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Mirage 2000 performances


sedenion

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Le sigh.

 

Just like that you reduce the credibility of anything you say to nought.

 

don't get personal kiwi, i didn't...

 

i'm not going to fight this, there is an issue, it's being acknowledged.

 

it's beyond me some of you keep talking about delta wing drag or data (which you lot don't have anyway) to justify the inability for a FIGHTER to maintain its altitude with 15 degrees alpha even with burner on, and that the only way to recover is to order a down stick to unload the wing, as if the plane was powered by a piston engine...

 

 

i'm out on this subject, and i'll wait for a module update.


Edited by Tripleinside
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don't get personal kiwi, i didn't...

 

Sorry, that wasn't directed at your nationality, I actually live in an town settled by the French and everything around here is "Le" this or "Rue" that. So "Le sigh" is in the local lexicon, and it's a French plane so I thought it felt right.

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More time, or infinite time ? I very quickly reached the state where the Mirage 2000 simply fall without ability to regain energy... Never seen that before, especially without payload !...

 

How about you don´t pull too much AoA, starving the engine of air and thus thrust and producing incredible drag from your delta wing design and thus keep your energy and speed where it should be?

 

And how about you don´t compare yourself to AI that uses simple flight models.

 

I did guns-only dogfights against a very good SU-27 pilot in DCS and managed to beat him 2-1...Just don´t be too stick heavy.

 

Also, if you are having trouble, keep the AOA limiter in stores mode, you won´t overturn then.

 

If you do find yourself with no energy, NOSE DOWN IMMEDIATELY and hope you have altitude left...the engine is, as I said, air-starved at high AoAs so simply pointing the nose up and expecting the engine to perform magic for you ain´t gonna cut it.

 

The drag may be too high, but it´s not like it can´t be counteracted easily by more sensible flying.

 

--All statements refer to current M2000 build--


Edited by Chrinik

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GCI: "Control to SEAD: Enemy SAM site 190 for 30, cleared to engage"

Striker: "Copy, say Altitude?"

GCI: "....Deck....it´s a SAM site..."

Striker: "Oh...."

Fighter: "Yeah, those pesky russian build, baloon based SAMs."

 

-Red-Lyfe

 

Best way to troll DCS community, make an F-16A, see how dedicated the fans really are :thumbup:

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Delta wings ARE draggier than regular swept back wings at high angles of attack. However as Cpt. Smiley acknowledged, the DCS M2000C drag is too high, even for a delta wing, and this will be addressed. It's probably not a simple matter to do so, otherwise we would have had a fix by now.

^ this!

I don't get why this discussion continues... There is nothing wrong with reminding caracteristics of delta wings. And there is nothing wrong with assessing something's not quite OK with the current FM.

Both are not incompatible. There is not a "right" side and a "wrong" side.

 

So. What about learning to let it go, and waiting for the update announced by Cpt Smiley?

And in the meantime, I don't know... continue flying @ lower AoA on DCS? :joystick: Going out? :D

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^ this!

I don't get why this discussion continues... There is nothing wrong with reminding caracteristics of delta wings. And there is nothing wrong with assessing something's not quite OK with the current FM.

Both are not incompatible. There is not a "right" side and a "wrong" side.

 

So. What about learning to let it go, and waiting for the update announced by Cpt Smiley?

And in the meantime, I don't know... continue flying @ lower AoA on DCS? :joystick: Going out? :D

 

THIS! :thumbup::thumbup::thumbup:

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FYI,

I came across a former IAF M-III/Nesher/Kfir driver. and asked him about the actual performance.

 

it seems that current M2K performance is up to par with the typical behavior of Delta winged fighters. high speed allows a very quick instant turn rate leading to a massive energy bleed off and the the aircraft "stopping in mid-air".

 

He had said one tip, "when you are in a Mirage, you need to think ahead before you burn off energy. You must always know where you can get your energy back and if you'll have time for that.". as an example he gave the M3's difficulty go get it's energy back in straight and level. they would always unload to pick speed back up.

 

He also stated, that the Kfir was loosing more energy in a turn due to higher weight on the same wing area. (higher wing loading). but would pick up speed faster (j79 was more powerful then the Atar9c).

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FYI,

I came across a former IAF M-III/Nesher/Kfir driver. and asked him about the actual performance.

 

The common error.... The Mirage 2000 is NOT a Mirage III/Kfir and is NOT comparable to Mirage III/Kfir despit its delta wing config... We have discussed this confusion many time before. Extrapolating M2k performances from the Mirage III/Kfir is somewhere like extrapolating the F-16 performances from F-4 phantom...


Edited by sedenion
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The common error.... The Mirage 2000 is NOT a Mirage III/Kfir and is NOT comparable to Mirage III/Kfir despit its delta wing config... We have discussed this confusion many time before. Extrapolating M2k performances from the Mirage III/Kfir is somewhere like extrapolating the F-16 performances from F-4 phantom...

 

You can say a lot of things about comparability, and you are correct, you cannot extrapolate performance. However, aerodynamic behavior is something else completely.

 

However, comparing f4 to f16 and m3 to m2k is not the same.

 

Using M3 to predict airframe behavior of the m2k is more along the lines of predicting how the KAI T-50 will behave compared to the F-16. Wing and fuselage design is similar enough to say "the F-16 has issues in this part of the envelope, the T-50 should have a weakness there too"

It does not directly predicts performance.

 

Same applies. M3 has difficulty in maintaining speed at a tight turn. It can be mitigated by increased wing area and more engine power, but the aerodynamic characteristics that case it still exist in the form of the delta wing.

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Same applies. M3 has difficulty in maintaining speed at a tight turn. It can be mitigated by increased wing area and more engine power, but the aerodynamic characteristics that case it still exist in the form of the delta wing.

 

It is well heard that delta wings produce more drag on turns than other configuration, this is well known. However, the delta wings of the Mirage III and the delta wings of the Mirage 2000 are not the same... and if you look closely, this is obvious.

 

Think that the Rafale and EF-2000 are also delta wings...

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You can say a lot of things about comparability, and you are correct, you cannot extrapolate performance. However, aerodynamic behavior is something else completely.

 

However, comparing f4 to f16 and m3 to m2k is not the same.

 

Using M3 to predict airframe behavior of the m2k is more along the lines of predicting how the KAI T-50 will behave compared to the F-16. Wing and fuselage design is similar enough to say "the F-16 has issues in this part of the envelope, the T-50 should have a weakness there too"

It does not directly predicts performance.

 

Same applies. M3 has difficulty in maintaining speed at a tight turn. It can be mitigated by increased wing area and more engine power, but the aerodynamic characteristics that case it still exist in the form of the delta wing.

 

There are 3 things which make the Mirage 2000 to perform a lot better in turn compared to Mirage III family:

- relaxed stabilty + fly by wire = elevons (wing control surfaces) are creating positive lift during the turn.

- SLATS on the wing = decrease wing drag during the turn. It isn't possible to use on Mirage III without FBW because it would make it too unstable.

- "streaks" on air intake = it improves lift on wing root at high AoA. It's the same idea as the canard plane on Mirage III family.

 

Once more, the FM is said to be under review, so lets wait...

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Note that high AoA with vortex generates a lot of lift on a delta.

 

When you expect to stall out and drop nose, you are still flying due to vortex.

More thrust means you hit this state at higher AoA.

Not sure if lack of thrust in this module is the answer.

 

Lift coefficient increases from 0.4 to incredible 1.2 with vortex at AoA 30. (Ref below Mirage vortex burst at 18 AoA. Stall 24 AoA)

 

https://www.quora.com/Do-delta-wing-aircraft-generate-more-lift-than-an-aircraft-with-standard-wings

 

 

https://forums.bharat-rakshak.com/viewtopic.php?t=6663&start=3240

..

EDIT.

LIKE TO ADD EXCERPTS FROM LOWER LINK:

 

3b) Instantaneous and Sustained Turn Rates: The turn-rate you achieve at corner velocity is the Max Instantenous turn rate (and minm turn radius).

Now let's look at how Lift Coeff comes into play for different wing geometries.

 

For a rectangular wing planform, the lift co-eff has been explained above - wherein the lift co-eff increases steeply and monotonically with increasing AoA, until a point it stops and starts reducing. But, with a delta plan-form this dipping of Lift Co-eff beyond a certain AoA, doesn't happen at all ... aka, THEORETICALLY, the lift co-eff can continue to increase with increasing AoA.

Thus, again THEORETICALLY, the turn-rate will be higher than that of the normal wing planform design - and so, traditionally the Deltas will have higher Instantaneous turn rate than that of rectangular planform design.

 

But of course, there's a huge catch - pls wait a minute, and pause for the drag-bhaiya to play it's part as well. The drag co-eff, however will also continue to increase and eventually negate all lift.

 

So your turn-rates (and thus the Instantaneous turn rates) will be impacted as you would rapidly bleed energy (due to drag) and your turn velocity will start reducing quite dramatically. The only way to negate this drag is to use addn thrust and overcome it and thus maintain/sustain this turning velocity. This is called the sustaining turn rate which obviously is lesser than the pure lift-coeff-influenced-instantaneous turn rate.

 

Moreover, for a delta wing, because of relatively higher wing area, will have more drag compared to that of a normal wing design i.e. for a delta planform, because of a higher wing area (compared to that of a normal wing geometry) BOTH lift and drag would be higher than that of a normal wing design.

 

So for a delta planform, the limiting factor for higher turn-rates, is not the lift co-eff so much, but it's the amount of thrust available to overcome this drag that turns out to be the limiting factor - which would mean a higher Instantaneous turn rate (due to higher Lift Co-eff) but a lower Sustained turn rate (due to again higher Drag co-eff) for the deltas, when compared to a rectangular wing design.

 

But, unfortunately, that's not the end of the story.

 

 

3c) The Vortex influence on Lift: Now plane designers are constantly looking at ways and means of increasing lift co-eff while postponing, as much as possible, the corresponding and inevitable drag increase. An "artificial way" of getting this done is to have the flow on the upper surface of a wing rejuvenated/energised by vortex generated upstream.

The energised airflow on the top-surface of the wing provided greater "suction", increasing the lift, without corresponding exponential increase in drag.

This is called postpoing the wing-stall.

 

Now leading edges of a delta are good vortex generators - for any delta wing, all along the leading edge, vortex are generated (until they are unaffected by a phenomena called vortex breakdown) and thus contribute to vortex lift which increases with increase in AoA.

 

 

3d) Vortex Burst Limitations: But then again, as with everything else, there's a catch ... vortex getting generated tend to "burst" or destroyed (due to adverse pressure gradients acting on them) resulting in a loss of most of the vortex lift - pls do note vortex bursting is not an issue as long as it can be postponed to a far-enough point downstream to a wing.

 

And there-in lies the problem ... for a slender delta-wing (aka with high-wing-sweep of say 65deg, found in most modern delta-winged aircraft like Mirage etc) this vortex busting phenomenon is observed to start from around 18deg AoA for a 0.85M flight regime. Increasing the AoA beyond that, the vortex bursting point moves upstream very quickly resulting in abrupt reduction of Lift etc - and about 24deg the wing starts to stall.

 

 

3e) The Canard Solution: The TFTA solution to counteract this phenomenon is of course to introduce the close-coupled canard surfaces located just above and forward of the main wing that'll direct airflow downward over the wing. At slow-speed and high AoA it generates vortex which attaches to the upper surface of the wing, stabilising and re-energising the airflow over the wing reducing drag and increasing lift.

 

 

3f) Non-Slender Delta planform Impact: But SDREs, being insufferable fools that they are, thought of something else ... how about a non-slender delta (aka with relatively low-wing-sweep of say ~50deg) wing. And like bumbling fools, they soon found out that vortex bursting would onset at a even smaller AoA for a non-slender wing.

But like a true SDRE, they kept their patience to soon found out a phenomenon called flow-reattachment which re-energises the airflow over the wing reducing drag and increasing lift.


Edited by zero
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Since so many are upset about the Mirage and since we should know by now updates and fixes are forthcoming stop flying it and play this:

http://letsplay.ouigo.com/

We will let you know when it is done, can we please move on?

To whom it may concern,

I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that.

Thank you for you patience.

 

 

Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..

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