Razbam's Mirage 2000C Flight Caracteristics

Hello DCS community ;)

There has been a lot of talk about the (simulated) M2000C flight characteristics, for example here and here and a lot of it is revolving around feelings and hearsay.

I wanted to test as rigorously as possible our beloved M2000C.

For now I only tested at 15000ft, in a 2xMagics and 50% fuel configuration. I tryed with the FBW in both "Vrille" and "AA" modes, I plan on trying the "Charge" mode asap.

Test Protocol

Instantaneous Turn Rate

I binded a new axis of my joystick to the pitch axis, and increased the saturation as much as possible, to be sure that I "pull the stick" even harder than is actually possible realistically. Then I flew at different speed, banked to 90°, and then used the newly binded axis.

I carefully reviewed the results with Tacview, and noted the TAS(knots), the number of g pulled and the turn rate (°/s). I produces around 40 data points this way.

I then compared this turn rate to the theoretical one given by the following equation, being especially careful with the unit conversion.

I discarded the values that where to far from the theoretical ones, and then only kept the values when the I pulled the most Gs. After the cleaning up, I kept only around 12 data points.

The theoretical ITR is largely guesstimated.

Sustained Turn Rate

The protocol is almost the same as above, but instead of trying to pull the maximum number of G, I try to keep a constant speed during a level turn. I recorded around 12 data points for each.

The Results

You can either access all the data here https://1drv.ms/x/s!Aks3P6QLVda0iQsBSGkE_4fNG6zB, or refer the EM diagram below. Keep in mind that those results are experimental, and there is a low to moderate margin of error, despite my best efforts to reduce it.

Comparaison with the real one

Obviously, I couldn't resist comparing my results to the only publicly available data that I know of, the chart below. They happen to match my setup, both in term of altitude and payload (which is not totally a coincidence).

I resized both picture to match them as close as possible. Note that the chart is using CAS as a speed unit, and I'm using TAS, but I (kinda) compensated for that, but it might not be accurate at low speeds. The red line is the STR from the chart, and the green one is my STR. I'll let you draw your own conclusions.

I'm a computer science engineer, and my knowledge in fluid dynamics is as non existent as it can be, so please, if I made a mistake somewhere, feel free to correct me. Especially, if someone knows which line of the chart is the instantaneous turn rate, I'll add the colored line.

If this data doesn't match your experience, please do comment and provide me with ACMI files I can analyze. If you don't do the latter, it's not even worth mentioning your data. ACMI or it never happened :). All my ACMI files are available on demand - just ask, but be aware that there is around 130 data point on 27 files.

I know this kind of topic can rapidly become rather unproductive, so I ask you, the potential commentator, to kindly refrain from bringing up any other aircraft than our beloved Mirage 2000C, both in sim and IRL, if you have hard data. Let's keep it on topic and interesting:thumbup: !

Have a great flight in your Mirage !

PS : I want to thank myHellJumper, who gave me the first data, after which I went a bit wild... Merci ;)

Hi,

Why is your black curve so much away from the diagram you take as reference?

This leads to think at first glance that there is a big gap between "expected" and "measured in DCS", when the gap is much narrower in fact (and at some point reversed).

Thanks :)

++

Well, as I said, my Theoretical ITR is largely guesstimated. As far as I'm aware, there is no way to pull the maximum number of g because the FBW prevents it, so there is no way to get the real corner speed.

I think I made it clear enough though, but if it confuses people, then I may just remove it.

I'd say that the gap is between the chart and my data is way smaller than I expected, Razbam did a very good job on this one.

Your chart is TAS, the reference chart is CAS, the difference at 15000ft is significant.

I don't know if you accounted for it when you scaled for comparison

Moreover CAS is what the pilot read on it's HUD, so it's better to use CAS in charts.

Anyway goo job :thumbup:

Isn't the player seeing IAS instead of CAS on his hud ?

Anyway, like I said I did account for it, otherwise the G curves and the radius of turn curves wouldn't match. I used this tool : http://www.hochwarth.com/misc/AviationCalculator.html.

Since I used the default weather, without wind, it should be accurate enough.

Well, as I said, my Theoretical ITR is largely guesstimated. As far as I'm aware, there is no way to pull the maximum number of g because the FBW prevents it, so there is no way to get the real corner speed.

The FBW limits you - without overriding the elastic stop of the stick - to 9g above corner speed, and to 29° AoA below corner speed.

Now, my issue isn't about g. Here:

(click to enlarge)

In pink/bold, I highlighted the curve from the public diagram (which also is estimated, by the way). In pink/not bold, I "crossed" the part of your black curve that is offset re: this diagram.

Isn't the player seeing IAS instead of CAS on his hud ?

No.

That's what I meant. I can't reliably find the corner speed because I can't test which is the minimum speed at which I can pull 9Gs (the corner speed). That's why I guesstimated the theorical ITR, and I was probably quite far off.

Now, I realize that it is confusing, and since it is probably wrong, I removed it from the post.

I also added CAS, since it was requested. It's kind of a makeshift solution for the moment though.

For the speed, I'm not sure though :

Either the hud gives you the IAS, or both DCS and TacView are wrong.

CAS is IAS corrected of instrument error. So I don't know it is handled in DCS or how TacView would correct IAS for a specific aircraft ?

I don't know either. I was refering to real A/C which displays CAS.

Then I'm gonna go ahead and use the IAS given in Tacview going forward, since it's what the player sees in game.