Maverick Su-35S

Let's hope, but now because a lot of fanboys in DCS have found a pot of gold in how much thrust to weight ratio this plane develops in contrast to the DCS F-15 by beating the F-15 in vertical climb (climbs higher than the F-15C in vertical climb between 500 to 3000m, depending on climbout conditions). Right now the Mirage 2000C beats every aircraft in DCS in vertical climb and horizontal acceleration. Test please! Although this might happen (from what I concluded through calculations) because ED Flaming Cliffs 3's fighter planes engines (of F-15, Su-27/33 and MIG-29) develop lower maximum thrust than the real engines do or the Mirage 2000C's engine develops higher maximum engine thrust than the real engine can do, so it's a bit blurry to say the Mirage has too much output thrust or the Eagle has too low as compared to reality. I believe that a thorough investigation must be done by both producers to find the cause for this simulated aberration. The Mirage also turns better than the F-15C. Yes, it proves relatively the same ITR (instantaneous) and STR (sustained turn rate) performance as the Su-27, which is utterly absurd and it doesn't seem to be due to an apparent higher engine thrust, but due to incredibly higher simulated lift for any given AoA and airspeed. Here are some tests I did right now. The 3 aircraft are having 50% fuel, turning at around 1000m MSL while holding around 30 AoA (Mirage has around 27-28). The results speak for themselves and everyone can test them. Regards!

Hello Frederf, I know what you say and by documentation the Mig-21 has 0 wing incidence and yes the AoA shown in outside view is grossly taken as the angle between the undisturbed airflow upstream of the plane and the plane's X-axis. It's not correct giving the definition of the angle of attack, but anyways, the difference between what this wing should have as a maximum AoA and what it would be even if it would be 16 (as you'd suggest with that 1 degree of positive incidence) is unacceptably great. I'll relate this on the bugs forum then;). Kind regards!

Thank you Jojo! I'll try to talk with them and share some thoughts! Regards!

For instance, have a look at this: While holding full aft stick during the glide (no engine thrust for pure aerodynamic lift), the AoA settled at around 28. The CAS settled at 155km/h. The plane's weight at the time was 9300kgf (20500lbf). With a reference wing area (41m^2), the lift coefficient resulted as 1.96. Tremendously high for this type of wing. Rather said, almost twice as high. 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? I've opened the file called "M-2000C.lua" in CoreMods folder and at the aerodynamic data section, I do indeed see 1.14 at Mach 0.05 and (surprisingly / abnormally) the maximum CL drops continuously until reaching Mach 0.3. From my personal experience (being an ex-aerodynamicist), the CL max increases up to Mach 0.3 and only afterwards it decreases (especially at shock stall Mach), so I find this a bit strange too. Still, it baffles me to find that during simulation the max CL (Cymax) gets to 1.96. Also during deep stalls at around 90 AoA (achievable through pitch limiter disengage), the fall speed was only 125km/h CAS. This determined a CD (drag coefficient) at alpha 90 to be 2.7 o.O!! Tests and experience show that the majority of planes share a CD at 90 AoA around 1.15, very similar to that of a flat plate in 3D flow, not 2D tests. So both the lift and the drag functions are exaggerated. Can someone explain this? The Flanker's speed at a held alpha of 30 is 183km/h CAS with maneuvering flaps down. While weighing 22300kgf (49100lbf), it's lift coefficient proved to be 2.2. So the Mirage is almost as good as the Flanker in terms of aerodynamic lift? Keep in mind that the Mirage doesn't benefit from high energy vortexes generated by the LERX which usually increase the maximum lift coefficient by at least 50%. The Mirage doesn't have flaps (can't have) which also increase the maximum lift coefficient (even though the critical alpha becomes lower, the CL with flaps is higher). This should be a good enough proof that the DCS Mirage has too high lifting performances as compared to the real plane. Kind regards!

At what speed and altitude? If you fly vertically at a low enough TAS (to reduce the drag),let's say 300km/h starting from SL, even 1.1 T/W should get you at least a higher than 1 T/ W+D) and slightly accelerate (TAS increase, not IAS) in the vertical.

The F-15 can't accelerate straight up empty, for example? I read that very useful and interesting document about this guy who flew the F-15, F-16 and MIG-29, yet he says that the T/W ratio was less than 1/1 due to loadout and perhaps he didn't benefit from the 25000lbf engines that the DCS F-15 should have. The real F-15C should be able to prove a T/(W+D), where D is drag force (it matters even at null lift AoA) above 1 even with full fuel empty weight while starting a vertical climb (90 degrees pitch) from sea level if he manages to remain with at least 300-400km/h after reaching 90 pitch. In this condition, the F-15C with 25000lgf engines should normally find an initial TAS (not IAS) increase up to 1.5..2km height before it starts to decelerate (TAS decrease). Under the mentioned conditions, our DCS F-15 has it's TAS drop quite quick instead of slightly increasing. I have the feeling (at least by the numbers) that our DCS F-15C has it's engine thrust lower than it should at low altitude. At high altitudes, it can reach Mach 2.5 so the thrust to drag ratio is relatively correct, even if the drag and thrust may not be correct/realistic, their ratio is as long as it reaches Mach 2.5. For some reason, in DCS, the F-15 has a lower T/W and also T/(W+D) than the Mirage 2000C from RAZBAM and also lower than the Harrier O.o from RAZBAM. Who hasn't inputted the right engine performance data, ED or RAZBAM? If you try a Mirage vs Eagle player vs player battle in DCS, the Mirage outaccelerates the F-15 in the vertical. I've done a test in which I had both planes with 50% fuel, started from 1000MSL and at 700km/h IAS I started a 3G climb until I reached 90 and held 90 pitch until the tailslide took place. The Eagle only reached 8400 meters, while the Mirage passed through 9000m. How come?

Regarding the T/W ratio, it seems that the Mirage has it right (after I've made some further tests) and it only seems that ED (somehow) didn't correctly input the engine thrust performance into all the Flaming Cliffs 3 aircraft (MIG-29, Su-27, Su-33), because for a simple instance, we know what a thrust to (weight+drag) ratio is and how it affects the plane's X axis acceleration. For some reason, all the FC3 planes might be plagued by a relatively low acceleration from what they should have, but this is another discussion and I will address it in it's appropriate thread. So I now take back my words when I said it's "rubbish" the fact that the Mirage out accelerates the F-15 (which normally should be the best in this area) in DCS, cause it seems this is not a DCS Mirage 2000C's T/W ratio problem.

You might be right! But I didn't do the analysis performed by the one who showed the STR and ITR charts, so I took his word for granted and didn't re-check this on my own. Otherwise, although I didn't yet install Tacview I've done other tests, like CL max determination (through stall speed test), CD 90 (drag coefficient at alpha 90) and post stall pitching moment behavior and what I found proves that the plane needs other aerodynamic data fixes. If I could have a word with the ones at RAZBAM who control or can modify the aerodynamics of this plane, I will sure be useful. Right now, the plane's maximum lift coefficient and also lift slope is way too high for this plane's wings, of course, taking into account not only the wing shape but also the slats and generated vortexes (which can be neglected for not being too strong). I would like to put things into detail with someone from RAZBAM involved in the flight model. Regards!

Hello, While playing I've noticed something odd regarding the IAS/TAS (while using the outside view IAS/TAS). Every time I reached 22.5 to 22.8 AoA, which seems to be the alpha where the engine surge takes place (you hear bangs from cockpit view), the IAS jumps by adding a couple of knots at every engine surge that occurs. It seems the testers have missed this (couldn't guess this to happen) when they modeled how the engine surges take effect upon the developed engine thrust, because now after every engine surge the engine gives a massive thrust increase for a split second, before it would actually start decreasing. Here's a track providing just what I've said: JAS-37 engine surge thrust increase.trk Besides this unexpected weird engine thrust behavior at surges, this aircraft and "Heatblur" truly deserve their money for a very well and very realistically developed flight model. Hats down!

It is a problem indeed! If it would be right, then that peak in greater STR should be spread across a higher range of speeds, not just for a particular speed. Otherwise said, in terms of alpha (which governs the lift to drag ratio, or the aerodynamic polar), the better L/D ratio which would translate in higher STR in the end should be found over a higher alpha range (2 to 4 degrees I'd say). Moreover, simply the fact that at some point the STR becomes greater than the ITR=))LMAO tells how professionally this flight model was worked out! The way it looks right now definitely confirms that for an exact alpha (doesn't show up on your graphs though) the L/D suddenly becomes very high. Slightly above or below that alpha, the L/D gets back to the original polar's function and not outside it. So, this problem is either due to the fact that the lift might suddenly jump higher at that particular alpha or the suddenly drops. Anyway it might be, this must be fixed along with a lot more flight model problems that I personally found regarding: lift slope, critical AoA, drag curve to AoA, drag at 90 AoA, pitching moment vs AoA and engine thrust which reflects into a thrust to weight ratio which is almost 20% higher than that of the F-15C which is total rubbish. The Mirage 2000C must enter a complete flight model overhaul before things get messy with it!

Again..., I don't even know what to do to convince these guys who made the MIG-21 in DCS that THE SIMULATED CRITICAL ANGLE OF ATTACK IS TOO LOW FOR THIS PLANE'S WINGS! All the facts are gathered around and still they won't review this problem? There are 3 modifications that need to be done inside the aerodynamic input data tables: 1. Reduce the CL0 - the AoA 0 lift coefficient. It is too high and for this reason this aircraft would be flying supersonic (through shockwaves) at a negative AoA at 1G, which is only possible if this plane has a highly cambered airfoil section, which is not true! The MIG-21 has an almost symmetrical wing airfoil from root to tip (Tsagi S12 has a very low camber), therefore, the CL0 must be very low (quite close to zero). Some data on the internet says it is in fact purely symmetrical, but actual airfoil coordinates show that it is very lightly cambered. Still, the CL0 value must be very low as compared to what it is right now. 2. Increase the critical AoA from 15 to 20..20.5, which corresponds to this wing, NOT airfoil, but whole wing. 3. Reduce the lift versus AoA slope according such that the maximum CL (or lift coefficient) would not be altered after correcting the critical AoA. 3 steps and everyone's happy again. What makes it so hard? You don't trust what I'm saying, right? You need "proof" as always. OK! But one thing's for sure: Even if we don't have access to real wind tunnel data, we should at least agree to the following logic: If the A-10's higher AR wing, zero wing sweep, very high camber as compared to MIG-21's wing, has a critical AoA of 16, the MIG-15, a higher AR, relative sweep, non delta, has a critical AoA of 18, the Su-25, higher AR, very low sweep, has a critical AoA of around 17, how come someone forced a critical AoA on the MIG-21's wing to just 15? Keep in mind that between 2 wings with the same AR and sweep for example, one being a delta and the other a non-delta, the delta wing will always have a higher critical alpha if the airfoils don't differ too drastically (ie: if one is being symmetrical and the other highly cambered)! Just by these contradictions one should understand that even if the true critical AoA isn't exactly known, it should definitely be higher than those of the mentioned aircraft. This is common sense for anyone with a good knowledge and experience in aerodynamics.

Please let me know how would you find these differences affecting what I'm trying to say. Let's openly discuss about it:thumbup:! Sorry to contradict you here, but this can only be physically possible (for a Su-27, F-15,etc.) at an AoA quite low or at a G-load far below 1 while holding full aileron and rudder just to neutralize the rolling tendency, so all the flight becomes nothing but a long plunge towards earth. Don't listen too easily on what's being said of that Israeli F-15 flying back home with a whole wing gone. If this was true, then it can only be physically possible if the lift produced by the wings is far below the one produced by the fuselage, which is absurd. Most definitely that wing was only about half gone, not completely gone as people lie about just to make it look like a wonderful story or to make the F-15 look like some magical craft defying physics. I trust only physics and validated numbers as they won't lie to me, not fructified stories from Youtube. Because the MIG-21's wings lift is so precious might drive you to believe that the ailerons have a huge impact on the lift differential on the wings, when in fact they don't. Maybe on drag, yes, they have a huge impact generating the known yawing moment due to roll inputs which looks correctly simulated, but not on lift. If the aileron would have an effect on the wing at stall AoA that would would take place only on the aileron's region, not affecting the whole wing, but only a small area (less than a quarter of the aileron's span/lenght) slightly inboard of the ailerons. These are facts, not aberrations. Not what you're saying is aberration, but what's being simulated at this moment. Extremely high roll rate? Compared to DCS MIG-21, it's twice as worse under same conditions of AoA and IAS, not to mention how badly the Mirage's roll rate decays when approaching critical AoA and keep in mind the huge difference between the Mirage's aileron area to total area ratio and comparable deflection and the aileron area to total area of the MIG-21 and both aircraft comparable rolling moment arm (arm between the aileron's center of pressure and plane's rolling axis), plus the fact that the Mirage has a some sort of ARI (aileron-rudder interconnection) system which deflects the rudder towards aileron input. All these factors combined affect the resultant roll rate. It should be clear that there's something still in need of work on the MIG-21 and not on the Mirage-2000C which behaves remarkably accurate. The JAS-37 also flies remarkably realistic and does not develop the strange aerodynamic forces present on the MIG-21. So far, the 21's aerodynamics still look like a WIP. Initially, when the MIG-21 came in DCS, it was far more realistically behaving than it does now. Some aspects have been fixed, but a lot more got worse somehow. If tweaks made it worse, then tweaks can also save it and make it better. Correct, but it's much more important which areas get wetted (as our discussion seems to lead to) by these vortexes and their intensity for a particular AoA or somewhat to say, the intensity of the vortex versus AoA slope, which drastically affect the vortex breakdown AoA, known as supercritical AoA. If such a powerful vortex can "wash" the wing as far outboard as where the ailerons are, then the ailerons effectiveness decay would be delayed and take place at a higher AoA, closer (yet below) to the vortex breakdown AoA. After passing the supercritical AoA, any aileron movement should find almost (yet not null) no roll response or as life tests show, the ailerons lift vs deflection slope becomes about 10..15% of what it was below stall. But there is NO such thing as high energy vortex developed on a MIG-21's wing and furthermore not possible for the tiny vortices developed along the wing's leading edge that cannot wash out the nasty boundary layer separations and flow reversals that take place very close to the ailerons. Here, this might be very useful and you may find out that there isn't a very big difference between the general wing shape (delta or swept wing) on how it affects the general airflow and flow separation / flow reversal patterns. When a wing becomes more swept, these effects will be less and less different for different wing types. The flow separation effects that take place closer to the wingtips are more affected by wing sweep angle rather than planform shape: "The videos are a valuable tool of information" If they were to be more effective due to vortexes (which you presume might reach the ailerons and beyond) then how come we don't see at least the same amount of aileron effectiveness at AoAs above 20 (look how low it is...) on aircraft such as Su-27 which has a far more effective vortex spreading across it's wing as compared to the MIG-21's wing. It's all about the contradictions that emerge from this. Even the Mirage-2000's wing (which you thought to be rather comparable) with slats (which drastically improve the airflow on the ailerons) still has a roll response very comparable to that of an F-15 (slatless wing as the MIG-21) of Su-27. Same goes with the JAS-37. Do you want to say that somehow, irrationally, the MIG-21's ailerons are washed by a tremendously well stabilized and firmly attached vortex which keeps the aileron's lift versus deflection unaffected by alpha? There's definitely something out of the ordinary going on right now and because this didn't happen in previous patches, it's certain that this can be fixed. Kind regards, Mav.

Hello, The moments of inertia about the 3 axis with their respective radii of gyration have been personally calculated after splitting the plane into the major components that take part in the plane's general weight by knowing their 3D positions and mass. I could not find the real value anywhere and this determined me to try and estimate them. I cannot guarantee how highly accurate these determined values are, but giving the fact that I've used the same model to determine those of an F-16C, for which I had comparison data and the mean error was around 2% (98% accurate), I am confident that in this case they cannot be lower than 94-95% of the real values. About the ailerons, yes, as far as I know they are being driven by some clutch systems which are designed to maintain a relatively constant aerodynamic load on the ailerons. Because the aerodynamic loads vary with the square of the equivalent airspeed, the ailerons deflections will increase with a square function of decreasing airspeed or the deflections will decrease with a square root function of increasing airspeed. Yet I still believe the roll rate to be too high at low speeds between 100 to 400km/h. As compared to an F-15 in DCS, the DCS MIG-21's roll rate at 200km/h with it's small ailerons is 43% higher. It takes 2.1 seconds for the MIG-21 to complete a 360 roll at constant roll rate at 200km/h, while for the F-15 which has elevons (that should further enhance the roll rate) it takes 3.7 seconds to complete a 360 roll at constant roll rate at 200km/h, which seems exaggerated for the MIG-21 to roll so fast. Only by putting into balance or comparing the ratio of aileron area to wing area of the MIG-21 to that of a Su-27 (I took the extreme examples as a better proof) combined with the ratio between the MIG-21's full ailerons deflection and the Su-27's flaperons + elevons deflections, one can notice that something doesn't add up for making the MIG-21 reach such roll rates. Although the ratio between the aerodynamic rolling moment of the MIG-21 and it's rolling moment of inertia may give a rolling acceleration higher than that of an F-15 and Su-27, this ratio (roll angular acceleration) still seems quite too high. Even when flying at 80km/h (using a ballistic trajectory) and jerking the stick full from side to side, the rolling response looks obviously short, the plane would act as if it's very light. As far as I remember, I had given a link of a real MIG-21 which performed a 360 roll after takeoff at around 450-500km/h. That video could've been used as an inverse engineering to determine the rolling moment of inertia and roll rate with quite good accuracy. If we don't have any other reliable data, the videos, if used with precise measurements can give very accurate true data, but of course, this depends on whether we want to make it better or not. Here is the track regarding the MIG-21's roll rate vs airspeed and rolling inertia: Roll rate and rolling inertia problems.trk About the highly swept deltas (the mig-21 has 49 degrees at the 25% chord spanwise line), I am very sure that the flow separations close to the ailerons gradually reduce the ailerons lift vs deflection slope as the wing's AoA gets closer and closer to critical and render them completely useless (lift vs deflection becomes almost null) by the time the wing reaches critical alpha. Tip stalls which usually engulf the ailerons as well, occur a lot more prematurely with higher sweep angles. For the MIG-21, the ailerons stall/ineffectiveness is a true fact. This is the main reason why the pilots are told to use rudder instead of ailerons for controlling the roll as they approach the critical alpha. Not only that the ailerons lift effectiveness should decay with increasing alpha (both positive and negative) and become null once the whole wing is stalled, producing differential drag only, but as it is right now, the ailerons produce about the same differential lift between the wings when fully deflected at angles of attack as high as 50 as they would at produce at low AoA (0..10 degrees), which is abnormal to say the least. Here is the track to review the abnormal aileron lift effects at angles of attack more than double that of stall: High AoA ailerons response is same as for low AoA.trk (Now, I wish you luck with the tracks, because they don't seem to follow exactly what I did so the plane may crash randomly at each retry to replay, although I didn't crash and showed everything that's not alright) Again, take into comparison the DCS F-15's roll response when the wing as at or near critical AoA. What do you get? The wing (which is a delta with an even lower sweep than that of the MIG-21) is still capable of slightly increasing the lift coefficient between 20 (30 on the indexer) to 25 AoA (35 on the indexer) while the ailerons effectiveness has already become very low by the time 20 AoA was reached. The same goes for the Su-27. You can't say that ED had simulated them wrong or copy pasted one's values to another. By tests, they match each real individual plane remarkably. Another discussion which has the highest priority of all is that of the true critical AoA of the MIG-21, which is in no case 15 degrees. Even high sweep and relatively high aspect ratio wings (for fighters) like those of the F-86, MIG-15, etc. have a critical AoA of +18 AoA. The delta which always has offered a benefit in critical AoA increment should in fact give the MIG-21 around 20-21 degrees critical AoA. Another discussion would be that of the MIG-21's wing lift at zero AoA and also lift slope (CL vs AoA). I am personally involved in enhancing/correcting the flight behavior of various aircraft in another simulator (not giving name) and I feel an urge to see owned aircraft in DCS respect real data, and if real data is not found/available, use all the engineering methods that you have to determine the data or at least get closer and closer to it by whatever means..., of course, if our goal is to have that aircraft behave as close as possible to the real thing. My wish is that at least one after another, as the time permits, all these aspects will be revisioned. Kind regards!

Hello, After doing a research on some flight dynamics constants of the MIG-21, this is what resulted: For a given weight of 8700kgf, which corresponds to a clean loadout, full fuel + the pilot, the moments of inertia should be as follows: Ixx (rolling moment of inertia) = 6147 kg*m^2 or 145880 lb*ft^2 Iyy (pitching moment of inertia) = 67510 kg*m^2 or 1602052 lb*ft^2 Izz (yawing moment of inertia) = 77091 kg*m^2 or 1829398 lb*ft^2 The following are the corresponding gyration radii of inertia: Rolling radii of gyration: 0.8406m or 2.758ft Pitching radii of gyration: 2.786m or 9.14ft Yawing radii of gyration: 2.977m or 9.767ft If one may introduce these constants in the flight model file of the MIG-21Bis in DCS will finally have this bird responding authentically. Right now, the pitch and yaw moments of inertia seem appropriate (by how the plane responds to sharp full elevator and/or rudder deflections), but the rolling moment of inertia is still quite lower than expected. You can make the plane roll left and right so quickly at 200km/h as if it were at 300km/h...! Another thing is that the ailerons are as efficient way above stall AoA as they are for low AoA, which is abnormal. Above stall AoA, the ailerons efficiency should become greatly degraded if not null, especially if the leading edge has no droops/slats to enhance the flow. My only goal is to enhance or to help enhance the flight behavior of aircraft in DCS. Best wishes, good day!

Thanks for letting us know about the Chap and appreciate your replies!;)

It seems that after the last updates, the IR missiles got even better. It became more difficult to make the IR seeker (of Chaparral and Avenger) break it's lock with the initially required number of flares (before the last updates) and high-G maneuvers. Now you need to puff a lot more flares giving the same conditions of distance between IR missile and target, target's heading, alt and speed. Judging by the simulation, I understand that these missiles (of Chap and Avenger) can still be deluded with flares, so they're not in the category of image processing target recognition? Or even the imaging seekers can still be deluded with flares (if the Chap and Avenger have such advanced missile seekers)? If the FIM-92 and MIM-72 seekers are still older ones (not IR imaging seekers), why have they been made more resistant to flares now? Wikipedia's (quickest info helper) description on FIM-92 and MIM-72 can be useful for enhancing the performance levels of our missiles in DCS. For instance the MIM-72 seems to be much easier to trick with flares, requires more time to lock and is generally worse than Stinger (FIM-92). Although it says that the F and G(used in DCS) models have been improved, i'm not sure about how greatly was their performance increased over the A/B/C versions. In DCS, the performance between MIM-72 and FIM-92 seems almost the same, expect for max range, max. speed and possibly G-loads. Thanks you for your time and patience!

Speaking of witch, I've read somewhere about the F-5E's in flight performance and was amazed to notice that although it's wings start stalling above 25 true AoA when droops are fully deployed, the flow that remains attached to the wing surface along the path of the strong vortexes created by the LERX (leading edge root extension) only separates above +70 AoA where the vortexes break up (supercritical AoA). Although the F-5's wings have a higher wing aspect and lower wing sweep than those of a MIG-21, which mandatorily reduces the critical AoA, the early F-5's wings which were fitted directly to the fuselage without any LERX or apexes were stalling above 18..19 AoA when the droops and flaps were fully retracted. The droops usually increase the AoA with around 4..7 AoA depending on their design. Slats (fowler leading edge devices) however can increase the AoA with as much as 8..12 AoA (737s slats do so). So even like that (without droops and flaps) the F-5's wings had higher AoA than what those on the MIG-21 right now. The Su-25s indeed start to encounter aerodynamic buffet when the AoA indexer reaches critical and the true AoA is around 15, but the lift to AoA slope is still positive (although curved) between 15 and 18 AoA. Only above 18 AoA the wings of the Su-25s physically start to develop stall (flow separation). The Su-25s, A-10s and L-39s with their straight and high aspect ratio wings still have a critical AoA above 17..18 AoA, so it makes no sense for the 21's wings to stall even earlier than that. The maximum thickness and camber of airfoils indeed affect the critical AoA (higher thickness and camber give higher critical AoA), but only by 2..4 degrees of AoA (so not that much) between a very thin and straight and very thick and cambered one. The strong impact on critical AoA is controlled by wing aspect ratio and sweep. Although both the airfoil shapes and wing aspect ratio and sweep (combined) govern the maximum achievable critical AoA, the airfoils used only affect about 25..30% while the aspect ratio and sweep affect 70..75% of it. So, once more, through every example the MIG-21's wings should provide a much higher AoA before the flow separates. I'm not making this up nor wanting to waste my time, but what I'm saying is based on years of research/experience and can be found on the internet (if one has the proper patience and knows what to search) and technical reports and LN or other 3rd party members can start researching to make sure that people are right and not trolling or trying to create confusion. Here's an interesting article regarding the MIG-21's in flight performance: http://www.military-quotes.com/forum/fighter-performance-actual-plane-analysis-t86206.html Exactly what I'm saying about the critical AoA is also stated here. Just scroll down to about half of the discussion and you'll find this: "Aircraft’s stall speed (speed at which dynamic directional stability breakdown occurs) is function of Mach number, because directional and lateral static stability usually decreases with speed. Stall angle of attack decreases from above 30º (far beyond indicated α) at Mach 0.2 to 20º (i.e. 33 units local angle of attack on indicator) at Mach 0.95. In those days when MiG-21 was designed, electronic flight controls to limit the angle of attack in function of Mach number didn’t exist. A fighter was built primarily for high speeds, high altitude interceptions. At slower speeds previous generations MiG-19/17 were better. Designers put the angle of attack indicator, calibrated in local angle of attack, to warn the pilot of approaching stall limit. At recommended and allowed limit 28 units (about 17º true angle of attack) safety margin to stall is from 13º at Mach 0.2 to 3º at Mach 0.95." "Just before stall α, aircraft nose would start wandering accompanied by more noticeable wing rocking (roll oscillations that intensify thru the stall), symptoms of dynamic directional instability. Stalling proceeds more vigorously with fewer signs at higher subsonic speeds." The statements tell important (and nice) effects that need to be considered for more accurate/correct simulation. The fact that near stall AoA (18.20) the MIG-21 should experience reduced lateral (roll) and directional (yaw) stability which allows the wings to start rocking more and more as the AoA passes stall (above 20). The rocking effects will normally dissipate a couple of more degrees of AoA above stall (some 2..3 more) while the lift would still remain high (perhaps with slight drops). If not asking too much, we're expecting to see this simulated as well (if possible) in the future updates. Regards.

Good job Leatherneck! Great work and progress on the 21! After the last patches it seems that the relation between aerodynamic moments and inertial moments has passed through step by step enhancements. Now the pitch and yaw aerodynamic moments to inertial moments ratio seems pretty authentic. Even without maths to prove it, the pitch and yaw stability derivatives and aero moments look very right. The maximum roll rate and aerodynamic rolling moments to inertial rolling moments are also realistic/authentic now, but, there's still some last work to be done: the variation of aerodynamic rolling moments with AoA. So far, no matter the AoA, the aerodynamic rolling moments seem to have the same value from null lift AoA to critical AoA, which still isn't right. The rolling moments and roll rates should drop exponentially from the highest value (found near zero lift AoA) to the lowest value at stall AoA. Above stall, the rolling moments should be very low and become zero once the beta (sideslip) angle reaches a certain amount combined with the AoA. Even so with these aspects still requiring attention, we saw efforts and great implication from the guys at LN regarding the authenticity of the MIG-21s FM, we're almost certain they'll carry this one out as well. In the near future, the MIG-21's critical angle of attack will also be brought back to +20 (as it was when MIG-21 first appeared in DCS), lower and correct lift to AoA slope and lower/correct maximum lift coefficient. That's all we ask for;). Again, with honest respect and gratitude, good job LN for not letting this baby down! Waiting for the rest! Best wishes!

So you're saying that there is a contradiction between what the TacView's AoA says and what the F2 view's AoA says? If that's the case, then I'm pretty sure the TacView is lying because if you take the MIG-21 and constantly (but slowly) decrease the airspeed while trying to maintain 1G at a vertical speed as close to zero as possible, you'll notice that the plane's pitch attitude angle is exactly +15 degrees when the AoA indexer in cockpit reaches 33 units (as you have zero vertical speed in horizontal flight, the pitch attitude angle and the AoA matches), so TacView is almost certainly not telling the truth and the F2 view tells the truth. This makes me lose some trust in TacView's data. Best wishes!

I got you now friend and sorry I misunderstood your first statement! You're right about the computational results which indeed emerge depending on formulas used and that there's a complex mechanism between many formulas which give a final result such as: lift, drag, moments, etc. But, the input to those formulas can be (and most certainly are momentarily) the key to control the output values that the aircraft presents in flight. That's what I'm trying to get to. The key to success is part inputs and part mathematical model used, so if one isn't too accurate enough, the other one has to compensate. Only ED who created the aerodynamic model may have control over it and rather suggest Leatherneck (and other 3rd parties) what must be changed in order to correct flight behavior and increase realism, otherwise it's up to the 3rd parties to adjust the input values in order to obtain the right result with the given model. I have done quite some research on the MIG-21's aerodynamic lift, drag and their functions to AoA alone and by comparing the results with the ones shown by the MIG-21 in DCS, I discovered great differences. For instance, the lift/AoA (one of the most important) slope for the MIG-21 in DCS is almost double (1.81 times higher) that of the real jet. In DCS, for subsonic flights, the lift/AoA (in radians) slope is approx. 3.7, when it should be 2.6. There also seems to be no difference in lift/AoA slope with Mach number either. In reality all the aerodynamic coefficients and their derivatives vary drastically with Mach and Reynolds number. Also the maximum lift coefficient (or maximum lift) is almost 60% higher (1.6 times) than that of a real MIG-21, which drastically affects the realism of turning performance, correct landing approach speeds or flight performance all in one. For instance, the real life experimental data shows that the maximum CL (lift coefficient) for MIG-21 is near 0.9 for a clean configuration (no ordnance, no flaps, no BL control). Only with BL and full flaps it rises to about +1.25. In DCS however, the maximum lift coefficient at currently 15 AoA is found to be around 1.43 just in clean configuration (no flaps, no BL)! I didn't even want to further test how high it gets with full flaps and BL activated. I don't know where to discuss it (maybe another thread regarding just this or still here), but I find it extremely important if we need to feel like flying the real MIG-21 and not some video game. ED was created with this in mind: realistic in-flight aircraft behavior. So..., that's what we're all looking for. All ED's aircraft have more than 95% realism proven (with the existence of AFM and PFM). The 3rd party members however vary drastically at this aspect. Belsimtek "somehow" proved to have aircraft modeled as realistic as ED! How is it that they could do it right the first time and Leatherneck still has to do some work to it? The MIG-21's FM still needs work so far. I didn't test the Viggen yet although I also bought it. It's almost obvious that it's up to each one's interpretation of DCS's flight model and thus, the input values to be used. Sorry for the long talk, but, it's important to address these aspects. Best wishes!

Please show me the paragraph that you refer to so we can discuss it. If I provided some aerodynamic data (some means nothing else than real world and reliable data) I did so with the purpose to help fix what is off course. Best wishes!

Although the changes weren't right, we must admit that Leatherneck at least tries to fix the flight model of their product and won't disappoint us on long term. I only wish they would take a look at the charts provided and try to re-model the lift and drag vs AoA curves to match the real ones. The chart called "MIG-21 aero" that I posted is as close as possible to the real MIG-21's aerodynamic performance. If I could only have access to the MIG-21's flight model code, I would patiently correct the default values with the ones in that chart and also calculate/determine the correct moments of inertia. Only then I will really feel that I'm flying the MIG-21.

They either exaggerated the aerodynamic moments (too high) or the moments of inertia (too low), but anyway, I believe they'll quickly fix this one. The harder part to fix is to re-arrange the lift to AoA functions in order to fly a realistic MIG-21. The SAU indeed is affected. I don't know if they modified the SAU also or simply does the aero/inertial moments ratio affects it's behavior, but now the plane finds an induced pitch oscillation form the SAU system. The track I provided shows that you can do the types of powerloops shown on your video (good video showing it) even in straight line, one after the other, so the aero to inertial moments ratio is very high.

You are perfectly right my friend. If someone would look into how the aerodynamic model (lift, drag, pitching moment vs AoA, Beta and Mach) is done will see that it's very simplistic, very few curved functions, mostly constant values (at least with Mach) or simple linear functions. I don't want to spark disputes by talking about other simulation names, but there are simulators which are highly advanced in flight mechanics and aerodynamics and DCS is kind of falling behind if not taking actions for improvement. The picture which shows how the aerodynamic values vary from +180 to -180 is one of those sims and was here long before DCS. Yeah, that's because the high sweep delta (with a 2.2 AR (aspect ratio)) generates some relatively strong vortexes (in comparison to a non-LERX lower sweep wing) near the wing's root which has the energy to smooth out or reduce the flow separation in areas closer and closer to the root. This way, beyond a stall angle of 20 AoA (as the MIG-21 should re-find in DCS, which it had when it first appeared), the lift should gradually drop in a curved pattern up to 30..32 AoA (bottom of stalled lift where the flow separation reaches 100% of the chords length as the vortex broke-up), then start rising again naturally (with about half of the non-stalled lift slope) up to 40..45 AoA and because the flow is separated already and the vortex is already dissipated as the lift increases towards 45 you'll get a smaller hump than that for stall. Here's how a LERX affects the lift/AoA slope: https://s23.postimg.org/jhiphb4h7/LERX.jpg The double hump lift curve to AoA is normal for all known airfoils (infinite span wings) and 3D wings, the only differences are indeed the points where the humps lie on the diagram and their curvatures from one wing/airfoil to another. The F-18 for example has a single big hump on the lift/AoA graph somewhere at 40..50 AoA (F/A-18's critical AoA). It's lift to AoA function becomes curved between 30 and 40..50 AoA (from 30 AoA the vortex near the root starts to brake down and the flow starts to separate, that's why the function becomes curved) and between 40 AoA to +70 AoA the lift to AoA function finds a moderate drop which is almost linear. Between 70 and 90 AoA the lift starts dropping rapidly to 0. The F-16 has 2 humps also, the one at the stall and vortex core breakdown (35AoA) is much greater than that at 40..45 AoA, so again you'll have a higher radius lift/AoA curve at stall than at 40..45 alpha. The Su-27 (although I haven't seen any aerodynamic charts anywhere yet) may also have a single bigger hump on the graph or anyway a quite large one before the 2nd and commonly rounded one at 40..45. Here's a crude example of lift to AoA function between +180 and -180 AoA: http://www.aerospaceweb.org/question/aerodynamics/systems/cl-cn.gif Here's the F-18's lift/AoA graph: http://www.rollinghillsresearch.com/Water_Tunnels/F18%20tests.html Here's the F-16's lift/AoA slope: https://s16.postimg.org/eokb6b96t/F-16_Ao_A_CL.png The real MIG-21's lift/AoA diagram should be similar to what I posted. Best wishes.

Wow! So tweaking aircraft's reactions isn't the problem, the problem is getting the right values correctly. With the latest update: https://forums.eagle.ru/showthread.php?t=147601&page=5, the MIG-21 has somewhat closer to real aerodynamic moments in relation to the moments of inertia which are responsible for the pitch, roll and yaw accelerations, but, now they're exaggerated. It's a step closer to real than what it was before, but now on the other extreme! Although I had started this topic about the critical AoA value being too low (and it still persists that way, because instead of about +20, we have 15) and the fact that the lift vs AoA slope is too steep and the null AoA lift is too high for MIG-21, I slide for a bit to also talk about the angular accelerations about the 3 main axis which are also a concern. About 2 months ago I posted 2 video links, where the first one shows exactly the time (can be calculated) needed for the MIG-21 to accelerate in roll from 0 to maximum roll rate when flying at about 500 km/h and weighing around 7500kg (50% fuel) within an air density of around 1.12, from where an initial roll acceleration can be derived. The calculated rolling acceleration can be used either to estimate the correct rolling moment of inertia or the output aerodynamic rolling moment. Now after the latest update the MIG-21 seems to accelerate in roll (although pitch and yaw are also affected) at about 200..250km/h with the same amount of rolling acceleration as the real aircraft at 500km/h. Keep in mind that all the aerodynamic forces and moments vary with the square of the airspeed, so you can estimate/calculate how great the accelerations about all 3 axis are at 500km/h if the required amount for that speed is already there at about just 230km/h. The good thing is that now the general aircraft motions or dynamics (especially in pitch and roll) are better (much closer to real) and we don't see those twitchy/sudden and very high pitch and roll moments/motions anymore above stall AoA, which makes the aircraft feel again like something real. So now the airplane's responses are as smoother as they should, but the accelerations are too great. Here are the good and bad that can be found after the latest update: The good: -Smoother dynamics/motions of the aircraft about the 3 axis between -180 and +180 AoA and beta angles. -G or lift above stall AoA is now higher than before (about 0.6 times that at stall AoA), but still not high enough to be realistic. Take for example the A-10 or Su-25 or F-15 and compare how much their lift drops well above stall in relation to that of the MIG-21. You'll find out that the MIG-21 still drops like a rock well above stall, so it still needs refine. I'd guess that the 21's wings should still produce about 80%..85% of the maximum lift some 10 degrees above stall AoA and not just 55%..60% as it is right now. -Other FM fixes. The wrong: -Although it's very good that the ratio of aerodynamic moments to inertial moments is higher for "X" airspeed, it now became exaggeratedly high and must be lowered by some amount to become realistic. -The lift drop above alpha stall is still sharp. Just 0.5 degrees of AoA above stall are needed to make the lift drop instantly from maximum to minimum. The lift above stall AoA should have a curved pattern that is generally spread between 5 (for low sweep & high aspect ratio wings) and 10 (for high sweep & low aspect ratio wings) to almost 50 degrees of AoA (for wings covered by high energy vortexes, such as those generated by LERX on various fighters like F-18/Su-27/F-16/MIG-29). The MIG-21's wings in reality are capable of allowing around 10..12 degrees of AoA (from my aerodynamics experience) over which the stall pattern should spread until the lift finally drops to 80% that of maximum. For short, as the MIG-21's wings should start stalling beyond 20 degrees AoA, the lift should gradually drop (with quite a smooth curved function) from 20 until 30..32 AoA is reached and above 30..32 AoA as the alpha continues to increase, the lift should again start to increase with an initial slope which is about half the normal (non-stalled) slope through a secondary curved lift to AoA function up to about 45 degrees AoA, from where the lift should finally start dropping with a cosine function of AoA until reaching zero at exactly 90 AoA. That is how a correct lift pattern versus AoA looks like for a real 3D wing. I provided a track showing how easily you can do power-loops (kulbits) one after another with MIG-21 or obtain some insane instant yaw rates and beta (sideslip) angles when jerking the rudder, either due to it's too low moments of inertia or due to too high aerodynamic moments: MIG-21's new aerodynamic moments too high or inertial moments too low.trk Here's an illustration of how the lift should generally vary with AoA from -180 to +180 for a high sweep delta like the 21's: Here are some real lifting performance info for the 21: I'm sorry I turned the topic regarding the abnormally low critical AoA alone into a more detailed subject, yet I hope I don't have to start 2 more topics for linked subjects regarding lift, AoA and moments of inertia. I wish that the devs will have a look at it and keep tweaking the values until they get right. I don't know how the mathematical model used by ED/Leatherneck works to get lift and drag vs AoA values, but if this aircraft is to become realistic, it's lift, drag and critical AoAs must get as close as possible to the values given by available charts. Although I may be a critic throughout all my forum discussions regarding how aircraft behave in DCS, I'm only doing it to help get them better in areas where they should normally get better, otherwise I could simply not care and leave all sorts of abnormal things neglected and lie to myself that I'm playing a realistic flight sim. That is simply not what I desire! Best wishes!