FM in 1.5.5

using emergency afterburner

...НА РЕЖИМЕ ЧР С ДВУМЯ РАКЕТАМИ Р-3С...

H~ 3000:

DCS 25 s.

Graph ~ 35 s.

Yes, in DCS and graph emergency mode ON.

 

 

H~ 3000:

DCS 25 s.

Graph ~ 35 s.

Ok yeah, something definitely looks off there.

What ? is the FM bad in the 21 ?

I find her terrific but hey how am i supposed to know

Yes, in DCS and graph emergency mode ON.

 

 

H~ 3000:

DCS 25 s.

Graph ~ 35 s.

You really hate LN for some reason, do you?

But, as with your previous videos in the other thread, your execution is flawed and shows in no way a problem.

You are flying the turn at an unsustainable AoA. Consistently over 20, the Mig-21 cant sustain even 20 at 700 kph.

What you are doing is trade speed AND altidude for energy. You can see that your speed is going down during your turn and your variometer is consistently pointing down.

The extra energy you get from trading in speed and altidude you put in a higher AoA during the turn. That is where your extra seconds are coming from.

That video shows your VSI dropping , you have to roll her back some again and level and then bank again. try and maintain the nose level during a turn. best is to learn the cockpit reference points rather than chasing the VSI , VSI is little slow.

Look my track.

And the second graph is for normal AB.

Even doing the turn not perfect enough the difference in seconds is so wide that doesnt matter if i can´t keep perfectly 2000 meters.

We dont hate anyone-anything, we want the 21 coded the right way.

If we are doing it so bad try yourself and post your results.

Look my track.

 

And the second graph is for normal AB.

 

Even doing the turn not perfect enough the difference in seconds is so wide that doesnt matter if i can´t keep perfectly 2000 meters.

 

We dont hate anyone-anything, we want the 21 coded the right way.

 

If we are doing it so bad try yourself and post your results.

I too want a good FM, and when i see a problem, and the Mig-21 certainly had a few, especially with the radar, i will complain about it.

But the few second differences you get are easily explained without needing a FM issue for it.

The problem is the AoA, i think you might underestimate how much a slightly higher angle of attack in a turn can make.

And i am sure the test in that chart was flown with a fixed AoA that was deemed sustainable, making it a sustained turn.

If you look at your track, which is pretty good btw, you can still see that when you turn into your first turn you are at 820 TAS (accelerating as you turn into the first turn) and 1850m AGL.

At the end after a few turns its 720 TAS and 1790 AGL, that energy had to go somewhere.

If you did not throttle back, it went into a higher AoA than a true sustained turn would be flown at. And that is simply enough to explain a turn that is a few seconds faster.

Yeah, sorry guys I thought the execution was flawed too at first but in this video

50m = 164ft ÷ 26 = 6ft per second

If you look at EM charts you'll see that even in a 100fps decent, max sustained turn rate only increases by approx 1 degree per second, which would reduce the 360 degree turn by ~2 seconds.

That's -100fps remember and were talking about -6fps so the difference is actually more like -0.125 seconds.

Losing 50kph equates to 2kph per second which also makes close to zero difference.

As for this : "You are flying the turn at an unsustainable AoA. Consistently over 20, the Mig-21 cant sustain even 20 at 700 kph"

Since we've now ruled out the 'trading speed and altitude for AoA' accusation, are you accusing him sustaining an unsustainable AoA? If so, either the MiG-21's flight model is invalid or your argument is.

I think one of you chaps needs to add an entry to LN's bug tracker.

This thread was started a month ago, and yet oddly, no-one has reported the problem on there.

Bug tracker has already similar posts in it. However last patch I noticed improvements.on flight behaviour. So maybe LN noticed.

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From my testing the MiG's sustained turn performance at 2000m and Mach 0.7 with a weight of 7500kg and carrying 2 R-3R missiles was around 13.5 deg/s in the sim where as the charts say it should be around 11.5 deg/s.

The F-5E sustained a rock solid 13 deg/s at Mach 0.7 and 5000ft at 13750lbs with 2 aim 9's as per the EM diagram.

From my testing the MiG's sustained turn performance at 2000m and Mach 0.7 with a weight of 7500kg and carrying 2 R-3R missiles was around 13.5 deg/s in the sim where as the charts say it should be around 11.5 deg/s.

 

The F-5E sustained a rock solid 13 deg/s at Mach 0.7 and 5000ft at 13750lbs with 2 aim 9's as per the EM diagram.

Aaand that right there is were I call BS on this Mig-21 EM chart.

The F-5E has a thrust to weight ratio of 0.73 in this example and about 3000 lbf less thrust than weight.

The Mig-21bis with emergency mode well over 1. With about 3000 lbf more thrust than weight. That is an extremly impressive thurst with the emergency AB, even for modern fighter standards.

Yes, the Mig is a delta which creates more drag in a turn and the F-5 is not, but that is simply not enough to make up for such a huge thrust difference.

Especially sicne the F-5 with its higher wingloading turns at a somewhat high AoA as well.

The F-5 was never known for havign a great sustained turnrate anyway.

So, if that chart claims that the Mig-21Bis has less sustained turnrate at M0.7, than there is something wrong with the chart.

Either it is not with emergency AB no matter what it says on it (would be understandable, considering the strain that it puts on the engine and the extra maintanence required after use) or there are other factors in play we dont know about and are not mentioned directly on those two sheets.

That is always a danger with charts like that, that you dont know the whole story behind them most of the time.

Also, 11.5 degree is actually worse than what you find in charts of older Mig-21 which have no emergency Ab and a much lower thrust to weight ratio.

While those older models are lighter and should often have a better instantaneous turnrate, sustained should be better on the bis with emergency ab than any earlier variant.

This is supposedly a Fishbed C. Though cant confirm that.

Aaand that right there is were I call BS on this The Mig-21bis with emergency mode well over 1.

No.

7100 кгс ~ 69,6 kH. (emergency mode)

6850 кгс ~ 67,2 kH. (afterburner)

turn time in emergency on graph.

Aaand that right there is were I call BS on this Mig-21 EM chart.

 

That is always a danger with charts like that, that you dont know the whole story behind them most of the time.

 

Also, 11.5 degree is actually worse than what you find in charts of older Mig-21 which have no emergency Ab and a much lower thrust to weight ratio.

 

This is supposedly a Fishbed C. Though cant confirm that.

The chart you referenced is for a MIG-21 F-13 at 5,620kg.

The chart I referenced is from the Russian MiG-21 bis manual with second reheat, so probably more accurate than your guesswork.

It quite clearly shows a turn time ~31 seconds at 2000m and 7500KG.

11.5 deg/s × 31.3 seconds = 360 degrees

The MiG-21 may currently overperform in sustained turn rate. We are looking into it.

Thank you Cobra, that's great to hear.

I've seen this chart floating around on other threads which nicely compares the sustained turn performance of the MiG-21bis for the Soviet PVO (NATO: "Fishbed-L") and the F-5E at 15,000ft.

It gives the advantage to the F-5E by quite some margin, despite the lower T/W ratio.

According to my tests and the US Navy EM chart Fishbeds overperformance gets even greater at 600km/h. I can't really decipher the Russian charts so can't tell if they tell the same thing.

Yeah... I thought the MiG put up a little too good a fight against the F-5E and Viggen during the grudge match ;D

So finally a official statement. Thanks Cobra.

Lets hope this and other problems could be fixed soon.

Thanks Cobra keep the good work up!

Hi, guys... quick interjection here.

Thrust to weight has nothing to do with sustained turn rate. simple.

What DOES have to do with it is P Specific Excess Thrust. When P=0 it is sustainable. Its basically Thrust vs Drag... NOT weight. Therefore: if you cannot determine drag then you cannot determine P, its that simple and no, guesses about wing forms can be so incredibly way off the mark that even generalizations should be taken as pure guess work. That means DRAG for a given LIFT directly influences sustained turn rate which means you can't guess or generalize at the drag in a turn if it is not measured.

Please gents stick to the facts. regards.

btw - the "zero" curve on the EM chart is P=0 and are usually equivalent in feet/sec until you reach max lift or max structure limitations. That's why better rates have negative values b/c the plane needs to make up for a deficit of so many ft/sec in potential energy. Run it down to zero g's and you get the max energy recovery ability of the plane. So when u need to regain energy the charts clearly show that you have to be very close to zero g's to really accelerate, or you'll just keep 'dragging' around at low energy... also key to extending from an engagement, you gotta hit zero g's even if you are banked.

Personally i think its a more interesting discussion on how the planes FM simulates instantaneous turn falloff rate down to sustained as much more interesting than minor tweaks in sustained, which don't really determine the outcome of matches much anyways.

Love the viggen since childhood reading "air combat" magazines... glad to see it "come to life" Thank you LN studios.:pilotfly:

Thank you Cobra, that's great to hear.

 

I've seen this chart floating around on other threads which nicely compares the sustained turn performance of the MiG-21bis for the Soviet PVO (NATO: "Fishbed-L") and the F-5E at 15,000ft.

 

It gives the advantage to the F-5E by quite some margin, despite the lower T/W ratio.

 

Personally this chart... the sooner it goes away the better. But lets assume its mostly correct it shows the F-5e @ 9deg/s and the mig-21 @ 8deg/s... Not a "wide margin" and considering that its a single data point, the less value that graph has. My guess its taken from some airplane encyclopedia book with its source already diluted, or maybe its out of context from the relevant passage in the book.

remember to read critically charts and statistics as they can be misleading. best regards fellow enthusiasts.:)

For example:

On this graph what leaps out at me right away is the comparison between the F20 tigershark and the F-5e both showing almost the same sustained turn rates, even though the F20 has at worst, the same drag per AoA & speed, at best better.. and... it has significantly stronger thrust from a new engine, yet they show as almost the same sustained turn rate (less than +/- 1 deg per second). Something is NOT jiving there. This also considering that the F20 was the first plane to encounter G-LOC due to the rate of gain in g's (ie how fast it could gain g's) causing the loss of two planes and their pilots. But, it's really to bad the author chose to place one scale as thrust-to-weight and the other Sustained turn rate since they are not even directly related, thus leaving any reader to pry out of the graph relevant data about drag and excess thrust. But in the end what can be seen is the effect of drag vs thrust "if" its correct.. along with the single data point issue. :P

I would be interested to see if this stacks up against Viggen or other known EM graphs. Makes a strong case for the Canard deltas low drag @ high AoA vs Lift... maybe the Rafale-typhoon-Gripen are on to something ?

http://www.avialogs.com/en/aircraft/ussr/mikoyangurevitch/mig-21/mig-21bis-pilot-s-flight-operating-instructions.html

Towards the beginning of this document it describes a "pancaking" stall.

Sadly it doesn't go into much detail. Later it mentions that accelerated/aggravated stalls can result in violent roll reversals, up to 50° per second. This seems to match the Sim although I feel our roll reversals are, like, an order of magnitude too violent.

I am trying to take the fishbed for a spin entry and recovery. I fly at alt (10000m)

bleed speed, staying level at indicated speed below 400km the first buffet is there taking my time and counting back 1 2 3 stick in my guts right eleron left rudder! The spin coming very slowly giving the feeling that if i let the stick neutral it will recover alone so I keep it there, I am now on a beautifull air ballet spining around flat, still i dont feel i stalled the plane It wants to recover by its own..5000..4000..ok time to let go..stick neutral a bit if opposite rudder 2000m go level go land and feel lucky your engine didn't flameout.. bye bye..

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Why are we not refering to this?