Thank you for the new FM

[Argo Navis]

My only problem with the graph riojax is using here is that we don't know where it is from. It is just a page that does not mention aircraft type. Yes, there are lots of clues that it's for the Mig-21 like the 33/28 degree AoA which is typical of the 21. The UUA-1 instrument is also mentioned, but still, there is no proof this graph is for the Mig-21bis. The UUA-1 was used in every variant that followed the Mig-21PFM like the M, SM, SMT, MF, Bis, UM etc. On the other hand, there are no huge differences between variants when it comes to flying characteristics.

 

You can find this graph in a simpler version in the real manual. It is a bit different though. It is clear that at certain M numbers there is no buffet at all before the stall.

 

I still agree, the flight model is on a good track, though.

 

Now, it might be a confusing or even a disturbing fact, but not even a real Mig-21 pilot can really tell you how the aircraft stalls, or how it behaves prestall and during a stall. I know a bunch of ex 21 drivers from Eastern Europe. Most of them flew the type for 20+ years. I asked them about slow speed characteristics and the answer is always the same: they simply don't know. They were not allowed to fly the aircraft below 400km/h. They did not practice stalls and spins in this aircraft at all.

If you get hold of the real flight manual it does tell you that the minimum speed is 190-220km/h depending on thrust and flaps settings. However, the flight manual also states that flying below 400 km/h IAS is prohibited unless you are landing. In a dogfight the minimum speed with two missiles is 450km/h, and with four missiles it is 500km/h.

 

There are only three nations that I can think of that flew the aircraft differently than what the Russian AFM allows.

The first one is the Americans. Under the Constant Peg program the Mig-21 was exploited to its max and there are a bunch of interviews online about flying the aircraft at around 100kts and beating even the F-15 in a dogfight. Under Constant Peg they flew the F-13 and the MF versions. It must be kept in mind that the US pilots who flew in this program were way more experienced than the average guy in any air force even in the US. Here is a quote from an ex constant peg pilot:

"Because its delta wing, it has good low speed handling characteristics. I have flown it around at full aft stick. It gets down to around 110-115 KIAS, and goes into a wing rock, but there is no stall break, no tendency to depart. Longitudinally, the airplane handles pretty well. In terms of gross maneuvering you can sure move the nose around. It's got good pitch authority. I think it's an excellent airplane over all. It has excellent slow speed characteristics, high roll rate, almost carefree maneuvering in terms of no tendencies for departures."

 

The second nation is the Syrians. There are stories that they did exploit the aircraft to its maximum and happily flew it down to minimum speeds. Because of this they had more trouble with the engines than other nations and they complained about it. The manufacturer sent their engineers and test pilots to investigate why they had more wear and tear than other operators. When they realized that they flew the aircraft around way below the 400 km/h limitation they were able to dismiss their claims about manufacturing problems. This is from a Russian article: "The Syrians quickly realized that on the MiG-21 you can literally do everything without fear of stalling, because it is difficult to drive the MiG-21 into a stable spin, and it easily comes out of stalling. While flying at low speeds, losing speed to “zero”, falling on the tail in a hammerhead the engine worked stably on all “exotic” flight modes. At low altitude, the R-11 engine worked in afterburner operation stably at any low speed, up to zero, but there was the so-called “pulsating combustion” in the afterburner, which led to vibration of the turbine and, therefore, the compressor, especially the first stage. Cracks appeared in the compressor disk, in some cases leading to engine destruction."

 

The third nation is the Romanian. Look at the Lancer's HUD footage during airshows. The AOA is maxed out at 33 and you can see speeds below 200 km/h. There is no stall or even wing rocking. Of course, the aircraft has much more advanced avionics than the original Mig-21MF and there might be an AOA limiter to avoid stalls. The wings and the engine, however, are the same as in the original airframe.

 

I know there are the F-13 and MF versions, and R-11 engines mentioned above while we have the Bis with the R-25 engine in DCS. I know a guy who flew all versions. He says above 4000 meters they all behave about the same aerodynamically. Below 4000 meters the Bis beats all earlier versions in a dogfight.

I asked him recently which version he would take to a guns only fight. His answer: the Bis. I might share our conversation next time.

 

To summarize all of the above, yes it is incorrect that the aircraft can fly around at zero speeds without stalling in DCS, but in previous flight models the aircraft became uncontrollable way too easily which is clearly not the case. Hopefully the devs will get it right soon.

Edited April 29, 2020 by Argo Navis

[Fri13]

I still agree, the flight model is on a good track, though.

 

If the comparison to the engineers flight envelope graphics match, then things are going to better direction/better situation.

 

But that doesn't explain the years situation where flight modeling changed radically to either way, making it difficult to believe anything that what is its condition, because if they ain't documented by the specs.

 

Now, it might be a confusing or even a disturbing fact, but not even a real Mig-21 pilot can really tell you how the aircraft stalls, or how it behaves prestall and during a stall. I know a bunch of ex 21 drivers from Eastern Europe. Most of them flew the type for 20+ years. I asked them about slow speed characteristics and the answer is always the same: they simply don't know. They were not allowed to fly the aircraft below 400 km/h. They did not practice stalls and spins in this aircraft at all.

 

That has been my point along years that people don't just understand, normal pilots does not know much about aircrafts because their job is to fly it by the book, by the safe side. And when you have aircraft that has even special modes like war time and peace time settings or even peace time rules how to fly the aircraft, then they don't break the rules but obey them.

 

Then there are another breed of the pilots, they are the test pilots that job are to test the flight characteristics for the manufacturer, so go and fly dangerously and find the limits. Test the procedures to find the safe ways, as well test the happened accidents situations if they can repeat the accident and find what was problem.

There are as well those test pilots that are responsible to test the aircrafts flight characteristics as manufacturer states in their documentation before a country purchases those aircrafts. And they know more than the normal pilots about the situation. But they don't talk about their job by details.

 

It can be made as analogy this way: Normal pilot is as good to talk about their aircraft as is average driver to talk about their car. They don't need to know everything, just how to use it right.

Then there are those who are test drivers for the manufacturer, their job is to know everything about the car as they are participating building it, so they know exactly how it behaves and why.

And then there are those enthusiasts drivers who can be professional drivers, hobbyists who tunes and pimps their cars, they know a lot about them and some are even hired by other companies to test drive cars for various commercial purposes.

 

The normal pilots (drivers) are good to give generic information, like "It doesn't turn so well at X speed...." or "There is odd noise coming from that part of the car when I do this...."

But they don't just know more than "Do not drive faster than speed limit...." kind information.

 

So when talking to pilots, they are not going to risk their lives, others lives and the aircraft to perform some stupid maneuvers like "barrel roll just before landing".

In simulator we can do all kind stupid things, but that is when we are breaking clearly away from the documentation and experience from normal pilots, and we are putting all our trust just to simulator conclusions to do things "right, as expected".

 

 

The third nation is the Romanian. Look at the Lancer's HUD footage during airshows. The AOA is maxed out at 33 and you can see speeds below 200 km/h. There is no stall or even wing rocking. Of course, the aircraft has much more advanced avionics than the original Mig-21MF and there might be an AOA limiter to avoid stalls. The wings and the engine, however, are the same as in the original airframe.

 

You mean footage like this?

 

w34gErsai3U

 

The AoA is probably the value below the left side speed bar?

The G-value is the top number above speed bar.

And altitude is at the right side in kilometers (so 00,2 means 200 meters altitude)?

But if that is the AoA value, then it is constantly going 25 and above and having no problems what so ever.

 

And that is how I remember the MiG-21Bis being when it got released, it was a rocket that handled very nicely even at low speeds. But then it got dramatic change after studio split and it went to all directions since then.

 

To summarize all of the above, yes it is incorrect that the aircraft can fly around at zero speeds without stalling in DCS, but in previous flight models the aircraft became uncontrollable way too easily which is clearly not the case. Hopefully the devs will get it right soon.

 

IMHO the MiG-21Bis became completely uncontrollable too easily before this thread update. You could be well in good 30 degree dive at speed of 550 km/h and stalling with just a 3-4 units of AoA at 3000m altitude. No controllability, you just crashed to the ground.

To get away from a such diving it was required to start very very carefully pulling up by 1-2 units until you get somekind a "grip" and could pull more. But it was stalling all over places if not flying straight.

Edited April 29, 2020 by Fri13

[HWasp]

 

This is a false dilemma fallacy. No-none talked about "pull as much as you want". We are talking about that the current FM have CLmax issues. Some problems shows a possible slight gain on <0.6M (but also we discovered a possible DCS bug that can trigger this problem) and a gain on >0.9M at ground level using the ARU-3V on manual but a huge performance loss using the ARU-3V on auto.

 

About your feeling of "pull as you want" it's more an actual ARU-3V issue than a FM one. Test it yourself, the data is here and peer reviewed.

 

 

Finally got around to test this myself, and here are the values, just clear things up. They are from Tacview, and at around 500m altitude

 

 

 

At Mach 0.7--> G = 10

Mach 0.8--> G = 14,9

Mach 0.9--> G = 17,4 <--- thats what I calculated to be 16G according the chart in previous post

Mach 1.0--> G = 19

 

 

So if you set the ARU to manual and max deflection, there is no drop on the chart, on the contrary DCS max CL will stay above IRL max CL according the chart.

(BTW damage due over G is not modeled, pulling 19Gs will not do anything to the plane)

 

 

In that romanian Lancer video, there is a point where he is right on the limit pulling 32 uaa

For that 32 uaa in the vid at 515 km/h indicated, he gets 3,2 Gs <---> in DCS for 32 uaa at the exact same speed you get 4,4 Gs. Thats a big difference. (Tacview shows AoA=24 for uaa = 32 btw)

 

 

 

Regarding the stall or the lack of it, it's clearly missing, you can pull full aft stick violently with ARU manual max deflection at any speeds, the plane will not depart, ever.

You can even kick the rudder and throw the aileron around at full aft stick and the plane will not depart.

 

This part is so obious and wrong, that it makes no sense even to discuss it. I did like how it behaved in previous patch though, I think the previous patch was a step in the good direction, and this one is just bugged or broken.

 

They did say that it is work in progress though, so I would just wait for the next patches before discussing this any further. I'm sure this will get fixed soon.

[Frederf]

This is very good discussion.

 

However, first there must be a renewed understanding of what is meant by "stall." Stall has one and only one meaning: peak value of coefficient of lift in graph of CL vs. AOA. That is it. It does not mean airplane falls from sky, engine breaks, dog gets sick, wife leaves, rains on your picnic, or anything else. Example if airplane stalls at 15° AOA and you fly around at 16° AOA, this is flying a stalled airplane. Does it mean airplane cannot fly? Does it mean lift is gone? Does it mean airplane it out of control? Does it mean everything is on fire? No, just that CL is less value now than it was at smaller AOA.

 

Controllability of airplane is separate issue than stalling. Airplane can depart controlled flight but not stall or can stall without departing controlled flight. Controllability is due to stability vs authority of control surfaces. Post-stall doesn't mean post-departure. That DCS MiG-21 reaches CLmax and then abruptly loses all lift and control at AOA beyond CLmax is very suspect. Generally it is known that delta wing plan has relatively gentle post-stall CL slope. Perhaps DCS is fine in this regard because it is impossible to test. If control surface is sufficient in authority it should be possible to fly at 34, 35, 36, 37, etc. UUA regardless of lift and measure CL to continue the graph curve. But in DCS this appears impossible since it is tail authority which seems to explode post-CL-max. One thinks that at max stab deflection that stab AOA is much less than wing AOA and stab remains in good regime for control.

 

We say that UUA = 32 is the limit but this is only true at very specific Mach range. It is easy to see from chart that at lower Mach that UUA = 32 is far from CL maximum.

 

From video of demo above it does look like AOA readout of some kind. Notably it is not simply the difference between pitch cross and flight path marker. Speed dependence is of large interest. Watch at 0:22 where 4 geoAOA is 4 on the display with 700 km/h. Later at 0:38 at 540km/h 5 geoAOA = 10 displayed.

 

This makes some sense if UUA "over reads" at slower speed compared to closer to M0.9. Remember the chart of UUA vs. CL where CLmax occured at about 33 UUA at higher speed but at much more UUA reading at lower speed. Hypothesis is that CLmax occurs at about the same geometric AOA at all speeds but ratio of UUA to AOA is larger at low speed and smaller at high speed.

[HWasp]

https://forums.eagle.ru/showpost.php?p=3457419&postcount=2

 

 

Again here is the link for link for the rl manual, from page 132 it discusses stalls and spins.

 

 

I'm not suggesting that the 21 should depart violently 1 degree over the red line all the time, but still, from the manual:

 

 

"When excessive back pressure is applied on the stick ...... at high normal g-loads, the stall proceeds more vigorously. If the stick is not set neutral immidiately after the onset, during 3-4 seconds, the plane will start oscillating briskly and unsteadily about it's 3 axes with high lateral G loads and rudder forces."

 

 

On the spin entry:

 

 

"....... exceeding the permissible AoA on the UAA indicator and pushing the rudder at the same time creating sideslip....."

 

 

"The normal spin features high instability, vigorous oscillations in yaw pitch and roll, unsteady rotation involving inadvertent changes of direction"

[Fri13]

If I remember correctly, I have managed to get MiG in spin only in the first FM state at the release.

 

Since then I didn't get it depart by any means but just serious stalling very easily and not able to really fly than straight and doing very wide 7-10 km turns to avoid stalling and dropping speed below 400 super quickly.

 

Why I didn't like to fly MiG as it was nothing like F-5E that should be closest to it in performance, almost identical.

 

I haven't tested this new FM but I am waiting to get hands on it.

[Argo Navis]

I got this module on release in 2014. I seem to remember, that we even had the wing rocking at low speeds, or am I just imagining things?

[Blinde]

I've had this module from 2016 and few months ago landings were far more difficult to perform. It would stall and start shaking easily. Landing speed had to be at least 220 knots instead of now, as you can perform nice landing at 170 knots.

[AeriaGloria]

I got this module on release in 2014. I seem to remember, that we even had the wing rocking at low speeds, or am I just imagining things?

 

At low speed I think it was always there, but during that one patch it was doing it at high speed where it didn’t seem to do it before

[Ikaros]

I've had this module from 2016 and few months ago landings were far more difficult to perform. It would stall and start shaking easily. Landing speed had to be at least 220 knots instead of now, as you can perform nice landing at 170 knots.

 

Knots or km/h?

 

220 knots comes out to 414 km/h which seems a little too high compared to the speeds I've landed at in the DCS Mig-21 over the years, but there might be some other variable I'm missing.

Edited May 2, 2020 by Ikaros

[Fri13]

Landing should be possible easily at 280-320 km/h regime. Even possible at 230 km/h without damages, but riskier.

[Shmal]

Now the developer just turned off the stall and spin behavior of the aircraft after 32° AOA (on the cockpit indicator it is 35°).

Also, seems to me, the effectiveness of aelerons close to critical AOA is little reduced and reaction for the pedals are better as it has to be!

Obviously, now it has more softer reaction for gear and aircraft is unrealisticly jumpy while running.

It has no buffet before critical AOA.

It has no rocking from wing to wing on critical AOA.

So... we just have to wait and ask the developer to continue the work have been started after very long break!

 

 

I picked here some pages from the MiG-21Bis - Pilots Flight Operating Instruction:

Edited May 2, 2020 by Shmal

[Shmal]

and more pages

[Shmal]

and last one

[Shmal]

Last days I was flying against MiG-21 on ColdWar and i may say - it looks terrible from the side! The pilots of MiG-21 now are flying constantly on hi AOA at low speed with afterburner!

It's absolutely unreachable for F-5 now to get his six and its is not correct!

I know it because F-5 has better turn rate at speed range 300-500 knots on ground level!

The turn rate of the F-5E with full internal tank starting from 12°/sec and growing to 17° per second when fuel is burning to 1/4-1/5 of the tank quantity. That is pretty good for this generation! Defenetly MiG-21 has worse aerodinamic and cant compete with him in horisontal maneuvers!

MiG-21bis has almost the same turn rate only with emergency afterburner! It cant keep this rate for long period of rate fight! Usual picture of the fight with similar amount of fuel is like the MiG-21 keeping the same turn rate around one circle and after that his speed goes below effective range and he is slowing down in turn! Immideately F-5 is closing to his six!

MiG-21 has the similar parameters of the turn but now without stall, the pilot watching like F-5 going for him in the turn, just pulling the stick back and loosing the speed and reducing the radius of the turn. F-5 loosing the speed trying to follow but he cant to reduce the radius of the turn because in this case he is going to slow below 260 knots and just freeze in the air like a bait!

 

This is good example of what i mean:

 

The style of flight on the MiG-21 for those pilots who are not worring about realistic - on the Cold War server:

Edited May 4, 2020 by Shmal

[Shmal]

Look at his broken trajectory!

 

Something wrong with this flight model ))

 

He is able now to pull the stick as hard as need the pilot to reduce the radius of turn to very low value!

 

Please guys dont fly like that on Cold War! Fly realistic! Use the better thrustweight ratio of the MiG-21!

Use the vertical oblique loops against F-5 in the BFM fighting! Dont drop the speed! Its the death for any aircraft in all times!

 

Study how to fight and lets do it in proper way!

 

Good luck! See you in the sky

 

Your _SkyRider_

Edited May 2, 2020 by Shmal

[Blinde]

Knots or km/h?

 

220 knots comes out to 414 km/h which seems a little too high compared to the speeds I've landed at in the DCS Mig-21 over the years, but there might be some other variable I'm missing.

 

Knots like I said. Earlier it required much more speed to land since that small delta wing just doesn't lift the plane at low speeds. Now it's easy to land like fbw equipped modern planes.

[lucky-hendrix]

I just tested the Mig21 in latest realease. And it is outrageous that any can ssay that the FM is improved !

This is the worst FM has ever been.It feel likes "GAME" FM has been activated ! the plane just simply point were you point it ! Never complains, can sustain any AOA ! This is ridiculous!

 

How can anyone say that this is an improvement is beyond me !

 

This is so bad that I can't beleive the dev put this intentionaly ! They must have confused the FM for 'MAC ' or 'GAME mode' with the regular FM, it can't be otherwise ....

[rossmum]

Right... because of my particular flying habits, I've always held the MiG on the edge of its ability. Maybe it's not the official way of doing things, and against a good F-5 pilot who knows his plane and has patience it doesn't work, but it was challenging and rewarding if the other pilot fell for the trap. Now, there is no edge. There are no consequences at all - you can do whatever you like, the aircraft will almost never stall, will never spin, etc. It is easier to fly than the FBW F-18 or F-16, or Su-27. Maybe if you never fly at low speed you won't notice the problems, and will think the FM is fine now, but for those of us who do it is very apparent that something went wrong last patch.

 

There seems to be a fundamental misunderstanding of an aircraft being very capable at low speed when handled correctly, and an idiot-proof magic machine that will not let you kill yourself through just yanking the stick without thought. Before, the MiG-21 in DCS was the first type. Now it's the latter.

 

As for it being 'very hard' to land before... really? I don't understand how anyone had trouble landing this plane, I've always said this but still I see claims it's hard to do, even if you follow the pilot's handbook. Whether I follow it or not, it's not hard. It might sound brash to say it, but maybe just practice? With an approach speed of 380-400km/h and slowing to 280-300 for touchdown I have never, ever had problems.

 

Hopefully this is fixed soon, as I can't bring myself to fly my favourite module until it is. I don't want to have an easy mode against F-5s and I don't want to learn even worse habits than I already have.

[TaxDollarsAtWork]

The Hollywood FM really is a laugh but can it please be rolled back to something believable?

 

It's able to out sustain all the 4th gens in its current state by a wide margin...

[SwatKat]

If we can do it why would we limit ourselves to your idea of how to fly "realistic"?

Look at his broken trajectory!

 

Something wrong with this flight model ))

 

He is able now to pull the stick as hard as need the pilot to reduce the radius of turn to very low value!

 

Please guys dont fly like that on Cold War! Fly realistic! Use the better thrustweight ratio of the MiG-21!

Use the vertical oblique loops against F-5 in the BFM fighting! Dont drop the speed! Its the death for any aircraft in all times!

 

Study how to fight and lets do it in proper way!

 

Good luck! See you in the sky

 

Your _SkyRider_

[Brown Floyd]

The Hollywood FM really is a laugh but can it please be rolled back to something believable?

 

It's able to out sustain all the 4th gens in its current state by a wide margin...

 

I'm half-tempted to sign up for the Merge For The Cure event with the MiG-21 to see what happens.

[TaxDollarsAtWork]

I'm half-tempted to sign up for the Merge For The Cure event with the MiG-21 to see what happens.

:megalol: You're a mad man and a legend if you do it

[Lovcar]

Когда починят FFB МиГ21?

[Lovcar]

И вобщё можно так зделать чтобы не льзя было высовывать голову из за крытого фонаря кабины?А то у МиГ21 текстуры отсутствуют.Их просто нет)когда на это смотришь приходиш в ужас)