for fighters won't result in a too great error) and determining the actual lift coefficient by knowing the G-load, airspeed (it's very important which airspeed indication, IAS, EAS, TAS) and actual weight. So if one can find out the current weight of the plane and what type of speed is indicated on the left top corner, this is the formula (using metric system) on which anyone can determine the lift slope (lift versus AoA function) which is very important to be similar in the DCS M-2000 simulation as well. As for the zero AoA lift coefficient variable, I'll arbitrarily use 0.04 (instead of 0, to increase the accuracy of the result) by my quick estimation for supersonic.

Lift slope in degrees = (ZG load*Weight / (0.5*1.225*(KIAS/1.944)^2*Area)-0.08 ) / AoA

Lift slope in radians = (ZG load*Weight / (0.5*1.225*(KIAS/1.944)^2*Area)-0.08 ) / AoA*pi/180

Area stands for wing are and for Mirage is 41 m^2.

1.944 is the ratio between knots and meter/second.

If someone knows the actual plane's weight and determine the IAS, the rest comes easy!

Cheers/regards!

...

From my experience and analysis, this wing, with full slats, at Mach 0.2 produces no more than a 1.3 CL at alpha 30. How come this gets 1.96 in actual simulation?...

Well, sorry I tried approaching the stall speed in the conventional manner without knowing what weirdness I'd get by doing so and holding the critical AoA while gliding (engine idle) and waiting until the speed settles, then from that data determine the lift coefficient. If I could've known what would happen and get that false result of 1.96 I would've determined the maximum lift coefficient another way at any higher speeds than that of stall. It still kind of puzzles me why at very low speeds and critical AoA (28-29 limited by the FBW), the lift coefficient goes towards 2, but I don't have to worry about it anymore as long as it's correct in dogfights.

After re-doing the tests (as I check after sim updates) I no longer tried using the stall speed as a reference to calculate the CL max, but the aircraft's performance at some constant or instantaneous turn rates actually proves that the maximum lift coefficient becomes ~1.3. I don't brag about it, but from the start (even before looking into that AI M-2000 lua file) I have personally determined on my analysis that the lift coefficient should be around this value for this wing with it's airflow enhancing devices for that alpha.

So...good job RAZBAM! You grown back into my eyes and I feel a bit relieved with the results of the later tests that I've done again, but your general aerodynamics knowledge should've been proven right away from the start through pinpoint replies and not letting me search for the truth on my own for so long! The only answers I've got were that the Mirage 2000's wing has 70% greater max CL than the Mirage III. On another thread or here (don't remember) I have also determined by analysis that the Mirage III's maximum CL at M=0.2 should be about 0.78..0.8, so all I could do was to determine some accurate numbers by analysis while others were telling me only what they know. It was a sort of discussion between people speaking only in their own language but in the end they were telling the same! I'm still kind of puzzled why couldn't someone rapidly correct me and say that the simulated maximum CL for the player M-2000 is also around 1.3, so I wouldn't need to worry in the way that I did and tell all I've said...!

Cheers/regards!

Now, the thing with the lift is settled and realistic (but only above very low speeds though), but what about the thrust tables? After retesting the lift capabilities, the tests on the outstanding climbing performance of the Mirage's FM in DCS show no corrections and the Mirage 2000 still has a tremendous thrust/weight versus altitudes. At much higher altitudes, the Mirage still outaccelerates the F-15.

Regards!

Hello man,

 

 

 

 

 

If someone knows the actual plane's weight and determine the IAS, the rest comes easy!

 

 

Cheers/regards!

See my post above yours. 2000-5 MkII, Clean configuration , ~50% (internal) fuel. If someone can do the maths to determine the aircrafts weight

Hello man,

 

It is a useful picture from which someone can rapidly determine the lift slope by having the actual alpha, knowing the zero AoA lift coefficient (using 0 for fighters won't result in a too great error) and determining the actual lift coefficient by knowing the G-load, airspeed (it's very important which airspeed indication, IAS, EAS, TAS) and actual weight. So if one can find out the current weight of the plane and what type of speed is indicated on the left top corner,

 

50,000 feet 399kts mach 1.47 Looks like IAS to me.

To be accurate, the HUD displays CAS (Calibrated AirSpeed).

To be accurate, the HUD displays CAS (Calibrated AirSpeed).

I was close.

50,000 feet 399kts mach 1.47 Looks like IAS to me.

Oh, right! I didn't look at every detail on the HUD although it was right underneath the speed indication.

I was close.

Indeed :thumbup:

Perhaps this picture can provide some clue about the thrust / lift performance.

It's a -5 but performance should be similar

If the plane's weight matches that of a 50% fuel, clean config, it could be 9325kgf (from DCS, if it's correct) and if the zero AoA lift coefficient would be 0.04 (although it may be a bit lower), the resultant lift slope may become 1.068 in radians or 0.019 in degrees. So it's lifting performance could drop to about half (as it usually happens to every fighter aircraft) of what it used to be at lower subsonic Mach.

I can't tell much about it's engine, but giving the fact that it's a combination of very low bypass single shaft turbofan engine, in theory, it's thrust performance should still be able to increase with Mach number, yet only a testbed chart could provide true data. If I correctly recall, theoretically, for a given inlet geometry the higher the fan's diameter and/or bypass and the higher the number of compressor stages, the worse the thrust increase slopes with Mach, while opposite to that (for the same inlet) gives a more rapid thrust increase with Mach. On the other hand, it's engine should be a rather reliable one for having just a single spool (easier/cheaper to maintain).

Regards!

Originally, the M53 engine was designed with Mach 3 twin engined aircraft in mind (MD 750)

Eventually this one has been designed and built: Super Mirage 4000.

Mach 1.6 on first flight, Mach 2 less than 2 weeks later on 6th flight, Mach 2.0 during 18mn demonstrated.

https://www.museeairespace.fr/aller-plus-haut/collections/dassault-super-mirage-4000/

Eventually it was deemed to expensive for French budget :cry:

Engine was adapted to single engine use.